An effective method has been developed to remove ferromagnetic metals for the large scale purification of single-walled carbon nanotubes (SWNTs) produced by arc-discharge, which are generally regarded as the most challenging soot to remove metallic catalyst residues. The efficiency of the method has been evaluated by electron microcopy, magnetic and thermogravimetric analysis. As a result, at least 200 mg SWNTs with 99% purity were obtained from 3.6 g raw soot. The metal percentage dropped from ∼24.0% to ∼1.0% and the magnetic metal percentage in the purified sample was as low as 0.2 wt %. Nearly all ferromagnetic metals were eliminated from the process.

A new electrocatalyst exhibiting enhanced activity and stability is designed from SnO2-covered multiwalled carbon nanotubes coated with 85 wt % ratio Pt nanoparticles (NPs). This catalyst showed a mass activity 6.2 times as active as that of the commercial Pt/C for methanol oxidation, owing to the unique one-dimensional structure. Moreover, the durability and antipoisoning ability were also improved greatly. The enhanced intrinsic performance was ascribed to the densely connected networks of Pt NPs on the SnO2 NPs.Keywords: carbon nanotubes; electrochemical stability; methanol oxidation; Pt electrocatalysts; SnO2;

To overcome the low conductivity and large volume variation of metal oxide anodes, the electrode microstructure design for these metal oxides appeared to be the most promising strategy for achieving the desired Li storage performance. In this article, we report on a rational design of the carbon/SnO2 microstructure, in which porous SnO2 nanoparticles are encapsulated into the graphene matrix and additional carbon coating layer. As an anode material for LIBs, the as-prepared G@p-SnO2@C composite exhibited an ultra-long cycling life up to 1800 cycles. It can sustain high specific capacities of 602 and 418 mA h g−1 at 1.5 A g−1 after 1000 and 1800 cycles, respectively. The excellent battery performance could be attributed to the unique architecture of this composite, which enhances electrical conductivity, provides sufficient interior void space to accommodate the volume variation of SnO2, mitigates the aggregation, and preserves the integrity of electrodes during cycling.

•The PtRuCu6-A/C with an alloy core and surface Pt–Ru defects was synthesized.•The PtRuCu6-A/C has higher mass and surface activity for methanol oxidation.•The synthetic strategy is helpful for preparing highly active Pt-based catalysts.Until now, Pt is commonly used as anode catalyst for methanol oxidation in direct methanol fuel cells. Here we report that chemical corrosion of PtRuCu6/C, which was prepared by microwave-polyol technique, promotes the activity of Pt for methanol oxidation. The PtRuCu6/C is chemically corroded, and the obtained sample is denoted as PtRuCu6-A/C. The PtRuCu6-A/C contains a Pt–Ru–Cu core and Pt–Ru shell with surface defects. The PtRuCu6-A/C has surface activity and mass activity 10.6 and 6.0 times higher than those of Pt/C for methanol oxidation. And the surface activity and mass activity of PtRuCu6-A/C are 3.3 and 3.9 times higher than those of PtRu/C for methanol oxidation. The enhanced activity of PtRuCu6-A/C is attributed to the surface defects and the stronger electronic modification of Pt. This facile preparation strategy provides a new route of synthesizing highly active catalysts for methanol oxidation.The PtRuCu6-A/C contains a Pt–Ru–Cu core and Pt–Ru shell with surface defects. The PtRuCu6-A/C has superior catalytic activity than those of Pt/C and PtRu/C for methanol oxidation. The enhanced activity of PtRuCu6-A/C is attributed to the surface Pt–Ru defects and the stronger electronic modification of Pt. The preparation strategy provides a new route of synthesizing highly Pt-based active catalysts for methanol oxidation.

We report an efficient method for enriching high-purity metallic single-walled carbon nanotubes (m-SWCNTs) by using NO2 as oxidant to remove semiconducting components at 220 °C. After etching, m-SWCNTs with purity higher than 90% were obtained. The surviving m-SWCNTs retain an intact structure without any extra defects on their surface.

