The utilization of a highly active and robust bifunctional catalyst for simultaneously producing H2 and O2 is still a major challenging issue, which is vital for improving the efficiency of overall water splitting. Herein, we employ a novel plasma-assisted strategy to rapidly and conveniently synthesize the three-dimensional (3D) porous composite nanosheets assembled on monodispersed Co nanoparticles encapsulated in a carbon framework (CoNPs@C) on a carbon cloth. Such a novel 3D hierarchical porous nanosheet improves the exposure and accessibility of active sites as well as ensures high electroconductibility. Moreover, the coating of a few graphene layers on the surface of catalysts favors improvement of the catalytic activity. Benefited from these multiple merits, the CoNPs@C composite nanosheets enable a low overpotential of 153 mV at −10 mA cm–2 for hydrogen evolution reaction. Furthermore, they are also capable of catalyzing the oxygen evolution reaction with high efficiency to achieve current density of 10 mA cm–2 at the overpotential of 270 mV. Remarkably, when assembled as an alkaline water electrolyzer, the bifunctional CoNPs@C composite nanosheets can afford a water-splitting current density of 10 mA cm–2 at a cell voltage of 1.65 V.Keywords: 3D porous structure; bifunctional catalyst; binder-free; cobalt nanoparticles; overall water splitting;

Herein, we report a simple and quick synthetic route to prepare the pure CuFeS2 quantum dots (QDs) @C composites with the unique structure of CuFeS2 QDs encapsulated in the carbon frame. When tested as anode materials for the lithium ion battery, the CuFeS2 QDs @C composites based electrodes exhibit excellent electrochemical performances. When charge–discharge occurred with a current density of 0.5 A g–1, the electrodes exhibit a high reversible capacity (760 mA h g–1) for as long as 700 cycles, which indicates the superior cycling life. Detailed investigations of the morphological and structural changes of CuFeS2 QDs by ex situ XRD, ex situ Raman, and ex situ TEM reveal an interesting electrochemical reaction mechanism, a hybrid of a lithium–copper iron sulfide battery and lithium–sulfur battery. The direct observation of orthorhombic FeS2 by HRTEM and the existence of Li2FeS2 detected by Raman support our assertion. We believe such an electrochemical mechanism would attract more attention to the CuFeS2 nanomaterials as lithium ion battery anode materials. The excellent electrochemical properties would be derived from the unique structure, which include CuFeS2 QDs encapsulated in the carbon frame.Keywords: high capacity; hybrid of lithium−copper iron sulfide battery and lithium−sulfur battery; long cycling life; quantum dots; transition metal sulfides;

Sodium-ion capacitors (SIC) combine the merits of both high-energy batteries and high-power electrochemical capacitors as well as the low cost and high safety. However, they are also known to suffer from the severe deficiency of suitable electrode materials with high initial Coulombic efficiency (ICE) and kinetic balance between both electrodes. Herein, we report a facile solvothermal synthesis of NaTi2(PO4)3 nanocages constructed by iso-oriented tiny nanocrystals with a mesoporous architecture. It is notable that the NaTi2(PO4)3 mesocrystals exhibit a large ICE of 94%, outstanding rate capability (98 mA h g–1 at 10 C), and long cycling life (over 77% capacity retention after 10 000 cycles) in half cells, all of which are in favor to be utilized into a full cell. When assembled with commercial activated carbon to an SIC, the system delivers an energy density of 56 Wh kg–1 at a power density of 39 W kg–1. Even at a high current rate of 5 A g–1 (corresponds to finish a full charge/discharge process in 2 min), the SIC still works well after 20 000 cycles without obvious capacity degradation. With the merits of impressive energy/power densities and longevity, the obtained hybrid capacitor should be a promising device for highly efficient energy storage systems.Keywords: anode; energy storage; iso-oriented growth; mesocrystal; NaTi2(PO4)3; sodium-ion capacitor;

Three-dimensional (3D) microstructured building units have replaced layer-to-layer stacked designs in transparent graphene films to fully exploit the advantages of two-dimensional graphene. However, it is still challenging to precisely control the size and microstructures of these building blocks to develop multifunctional graphene-based materials that satisfy the performance requirements of diverse applications. In this study, we propose a controllable method to regulate the microstructures of building units to form structures ranging from opened bubbles and cubes, while the size decreased from 20 to 3 μm, via an in situ template-modulating technology. NaCl was used as either a liquid or solid template by changing the dc bias. The reduced size and dense arrangement of the building units not only provide an improved mass loading for the transparent films but also build multiple pathways for fast ion/electron transmission, enhancing their promise for various practical applications. Generally, we provide a convenient protocol for finely regulating the microstructure and size of these building units, resulting in multifunctional films with a controllable transmittance, which enables the use of these graphene-based architectures as transparent electrodes in various applications and extends the family of multifunctional materials that will present new possibilities for electronics and other devices.Keywords: graphene opened-bubble; graphene opened-cube; template-modulating; transparent film; tunable microstructure;

A composed material of amorphous carbon nanotubes (ACNTs) and encapsulated transition metal oxide (TMOs) nanoparticles was prepared by a common thermophysics effect, which is named the Marangoni effect, and a simple anneal process. The prepared ropy solution would form a Marangoni convection and climb into the channel of anodic aluminum oxide template (AAO) spontaneously. The ingenious design of the preparation method determined a distinctive structure of TMOs nanoparticles with a size of ∼5 nm and amorphous carbon coated outside full in the ACNTs. Here we prepared the ferric oxide (Fe2O3) nanoparticles and Fe2O3 mixed with manganic oxide (Fe2O3&Mn2O3) nanoparticles encapsulated in ACNTs as two anode materials of lithium ion batteries’ the TMOs-filled ACNTs presented an evolutionary electrochemical performance in some respects of highly reversible capacity and excellent cycling stability (880 mA h g–1 after 150 cycles).Keywords: carbon nanotubes; lithium batteries; Marangoni effect; self-climbed; transition metal oxide;

Recently, metal organic framework (MOF) nanostructures have been frequently reported in the field of energy storage, specifically for Li-ion or Na-ion storage. By inter-separating the active sites of metal cluster and organic ligands, MOF nanostructures are exceptionally promising for realizing fast ion exchange and high-efficiency transportation and addressing the intricate issues that the energy-intensive Li-ion batteries have faced over many years. The related ion-storage mechanism remains to be explored. Is the traditional redox reaction mechanism operative for these nanostructure, as it is for transitional metal oxide? Herein, taking [Fe3O(BDC)3(H2O)2(NO3)]n (Fe-MIL-88B) as an example, an Fe-based metal organic polyhedral nanorods of MIL–88 B structure was designed as an anode for Li-ion storage. When tested at 60 mA g−1, the nanoporous Fe-MIL–88 B polyhedral nanorods retained a reversible capacity of 744.5 mAh g−1 for more than 400 cycles. Ex situ characterizations of the post-cycled electrodes revealed that both the transition metal ions and the organic ligands contributed to the high reversible specific capacity. The polyhedral nanorods electrodes held the metal-organic skeleton together throughout the battery operation, although in a somewhat different manner than the pristine ones. This further substantiated that some MOF nanostructures are more appropriate than others for stable lithiation/delithiation processes. State-of-the-art CR2032 full cells showed that a high capacity of 86.8 mAh g−1 that was retained after 100 cycles (herein, the capacity for the full cell was calculated based on both the weight of the anode and the cathode, and the charge-discharge rate was 0.25C), when commercial LiFePO4 powders were used as the cathode.Download high-res image (204KB)Download full-size image

Fayalite was synthesized by a simple process. As an anode materials for lithium ion batteries, fayalite was mixed with acetylene black to prepare electrodes. The electrochemical properties of Fe2SiO4 particles were systematically investigated and our results proved that fayalite presents great specific capacity, superior rate capability and long battery cycle life when tested in the form of a half-cell. As a new anode material, fayalite showed a room-temperature invertible specific discharging capacity of 800 mA h g−1 at a current of 100 mA g−1 after 100 cycles, and that its reversible specific capacity reaches 520 mA h g−1 at a current density of 1600 mA g−1. This splendid lithium storage performance may result from the unique crystal structure of fayalite to form a channel that promotes the lithium ion insertion and extraction process and the formation of lithium silicate as a solid electrolyte. Therefore, fayalite could be a prospective alternative material for lithium-ion battery anodes.

Two-dimensional (2D) free-standing Ge-doped ZnO nanostructures were synthesized on graphite substrate. A single nanosheet composed of amounts of nanograins with size of ∼20 nm exhibits excellent field electron emission capability that can deliver a current as large as 30 mA cm−2 at E = 9.0 V μm−1. The amazing performance originates from the high electron conductivity owing to Ge doping, as well as the enriched emitting spots on the surface of the structure. Additionally, we observed the temperature- and excited-power-dependent redshift of photoluminescence (PL) in the temperature range of 77–300 K, which was attributed to the local thermal effect driven nonradioactive enhancement. The rich defect and impurity levels result in alternative recombination mechanisms in the temperature range.

Iron phosphide (FeP), as a low-cost and earth-abundant electrocatalyst, has received increasing attention in recent years. However, its hydrogen evolution reaction (HER) performance is still far from satisfactory in terms of both activity and stability. In this study, by employing vertically aligned graphene nanosheets (VAGNs) as the backbone, we synthesized a novel three dimensional (3D) FeP/VAGN hybrid nanostructure on carbon cloth (FePNRs/VAGNs/CC) as a binder-free efficient electrocatalyst for the HER. The villiform FeP nanorods with diameters of ∼50 nm and lengths of 100–300 nm were successfully grown on the surface of VAGNs by an electrodeposition process followed by a phosphidation treatment. The separate VAGNs not only provide a 3D architecture for FeP growth, but also facilitate charge transfer. As expected, this 3D hybrid electrocatalyst exhibits an enhanced HER activity with an onset potential of 19 mV, an overpotential of 53 mV at 10 mA cm−2, a Tafel slope of 42 mV dec−1, and a remarkable stability and durability in an acid solution. The superior hybrid FeP electrode might pave an efficient way for the practical application toward hydrogen generation.

Transparent all-solid-state supercapacitors are advanced power supply devices for multifunctional high-end electronics. However, the areal capacitance is seriously limited due to the low mass loading, as high transmittance usually corresponds to ultra-small electrode thickness, which hinders practical applications. Here, we develop an effective three-dimensional (3D) architecture using plasma-etched micro-structured NaCl as the template. The film is assembled by graphene hollow-cube building units, and the faces of the cubes are graphene network microstructures. The graphene-network-face hollow-cube units (GNHC) fully exploit the large surface area of graphene, ensure the transparency of the film and reduce junction contact resistance between the graphene sheets. As expected, the film exhibits improved areal capacitance (5.48 mF cm−2), high volumetric energy (657.2 μW h cm−3), and power densities (954.3 mW cm−3). Generally, GNHC based films will be promising energy storage materials and very suitable supports or templates for construction of graphene-based composites.

The design and development of non-noble metal electrocatalysts for the hydrogen evolution reaction (HER) is highly desirable, but still cannot satisfy actual requirements in terms of superior activity, ultrahigh stability and ability to carry large current densities. In this study, Ni nanoparticles anchored onto MoO2 nanowires have been synthesized on carbon cloth via in situ exsolution under a reducing atmosphere. Impressively, the obtained Ni–MoO2-450 NWs/CC exhibits an excellent platinum-like HER activity with a nearly zero onset overpotential and a small Tafel slope of ∼30 mV dec−1, which implies that the fast recombination step is rate-limiting. Surprisingly, our sample gives an unprecedented stable catalytic activity over 320 hours in 1 M KOH, and can retain its activity at large current densities, even in the order of 1000 mA cm−2, which is far better than other reported catalysts. Such an outstanding performance should be mainly attributed to the integrated 3D self-supported nanocatalyst, the high electronic conductivity framework and the synergistic coupling effect between Ni and MoO2 interfaces. This work may thus provide an insight into the design and fabrication of alternative catalysts to Pt-based catalysts for the HER.

