Two-dimensional graphene-like N, Co-codoped carbon nanosheets (N, Co-CNSs), which exhibit excellent stability, competitive catalytic activity and superior methanol tolerance compared to the commercial Pt/C catalyst, have been successfully fabricated using Co-based zeolitic imidazolate framework (ZIF-67) polyhedrons as precursors in a molten salt medium.

•Hierarchical porous carbon mosaiced with ultrasmall MoS2 nanosheets was fabricated.•Superior sodium ion half/full batteries performance was achieved.•Structure and composition were correlated with the sodium storage performance.MoS2 has recently been regarded as a promising anode material for sodium ion batteries (SIBs). However, it remains challenging to attain high-performance MoS2-based anodes for SIBs integrated robust cyclability with rate capability more cheaply and scalably until now. Herein, via a facile polysterene nanosphere (PS)-templated sol-gel method, nitrogen-doped hierarchical porous carbon (NHPC) matrix mosaiced with ultrasmall MoS2 nanosheets (MoS2@NHPC) has been synthesized as anode for SIBs. In half batteries, the MoS2@NHPC shows high reversible capacity (500 mA h g−1 at 0.1 A g−1), excellent rate capability (330 mA h g−1 at 5 A g−1) and robust cycling stability (340 mA h g−1 at 1 A g−1 over 550 cycles). Moreover, when coupled with the Na3V2(PO4)3 (NVP) cathode in a full battery, the MoS2@NHPC anode also displays high reversible specific capacity of 350 mA h g−1 at 0.2 A g−1, and robust cycling stability of over 130 cycles. The excellent performance is benefited from the uniform mosaic of ultrasmall MoS2 nanosheets into the NHPC, which effectively facilitates the ionic and electronic conductivity, and accommodates the volume changes during desodiation-sodiation process. Such design may enlighten to develop the other high-performance materials for energy storage.Nitrogen-doped hierarchical porous carbon matrix mosaiced with ultrasmall MoS2 nanosheets (MoS2@NHPC) were synthesized as anode material for sodium ion batteries, showing an excellent rate capability and robust cycling performance.Download high-res image (210KB)Download full-size image

Nanostructured CoSe2 anode materials hold great promise for sodium ion batteries (SIBs), drawing much recent research attention. However, high-performance CoSe2 based anodes are still challenging to obtain. Herein, using zeolitic imidazolate framework-67 (ZIF-67) particles as the starting material, nondestructive hollow polyhedral hybrids have been synthesized successfully, which are structured from CNT-bridged carbon-coated CoSe2 nanospheres (CoSe2@C/CNTs). During the synthesis, the controlled in situ growth of CNTs introduces additional mesopores and open channels to the hybrids, and avoids serious agglomeration of the CoSe2 nanospheres. When employed as anode materials for SIBs with ether-based electrolyte, the CoSe2@C/CNTs show overwhelming merits over graphitic carbon-coated CoSe2 nanosphere polyhedral hybrids (CoSe2@GC) and bare CoSe2 particles. Specifically, the CoSe2@C/CNTs anode displays a high reversible capacity (∼470 mA h g−1 at 0.2 A g−1), a good rate capability of ∼373 mA h g−1 even at 10 A g−1, and an excellent cycling stability of over 1000 cycles with a capacity retention of ∼100% calculated from the 70th cycle. In addition, the electrochemical reaction dynamics analysis indicates a considerable capacitive contribution during the discharge–charge cycles, which is beneficial to enhance the rate capability and cyclability of the CoSe2@C/CNTs anode. Such results could be ascribed to the stable ether-based electrolyte-active material intermediates, improved electrolyte-active material contact, and shortened charge transfer paths afforded by the unique hybrid nanostructure.