Platinum is commonly chosen as an electrocatalyst used for oxygen reduction reaction (ORR). In this study, we report an active catalyst composed of MnO2 nanofilms grown directly on nitrogen-doped hollow graphene spheres, which exhibits high activity toward ORR with positive onset potential (0.94 V vs RHE), large current density (5.2 mA cm–2), and perfect stability. Significantly, when it was used as catalyst for air electrode, a zinc–air battery exhibited a high power density (82 mW cm–2) and specific capacities (744 mA h g–1) comparable to that with Pt/C (20 wt %) as air cathode. The enhanced activity is ascribed to the synergistic interaction between MnO2 and the doped hollow carbon nanomaterials. This easy and cheap method paves a way of synthesizing high-performance electrocatalysts for ORR.Keywords: nitrogen-doped graphene; oxygen reduction reaction; synergistic effect; Zn−air battery;

Due to the high cost of Pt-based materials used in the electrocatalysis of the oxygen reduction reaction (ORR), an alternative composed of non-precious metals is highly desirable. Herein a hybrid with cobalt monoxide nanocrystals spatially confined in holey N-doped carbon nanowires (CoO/NCWs) was synthesized via metal oxide assisted surface pitting of chemical vapor deposited carbon nitrogen nanowires and colloidal assembly. The catalyst consists of a Co2+ enriched surface and delivers a remarkably higher ORR electrocatalytic activity and stability than its surface smooth N-doped carbon nanotube supported counterpart, with a kinetically limited current density (30.3 mA cm−2 at 0.7 V) nearly three times that of the latter. It also outperformed the commercial Pt/C catalyst. As characterized by cyclic voltammetry and XPS, the enlarged interfacial area by spatially confined hybridization is believed to be responsible for the improved ORR performance, which might create more active catalytic sites for the ORR. We propose that in-depth consideration of interfacial construction is essential when designing carbon supported metal oxide catalysts for the ORR in alkaline media.

Porous cobalt–nitrogen-doped hollow graphene spheres were prepared by a template synthesis method. As a catalyst for the oxygen reduction reaction, they exhibit an excellent electrocatalytic activity, superior methanol tolerance and strong durability, not only in alkaline solution, but also in acidic solution. The unprecedented electrocatalytic performance of the catalyst is attributed to the well-defined morphology, high specific surface area (321 m2 g−1), large pore volume (1.8 cm3 g−1) and homogeneous distribution of cobalt–nitrogen active sites.

Hierarchically nanoporous N-doped carbon nanowires (N-CWs) were prepared by a novel space-confinement-induced assembly strategy, for which nitrogen-enriched pyrimidine and anodic aluminium oxide (AAO) template bearing metal oxides are employed as precursor and nanoscale channels, respectively, and the Fe/Co metal oxide not only blocks the AAO surface from the original surface-templating carbonization, but also introduces nanoporosity with acid etching. Thus-obtained carbon nanowires composed of N-doped graphene-like carbon nanosheets not only contain a high N content (up to ∼12%), but also possess a hierarchically meso/microporous structure (∼1.3 cm3 g−1) with high specific surface area (∼455 m2 g−1). This protocol allows for the simultaneous optimization of graphitization, porous structure and surface functionalization. As a result, the prepared N-CWs demonstrate an attractive electrocatalytic capability towards oxygen reduction reaction (ORR). Specifically, in addition to the improved kinetic current density and overpotential, the N-CWs prepared at 700 °C show the optimized ORR performance with an electron-transfer number of ∼4.0, which very close to that of a commercial Pt/C catalyst.

We artfully synthesized Pt defects and SnO2 on the surface of a carbon-supported Pt2SnCu nanoalloy (Pt2SnCu–O-A/C) by in situ surface oxidation and acid treatment. The Pt2SnCu–O-A/C modified in this way exhibits excellent electrocatalytic activities for the ethanol oxidation reaction (EOR) in comparison to the commercial Pt/C and PtRu/C. The surface activity and mass activity are, respectively, 3.1 and 4.3 times greater than those of Pt/C. The enhanced activity for ethanol oxidation is attributed to the synergistic catalytic effect of Pt defects and SnO2.