Due to its high theoretical capacity (978 mA h g–1), natural abundance, environmental friendliness, and low cost, zinc oxide is regarded as one of the most promising anode materials for lithium-ion batteries (LIBs). A lot of research has been done in the past few years on this topic. However, hardly any research on amorphous ZnO for LIB anodes has been reported despite the fact that the amorphous type could have superior electrochemical performance due to its isotropic nature, abundant active sites, better buffer effect, and different electrochemical reaction details. In this work, we develop a simple route to prepare an amorphous ZnO quantum dot (QDs)/mesoporous carbon bubble composite. The composite consists of two parts: mesoporous carbon bubbles as a flexible skeleton and monodisperse amorphous zinc oxide QDs (smaller than 3 nm) encapsulated in an amorphous carbon matrix as a continuous coating tightly anchored on the surface of mesoporous carbon bubbles. With the benefits of abundant active sites, amorphous nature, high specific surface area, buffer effect, hierarchical pores, stable interconnected conductive network, and multidimensional electron transport pathways, the amorphous ZnO QD/mesoporous carbon bubble composite delivers a high reversible capacity of nearly 930 mA h g–1 (at current density of 100 mA g–1) with almost 90% retention for 85 cycles and possesses a good rate performance. This work opens the possibility to fabricate high-performance electrode materials for LIBs, especially for amorphous metal oxide-based materials.Keywords: amorphous metal oxide-based materials; high-performance electrode; lithium-ion batteries; quantum dots; zinc oxide;

The development of non-noble metal electrocatalysts for the hydrogen evolution reaction (HER) has attracted much attention. Metal nitrides have been considered as promising alternatives in recent years. Nevertheless, the preparation of tungsten nitride still suffers from disadvantages such as environmentally unfriendly sources and poor morphologies, which induce a relatively low activity. Herein we employed clean N2-plasma to develop a 3D WN nanowire array on carbon cloth (WN NW/CC) with a porous structure. As expected, the resulting WN NW/CC is highly active, giving a small η10 (overpotential to drive a current of 10 mA cm−2) of 134 mV and a Tafel slope of 59.6 mV dec−1 in acidic solution, and an η10 of 130 mV and a Tafel slope of 57.1 mV dec−1 in alkaline solution, respectively. Additionally, it maintains its catalytic activity for at least 14 500 s in both acidic and alkaline media.

The platinum-like behavior of tungsten carbides has made them one of the most promising electrocatalysts for the hydrogen evolution reaction (HER). So far, however, their poor activity has kept them far away from practical application. Related research has been basically focused on the form of particles with poor nano-structures, which is not conducive to further development. There is an urgent need to develop a versatile and facile method to synthesize tungsten carbide nanostructures with high active site density. Here we developed a plasma-assisted carburization method to synthesize porous tungsten carbide hybrid nanowires (p-WCx NWs) on carbon cloth. Benefitting from the rapid carburization process with a unique etching-effect in the plasma, the resulting p-WCx NWs are provided with porous nano-structures and an appropriate carbon coating layer. They exhibit excellent HER performance with a small onset potential of 39 mV, η10 (overpotential to drive a current of 10 mA cm−2) of 118 mV, and Tafel slope of 55 mV dec−1 in acid solution, and an onset potential of 56 mV, η10 of 122 mV, and Tafel slope of 56 mV dec−1 in alkaline solution. These performances are superior to those reported for W-based carbide electrocatalysts to date. Impressively, the p-WCx NWs/CC electrode could sustain more than 40 h of hydrogen production at the current density of 20 mA cm−2 without observable deterioration in both strong acid and alkaline solutions.

Individual graphene ribbons, which fully exploit the large surface area of graphene sheets, have been fabricated. Constructing these unique structures into efficient macroscopic functional architectures is an important and challenging step towards practical applications. Here, we produce micro-structured interconnected ribbon-like graphene sheets (MRGs), which were induced by the multistage-recrystallization of NaCl templates in a microwave plasma chemical vapor deposition (MPECVD) system. The MRGs along different directions hang in polygonal graphene walls, which connect with each other forming a three dimensional (3D) transparent and self-supporting graphene film (MRG-GF). The MRG-GF with a large surface area, enhanced flexibility and fast ion/electron transport pathways exhibits improved capacitance (4.88 mF cm−2) and super-long cycle life with good cycling stability (capacitance retention was ∼95.5% after 20 000 cycles). Herein, we provide a novel approach for controlled synthesis of graphene ribbons, and graphene ribbon-based functional structures and composites.

•For the first time, we reported a controllable heteroepitaxial nucleation of NVP on graphene oxide nanosheets.•The strongly–coupled NVP/C and bottom–up assembly together contributed to a highly–conductive nanocomposite.•The NVP/C nanocomposite demonstrate an extraordinarily high-rate and long-durability Na-storage performances.Herein, a three–dimensional (3D) Na3V2(PO4)3–based hollow nanosphere with hierarchical pores (3DHP–NVP@C) has been firstly reported. Detailed studies reveal that this novel architecture is made up from the bottom–up assembly of carbon–coating NVP nanoparticles. The hierarchically porous structure offers ample space for the intimate contact between electrode/electrolyte and eliminates the disadvantageous reducing of effective surface areas in manufacturing the electrodes, as well as stabilizes the structure upon repeated sodium ions insertion/extraction, resulting to the barrier–free sodium ion diffusions and long–term cycling life. On the other hand, the graphitic carbon shells construct into a highly–conductive framework that can ensure the ultrafast electrons transfer. Consequently, extraordinary high–rate and ultralong–cycle capabilities that are superior to any other NVP–based material are obtained: the outstanding high–rate capacity retention (over 80% of the 1 C capacity is retained at 400 C), ultralong life span (90.9% and 92.5% capacity retention after 10,000 cycles at 1 C and 5 C), and extremely high–rate stability (80% capacity retention after 30,000 cycles at 50 C), demonstrating its promising application in sodium ion battery.Download high-res image (446KB)Download full-size image

Exploring ternary metal oxides that can in situ form an elastic medium to accommodate volume changes upon lithium intercalation is now a popular and effective way to achieve high-performance lithium ion batteries with enhanced cycling stability. Herein, we report an ultrathin zinc pyrovanadate nanosheet of atomic thickness with exposed (001) facets via a facile hydrothermal method. Morphological and structural evolutions of the zinc pyrovanadate are investigated to reveal the electrochemical reaction mechanism of this compound towards lithium ion intercalations for the first time. It is found that the initial zinc pyrovanadate transforms into ZnO nanoparticles and LiV2O5 in the first cycle, and the subsequent reaction mainly occurs between ZnO and LiZn and lithiation/delithiation of the lithium vanadate. Interestingly, the in situ formed lithiated vanadate matrix could serve as a conductive network for the reversible electrochemical process of ZnO. The ultrathin thickness is in favour of shortening pathways for lithium ions, while the specific exposed facets are facilitated to form the architecture of ZnO nanoparticles embedded in the amorphous lithiated vanadate matrix owing to the sandwich-like skeleton of the zinc pyrovanadate that is constructed from the layer-by-layer stacking of the [ZnO6] and [V2O7] polyhedra chains projected along the c axis. Benefiting from these inspiring merits, the as-synthesized ultrathin zinc pyrovanadate nanosheet exhibits a high specific capacity (963 mA h g−1 at 0.05 A g−1), outstanding rate capability (344 mA h g−1 at 10 A g−1), and long cycle life (602 mA h g−1 could be maintained after 980 cycles at 1 A g−1) and is regarded as a promising candidate for lithium ion battery anode materials.

We have made a supercapacitor electrode based on carbon fabric, vertically aligned graphene nanosheets (VAGN) and Mn3O4 nanoparticles. The unique structure constructed by VAGN endows the electrode with high specific capacitance up to 670 F g−1. Additionally we assembled two pieces of the electrode to make a highly flexible all-solid-state symmetric supercapacitor. This device demonstrates a high capacitance of 562 F g−1, high energy density of 50 W h kg−1, high power density of 64 kW kg−1 and good stability after 10000 cycles. Due to the flexibility of the carbon fabric, the device expresses an excellent flexibility without sacrificing the electrochemical performance when bended to 150 degrees. We believe that this electrode with its excellent electrochemical performances has an enormous potential in energy storage applications, especially for flexible and lightweight electronics.

Nowadays, exploiting novel electrode materials is widely accepted as a key for meeting the growing demands of high-performance lithium ion batteries. Several transition-metal vanadates, which can in situ form an elastic buffer to adapt the volume expansion during lithium uptake/removal, have recently attracted much attention as anode materials, since they have high capacity and superior cycling stability. Herein, Zn2(OH)3VO3 nanostructures are successfully fabricated for the first time by a facile hydrothermal method and also first studied as lithium ion anode material. The ultrathin Zn2(OH)3VO3 nanosheets deliver a high reversible capacity close to 900 mAh g–1 at a current density of 1 A g–1 over 100 cycles. Even at a high current rate of 5 A g–1, capacity retention as high as 83% (by compared with the second discharge capacity) is still obtained after 500 cycles, showing a high-rate capability. Moreover, we also carefully investigated the lithium-storage mechanism of Zn2(OH)3VO3, and corresponding results reveal that the Zn2(OH)3VO3 nanosheets have in situ transformed into ZnO nanoparticles anchoring on lithiated vanadium oxides matrix. The synergistic effect of zinc and vanadium oxides upon lithium ions intercalation and the stable conductive skeleton of amorphous lithiated vanadium oxides matrix both contribute to the excellent battery performance of Zn2(OH)3VO3 nanosheets. Finally, a full cell composed of lithiated Zn2(OH)3VO3/LiFePO4 with a high energy density of 293 Wh kg–1 (vs total mass of active materials) at the current density of 100 mA g–1 was successfully assembled, which could cycle well over 100 cycles with 79% capacity retention and also exhibit good rate stability. Thus, we believe that our research demonstrates a promising anode material for lithium ion batteries.Keywords: anode; full cell; lithium-storage mechanism; nanosheets; Zn2(OH)3VO3

Novel 3D ZnSb nanowire balls composed of ultra-thin nanowires were achieved through simple self-assembly method based on typical thermodynamics in chemical vapor deposition (CVD) system. The elliptic cylinder-shaped nanowires with cross-section size of ∼25nm × ∼ 10 nm display impressive performance in sodium-ion battery (SIB) application as anode material. Comparing to pure Sb, ZnSb is advantageous in resisting huge volume change and possess enhanced conductivity, which would do much better to offer a long-time cycling stability and rate performance. Such a small size of the low dimensional structures can further improve the electron/ion transfer efficiency. Through systematic measurements, we found that, at 20 mA/g, the capacity remains 377mAh/g after the 100th cycle with the coulombic efficiency at ∼99%. Even if the current density increased to 750 mA/g, the value was still higher than 225mAh/g. The half-cell device also provides a rapid response and stable output in the rate tests (20–650 mA/g). The good performance originates from the unique structural configuration, implying the huge potential value of ZnSb in SIB application. We hope the results also can expand the Sb based anode material family.

Developing two dimensional (2D) graphene-based nanomaterials with surface-to-surface architectures has been an important strategy for achieving high-performance lithium ion electrodes. However, almost all of them involve multistep procedures and expensive precursors. This paper reports a novel 2D nanocomposites composed of ultrafine SnO2 nanoparticles anchored on V2O5 nanosheets via a one-pot hydrothermal method, which exhibit high reversible capacities and rate stabilities. The enhanced electrochemical performances compared to pure SnO2 nanoparticles have been attributed to the effective prevention of self-agglomerations of the pulverized nanograins upon cycling. We speculate that the 2D V2O5 nanosheets with layered structures maybe a good substitute for the graphene nanosheets.

Vapor–solid–solid (VSS) process has recently received continued attention as an alternative to grow Si nanowire. In comparison with common vapor–liquid–solid (VLS) growth with liquid catalyst, VSS growth can prevent the catalyst species from incorporating into nanowires with deep-level impurity, and achieve the compositionally abrupt interfaces by restraining the so-called “reservoir effect”. However, despite the huge advances in experimental observations with in situ electron microscopy, VSS growth still remains much less understood in theory. Here, we developed a general mass-transport-limited kinetic model to describe the VSS growth process of Si nanowires by considering three surface diffusion processes and a slow interface diffusion process, where the former determines the atoms supplies way, while the latter dominates the growth of nanowires. The present model is not only well consistent with the available experimental data of Si nanowire, but also gives a clear physical image for the successive side-to-side ledge flow VSS growth.

Transparency has never been integrated into freestanding flexible graphene paper (FF-GP), although FF-GP has been discussed extensively, because a thin transparent graphene sheet will fracture easily when the template or substrate is removed using traditional methods. Here, transparent FF-GP (FFT-GP) was developed using NaCl as the template and was applied in transparent and stretchable supercapacitors. The capacitance was improved by nearly 1000-fold compared with that of the laminated or wrinkled chemical vapor deposition graphene-film-based supercapacitors.