Nitrogen-doped three-dimensional (3D) porous carbon materials have numerous applications due to their highly porous structures, abundant structural nitrogen heteroatom decoration and low densities. Herein, nitrogen doped hierarchical 3D porous carbons (NHPC) were prepared via a novel metal–organic aerogel (MOA), using hexamethylenetetramine (HMT), 1,3,5-benzenetricarboxylic acid and copper (II) as starting materials. The morphology, porous structure of the building blocks in the NHPC can be tuned readily using different amount of HMT, which makes elongation of the pristine octahedron of HKUST-1 to give rise to different aspect ratio rod-like structures. The as-prepared NHPC with rod-like carbons exhibit high performance in lithium sulfur battery due to the rational ion transfer pathways, high N-doped doping and hierarchical porous structures. As a result, the initial specific capacity of 1341 mA h/g at rate of 0.5 C (1 C = 1675 mA h/g) and high-rate capability of 354 mA h/g at 5 C was achieved. The decay over 500 cycles is 0.08% per cycle at 1 C, highlighting the long-cycle Li–S batteries.Download high-res image (201KB)Download full-size imageN-doped hierarchical porous rod-like carbons fabricated from metal organic aerogel show potential application in lithium-sulfur batteries.

Hierarchical porous carbon nanosheets (HPCSs) were prepared from acrylic resin using FeCl3·6H2O as catalyst and ZnCl2 as activator. The as-obtained materials possess a nanosheet structure and a combination of high graphitization degree and large surface area (2109 m2 g−1). When incorporated into the anode of a Lithium Ion Battery (LIBs), the HPCSs achieve a maximum specific capacity of 1642 mA h g−1 at 100 mA g−1 and 1100 mA h g−1 at 500 mA g−1 after 150 cycles, exhibiting enormous potential in developing advanced high performance LIBs. This work offers a facile strategy for the preparation of hierarchical porous carbon materials with high performance in LIBs from resin.

Sodium ion batteries (SIBs) have been considered as a promising alternative to lithium ion batteries, owing to the abundant reserve and low-cost accessibility of the sodium source. To date, the pursuit of high-performance anode materials remains a great challenge for the SIBs. In this work, carbon-stabilized interlayer-expanded few-layer MoSe2 nanosheets (MoSe2@C) have been fabricated by an oleic acid (OA) functionalized synthesis–polydopamine (PDA) stabilization–carbonization strategy, and their structural, morphological, and electrochemical properties have been carefully characterized and compared with the carbon-free MoSe2. When evaluated as anode for sodium ion half batteries, the MoSe2@C exhibits a remarkably enhanced rate capability of 367 mA h g–1 at 5 A g–1, a high reversible discharge capacity of 445 mA h g–1 at 1 A g–1, and a long-term cycling stability over 100 cycles. To further explore the potential applications, the MoSe2@C is assembled into sodium ion full batteries with Na3V2(PO4)3 (NVP) as cathode materials, showing an impressively high reversible capacity of 421 mA h g–1 at 0.2 A g–1 after 100 cycles. Such results are primarily attributed to the unique carbon-stabilized interlayer-expanded few-layer MoSe2 nanosheets structure, which facilitates the permeation of electrolyte into the inner of MoSe2 nanosheets, promoting charge transfer efficiency among MoSe2 nanosheets, and accommodating the volume change from discharge–charge cycling.Keywords: carbon stabilization; expanded interlayer spacing; few-layer MoSe2 nanosheets; oleic acid functionalization; sodium ion batteries;

Sandwich-type, two-dimensional hybrid nanosheets were fabricated by the infiltration of nanosized sulfur into graphene-backboned mesoporous carbon with a PPy nanocoating. They exhibit a high reversible capacity for as long as 400 cycles with an ultra slow decay rate of 0.05% per cycle at the high rate of 1–3 C due to the efficient immobilization of polysulfides.

Dually fixed SnO2 nanoparticles (DF-SnO2 NPs) on graphene nanosheets by a polyaniline (Pani) coating was successfully fabricated via two facile wet chemistry processes, including anchoring SnO2 NPs onto graphene nanosheets via reducing graphene oxide by Sn2+ ion, followed by in situ surface sealing with the Pani coating. Such a configuration is very appealing anode materials in LIBs due to several structural merits: (1) it prevents the aggregation of SnO2 NPs, (2) accommodates the structural expanding of SnO2 NPs during lithiation, (3) ensures the stable as-formed solid electrolyte interface films, and (4) effectively enhances the electronic conductivity of the overall electrode. Therefore, the final DF-SnO2 anode exhibits stable cycle performance, such as a high capacity retention of over 90% for 400 cycles at a current density of 200 mA g–1 and a long cycle life up to 700 times at a higher current density of 1000 mA g–1.Keywords: graphene; Li-ion batteries; phytic acid; polyaniline; tin dioxide