The poor conductivity of anodic carbon materials at low temperature hampers their high-level applications in Li ion batteries (LIBs). Introducing some reliable metals with good electrical conductivity into anodes could alleviate these problems. In this work, the novel composites of Fe-added Fe3C carbon nanofibers (Fe/Fe3CCNFs) were synthesized via facile electrospinning method and used as anode materials for LIBs. The resulting anodes with Fe/Fe3CCNF materials exhibited a high reversible capacity of 500 mAh g−1 tested at 200 mA g−1 even after 70 cycles and excellent performance at room temperature. Importantly, it delivered a high capacity of 250 mAh g−1 at 400 mA g−1 even after 55 cycles at a low temperature of −15 °C. The superior low-temperature electrochemical performance of the Fe/Fe3CCNF anodes is associated with an improved effect of the highly conducting Fe at low temperature.The assembled lithium batteries with novel composites of Fe/Fe3C carbon nanofibers as anodes can afford excellent low-temperature electrochemical performance.

Polypyrrole (PPy)-modified CuO nanocomposites (NCs) with various shell structures have been synthesized by controlling the polymerization time of pyrrole in the presence of leaf-like CuO nanobelts (NBs) as wire templates. The synthesized CuO/PPy NCs and CuO NBs are characterized by XRD, FT–IR, TGA, SEM, TEM, STEM, and EDX line analysis/elemental mapping. The formation mechanism of CuO/PPy core–shell NCs is also illustrated. Electrochemical lithium-storage properties of all the products are evaluated by using them as anode materials for Li-ion batteries (LIBs). It is found that the polymerization time of pyrrole plays a significant role in affecting the shell structures and subsequent lithium-storage properties of the hybrid CuO/PPy NCs. With the extension of polymerization time, CuO/PPy NCs gradually form typical core–shell structures, where the doped PPy with increasing content is steadily and uniformly coated on the CuO surface. Correspondingly, the discharge/charge capacity and cyclic durability of CuO/PPy NCs are significantly enhanced. For the core–shell NCs made by the 3 h polymerization, a greatly improved initial capacity of 1114 mAh g–1 and a high reversible capacity of 760 mAh g–1 are achieved, which are much better than those of the bare CuO NBs and the NCs without core–shell structures. The improved performance of core–shell CuO/PPy NCs can be attributed to their advantageous structure features that buffer volume variations of the rigid CuO, allow short Li-ion diffusion length, form good interface interaction between PPy and CuO for charge transfer, and avoid direct contacts between CuO and electrolytes during charge–discharge processes. This study indicates that the structural tuning of polymer/metal oxide composites by controlling the polymerization time is a simple and promising way to improve the electrode performance of NCs for energy storage.Keywords: Composite materials; Conducting polymers; Electrochemical properties; Green synthesis; Lithium-ion batteries; Metal oxides; Polymerization

•β-FeOOH/MWNT catalysts for lithium–O2 batteries have been synthesized by a wet chemical method.•The obtained electrodes exhibit high specific capacity, good rate capability and cycle stability.•The enhanced performance is ascribed to the synergetic effects between MWNTs and β-FeOOH.A novel composite of β-FeOOH nanospindles coated on multi-walled carbon nanotubes (β-FeOOH/MWNTs) has been synthesized via a wet chemical method and used as electrocatalysts for the cathodes of Li–O2 batteries (LOBs). The β-FeOOH/MWNT cathodes can afford a high reversible capacity of 6000 mA h g−1 tested at 200 mA g−1 and cycle stability for 19 cycles with a reversible capacity of 600 mA h g−1 and good rate capability. The LOB performance should be benefited from the fast kinetics of electron transport through the MWNT support and the electro-catalytic activity provided by the β-FeOOH nanospindles. The preliminary result manifests that the composites of β-FeOOH/MWNTs are promising cathode electrocatalysts for LOBs.Composites of β-FeOOH/MWNT are synthesized and used as high performance catalysts for lithium–O2 batteries.