Iron fluoride cathodes with good specific energy/power performance can hardly operate durably at room temperature due to poor conductivity and sluggish kinetics. Fabricating novel hybrid nanostructures is a promising approach to obtain a fast diffusion and transport process. In this study, a porous honeycomb-like iron fluoride hybrid composite comprising iron fluoride nanocrystals (∼1–4 nm) encapsulated in separate carbon nests constructed by multi-scale pores (∼1–100 nm) was fabricated through a combination of room-temperature fluorination and a mild annealing process for the first time. The iron fluoride topochemically evolved from a smaller iron oxide nanocrystal precursor (∼2–3 nm) is closely engineered with carbon creases nested in carbon microbubbles (CMBs) which exhibit a three dimensional (3D) porous honeycomb-like network structure. As a cathode material for lithium-ion batteries (LIBs), the hybrid electrode delivers a large capacity of nearly 500 mA h g−1 at 20 mA g−1 (normalized to the composite, i.e. the capacity is calculated based on the total mass of the composite). Meanwhile, a durable cyclability of more than 500 cycles and a large rate of 10 A g−1 were also realized at room temperature. The impressive specific energy/power performance (1100 W h kg−1/224 W kg−1) which is superior to that of today's Li-ion batteries (∼380 W h kg−1/∼80 W kg−1) reveals the efficiency of the novel hybrid nanostructure in speeding up the kinetics without sacrificing the storage capability. Direct insights into the lithiation process reveal that iron fluoride firstly undergoes a mild amorphization process, and then crystallizes as γ-Fe nanocrystals after in-depth lithiation; during the de-lithiation process, γ-Fe firstly becomes amorphous due to the injection of fluorine, and subsequently evolves into double-salt-like LixFeFy nanocrystals for further fluorine enriching. Reversible conversion between C-Fe0/LiF and T-FeF2, like LixFe3+Fy with a 3 mole electron transfer, lasts for more than 100 cycles without any obvious re-distribution of the active materials.

FeF2, as a promising cathode material for Li-ion batteries, has a high specific capacity of 571 mA h g−1, and a lot of research has been focused on overcoming its poor cycling stability associated with low electron conduction and large volume effect, mostly through nanostructured material design. However, FeF2 nanodesign itself is a challenge. Herein, we report the incorporation of an ordered mesoporous carbon (CMK-3) into FeF2-based cathodes. The FeF2 nanoparticles inside the conducting CMK-3 by topochemical conversion from an iron oxide precursor to iron fluoride hydrate in situ, form a well-connected three dimensional network structure. Such a hierarchical framework combines multiple advantageous features, including a continuous electrically conductive network and porous space for the volume expansion of the FeF2 particles. With this cathode, we demonstrate a cycle life of 1000 cycles with little capacity decay (less than 0.3‰ per cycle). The FeF2@CMK-3 electrode shows stable cycling and an extremely high-rate capacity, owing to the special porous structure and the nano-sized particles. In the potential range of 1.5–4.5 V, discharge capacities of 500, 400 and 320 mA h g−1 can be delivered at the high rates of 500, 2000 and 4000 mA g−1 after 100 cycles, respectively, which is the highest level for FeF2 so far.

Herein, honeycomb in honeycomb carbon bubbles (HHCBs) with macro-, meso-, micro-, and nanopores have been successfully obtained for the first time via a simple one-step direct templating method. Benefiting from unique features, the HHCBs demonstrate superior cycling stability and rate capability when employed as anode materials for both lithium and sodium-based batteries. For instance, hollow carbon bubbles used as lithium ion battery anodes deliver a high reversible capacity of 1583 mA h g−1 and nearly 100% capacity retention over 100 cycles at a constant current of 372 mA g−1 (1C). A high reversible capacity of 200 mA h g−1 also can be obtained at an extremely high current rate of 300C. When tested as sodium ion battery anodes, the electrode can deliver an initial reversible capacity of 373 mA h g−1 and retain 209 mA h g−1 after 400 cycles at 100 mA g−1. Even at a high current rate of 1000 mA g−1, the electrode still can release a substantial reversible capacity of 122 mA h g−1 after discharging–charging for 700 cycles, suggesting a high rate capability and cyclability. The approach provides a valuable candidate acceptable for use as both lithium and sodium ion battery anodes.

Besides targeting low-voltage intercalation, NaTi2(PO4)3 (NTP) is a promising negative electrode material for non-aqueous sodium-ion batteries (SIBs). However, the low electronic conductivity of this material inhibits its potential applications. Herein, we report the controllable synthesis of four interesting porous NTP nanocubes via a one-pot solvothermal method. The as-synthesized products have shown excellent high-rate performance and cycling stability as SIB anodes. After 10000 cycles at a 10C rate, 75.5% of the initial capacity is retained, which exceeds those of most of the reported SIB anode materials. Even at an extremely high rate of 100C, the NTP nanocubes can still deliver considerable reversible capacities after deep charging/discharging for 15000 cycles. The superior electrochemical performances can be attributed to their unique nanostructures. We hope that such a finding of the new construction will enrich the NTP system and provide several possible candidates for SIB anodes.

In this work we report the first synthesis of 2H-SiC-α-Al2O3 solid solution (SS) nanowires with 2H-SiC as the host phase. The one dimensional (1D) fake binary-system exhibits interesting room-temperature ferromagnetism and spin-glass-like (SGL) behavior. This novel diluted magnetic semiconductor (DMS) was designed on the basis of SiC which is the most promising fundamental semiconductor used in next-generation electronics as the substitute for Si. A systematic investigation of the magnetic properties reveals the origin of the material's room-temperature ferromagnetism and spin-glass behavior. Spin-polarized density functional theory (DFT) calculations reveal that the net moment originates from a strong coupling between atoms around local Si vacancies produced by the SS defect reaction. Unlike random defects derived magnetic behavior, the SS resulted magnetism is significant to be utilized in functional devices since it belongs to a stable crystal structure that is possible to be prepared rationally in a controlled manner.

Large volume changes cause a series of complicated problems in alloy-type anodes, such as pulverization, exfoliation and the capacity decay which results. Therefore, solutions for the problems caused by large volume changes in sodium ion battery (SIB) anodes are urgently needed. Herein, we report a novel route to encapsulate Sb2O3/Sb nanoparticles (Sb2O3/Sb-NPs) within a graphene shell nanostructure (Sb2O3/Sb@graphene) via microwave plasma irradiation of Sb(CH3COO)3 and a subsequent graphene growth procedure. The designed structure, Sb2O3/Sb@graphene NPs anchored on carbon sheet networks (CSNs), provides an ultra-thin, flexible graphene shell to accommodate the volume changes of Sb2O3/Sb, and thus demonstrates excellent cycling stability (92.7% of the desodiation capacity was retained after 275 cycles), a long cycle life (more than 330 cycles) and a good rate capability (220.8 mA h g−1 even at 5 A g−1). The stability could be compared to that of commercial graphite in lithium ion batteries.

The intrinsic electronic conductivity can be improved by doping efficiently. CoxFe3–xO4 nanostructures have been synthesized for the first time to improve the conductivity of lithium battery electrode. The solid solution CoxFe3–-xO4 were characterized by X-ray diffraction pattern (XRD), Raman spectrum, scanning electron microscopy (SEM), transmission electron microscope (TEM), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). The results show that the doping enlarge the lattice spacing but the structure of Co3O4 is stable in the Li-ion intercalation/deintercalation process. The AC impedance spectrum reveals the conductivity is well improved. In addition, the solid solution CoxFe3–xO4 exhibit excellent electrochemical characteristics. The electrodes with 20% molar ratio of Fe ions own a reversible capacity of 650.2 mA h g–1 at a current density of 1 A g–1 after 100 cycles.Keywords: ball-in-ball; hydrothermal; lithium-ion battery; solid solution; template-free;

As anode material used in power storage device, lithium ion battery (LIB) for example, ZnO has not been recognized as a promising candidate, although which shows advantages like environmental benign, low cost, and large reservation. Several problems, such as volume expansion, pulverization, and active substance detachment because of the particular lithiation kinetics, which result in very high irreversible capacity and following fading, can account for the present situation. Here in this work, we report the self-assembly of ZnxGe1–xO three-dimensional (3D) micronano structures and achieve enormous improvement on both recyclability and rate performance. After the 100th cycle, the capacity remains ∼690 mAh/g at the rate of 100 and ∼510 mA/g at the rate of 500 mAh/g. The capacity recovered rapidly even the rates alternating repeatedly between 50 mA/g and 3.5A/g. Ex situ observation reveals that substance detachment and nanoparticle agglomeration were avoided, benefiting from the firm 3D space configuration. As the Li+ insertion, the 3D architectures fracture hierarchically with releasing the volume-expansion produced strain. Stable and smooth Li+/electrons path would form in these nanoparticles integrated microfragments, which act as the working unit free of further detachment. These facts demonstrate that ZnO based anode materials are anticipant to be good candidate in LIB device through rational design of advanced mirco-nano structures without introduction of carbon coating.Keywords: Ge-doped ZnO; high capacity; LIB; long-term stability; self-assembly; three-dimensional nanostructures;

Two-dimensional (2D) nanostructures are a desirable configuration for lithium ion battery (LIB) electrodes due to their large open surface and short pathway for lithium ions. Therefore, exploring new anode materials with 2D structure could be a promising direction to develop high-performance LIBs. Herein, we synthesized a new type of 2D Ge-based double metal oxides for lithium storage. Ultrathin hexagonal Co2GeO4 nanosheets with nanochannels are prepared by a simple hydrothermal method. When used as LIB anode, the sample delivers excellent cyclability and rate capability. A highly stable capacity of 1026 mAhg–1 was recorded after 150 cycles. Detailed morphology and phase evolutions were detected by TEM and EELS measurements. It is found that Co2GeO4 decomposed into Ge NPs which are evenly dispersed in amorphous Co/Li2O matrix during the cycling process. Interestingly, the in situ formed Co matrix could serve as a conductive network for electrochemical process of Ge. Moreover, aggregations of Ge NPs could be restricted by the ultrathin configuration and Co/Li2O skeleton, leading to unique structure stability. Hence, the large surface areas, ultrathin thickness, and atomically metal matrix finally bring the superior electrochemical performance.Keywords: 2D materials; Co2GeO4; double metal oxides; Ge; lithium storage mechanism

Porous ZnO/C microboxes have been synthesized simply by annealing metal–organic framework carboxylate groups. The porous ZnO/C microboxes inherited the morphology and porous character of the carboxylate groups. The microboxes possess a large BET of 179 m2 g−1 and a uniform pore size distribution. The porous structure of ZnO/C microboxes enforces Li+ diffusion and helps to buffer the volumetric variation. When tested as anode materials for lithium batteries, the ZnO/C microboxes deliver an initial discharge of 1289.7 mA h g−1 and still reach a high reversible capacity of 716.2 mA h g−1 after 100 cycles at a current density of 100 mA g−1.

Herein, a method of synthesizing Co2SiO4 at a low temperature of 900 °C is reported. By synthesizing the precursor with a facile hydrothermal method and post-annealing in air at 900 °C, Co2SiO4 with good purity was obtained. The Co2SiO4 nanoparticles were characterized by XRD, XPS and TEM to analyze their structure and morphology. To evaluate their performance as the anode material for a lithium ion battery, the Co2SiO4-based electrodes were investigated by cyclic voltammetry (CV), galvanostatic cycling and a rate test. Such electrodes display superior electrochemical performance, such as providing a large reversible capacity as high as 650 mA h g−1 at a current density of 100 mA g−1 after 100 cycles, demonstrating excellent cyclic performance and good rate capacity.

We report a simple method to fabricate Ge–graphite core–shell nanowires on a large scale using a CVD (Chemical Vapor Deposition) system free of catalyst and complicated precursors, which demonstrates interesting V–L–S (vapor–liquid–solid) boundary induced self-catalyzed growth. The novel catalyst-free VLS (vapor liquid solid) mechanism is expected to be generalized for the design of other 1D (one dimensional) metal–graphite hybrids in a controlled manner, based on the fact that tunable shell thickness was achieved on Ge–graphite and a 1D Cu–graphite core–shell was realized in the same way. The Ge–graphite core–shell nanowires deliver very good field emission properties with a threshold field of about 5.33 V μm−1 and a turn-on field of 2.58 V μm−1. The surface wetting measurement confirms the superhydrophobicity of the sample with a WCA (Water Contact Angle) of about 150.8° ± 2°, which decreased to 84.7° after 300 °C (3 h) treatment under vacuum (10−3 Torr). Moreover, the wettability behavior is robust against 365 nm UV (ultraviolet) radiation with the WCA unchanged, indicating stable superhydrophobicity in a UV-rich environment. We hope that this study contributes to the design of 1D metal–graphite nanostructures with the aim to explore more novel functionalities.

Si with high theoretical capacity has long suffered from its large volume variation and low electrical transport linked to poor cycling stability and rate performance. Here, a facile approach is reported to mass produce nanostructured Si@carbon with a tunable size of silicon nanoparticles. We performed carbon coating of Si nanoparticles by polyacrylonitrile (PAN) emulsifying and then carbonization. The hollow Si@C nanostructure was obtained via direct etching of Si nanoparticles with HF solution which is more advanced and has better controllability. When evaluated as an anode material for lithium-ion batteries, the C–Si nanocomposites exhibit excellent reversibility and cycling performance. A high capacity of 700 mA h g−1 can be retained after 100 cycles at current densities of 250 mA g−1. The rate capability of the C–Si microfibers is also improved. The special structure is believed to offer better structural stability upon prolonged cycling and to improve the conductivity of the material. This simple strategy could also be applied to prepare other carbon coatings of hollow energy materials.