Strain sensors with excellent flexibility, stretchability, and sensitivity have attracted increasing interests. In this paper, a highly stretchable and ultrasensitive strain sensor based on reduced graphene oxide microtubes–elastomer is fabricated by a template induced assembly and followed a polymer coating process. The sensors can be stretched in excess of 50% of its original length, showing long-term durability and excellent selectivity to a specific strain under various disturbances. The sensitivity of this sensor is as high as 630 of gauge factor under 21.3% applied strain; more importantly, it can be easily modulated to accommodate diverse requirements. Implementation of the device for gauging muscle-induced strain in several biological systems shows reproducibility and different responses in the form of resistance or current change. The developed strain sensors show great application potential in fields of biomechanical systems, communications, and other related areas.Keywords: elastomer; reduced graphene oxide microtubes; sensitivity; strain sensor; stretchability

Compressible graphene aerogel (CGA) supported CoO nanostructures were synthesized via a hydrothermal strategy. Benefitting from good mechanical stability, they can be directly used as binder-free electrodes in lithium-ion batteries, which exhibit superior electrochemical performance to conventional electrodes made of powders and binders.

Transition metal oxide coupling with carbon is an effective method for improving electrical conductivity of battery electrodes and avoiding the degradation of their lithium storage capability due to large volume expansion/contraction and severe particle aggregation during the lithium insertion and desertion process. In our present work, we develop an effective approach to fabricate the nanocomposites of porous rod-shaped Fe3O4 anchored on reduced graphene oxide (Fe3O4/rGO) by controlling the in situ nucleation and growth of β-FeOOH onto the graphene oxide (β-FeOOH/GO) and followed by dielectric barrier discharge (DBD) hydrogen plasma treatment. Such well-designed hierarchical nanostructures are beneficial for maximum utilization of electrochemically active matter in lithium ion batteries and display superior Li uptake with high reversible capacity, good rate capability, and excellent stability, maintaining 890 mA h g−1 capacity over 100 cycles at a current density of 500 mA g−1.

We report a convenient and effective method to fabricate monolithic and conductive nanocomposites with various morphologies by directly infiltrating epoxy resin into the pores of ultralight graphene aerogels (ULGAs) with desired morphologies, followed by curing. These composites show linear ohmic behavior even with graphene filling content as low as 0.28 wt%. The electrical conductivity of the composites can be modulated in the range from 3.3 × 10−2 to 4.8 × 10−1 S m−1, superior to that of traditional composites by directly mixing the powdery graphene with the polymer. Furthermore, the conductivity of the nanocomposites remains unchanged in a wide range of temperature which may allow the structures to be promising candidates as resistance elements for integrated circuits (ICs).

A series of Mn-based mixed metal oxide catalysts (Co–Mn–O, Fe–Mn–O, Ni–Mn–O) with high surface areas were prepared via low temperature crystal splitting and exhibited extremely high catalytic activity for the low-temperature selective catalytic reduction of nitrogen oxides with ammonia.

The idea of extending functions of graphene aerogels and achieving specific applications has aroused wide attention recently. A solution to this challenge is the formation of a hybrid structure where the graphene aerogels are decorated with other functional nanostructures. An infiltration–evaporation–curing strategy has been proposed by the formation of hybrid structure containing poly(dimethylsiloxane) (PDMS) and compressible graphene aerogel (CGA), where the cellular walls of the CGA are coated uniformly with an integrated polymer layer. The resulting composite shows enhanced compressive strength and a stable Young’s modulus that are superior to those of pure CGAs. This unique structure combines the advantages of both components, giving rise to an excellent electromechanical performance, where the bulk resistance repeatedly shows a synchronous and linear response to variation of the volume during compression at a wide range of compressed rates. Furthermore, the foamlike structure delivers a water droplet with “sticky” superhydrophobicity and a size as large as 32 μL that remains tightly pinned to the composite, even when it is turned upside-down. This is the first demonstration of superhydrophobicity with strong adhesion on a foamlike structure. These outstanding properties qualify the PDMS/CGA composites developed here as promising candidates for a wide range of applications such as in sensors, actuators, and materials used for biochemical separation and tissue engineering.Keywords: compressibility; electromechanical performance; graphene aerogel; poly(dimethylsiloxane); superhydrophobicity; synergistic effect;