Despite the high theoretical capacity, pure Ge has various difficulties such as significant volume expansion and electron and Li+ transfer problems, when applied as anode materials in lithium ion battery (LIB), for which the solution would finally rely on rational design like advanced structures and available hybrid. Here in this work, we report a one-step synthesis of Ge nanowires-in-graphite tubes (GNIGTs) with the liquid Ge/C synergetic confined growth method. The structure exhibits impressing LIB behavior in terms of both cyclic stability and rate performance. We found the semiclosed graphite shell with thickness of ∼50 layers experience an interesting splitting process that was driven by electrolyte diffusion, which occurs before the Ge–Li alloying plateau begins. Two types of different splitting mechanism addressed as “inside-out”/zipper effect and “outside-in” dominate this process, which are resulted from the SEI layer growing longitudinally along the Ge–graphite interface and the lateral diffusion of Li+ across the shell, respectively. The former mechanism is the predominant way driving the initial shell to split, which behaves like a zipper with SEI layer as invisible puller. After repeated Li+ insertion/exaction, the GNIGTs configuration is finally reconstructed by forming Ge nanowires–thin graphite strip hybrid, both of which are in close contact, resulting in enormous enchantment to the electrons/Li+ transport. These features make the structures perform well as anode material in LIB. We believe both the progress in 1D assembly and the structure evolution of this Ge–C composite would contribute to the design of advanced LIB anode materials.Keywords: core−shell; Ge nanowires; graphite tubes; lithium ion battery; self-catalyzed growth;

We have synthesized the hybrid supercapacitor electrode of Co3O4 nanoparticles on vertically aligned graphene nanosheets (VAGNs) supported by carbon fabric. The VAGN served as an excellent backbone together with the carbon fabric, enhancing composites to a high specific capacitance of 3480 F/g, approaching the theoretical value (3560 F/g). A highly flexible all-solid-state symmetric supercapacitor device was fabricated by two pieces of our Co3O4/VAGN/carbon fabric hybrid electrode. The device is suitable for different bending angles and delivers a high capacitance (580 F/g), good cycling ability (86.2% capacitance retention after 20 000 cycles), high energy density (80 Wh/kg), and high power density (20 kW/kg at 27 Wh/kg). These excellent electrochemical performances, as a result of the particular structure of VAGN and the flexibility of the carbon fabric, suggest that these composites have an enormous potential in energy application.Keywords: all-solid-state supercapacitors; cobalt oxides; energy storage; graphene;

•We report on the first synthesis of 3D hierarchical AlV3O9 nanostructures.•The hierarchical nanostructures exhibit superior rate performance as lithium cathode materials.•The unique architectures and inclusion of Al3+ lead to the excellent Li-storage performances.Despite considered as promising lithium ion cathode materials, the practical applications of vanadium oxide and its derivatives still suffer from the poor kinetics linked to the low electronic conductivity and slow lithium ion diffusion upon cycling. Engineering three-dimensional (3D) architectures assembled from low-dimensional nanostructures has recently been of particular interests and proved an effective approach to enhance the electrochemical performances since the high surface area and intrinsic structural stability. Herein, we demonstrate the successful preparation of vanadium-based microspheres via a facile one-pot hydrothermal method. After the post-calcining in air, 3D hierarchical AlV3O9 nanostructures constructed from the assembly of ultrathin nanosheets were successfully obtained . When employed as lithium ion cathodes, the as-synthesized products exhibit outstanding reversible capacity (264 mA h g−1 retained after 100 cycles) and excellent rate performance (145 mA h g−1 at a high current density of 5 A g−1) for lithium storage. The superior electrochemical performances of the AlV3O9 microspheres can be ascribed to the unique 3D hierarchical morphologies with the ultrathin nanosheets building blocks.

Transition metal oxide hollow architectures are intensively explored for energy conversion and storage applications. Feasible strategies towards various hollow architectures, particularly those with non-spherical skeletons, are especially attractive. Quadrate Co3O4 nanoboxes are fabricated through controlled annealing of cobalt coordination polymer nano-solids with tunable dimensions. The cobalt coordination polymer in quadrate wires, cuboids, and cubes is synthesized by temperature and concentration dependent solvothermal method. Evolution of the nanoboxes involves Co3O4 shell formation and uniform depletion of the cobalt coordination polymer in the core. Benefitting from the well-defined hollow interior and nanosized crystals, the quadrate nanoboxes have large specific surface and abundant hierarchical pores. When evaluated as anode materials for lithium ion batteries, the boxes exhibited excellent electrochemical properties. Besides a superior storage capability of 1200 mA h g−1 at 0.2 A g−1, a remarkable retention of 625 mA h g−1 at a large rate of 10 A g−1 is also obtained.

Although widely used, the current Li-ion battery (LIB) technology still suffers from a lack of suitable electrodes with enhanced energy and power density, cycling stability, energy efficiency and cycling life. As an anode material for LIBs, metallic tin (Sn) has attracted tremendous interest, owing to its high theoretical capacity. Nevertheless, the practical implementation of metallic tin to LIBs is greatly hampered by the poor cyclability, because volume changes that occur during charging and discharging, result in both mechanical failure and loss of electrical contact at the electrode and the tin nanoparticle aggregates during the discharging process. Here, we report for the first time, a new strategy to grow self-assembled Sn@CNT on vertically aligned graphene (VAGN) by the microwave plasma irradiation reduction of SnO2 growth on VAGN and in situ encapsulating all the Sn nanoparticles in CNTs. The composite, as an anode material in lithium ion batteries, exhibits a high reversible capacity of 1026 mA h g−1 at 0.25 C (cycle lives of more than 280 times) and a capacity of 140 mA h g−1 is retained in a discharge time of 12 s, which represents the best performance values attained for a Sn anode to date. We expect the proposed route to be adopted by the rapidly growing energy storage research community.

ZnO has been regarded as a promising anode material for the next-generation lithium-ion battery. Unfortunately, the structure broken caused by the volume change of ZnO and the capacity degression due to the irreversible electrochemical reaction of ZnO still remain two major challenges. Here, we design a novel kind of in situ growth binder-free ZnO-based anodes via ZnO anchored on vertically aligned graphene. The composite anode retains physical integrity post cycling. Especially, the good conductivity of graphene and the ultrasmall size of ZnO particles help to produce a completely reversible electrochemical reaction of ZnO-based anode. The composite material exhibits a high capacity (810 mAh g–1), long cycle life, good cycle stability, and fast charge/discharge rate.Keywords: lithium-ion battery; reversion reaction; vertically aligned graphene; ZnO

Electrochemical pulverization, a commonly undesirable process for durable electrodes, is reinterpreted in popular yolk–shell nanostructures. In comparison with core–shell counterparts, the yolk–shell ones exhibit enhancing ion storage and rate capability for lithium ion battery anodes. The enhancement benefits from lowered activation barriers for lithiation and delithiation, improved surfaces and interfaces for ion availability contributed by endless pulverization of active materials. By controlled etching, stable cycling with significantly improved capacity (∼800 mAh g–1 at 0.1 A g–1, 600 mAh g–1 at 0.5 A g–1, and 490 mAh g–1 at 1 A g–1 vs 140 mAh g–1 at 0.1 A g–1) is achieved at various rates for Ni@Graphene yolk–shell structures. Meanwhile, large rate of 20 A g–1 with capacity of 145 mAh g–1 is retained. Given initial pulverization for the activation, the tailored electrodes could stably last for more than 1700 cycles with an impressive capacity of ca. 490 mAh g–1 at 5 A g–1. Insights into electrochemical processes by TEM and STEM reveal dispersive pulverized active nanocrystals and the intact protective graphene shells play the leading role.Keywords: core−shell; electrochemical pulverization; Lithium ion battery; Ni@Graphene; yolk−shell

Decreasing particle size has always been reported to be an efficient way to improve cyclability of Li-alloying based LIBs. However, nanoparticles (NPs) tend to agglomerate and evolve into lumps, which in turn limits the cycling performance. In this report, we prepared a unique nanostructure, graphene-coated Ge NPs are highly dispersed on vertically aligned graphene (Ge@graphene/VAGN), to avoid particle agglomeration and pulverization. Remarkable structure stability of the sample leads to excellent cycling stability. Upon cycling, the anode exhibits a high capacity of 1014 mAh g–1, with nearly no capacity loss in 90 cycles. Rate performance shows that even at the high current density of 13 A g–1, the anode could still deliver a higher capacity than that of graphite.Keywords: binder free; cyclability; Ge NPs; graphene coating; lithium-ion batteries; vertically aligned graphene

Novel carbon nanostructures, e.g., carbon nanotubes (CNTs), graphene, hierarchical porous graphitic carbon (HPGC), and ordered mesoporous carbon (CMK-3), have been significantly forwarding the progress of energy storage and conversion. Advanced electrodes or hybrid electrodes based on them are springing up one after another. To step further, a generic synthetic approach to large scale hierarchical porous graphitic carbon microbubbles (HPGCMBs) is developed by zinc powder templated organic precursor impregnation method. The facile technique features scalable (yield: once more than 200 mg), in situ heteroatom’s doping (doping ratio: more than 26%) and hierarchical-pore-creating traits (pore volume: 1.01 cm3 g–1). Adjustable graphitic content, doping species and amount are readily realized through varying the organic precursors. Rationally, good conductivity, fast kinetics, and abundant ion reservoirs are entirely achieved. To be applied in practice, state-of-the-art anodes for lithium-ion batteries are fabricated. Benefiting from the large specific surface area, rich heteroatoms, and hierarchical pores, the HPGCMBs electrodes exhibit excellent electrochemical properties. Besides superior storage capability of more than 1000 mAh g–1 at 100 mA g–1, stable cycling and excellent retention of 370 mAh g–1 at large rate of 10 A g–1 are achieved in the meantime.Keywords: graphitic carbon microbubbles; heteroatom-doped; hierarchical pores; Lithium ion battery; scalable strategy

In this work, an effective approach to engineer Si and crystal SiO2 nanoparticles with carbon for high performance electrochemical energy storage was presented. We designed an intercalated carbon mixed SiO2&Si nanoparticles/carbon multilayer structure on the Cu current collector for an electrochemically stable and high energy density Si based electrode and carried out by alternately depositing C and SiO2&Si by plasma decomposition of CH4 and SiH4. This design allows for increasing mass loading per geometric area and improving the energy density. The structure and chemical composition of the composites were characterized by SEM, TEM, XRD, XPS, etc. The electrode with 12 layers exhibited an excellent cycling retention and a reversible areal capacity of ∼ 0.46 mAh/cm2 at a current rate of 52 μA/cm2, which is much higher than most of previously reported values of various other materials. The versatile approach for fabricate the intercalated SiO2&Si/carbon films electrodes presented in this work can be extended to a variety of energy conversion and storage applications.

Various shapes of Cu@SiO2 nanowires were fabricated on a Cu substrate via simple thermal evaporation of SiO within a high-frequency induction furnace. The morphology and structure of the Cu@SiO2 nanowires were characterized by using SEM, TEM, EDS and EDX elemental mapping. The morphology and density of the nanowires are controllable by adjusting the substrate temperature. The Cu cores are chemically stable due to the protection of the SiO2 shell. The surface-enhanced Raman scattering (SERS) experiment on the shell-isolated nanowires showed excellent detecting performance compared with the bare Cu substrate. The cathodoluminescence (CL) investigation reveals that red, green and blue light emission was observed in the Silica sheath simultaneously. The as-synthesized samples have potential application in long acting and ultrasensitive SERS substrates and white light sources.

•A vertically aligned Sn@Graphene composite structure was fabricated.•The uniquely structure could provide large efficient areas, good conductivity, short transportation lengths for both Li ions and electrons.•The anode exhibits a high capacity, long cycle life, excellent cycle stability, and fast charge/discharge rate.It is well known that all high-capacity Li-alloy anodes for use in Li-ion battery (LIB) applications suffer from significant specific volume changes during Li-ion insertion/extraction. If the microstructure of the electrode materials can be designed properly, the volume change problems encountered during discharge (lithiation) and charge (delithiation) could be alleviated to some extent. We report on a novel route for the encapsulation of Sn nanoparticles (Sn-NPs) within graphene nanostructures via the microwave plasma irradiation of SnO2 for the fabrication of LIB anode materials. Here, the Sn@graphene nanostructure is synthesized in situ into a vertically aligned graphene host that sandwiches the nanostructures between rapid ion and electron transport pathways and demonstrates a structure that is highly suitable for solving the critical volume change problem. Binding of the Sn@graphene on the vertically aligned graphene product exhibits larger-than-theoretical reversible capacities of 1037 mA h g−1 even after prolonged cycling, in addition to a Coulombic efficiency in excess of 97%, which reflects the ability of the Sn@graphene nanostructure to prevent the volume change and agglomeration of the Sn-NPs. The cycling ability exceeds 5000 times in half-cells at a 6C rate while retaining 400 mA h g−1 reversible capacities (where a 1C rate represents complete charge or discharge after 1 h). We successfully increased the charging and discharging rates by nearly 30-fold over the highest rate reported to date while attaining high power and energy densities, which represent the best performance values attained for a long-cycle Sn anode to date. The excellent electrochemical performance observed is mainly attributed to the confined volume change of the Sn within the graphene, ensuring the permanent electrical connectivity of the immobilized Sn@graphene anodes.

•Fe2GeO4 nanoparticles are first applied in lithium-ion battery.•Fe2GeO4 NPs/RGO exhibits a reversible capacity of 980 mAh/g for 175 cycles.•The high cyclability should be ascribed to the in situ formed Fe/Li2O matrix.Recently, ternary oxides have emerged as a new class of anode materials for lithium-ion battery due to their intrinsic advantages in accommodating volume expansion as well as improving the electrical conduction. This offers a new way to improve the cyclability of Ge-based anode which has been long plagued by capacity fading. Up to now, the studies on Ge-based ternary oxides anode are still scarce. Herein, we produced a novel Fe2GeO4 nanoparticles(NPs)/reduced graphene oxide (RGO) hybrid nanostructure and investigated its electrochemical performance in LIBs. During the cycling, a mixture in which Ge nanoparticles uniformly distributed in the matrix of Fe/Li2O formed. The Fe/Li2O matrix as well as the graphene can not only offer an elastic buffer but also provide a conductive medium for the whole anode. With the alleviated mechanical stress and the enhanced charge carrier transport, the hybrid anode exhibited a high reversible capacity of 980 mAh/g for 175 cycles. Remarkable rate performance was also recorded. Our study shows that Fe2GeO4 NPs/RGO nanostructure could be a suitable candidate for high capacity lithium-ion battery.

•A general strategy for nanomaterials/bubble hybrid electrode is developed.•High power, ultralong lifespan and excellent cycling stability are achieved in the hybrid electrodes.•Both anodes and cathodes of the bubble hybrid electrodes exhibit superior cyclability.Although widely used, the current Li-ion battery technology still suffers from a lack of suitable electrodes with enhanced energy and power density, cycling stability, energy efficiency and cycling life. So far no reliable methods can satisfy all these requirements. There is therefore a need to seek novel electrodes that would combine all the advanced performances and satisfy the increasing demands for energy storage worldwide. Herein, we demonstrate a large-scale bottom-up assembly route for porous bubble hybrid electrodes with excellent electrochemical properties by creating composites based on nanomaterials uniformly dispersed on the outer and inner surfaces of a porous creased carbon bubble host, which serves to hold them tightly by the pores and creases during battery operation and sandwiches them between rapid ion and electron transport pathways. Such integrated electrodes exhibit ultrahigh specific capacity and excellent cycling stability at various rates. Long lifespan of 1000 cycles in half cells retaining more than 90% of their reversible capacity and large rates up to 327C for ensample electrodes are achieved with batteries' high energy density and supercapacitors' impressive power density (where 1C rate represents a 1-h complete charge or discharge).

Developing electrode materials with both high energy and power densities holds the key for satisfying the urgent demand of energy storage worldwide. Herein, we demonstrate the successful preparation of Co3V2O8 nanostructures that are constructed from self-assembly of ultrathin nanosheets via a simple hydrothermal method followed by annealing in air at 350 °C for 2 h. A “slipping–exfoliating–self reassembly” model based on the time-dependent experiments was proposed to elucidate the formation of the hierarchical nanosheets. When tested as lithium ion anodes, the as-synthesized multilayered nanoarchitectures exhibit outstanding reversible capacity (1114 mA h g–1 retained after 100 cycles) and excellent rate performance (361 mA h g–1 at a high current density of 10 A g–1) for lithium storage. Detailed investigations of the morphological and structural changes of Co3V2O8 upon cycling reveal an interesting kinetics toward lithium ion intercalations, where reversible conversion reactions between Co and CoO are found proceeding on the amorphous lithiated vanadium oxides matrixes. We believe that this observation is a valuable discovery for metal vandates-based lithium ion anodes. The superior electrochemical performances of the multilayered Co3V2O8 nanosheets can be attributed to the unique morphologies and particularly the surface-to-surface constructions that are generated during the lithium ion insertion processes.Keywords: Co3V2O8; electrochemical mechanism; excellent Li-storage property; lithium ion battery anodes; nanosheets; self-assembly

•We report on the first synthesis of novel ultrathin (α-Fe2O3)1−x(V2O5)x solid-solution nanoplates via a facile one-pot hydrothermal method.•The solid-solution nanoplates demonstrate more uniform morphologies, specific exposed crystalline plane, much larger surface areas.•This new solid solution materials exhibit superior capacity and high-rate performance compared with the irregular α-Fe2O3 nanoparticles.•The unique nanostructures lead to superior capacity and excellent cycle stability.In this work, we report on the first synthesis of novel ultrathin (α-Fe2O3)1−x(V2O5)x solid-solution nanoplates via a facile one-pot hydrothermal method. Shape selection and crystallographic orientation show closely interrelated with the V2O5-modification. Irregular α-Fe2O3 particles with random exposed facets were obtained in the absence of vanadium sources. When tested as anode materials for lithium batteries, the ultrathin (α-Fe2O3)1−x(V2O5)x nanoplates show greatly enhanced performance of Li storage. Under the condition of high current density of 1 C, the ultrathin (α-Fe2O3)1−x(V2O5)x nanoplates were capable of retaining a specific capacity of 771 mA h g−1 over 100 cycles. Even when cycled at 5 C and 10 C, comparable capacities of 482 and 365 mA h g−1 could be achieved, indicating an excellent rate capability.

•Adaptable silicon nanoparticles encapsulated in graphene nanosheets anchored on vertically aligned graphene trees with loose intersecting leaves (GrTr) was fabricated.•The uniquely structure could provide large efficient areas, good conductivity, short transportation lengths for both Li ions and electrons.•The anode exhibits a high capacity, long cycle life, excellent cycle stability, and fast charge/discharge rate.Silicon has been regarded as one of the most promising anode material for the next generation lithium ion battery. Unfortunately, the structure damage caused by the volume change of silicon and the continual interfacial reaction due to the electrolyte remain two major challenges. Here, we design a novel kind of in-situ growth binder-free silicon-based anodes. The adaptable silicon nanoparticles were encapsulated in graphene nanosheets (SiNPs@GNS). Simultaneously, the SiNPs@GNS composites anchored on vertically aligned graphene trees with loose intersecting leaves (GrTr). In the resulting samples, the GNS shells, as adaptable sealed wraps, could synergistically accommodate the volume change of the wrapped SiNPs, thus effectively avoiding the direct contact between encapsulated silicon and the electrolyte and enabling the interfacial and structural stabilization of encapsulated SiNPs during cycling. The GrTrs directly grown on current collector act as supporters of SiNPs, which ensure their dispersion uniformity and supply three dimensional short transportation paths for both Li ions and electrons. The in-situ growth of SiNPs@GNS–GrTr composites were proximately used as anodes in LIBs without adhesives and other complex brushing processes of the active material. The composite material exhibits a high capacity (1528 mAh g−1 at 150 mA/g), relatively good cycle stability (88.6% after 50 cycles), and fast charge/discharge rate (412 mAh g−1 at 8 A/g). The uniquely designed structure of the composites, which provide an ultra-thin, flexible GNS shell to accommodate the changes in volume, introduces large efficient areas, good conductivity, three dimensional transportation paths for both Li ions and electrons, and contributes to its excellent performance.

•Electrodes with nitrogen and oxygen co-doped carbon nanobubbles are fabricated.•Impressive storage capability and fast kinetic processes are realized in the electrodes.•The electrodes for both lithium ion battery and sodium ion battery exhibit superior cyclibility.Efficient electrodes with impressive storage capability and fast kinetic processes are urgently needed in meeting the demand for high energy and large rate powering devices. Through a simple silica templated ionic liquids (ILs) impregnating method and an annealing process, nitrogen and oxygen co-doped carbon nanobubbles are synthesized. The fabricated carbon nanobubbles feature multiscale nanopores and abundant few-layer graphitic zones in the thin shells of several nanometers. When used as anodes for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs), the nanobubbles not only exhibit excellent storage capability and rate performance, but also achieve enhancing cyclibility in the long-term cycles. Further analysis on the charging curves and the electrochemical impedance spectroscopy (EIS) reveal the enhancing cyclibility and storage capability might depend on the interfacial capacitance derived from quasi-connection between Li+ or Na+ and the hetero-atom evolving dissociative groups, while the superior rate performance might be attributed to the low interfacial charge-transfer resistance in the carbon nanobubbles electrode.

If the flexible transparent and free-standing paper-like materials that would be expected to meet emerging technological demands, such as components of transparent electrical batteries, flexible solar cells, bendable electronics, paper displays, wearable computers, and so on, could be achieved in silicon, it is no doubt that the traditional semiconductor materials would be rejuvenated. Bulk silicon cannot provide a solution because it usually exhibits brittleness at below their melting point temperature due to high Peierls stress. Fortunately, when the silicon’s size goes down to nanoscale, it possesses the ultralarge straining ability, which results in the possibility to design flexible transparent and self-standing silicon nanowires paper (FTS-SiNWsP). However, realization of the FTS-SiNWsP is still a challenging task due largely to the subtlety in the preparation of a unique interlocking alignment with free-catalyst controllable growth. Herein, we present a simple synthetic strategy by gas flow directed assembly of a unique interlocking alignment of the Si nanowires (SiNWs) to produce, for the first time, the FTS-SiNWsP, which consisted of interconnected SiNWs with the diameter of ∼10 nm via simply free-catalyst thermal evaporation in a vertical high-frequency induction furnace. This approach opens up the possibility for creating various flexible transparent functional devices based on the FTS-SiNWsP.

Highly efficient energy storage systems are in great demand for power source applications ranging from wearable electronics to hybrid electric vehicles. Graphene-based hybrid structure capacitors are ideal candidates for manufacturing these systems. Herein, we present the design and fabrication of heterostructured composites made of vertically aligned graphene nanosheets (VAGN) and MnO nanoparticles. Electrodes with various MnO mass contents were obtained by depositing nanosized MnO particles onto VAGN under different hydrothermal conditions. The VAGN served as an excellent backbone and electron collector, enhancing the specific capacitance of the VAGN/MnO electrode (37 wt% MnO) to 790 F g−1 at a scan rate of 2 mV s−1. The electrodes also showed high specific capacitance (381 F g−1) with high active material loading content (80 wt% MnO), and outstanding cycling stability (80% retention after 4000 cycles at 10 A g−1). These excellent electrochemical performances result from the particular three-dimensional structure of VAGN, which offers convenient access for electrolyte cations participating in the redox reaction of MnO. These composites show enormous potential for use in energy management applications.

A SnO2–graphene oxide (GO) hybrid composite was prepared by binding SnO2 nanocrystals smaller than 5 nm in GO using a facile hydrothermal method. Aided by hydrophilic radicals, such as hydroxyl and carboxyl, in in situ forming SnO2 quantum dots, the active material and the flexible support are highly coupled. When used as an anode material for lithium ion batteries (LIBs), the hybrid composite electrode delivers a high reversible capacity of nearly 800 mA h g−1 (based on the total weight of the composite, discharging at 100 mA g−1) with more than 90% retention for 200 cycles. Besides the excellent cycling performance at various rates, the composite also exhibits a superior rate performance at 10 A g−1 with recoverable initial reversible capacity and a long lifespan of 1000 cycles with 80% capacity retention, outperforming most previous SnO2–graphene hybrid electrodes.

2H-SiC–α-Al2O3 epitaxial heterostructures in a 1-D nanosystem were achieved via a simple CVD (chemical vapor deposition) process. Detailed structural characterizations and elemental analyses were carried out using methods such as elemental mapping, EELS (electron energy loss spectroscopy), XPS (X-ray photoelectron spectroscopy) and Raman spectroscopy, which identified the amounts of Al atoms that occupied the Si sites in the SiC lattice and that a small quantity of oxygen atoms were found on the SiC side. The carbon atoms dissolve in the Al2O3 crystal, substituting the oxygen elements, and there is only a small amount of Si in the Al2O3 part. These results supply a comprehensive understanding about the interface and information about the atoms that diffuse between 2H-SiC and α-Al2O3. We hope that this work contributes to the design of SiC–Al2O3 based epitaxial heterostructures.

Nowadays, the development of nano-synthesis has turned to controllable design for specific demands in micro-nano device application, to be integrated into functional units more conveniently with low-cost and efficiency principles. In this case, an appropriate approach for directly obtaining horizontally aligned nanowires in a large scale would be of great significance in future micro-nano device integration. Here, on the HOPG surface, we managed to achieve this. The approach is versatile to various kinds of materials. Horizontally aligned nanowires of Al–C based materials, such as Al4C3 and Al4O4C, were achieved. All of the nanowires exhibit a high degree ordered alignments and possess super aspect ratios with uniform widths of about 100 nm and lengths on the millimeter level. We believe the assembly mechanism lies in a step-edge induced ordered growth process, through which quaternary Al–Si–O–C nanoball alignment could also be obtained. It is expected that this method could be beneficial to adjust many useful materials for micro device integration in the future.