Here we report the finding of a new crumpled graphene structure – folded graphene belts (FGBs) – generated by means of shock cooling of an aqueous chemically converted graphene (CCG) dispersion. Unlike the traditional tubular hollow structures such as CNTs or CNSs, the as-made FGBs feature an accordion-like geometry in which the 2D graphene sheets were folded along multiple parallel axes. In situ scanning electron microscope (SEM) measurements revealed that the prepared FGBs were highly elastic and can keep their shape under repeated large strains. The formation and growth of ice crystals during the shock cooling step in liquid nitrogen are believed to be the driving force for the formation of such unique folded graphene structures.

Spilled oil represents a menace to the aquatic ecosystem and the whole environment in general and requires timely cleanup. Among all the avaliable technologies, oil sorption has attracted the most attention because of its simplicity and high level of effectiveness. The key for the development of this technology is convenient fabrication of high-performance oil sorbents that can be used repeatedly. In this work, a fast microwave irradiation-mediated approach has been proposed for manufacturing multiwall carbon nanotube (MWCNT)–graphene hybrid aerogels, in which MWCNTs are vertically anchored on the surface of cell walls of graphene aerogels. The hybrid monoliths show superhydrophobicity and superoleophilicity, a large pore volume, a large pore size, and excellent compressibility, demonstrating outstanding performance for recyclable oil sorption.

Nitrogen-doped mesoporous carbon nanosheets (NMCNs) were prepared from coal tar and melamine using a layered MgO as template. Porous structures and nitrogen doping levels were readily tuned by adjusting experimental parameters. NMCNs show high specific capacities and excellent cyclic stabilities as anode materials for lithium ion batteries. A sample prepared under optimum conditions shows a high reversible capacity of nearly 1 000 mAh/g at a current density of 100 mA/g, which can be ascribed to its unique mesoporous sheet-structure, a high specific surface area of 1 209 m2/g, and a uniform and high bulk nitrogen content of 8.6%. Our work demonstrates that coal tar can act as an excellent carbon source for the production of carbon materials with high performance in lithium-ion batteries.

Graphene oxide was produced using a modified Hummers method and used to produce a MnSO4-graphene oxide (MnSO4-GO) hybrid which was then transformed into a MnO-graphene hybrid by precipitation with NaOH followed by hydrogen reduction. The MnO-graphene hybrid shows a high specifc capacity of 870 mAh·g−1 at 100 mA·g−1 as an anode material for lithium ion batteries, which is much higher than that of bare MnO (around 456 mAh·g−1). A capacity of 390 mAh·g−1 could be maintained even at a high current density of 1 600 mA·g−1. This green and highly efficient approach offers a new technique for the synthesis of MnOx-graphene battery materials.

Nitrogen-doped carbon microfibers (N-CMFs) with porous textures have been synthesized by means of a floating catalyst chemical vapor deposition (FCCVD) with anhydrous ferric chloride as a catalyst precursor and melamine as both the carbon and nitrogen source. X-ray photoelectron spectroscope (XPS) characterization of the as-prepared N-CNFs reveals nitrogen atoms in the N-CMFs are mainly in the form of pyridine-like nitrogen and graphitic nitrogen. The sublimation and subsequent gas phase reduction of FeCl3 in H2 produces Fe micro-particles with high catalytic activity that leads to the growth of the microfibers. The electrochemical studies have shown that N-CMFs have a larger capacitance than the pure CMFs, showing promise for use as electrode materials in supercapacitors.