Metal W is employed as an efficient catalyst to grow AlN nanowires. High-density nanowires have been synthesized with a W catalyst cap at the tip. Transmission electron microscopy further reveals that the W-catalyzed AlN nanowires have an unusual [1 0 1] growth direction. The growth process of the nanowires has been studied by adjusting the experimental conditions and a growth kinetics model is proposed to describe the growth process of the W-catalyzed AlN nanowires. In addition, the surface wettability of a nanowire film is also observed and the sample shows smart wetting behavior. First, the as-grown sample exhibits a self-dewetting property with a water CA (contact angle) spontaneous transition from initial superhydrophilicity to final superhydrophobicity in the air. Then, the superhydrophilic surface can be recovered by illumination with UV light. The surface oxidation state of the catalyst may be responsible for the transition of the wettability.

•Vertically aligned graphene@ amorphous GeOx sandwich nanoflakes integrated electrodes exhibit ultrahigh specific capacity and excellent cycling stability at various rates.•Long lifespan of 100 cycles in half cells retaining more than 96% of their reversible capacity.•Large rates up to 15C for ensample electrodes are achieved with high energy density.•The electrode compatible with traditional coating electrodes easily scaled in commercial application.Germanium oxide is a promising anode material for lithium ion batteries due to its theoretical capacity (1100 mAh/g) is 3 times higher than the commercial graphite anode (only 372 mAh/g). However, so far only a few studies have reported the application of germanium oxide in LIBs and the cycling performance is unsatisfactory. In this report, we have prepared a unique VAG@ amorphous GeOx sandwich nanostructure by a non-toxic, low temperature CVD method with vertically aligned graphene(VAG) as templates. The graphene sheets form a fast electron transport channel duo to its superior electron conductivity and the vertically aligned sandwich nanoflakes can offer a short pathway for lithium ion thanks to the unified orientation. Additionally, the GeOx sediments that evenly distribute on the surface of graphene flakes have an amorphous structure and their thickness is less than 10 nm, which can mitigate the mechanical stress generating in the lithiation/delithiation process. Owing to these advantages, the as-prepared anode shows a stable capacity of 1008 mAh/g for 100 cycles (with capacity retention of 96%). Rate performance reveals the anode can maintain a capacity of 545 mAh/g even at the rate of 15C. Our results are demonstrated to be so far the most stable performance for germanium oxide anodes.

•We fabricated novel ZnO/C nanospheresvia a hierarchical bottom-up assembly route.•ZnO nanograins were tightly sandwiched in the conductive nanocarbon skeleton.•Final products can be controlled by simply adjusting the reaction temperatures.•The unique nanostructures lead to superior capacity and excellent cycle stability.Ultrafast rechargeable lithium-ion batteries made from low-cost and abundant electrode materials would satisfy the increasing demands for energy storage worldwide. Herein, we demonstrate a large-scale hierarchical bottom-up assembly route for the formation of lithium-ion battery anode with excellent electrochemical properties by creating composites based on embedding ZnO nanoparticles into nanocarbon matrix which uniformly dispersed on the outer and inner surfaces of a porous creased carbon bubble host, which serves to hold them tightly by the pores and creases during battery operation and sandwich them between rapid ion and electron transport pathways. We successfully increase the charging and discharging rates by nearly 300-fold over the highest rate yet reported while attaining high power density and energy density which represents the best performance for long-cycle ZnO anode so far.

Si nanowires have received continued increased attention because they keep the promise of monolithic integration of high-performance semiconductors with new functionality into existing silicon technology. Most Si nanowires are grown by vapor–liquid–solid mechanism, and despite many years of study, this growth mechanism remains under lively debate. For instance, contradictory results have been reported on the effect of diameter size on nanowire growth rate. Here, we developed a universal kinetic model of Si nanowire growth based on surface diffusion which takes into account adatom diffusion from the sidewall and substrate surface into the liquid droplet as well as the Gibbs–Thomson effect. Our analysis shows that the diameter independence for Si nanowires is affected by the interplay between the Gibbs–Thomson effect and the surface diffusion, whereas the diameter dependence is mainly influenced by the Gibbs–Thomson effect. The results based on the proposed model are in good agreement with experimental data.

Close-packing WC as a kind of metallic carbide, possessing good conductivity, high melting point and superior hardness, has numerous intrinsic properties that deserve to be investigated and then explored for use in micro or nano devices in the photoelectronics field. One of the main reasons why WC has not been considered much is that low-dimensional structures such as nanowires and nanowalls are hard to prepare. Here, we developed a novel method to overcome a series of difficulties in the growth of low-dimensional WC nanostructures and managed to apply eutectic solidification in W–Al–C solution to synthesize a high-quality WC nanowall forest and nanowires on a large scale. The experiment was carried out in a high-vacuum (∼10−4 Pa) chemical vapor deposition system pumped by a turbo molecular pump. We expect that it can be applied as a universal route to prepare low-dimensional nanostructures for refractory metals compound.

The Al–O–C–N system is known as a kind of Al2O3-based ceramic material with various different chemical compositions and structures. Considering its superior physical and mechanical properties, the corresponding one-dimensional Al–O–C–N system may have huge potential applications in future nanodevices. Herein, for the first time, two types of ultralong one-dimensional Al3CON nanostructures, nanowires and bicrystalline nanobelts, were simultaneously synthesized by asimple CVD process. The products were characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy as well as energy dispersive X-ray spectrometry. Corresponding property studies were carried out to explore the potential applications of the products. The force measurement based on a single nanostructure was performed by using an atomic force microscope (AFM) and the nanostructure showed high strength with a Young's modulus of 251 GPa. Semiconductor characteristics were also observed by electrical measurement at room temperature, which may be attributed to the doping and/or native defects. In addition, the Al3CON nanostructures showed deep-ultraviolet photoconductivity, in which the conductance increases only when illuminated with 254 nm light rather than 365 nm light.

Ceramic Al4C3 nanowalls were fabricated through a VS mechanism via a chemical vapor deposition (CVD) method. XRD (X-ray diffraction), Raman spectra, SEM (scanning electron micrograph) and TEM (transmission electron micrograph) methods were employed to characterize the product. The synthesized 2-D nanostructures are confirmed to be polycrystalline R-Al4C3 with a Al2O3 sheath outside the nanosheet. Field emission (FE) measurements show that the turn-on field (where the emission current reaches 10 μA cm−2) of the as-prepared sample is 6.0–7.0 V μm−1. According to several comparative experiments, we propose an atmosphere-controlled nanowall growth mechanism from self-assembling templates under a low-pressure environment to explain the growth process.

New layered SnS2 nanosheet arrays consisting of 1–5 atomic layers were synthesized directly on Sn foil as both the tin source and the metal current collector substrates by a simple biomolecule-assisted method. It is found that SnS2 nanosheets synthesized have excellent photoelectric applications, such as on lithium ion batteries, and photocatalytic, field emission, and photoconductive properties. Cyclic voltammetry and discharge and charge behaviors of the atomic SnS2 nanosheets were examined, and it shows that the average discharge capacity in 1050 mAh/g is much larger than the theoretical capacity at the 1C rate. The photocatalytic action driven by solar light is quite quick, and the degradation rate of RhB is 90%, only irradiated for 20 min when the content of SnS2 nanosheets is 0.4 g/L. The response of the SnS2 device to the incidence UV light is very fast and shows excellent photosensitivity and stability. In addition, field emission properties of SnS2 nanosheets were also researched, and we found that the turn-on field for SnS2 is 6.9 V/μm, which lowered ever reported values. The enhanced photoelectric properties are likely to originate in a graphene-like structure. Thus, graphene-like SnS2 materials are promising candidates in the photoelectric field.

As a kind of ionic (or salt-like) carbide, Al4C3 hardly any active functions have been found except for structure material purposes. However, considering the unique characteristic features of its crystal structure, we think Al4C3 in fact might have huge potential for exhibiting active functionality on field-emission application. Herein, we report for the first time the catalyst-free synthesis and excellent field emission properties of Al4C3 one-dimension (1-D) nanostructures. The 1-D nanostructures acting as cold electron emitters display excellent field emission performance with the turn-on field as low as 1.4–2.0 V μm−1 and the threshold field down to 4.2–4.4 V μm−1. Such emitters are technologically useful, because they can be easily fabricated on large substrates, and the synthesis process is simple and broadly applicable. The findings conceptually provide new opportunities for the application of Al4C3 ceramic material in vacuum microelectronic devices.

We have developed a general ion-exchange method of preparing a composite of low nanometre size carbide particles with controllable size less than 10 nm on carbon foams. The nanoarchitectures of the carbide nanoparticles on carbon foam are used to load Pt nanoparticles as electrocatalysts which show enhanced activity for the oxygen reduction reaction.

We report a novel Al2O3 nanoparticle-decorated tubular SiC nanostructure, which shows a remarkable enhanced field emission property with low turn-on and threshold field. The formation of Al2O3 nanoparticle-decorated tubular SiC on Si substrates is achieved in one-step via simple heating evaporation process for the first time. The nanostructure consists of tubular SiC and the Al2O3 nanoparticles, which homogeneously decorate on the surface of the tubular SiC with an average diameter of 7.8 nm and narrow diameter distribution. Moreover, compared with the same density and sized bare tubular SiC, the Al2O3 nanoparticle-decorated tubular SiC nanostructure has an obvious reduction in turn-on (from 8.8 to 2.4 V μm−1) and threshold field (from 23.5 to 5.37 V μm−1). The very low turn-on and threshold field is also comparable to that of carbon nanotubes, which indicates the Al2O3 nanoparticle-decorated tubular SiC is of huge potential application in future field emission display devices.

SiC@Al2O3 core-shell epitaxial nanowires have been synthesized via one-step process by simply heating evaporating Al source and C source on silicon substrate. Energy dispersive X-ray spectroscopy and transmission electron microscopy analysis of as-fabricated samples indicate that the core-shell nanowires consist of single-crystalline β-SiC core and thin cubic γ-Al2O3 shell. Epitaxial relationship is also observed between SiC core and Al2O3 shell. The corresponding growth model is proposed to describe the growth process of the core-shell epitaxial nanowires. Moreover, field emission measurement reveals the core-shell epitaxial nanowires have the excellent field emission property with low threshold electric field of 13.8 V μm−1.

Large scale and uniform SiO2 nanowires have been successfully fabricated in a high-frequency induction furnace via a Ge-catalyzed vapor liquid solid (VLS) mechanism. The nanowires were characterized by scanning electron microscopy, transmission electron microscopy, XRD and Raman spectroscopy. The results show that the as-synthesized SiO2 nanowires have an amorphous structure with diameters of 20–50 nm, and lengths up to tens of micrometres. The room-temperature photoluminescence measurement of the products show that they have a blue emission band at 420 nm, reveal that the high yield, and ultralong SiO2 nanowires might have potential applications in the future optoelectronic devices. Furthermore, the growth mechanism of the SiO2 nanowires is discussed.

The controllable synthesis and growth kinetics of new nanostructures has an enormous impact on the fabrication and application of nanomaterials, and continues to be a central challenge in nanoscience and nanotechnology. On the other hand, sophisticated helical structures have been an attractive subject due to its significance in understanding biological self-assembly and appealing application in nanoscience. Here, we report the synthesis of novel dual-chirality hetero nanoscrews with controllable backbones and circles of SiO2 spiral threads by a single-step method and reveal experimentally its growth kinetics imaging for the first time. The nanoscrews are composed of amorphous SiO2 winds around cone-shaped single crystal β-SiC backbone via linear-to-rotary growth process. Our finding might open a new door to understand the growth process of sophisticated helical nanostructures.

We report a simple, efficient method to in situ grow the Al2O3 coating on the surface of single-crystalline tubular SiC nanostructures with controllable morphology, size and population density. The nanostructures are fabricated by heating evaporation Al powders and C60 on the Si substrates. By varying the reaction temperature, we can conveniently control the size and density of Al2O3 nanoparticles coating. Moreover, the ultrathin Al2O3 coating is also achieved by decreasing the quantity of Al source. The electrical transport measurement from single nanostructure is carried out to further confirm the excellent electrical insulation of ultrathin Al2O3 coating. This result contributes to the development of SiC based-nanodevices, as well as nanocomposites.

As a kind of ionic (or salt-like) carbide, for Al4C3, hardly any active functions have been found except for structure material purposes. However, considering the unique characteristic features of its crystal structure, we think Al4C3 in fact might have huge potential for exhibiting active functionality on field-emission applications. Herein, we report the feasibility to approach such emitters by creating Al4C3-based nanowire superstructures. The conductive amorphous carbon (a-C) nanolayers are embedded quasi-periodically in Al4C3 nanowire and generate essential electrical contact to the insulating Al4C3. The superstructures acting as cold electron emitters display excellent field emission performance with the turn-on field as low as 0.65−1.3 V/μm and the threshold field down to 2.1−2.6 V/μm. We speculate that the emission characteristics, which are ever better than carbon nanotubes, are attributed to the unique crystal structure of Al4C3 and the enhanced electrons transport in the nanowires due to the existence of a-C nanolayers. Such emitters are technologically useful, because they can be easily fabricated on large substrates, and the synthesis process is simple and broadly applicable. The findings conceptually provide new opportunities for the application of Al4C3 ceramic material in vacuum microelectronic devices.Keywords (keywords): carbon-in-Al4C3; ceramic material; emitters; nanowire superstructures; vacuum microelectronic devices

Single crystalline one-dimensional (1-D) β-SiC nanostructures were synthesized by the CVD (chemical vapor deposition) method using single crystal silicon wafers and detonation soot as the raw materials. The phase, morphology, crystal structure, and defects of the products were characterized by X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. Within a 2 h reaction time, the morphology of the SiC nanostructures can be tuned to nanowires, hexagonal columns and nanopyramids by simply altering the reaction temperature from 1250 °C, 1300 °C to 1350 °C, respectively. Based on the VLS mechanism, we propose a model to explain the novel behavior of the temperature-dependent morphology considering the relationships between catalytic droplets and nucleation.

Large scale single-crystalline tubular β-SiC was prepared via a simple thermal evaporation method without any template and catalyst, and the nanostructure showed excellent field emission properties.

SiC nanowires have been fabricated by a simple catalyst-free method using detonation soot powders and silicon wafers. We characterize their microstructures by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. The results show that the nanowires consist of single-crystalline β phase SiC cores with diameters of 30−100 nm and lengths of 0.5−1.5 μm wrapped with a very thin amorphous oxide layer. The axial growth direction of each nanowire is preferentially along the κ direction, while the low density of planar defects are detected. Unique optical properties are found in the Raman spectroscopy that has a blue shift of about 8 cm−1 compared to the bulk β-SiC crystal. Furthermore, field-emission measurements show a relativly low threshold field of 6.2 Vμm−1, suggesting that it is a promising material for applications in flat panel display. Finally, a possible growth model based on a VS mechanism was proposed to explain the growth of the SiC nanowires.

A new kinetic model is suggested to describe the self-limiting oxidation of Si nanowires by only considering the diffusion step with the influence of stress due to the two-dimension nonuniform deformation of the oxide but not including any rate-limiting step for interfacial reaction. It is assumed the stress results in the change of distribution of diffusion activation energy in the high density region which rises monotonically along with the oxidation, and may be the main physical origin of the self-limiting oxidation behavior of SiNWs. Moreover, the present kinetic model can excellently describe the experimental results for the wide initial diameter over the range of self-limiting oxidation temperature.

To meet the power demands of various electronic devices, high-performance electrodes have been designed for use with multiple energy storage devices, from lithium batteries to supercapacitors. Graphene has many unique morphological and structural features and is important for developing highly effective devices because of its use for electrode fabrication and as a backbone for hosting other electroactive materials. Therefore, we constructed two types of novel graphene electrodes with different structures that both can be used to make binder-free electrodes: vertically aligned graphene nanosheets and freestanding, flexible, transparent graphene paper. The focus of this review is on the synthesis and properties of these graphenes and the application of related hybrid structure electrodes by our research group. The performances of these electrodes indicate that they have unlimited potential for application in the next generation of electrochemical storage devices.We review the synthesis and properties of the vertically aligned graphene nanosheet and freestanding, flexible and transparent graphene paper, highlight their applications in Li-ion batteries, electrochemical double layer capacitors and pseudocapacitors.Figure optionsDownload full-size imageDownload as PowerPoint slide

•Inorganic nano-domains were introduced into MOF bulks for LIBs anodes.•Inorganic-organic hybrids exhibited tripled Li-ion storage capability than MOF bulks.•Phase segregation and nano-crystallization are the main factors.•Exemplified full cells exhibited excellent energy/power performance.Recently, metal organic framework (MOF) materials in nano-scale have gained enormous interest in Li-ion batteries (LIBs), while those in bulks usually exhibit poor Li-ion storage performance. Herein, we report how to obtain impressive Li-ion storage performance by using MOF bulks firstly. Through suitable design, incorporating small inorganic nano-domains with various dimensions into the MOF bulks, the forming metal inorganic-organic hybrid composites (M-IOHCs) could store Li-ions twice more than that of the metal based MOF (M-MOF) bulks. Except for the good Li-ion storage performance, exemplified M-IOHCs also exhibit enhancing cyclibility of more than 400 cycles with tripled capacity and 100% capacity retention. The enhanced Li-ion storage capability and cyclibility is attributed not only to local phase segregation in MOF bulks induced by ultra small inorganic nano-domains and the self-nano-crystallization of MOF bulks and the later forming inorganic nanocrystals themselves, but also to the stabilized frameworks comprised of metal oxide inorganic nanocrystals and enwrapped C-N organic species which brought up no aggregation or grow-up of the inorganic active materials common in new generation electrode materials. Application of the M-IOHCs in full cells was exemplified by Ni-IOHCs anode and commercial LiFePO4 cathode, which delivers excellent energy and power performance.

Individual graphene ribbons, which fully exploit the large surface area of graphene sheets, have been fabricated. Constructing these unique structures into efficient macroscopic functional architectures is an important and challenging step towards practical applications. Here, we produce micro-structured interconnected ribbon-like graphene sheets (MRGs), which were induced by the multistage-recrystallization of NaCl templates in a microwave plasma chemical vapor deposition (MPECVD) system. The MRGs along different directions hang in polygonal graphene walls, which connect with each other forming a three dimensional (3D) transparent and self-supporting graphene film (MRG-GF). The MRG-GF with a large surface area, enhanced flexibility and fast ion/electron transport pathways exhibits improved capacitance (4.88 mF cm−2) and super-long cycle life with good cycling stability (capacitance retention was ∼95.5% after 20000 cycles). Herein, we provide a novel approach for controlled synthesis of graphene ribbons, and graphene ribbon-based functional structures and composites.

Iron phosphide (FeP), as a low-cost and earth-abundant electrocatalyst, has received increasing attention in recent years. However, its hydrogen evolution reaction (HER) performance is still far from satisfactory in terms of both activity and stability. In this study, by employing vertically aligned graphene nanosheets (VAGNs) as the backbone, we synthesized a novel three dimensional (3D) FeP/VAGN hybrid nanostructure on carbon cloth (FePNRs/VAGNs/CC) as a binder-free efficient electrocatalyst for the HER. The villiform FeP nanorods with diameters of ∼50 nm and lengths of 100–300 nm were successfully grown on the surface of VAGNs by an electrodeposition process followed by a phosphidation treatment. The separate VAGNs not only provide a 3D architecture for FeP growth, but also facilitate charge transfer. As expected, this 3D hybrid electrocatalyst exhibits an enhanced HER activity with an onset potential of 19 mV, an overpotential of 53 mV at 10 mA cm−2, a Tafel slope of 42 mV dec−1, and a remarkable stability and durability in an acid solution. The superior hybrid FeP electrode might pave an efficient way for the practical application toward hydrogen generation.

We report a novel Al2O3 nanoparticle-decorated tubular SiC nanostructure, which shows a remarkable enhanced field emission property with low turn-on and threshold field. The formation of Al2O3 nanoparticle-decorated tubular SiC on Si substrates is achieved in one-step via simple heating evaporation process for the first time. The nanostructure consists of tubular SiC and the Al2O3 nanoparticles, which homogeneously decorate on the surface of the tubular SiC with an average diameter of 7.8 nm and narrow diameter distribution. Moreover, compared with the same density and sized bare tubular SiC, the Al2O3 nanoparticle-decorated tubular SiC nanostructure has an obvious reduction in turn-on (from 8.8 to 2.4 V μm−1) and threshold field (from 23.5 to 5.37 V μm−1). The very low turn-on and threshold field is also comparable to that of carbon nanotubes, which indicates the Al2O3 nanoparticle-decorated tubular SiC is of huge potential application in future field emission display devices.

Nowadays, the development of nano-synthesis has turned to controllable design for specific demands in micro-nano device application, to be integrated into functional units more conveniently with low-cost and efficiency principles. In this case, an appropriate approach for directly obtaining horizontally aligned nanowires in a large scale would be of great significance in future micro-nano device integration. Here, on the HOPG surface, we managed to achieve this. The approach is versatile to various kinds of materials. Horizontally aligned nanowires of Al–C based materials, such as Al4C3 and Al4O4C, were achieved. All of the nanowires exhibit a high degree ordered alignments and possess super aspect ratios with uniform widths of about 100 nm and lengths on the millimeter level. We believe the assembly mechanism lies in a step-edge induced ordered growth process, through which quaternary Al–Si–O–C nanoball alignment could also be obtained. It is expected that this method could be beneficial to adjust many useful materials for micro device integration in the future.

The Al–O–C–N system is known as a kind of Al2O3-based ceramic material with various different chemical compositions and structures. Considering its superior physical and mechanical properties, the corresponding one-dimensional Al–O–C–N system may have huge potential applications in future nanodevices. Herein, for the first time, two types of ultralong one-dimensional Al3CON nanostructures, nanowires and bicrystalline nanobelts, were simultaneously synthesized by asimple CVD process. The products were characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy as well as energy dispersive X-ray spectrometry. Corresponding property studies were carried out to explore the potential applications of the products. The force measurement based on a single nanostructure was performed by using an atomic force microscope (AFM) and the nanostructure showed high strength with a Young's modulus of 251 GPa. Semiconductor characteristics were also observed by electrical measurement at room temperature, which may be attributed to the doping and/or native defects. In addition, the Al3CON nanostructures showed deep-ultraviolet photoconductivity, in which the conductance increases only when illuminated with 254 nm light rather than 365 nm light.

Highly efficient energy storage systems are in great demand for power source applications ranging from wearable electronics to hybrid electric vehicles. Graphene-based hybrid structure capacitors are ideal candidates for manufacturing these systems. Herein, we present the design and fabrication of heterostructured composites made of vertically aligned graphene nanosheets (VAGN) and MnO nanoparticles. Electrodes with various MnO mass contents were obtained by depositing nanosized MnO particles onto VAGN under different hydrothermal conditions. The VAGN served as an excellent backbone and electron collector, enhancing the specific capacitance of the VAGN/MnO electrode (37 wt% MnO) to 790 F g−1 at a scan rate of 2 mV s−1. The electrodes also showed high specific capacitance (381 F g−1) with high active material loading content (80 wt% MnO), and outstanding cycling stability (80% retention after 4000 cycles at 10 A g−1). These excellent electrochemical performances result from the particular three-dimensional structure of VAGN, which offers convenient access for electrolyte cations participating in the redox reaction of MnO. These composites show enormous potential for use in energy management applications.

A SnO2–graphene oxide (GO) hybrid composite was prepared by binding SnO2 nanocrystals smaller than 5 nm in GO using a facile hydrothermal method. Aided by hydrophilic radicals, such as hydroxyl and carboxyl, in in situ forming SnO2 quantum dots, the active material and the flexible support are highly coupled. When used as an anode material for lithium ion batteries (LIBs), the hybrid composite electrode delivers a high reversible capacity of nearly 800 mA h g−1 (based on the total weight of the composite, discharging at 100 mA g−1) with more than 90% retention for 200 cycles. Besides the excellent cycling performance at various rates, the composite also exhibits a superior rate performance at 10 A g−1 with recoverable initial reversible capacity and a long lifespan of 1000 cycles with 80% capacity retention, outperforming most previous SnO2–graphene hybrid electrodes.

Transition metal oxide hollow architectures are intensively explored for energy conversion and storage applications. Feasible strategies towards various hollow architectures, particularly those with non-spherical skeletons, are especially attractive. Quadrate Co3O4 nanoboxes are fabricated through controlled annealing of cobalt coordination polymer nano-solids with tunable dimensions. The cobalt coordination polymer in quadrate wires, cuboids, and cubes is synthesized by temperature and concentration dependent solvothermal method. Evolution of the nanoboxes involves Co3O4 shell formation and uniform depletion of the cobalt coordination polymer in the core. Benefitting from the well-defined hollow interior and nanosized crystals, the quadrate nanoboxes have large specific surface and abundant hierarchical pores. When evaluated as anode materials for lithium ion batteries, the boxes exhibited excellent electrochemical properties. Besides a superior storage capability of 1200 mA h g−1 at 0.2 A g−1, a remarkable retention of 625 mA h g−1 at a large rate of 10 A g−1 is also obtained.