Controllable production of graphene by simultaneously exfoliating and reducing graphite oxide (GO) under dielectric barrier discharge (DBD) plasma with various working gases, including H2 (reducing), Ar (inert) and CO2 (oxidizing), has been investigated. The deoxygenation level of GO is related to the type of working gases while regardless of the bulk temperature during plasma discharge, which implicates a high-energy electron/ion bombardment deoxygenation mechanism. Acting as electrode materials in a supercapacitor cell with KOH electrolyte, graphene nanosheets (GS) from various plasmas exhibit high specific capacitance and good electrochemical stability. With the assistance of low temperature plasma, this approach has the potential to enable the fabrication of a broad spectrum of graphene-based composites that are sensitive to high temperatures.

Coal has been used as an important resource for the production of chemicals, conventional carbon materials, as well as carbon nanomaterials with novel structures, in addition to its main utilization in the energy field. In this work, we present the synthesis of chemically derived graphene and graphene–noble metal composites with coal as the starting material by means of catalytic graphitization, chemical oxidation, and dielectric barrier discharge (DBD) plasma-assisted deoxygenation. It is found that the graphitization degree of the coal-derived carbon remarkably affects the properties of graphene obtained from chemical exfoliation, and high crystallinity of coal-derived carbon is essential for the preparation of high-quality graphene sheets (GS). GS decorated with highly dispersed noble metallic nanoparticles (NP) on their surface (NP/GS) were successfully fabricated via simultaneous reduction of graphite oxide (GO) and noble metal salts by H2 DBD plasma technique. The electrochemical performance of the GS as electrode in supercapacitor and the catalytic activities of NP/GS composites in selective reduction of nitrogen oxides (NOx) were investigated. This work demonstrates an alternative approach for the fabrication of graphene and its composites from coal with promising potential in energy storage and environment preservation.

We present a general method for the construction of 3D carbon nanotube (CNT) architectures with structural integrity and stability by the combination of capillary action and catalytic vapor-phase deposition (CVD). Using this method, patterned CNTs undergo the transformation from a vertically aligned structure to a hierarchically dual porosity material in a controllable way, which can be tuned by sequential modulation of the water-wetting and the CVD re-growth. By controlling the predesign of the substrate patterns, the CNT height, and the sequence of water wetting-CVD runs, diverse shapes and hybrid structures have been fabricated. This simple and versatile method might be extendable to the organization of other filamentary nanostructures for the construction of complex architectures made of various 1D building blocks.

High cost and scarcity of graphene boosts the great interests in seeking for its low-cost substitute, e.g., 2D carbons, for upcoming energy applications where extreme physical properties are not absolutely critical. Metal-organic frameworks (MOFs) are very convenient self-templated precursor towards carbon-based materials with tunable functionalities. However, the morphology of most MOF-derived carbons is largely limited to solid particles with limited active surface and diffusion kinetics. The morphology control is still remained the bottleneck for developing high-performance MOF-derived carbons with widespread applications until now. Here we report a general strategy for morphology control of zeolitic imidazolate framework (ZIF)-derived 2D carbon nanostructures by layered-nanospace-confinement growth of 2D ZIFs and in-situ carbonization. The process yields ZIF-derived porous carbon nanosheets with high level of planar N doping (over 93% in total N content) and highly tunable chemical compositions (pure carbon or decorated with various metals such as Co, Fe, Ni, NiCox, etc.). Unique 2D nanostructure renders them with extra exposed active surface area, more accessible porosity with much higher pore volume and shorter diffusion distance as compared to the particulate counterparts. Benefited from enhanced activity and diffusion kinetics, the ZIF-derived porous carbon nanosheets exhibit superior onset potential, current density and durability to commercial Pt catalyst and their particulate counterparts for oxygen reduction reactions in both alkaline and acidic medium.A general strategy is developed for the synthesis of ZIF-derived planar-N-doped porous carbon nanosheets with tunable composition and microstructure via the intercalation of ZIF into layer-structured template, followed by nanospace-confined carbonization and acidic etching. Benefited from unique structure, they exhibit superior electrochemical performance as electrocatalysts for oxygen reduction reactions.Download high-res image (258KB)Download full-size image

A series of Mn-based mixed metal oxide catalysts (Co–Mn–O, Fe–Mn–O, Ni–Mn–O) with high surface areas were prepared via low temperature crystal splitting and exhibited extremely high catalytic activity for the low-temperature selective catalytic reduction of nitrogen oxides with ammonia.