Herein, honeycomb in honeycomb carbon bubbles (HHCBs) with macro-, meso-, micro-, and nanopores have been successfully obtained for the first time via a simple one-step direct templating method. Benefiting from unique features, the HHCBs demonstrate superior cycling stability and rate capability when employed as anode materials for both lithium and sodium-based batteries. For instance, hollow carbon bubbles used as lithium ion battery anodes deliver a high reversible capacity of 1583 mA h g−1 and nearly 100% capacity retention over 100 cycles at a constant current of 372 mA g−1 (1C). A high reversible capacity of 200 mA h g−1 also can be obtained at an extremely high current rate of 300C. When tested as sodium ion battery anodes, the electrode can deliver an initial reversible capacity of 373 mA h g−1 and retain 209 mA h g−1 after 400 cycles at 100 mA g−1. Even at a high current rate of 1000 mA g−1, the electrode still can release a substantial reversible capacity of 122 mA h g−1 after discharging–charging for 700 cycles, suggesting a high rate capability and cyclability. The approach provides a valuable candidate acceptable for use as both lithium and sodium ion battery anodes.

Iron fluoride cathodes with good specific energy/power performance can hardly operate durably at room temperature due to poor conductivity and sluggish kinetics. Fabricating novel hybrid nanostructures is a promising approach to obtain a fast diffusion and transport process. In this study, a porous honeycomb-like iron fluoride hybrid composite comprising iron fluoride nanocrystals (∼1–4 nm) encapsulated in separate carbon nests constructed by multi-scale pores (∼1–100 nm) was fabricated through a combination of room-temperature fluorination and a mild annealing process for the first time. The iron fluoride topochemically evolved from a smaller iron oxide nanocrystal precursor (∼2–3 nm) is closely engineered with carbon creases nested in carbon microbubbles (CMBs) which exhibit a three dimensional (3D) porous honeycomb-like network structure. As a cathode material for lithium-ion batteries (LIBs), the hybrid electrode delivers a large capacity of nearly 500 mA h g−1 at 20 mA g−1 (normalized to the composite, i.e. the capacity is calculated based on the total mass of the composite). Meanwhile, a durable cyclability of more than 500 cycles and a large rate of 10 A g−1 were also realized at room temperature. The impressive specific energy/power performance (1100 W h kg−1/224 W kg−1) which is superior to that of today's Li-ion batteries (∼380 W h kg−1/∼80 W kg−1) reveals the efficiency of the novel hybrid nanostructure in speeding up the kinetics without sacrificing the storage capability. Direct insights into the lithiation process reveal that iron fluoride firstly undergoes a mild amorphization process, and then crystallizes as γ-Fe nanocrystals after in-depth lithiation; during the de-lithiation process, γ-Fe firstly becomes amorphous due to the injection of fluorine, and subsequently evolves into double-salt-like LixFeFy nanocrystals for further fluorine enriching. Reversible conversion between C-Fe0/LiF and T-FeF2, like LixFe3+Fy with a 3 mole electron transfer, lasts for more than 100 cycles without any obvious re-distribution of the active materials.

Although widely used, the current Li-ion battery (LIB) technology still suffers from a lack of suitable electrodes with enhanced energy and power density, cycling stability, energy efficiency and cycling life. As an anode material for LIBs, metallic tin (Sn) has attracted tremendous interest, owing to its high theoretical capacity. Nevertheless, the practical implementation of metallic tin to LIBs is greatly hampered by the poor cyclability, because volume changes that occur during charging and discharging, result in both mechanical failure and loss of electrical contact at the electrode and the tin nanoparticle aggregates during the discharging process. Here, we report for the first time, a new strategy to grow self-assembled Sn@CNT on vertically aligned graphene (VAGN) by the microwave plasma irradiation reduction of SnO2 growth on VAGN and in situ encapsulating all the Sn nanoparticles in CNTs. The composite, as an anode material in lithium ion batteries, exhibits a high reversible capacity of 1026 mA h g−1 at 0.25 C (cycle lives of more than 280 times) and a capacity of 140 mA h g−1 is retained in a discharge time of 12 s, which represents the best performance values attained for a Sn anode to date. We expect the proposed route to be adopted by the rapidly growing energy storage research community.

FeF2, as a promising cathode material for Li-ion batteries, has a high specific capacity of 571 mA h g−1, and a lot of research has been focused on overcoming its poor cycling stability associated with low electron conduction and large volume effect, mostly through nanostructured material design. However, FeF2 nanodesign itself is a challenge. Herein, we report the incorporation of an ordered mesoporous carbon (CMK-3) into FeF2-based cathodes. The FeF2 nanoparticles inside the conducting CMK-3 by topochemical conversion from an iron oxide precursor to iron fluoride hydrate in situ, form a well-connected three dimensional network structure. Such a hierarchical framework combines multiple advantageous features, including a continuous electrically conductive network and porous space for the volume expansion of the FeF2 particles. With this cathode, we demonstrate a cycle life of 1000 cycles with little capacity decay (less than 0.3‰ per cycle). The FeF2@CMK-3 electrode shows stable cycling and an extremely high-rate capacity, owing to the special porous structure and the nano-sized particles. In the potential range of 1.5–4.5 V, discharge capacities of 500, 400 and 320 mA h g−1 can be delivered at the high rates of 500, 2000 and 4000 mA g−1 after 100 cycles, respectively, which is the highest level for FeF2 so far.

Besides targeting low-voltage intercalation, NaTi2(PO4)3 (NTP) is a promising negative electrode material for non-aqueous sodium-ion batteries (SIBs). However, the low electronic conductivity of this material inhibits its potential applications. Herein, we report the controllable synthesis of four interesting porous NTP nanocubes via a one-pot solvothermal method. The as-synthesized products have shown excellent high-rate performance and cycling stability as SIB anodes. After 10000 cycles at a 10C rate, 75.5% of the initial capacity is retained, which exceeds those of most of the reported SIB anode materials. Even at an extremely high rate of 100C, the NTP nanocubes can still deliver considerable reversible capacities after deep charging/discharging for 15000 cycles. The superior electrochemical performances can be attributed to their unique nanostructures. We hope that such a finding of the new construction will enrich the NTP system and provide several possible candidates for SIB anodes.

Large volume changes cause a series of complicated problems in alloy-type anodes, such as pulverization, exfoliation and the capacity decay which results. Therefore, solutions for the problems caused by large volume changes in sodium ion battery (SIB) anodes are urgently needed. Herein, we report a novel route to encapsulate Sb2O3/Sb nanoparticles (Sb2O3/Sb-NPs) within a graphene shell nanostructure (Sb2O3/Sb@graphene) via microwave plasma irradiation of Sb(CH3COO)3 and a subsequent graphene growth procedure. The designed structure, Sb2O3/Sb@graphene NPs anchored on carbon sheet networks (CSNs), provides an ultra-thin, flexible graphene shell to accommodate the volume changes of Sb2O3/Sb, and thus demonstrates excellent cycling stability (92.7% of the desodiation capacity was retained after 275 cycles), a long cycle life (more than 330 cycles) and a good rate capability (220.8 mA h g−1 even at 5 A g−1). The stability could be compared to that of commercial graphite in lithium ion batteries.

Exploring ternary metal oxides that can in situ form an elastic medium to accommodate volume changes upon lithium intercalation is now a popular and effective way to achieve high-performance lithium ion batteries with enhanced cycling stability. Herein, we report an ultrathin zinc pyrovanadate nanosheet of atomic thickness with exposed (001) facets via a facile hydrothermal method. Morphological and structural evolutions of the zinc pyrovanadate are investigated to reveal the electrochemical reaction mechanism of this compound towards lithium ion intercalations for the first time. It is found that the initial zinc pyrovanadate transforms into ZnO nanoparticles and LiV2O5 in the first cycle, and the subsequent reaction mainly occurs between ZnO and LiZn and lithiation/delithiation of the lithium vanadate. Interestingly, the in situ formed lithiated vanadate matrix could serve as a conductive network for the reversible electrochemical process of ZnO. The ultrathin thickness is in favour of shortening pathways for lithium ions, while the specific exposed facets are facilitated to form the architecture of ZnO nanoparticles embedded in the amorphous lithiated vanadate matrix owing to the sandwich-like skeleton of the zinc pyrovanadate that is constructed from the layer-by-layer stacking of the [ZnO6] and [V2O7] polyhedra chains projected along the c axis. Benefiting from these inspiring merits, the as-synthesized ultrathin zinc pyrovanadate nanosheet exhibits a high specific capacity (963 mA h g−1 at 0.05 A g−1), outstanding rate capability (344 mA h g−1 at 10 A g−1), and long cycle life (602 mA h g−1 could be maintained after 980 cycles at 1 A g−1) and is regarded as a promising candidate for lithium ion battery anode materials.

We have made a supercapacitor electrode based on carbon fabric, vertically aligned graphene nanosheets (VAGN) and Mn3O4 nanoparticles. The unique structure constructed by VAGN endows the electrode with high specific capacitance up to 670 F g−1. Additionally we assembled two pieces of the electrode to make a highly flexible all-solid-state symmetric supercapacitor. This device demonstrates a high capacitance of 562 F g−1, high energy density of 50 W h kg−1, high power density of 64 kW kg−1 and good stability after 10000 cycles. Due to the flexibility of the carbon fabric, the device expresses an excellent flexibility without sacrificing the electrochemical performance when bended to 150 degrees. We believe that this electrode with its excellent electrochemical performances has an enormous potential in energy storage applications, especially for flexible and lightweight electronics.

Large scale single-crystalline tubular β-SiC was prepared via a simple thermal evaporation method without any template and catalyst, and the nanostructure showed excellent field emission properties.

Close-packing WC as a kind of metallic carbide, possessing good conductivity, high melting point and superior hardness, has numerous intrinsic properties that deserve to be investigated and then explored for use in micro or nano devices in the photoelectronics field. One of the main reasons why WC has not been considered much is that low-dimensional structures such as nanowires and nanowalls are hard to prepare. Here, we developed a novel method to overcome a series of difficulties in the growth of low-dimensional WC nanostructures and managed to apply eutectic solidification in W–Al–C solution to synthesize a high-quality WC nanowall forest and nanowires on a large scale. The experiment was carried out in a high-vacuum (∼10−4 Pa) chemical vapor deposition system pumped by a turbo molecular pump. We expect that it can be applied as a universal route to prepare low-dimensional nanostructures for refractory metals compound.

As a challenging issue, minimizing metal organic framework (MOF) bulks to nanoscale is of great significance in deepening their application for energy storage, catalysis, sensing, etc. MOF nanostructures, particularly nanowires, are highly desirable because of their fast transport kinetics, good flexibility, and universal structural compatibility. Taking a polycarboxylate based cobalt coordination polymer (CoCOP) as an example, we presented one-dimensional (1D) MOF nanowires by a facile and scalable method. The CoCOP nanowires deliver an impressive lithium ion storage capacity of more than 1100 mA h g−1 at 20 mA g−1. Besides the high energy and power performance (875 W h kg−1 and 6422 W kg−1) comparable to that of recently advanced metal oxide hybrid electrodes, they also exhibit excellent long term cycling stability for more than 1000 cycles for fully reversible lithiation–delithiation chemistry based on a joint mechanism of intercalation-like structural deformation and Co2+/Co conversion reactions. Typical full cells with CoCOP nanowire anodes and commercial LiFePO4 powder cathodes (CoCOP–LiFePO4) also demonstrate excellent cyclability and fast charge–discharge capability with a capacity retention of 83% for more than 300 cycles at a 1C rate (1C corresponds to a one hour discharge process). Besides, a large capacity of 138 mA h g−1 at 0.1C and a high specific energy of 222 W h kg−1 (based on the total weight of CoCOP and LiFePO4) also substantiate their superior performance to common commercial energy storage and conversion devices.

The platinum-like behavior of tungsten carbides has made them one of the most promising electrocatalysts for the hydrogen evolution reaction (HER). So far, however, their poor activity has kept them far away from practical application. Related research has been basically focused on the form of particles with poor nano-structures, which is not conducive to further development. There is an urgent need to develop a versatile and facile method to synthesize tungsten carbide nanostructures with high active site density. Here we developed a plasma-assisted carburization method to synthesize porous tungsten carbide hybrid nanowires (p-WCx NWs) on carbon cloth. Benefitting from the rapid carburization process with a unique etching-effect in the plasma, the resulting p-WCx NWs are provided with porous nano-structures and an appropriate carbon coating layer. They exhibit excellent HER performance with a small onset potential of 39 mV, η10 (overpotential to drive a current of 10 mA cm−2) of 118 mV, and Tafel slope of 55 mV dec−1 in acid solution, and an onset potential of 56 mV, η10 of 122 mV, and Tafel slope of 56 mV dec−1 in alkaline solution. These performances are superior to those reported for W-based carbide electrocatalysts to date. Impressively, the p-WCx NWs/CC electrode could sustain more than 40 h of hydrogen production at the current density of 20 mA cm−2 without observable deterioration in both strong acid and alkaline solutions.