Two-dimensional graphene-like N, Co-codoped carbon nanosheets (N, Co-CNSs), which exhibit excellent stability, competitive catalytic activity and superior methanol tolerance compared to the commercial Pt/C catalyst, have been successfully fabricated using Co-based zeolitic imidazolate framework (ZIF-67) polyhedrons as precursors in a molten salt medium.

Controllable production of graphene by simultaneously exfoliating and reducing graphite oxide (GO) under dielectric barrier discharge (DBD) plasma with various working gases, including H2 (reducing), Ar (inert) and CO2 (oxidizing), has been investigated. The deoxygenation level of GO is related to the type of working gases while regardless of the bulk temperature during plasma discharge, which implicates a high-energy electron/ion bombardment deoxygenation mechanism. Acting as electrode materials in a supercapacitor cell with KOH electrolyte, graphene nanosheets (GS) from various plasmas exhibit high specific capacitance and good electrochemical stability. With the assistance of low temperature plasma, this approach has the potential to enable the fabrication of a broad spectrum of graphene-based composites that are sensitive to high temperatures.

We present a general method for the construction of 3D carbon nanotube (CNT) architectures with structural integrity and stability by the combination of capillary action and catalytic vapor-phase deposition (CVD). Using this method, patterned CNTs undergo the transformation from a vertically aligned structure to a hierarchically dual porosity material in a controllable way, which can be tuned by sequential modulation of the water-wetting and the CVD re-growth. By controlling the predesign of the substrate patterns, the CNT height, and the sequence of water wetting-CVD runs, diverse shapes and hybrid structures have been fabricated. This simple and versatile method might be extendable to the organization of other filamentary nanostructures for the construction of complex architectures made of various 1D building blocks.

We report a convenient and effective method to fabricate monolithic and conductive nanocomposites with various morphologies by directly infiltrating epoxy resin into the pores of ultralight graphene aerogels (ULGAs) with desired morphologies, followed by curing. These composites show linear ohmic behavior even with graphene filling content as low as 0.28 wt%. The electrical conductivity of the composites can be modulated in the range from 3.3 × 10−2 to 4.8 × 10−1 S m−1, superior to that of traditional composites by directly mixing the powdery graphene with the polymer. Furthermore, the conductivity of the nanocomposites remains unchanged in a wide range of temperature which may allow the structures to be promising candidates as resistance elements for integrated circuits (ICs).

Nanostructured CoSe2 anode materials hold great promise for sodium ion batteries (SIBs), drawing much recent research attention. However, high-performance CoSe2 based anodes are still challenging to obtain. Herein, using zeolitic imidazolate framework-67 (ZIF-67) particles as the starting material, nondestructive hollow polyhedral hybrids have been synthesized successfully, which are structured from CNT-bridged carbon-coated CoSe2 nanospheres (CoSe2@C/CNTs). During the synthesis, the controlled in situ growth of CNTs introduces additional mesopores and open channels to the hybrids, and avoids serious agglomeration of the CoSe2 nanospheres. When employed as anode materials for SIBs with ether-based electrolyte, the CoSe2@C/CNTs show overwhelming merits over graphitic carbon-coated CoSe2 nanosphere polyhedral hybrids (CoSe2@GC) and bare CoSe2 particles. Specifically, the CoSe2@C/CNTs anode displays a high reversible capacity (∼470 mA h g−1 at 0.2 A g−1), a good rate capability of ∼373 mA h g−1 even at 10 A g−1, and an excellent cycling stability of over 1000 cycles with a capacity retention of ∼100% calculated from the 70th cycle. In addition, the electrochemical reaction dynamics analysis indicates a considerable capacitive contribution during the discharge–charge cycles, which is beneficial to enhance the rate capability and cyclability of the CoSe2@C/CNTs anode. Such results could be ascribed to the stable ether-based electrolyte-active material intermediates, improved electrolyte-active material contact, and shortened charge transfer paths afforded by the unique hybrid nanostructure.