•The PtCu3-A/C with a Pt–Cu alloy core and surface Pt defects was synthesized.•The PtCu3-A/C has higher mass and surface activity for methanol oxidation.•The chemical dealloying is suitable to prepare highly active Pt-based catalysts.Carbon supported Pt–Cu catalyst (PtCu3-A/C) with surface enriched Pt was synthesized by the microwave-polyol technique following acid-treatment. Physical characterizations indicate that the PtCu3-A/C has the core of Pt–Cu alloy below the Pt shell. Electrochemical measurements show that the surface activity of PtCu3-A/C is 5.4 and 1.7 times as high as that of the commercial Pt/C and PtRu/C for methanol oxidation, respectively. And the mass activity of PtCu3-A/C is 5.0 and 3.2 times as high as that of the commercial Pt/C and PtRu/C for methanol oxidation, respectively. The enhanced activity of PtCu3-A/C is attributed to the surface defects and the modified electronic properties of Pt. This facile preparation strategy provides a new route of synthesizing highly active catalyst for methanol oxidation.The PtCu3-A/C contained a Pt–Cu core and Pt shell with surface defects. The PtCu3-A/C has mass activity and surface activity 5.0 and 5.4 times higher than those of Pt/C for methanol oxidation. And the mass activity and surface activity of PtCu3-A/C are 3.2 and 1.7 times higher than those of PtRu/C for methanol oxidation. The enhanced activity of PtCu3-A/C is attributed to the surface defects and the modified electronic properties of Pt. This facile preparation strategy provides a new route of synthesizing highly active catalyst for methanol oxidation.

3D hierarchical porous graphene laminates (GLs) with high surface area and porosity were synthesized through self-assembly of functionalized graphene oxide embedded with SiO2 in situ. Thus, as a cathode material for Li–S batteries, the obtained GLs loaded with 73 wt% sulfur, deliver a high discharge capacity of 800 mA h g−1 after 100 cycles at a current density of 0.2C.

The hybrid materials of cobalt doped graphitic carbon nitride (g-C3N4) attached on single-walled carbon nanotubes (SWCNTs) were synthesized by a simple pyrolysis process. Electrochemical measurements revealed that the composites exhibited excellent electrocatalytic activity for oxygen reduction reaction (ORR), with a more positive onset potential (−0.03 V), half-wave potential (−0.15 V), high efficiency four-electron process (n = 3.97) and much higher stability than that of commercial Pt/C catalysts in alkaline media. The ORR activity mainly originates from the strong coupling of Co-g-C3N4 derived active sites on the SWCNTs.

A new layered porous nanostructure with ZrO2 nanoparticles attached on the reduced graphene oxide (ZrO2/RGO) was synthesized by a facile solvothermal process. The resulting ZrO2/RGO composite with well-designed mesoporous structure and excellent conductivity not only served as scaffold to house sulfur but also as polysulfide reservoir for lithium–sulfur batteries. This nanostructured S@ZrO2/RGO electrode exhibits enhanced cycling stability, high specific capacity, and superior coulombic efficiency.

Designing an efficient catalyst is essential to improve the electrochemical performance for Li–O2 batteries. In this study, the novel composites of Fe/Fe3C carbon nanofibers (Fe/Fe3C–CNFs) were synthesized via a facile electrospinning method and used as cathode catalysts for Li–O2 batteries. Owing to their favorable structures and desirable bifunctional catalytic activities, the resulting cathodes with a Fe/Fe3C–CNF catalyst exhibited superior electrochemical performance with high specific capacity, good rate capability and cycle stability. It is revealed that the synergistic effect of the fast kinetics of electron transport provided by the CNF support and the high electro-catalytic activity provided by the Fe/Fe3C composites resulted in the excellent performance for Li–O2 batteries. The preliminary result manifests that the composites of Fe/Fe3C–CNFs are promising cathode electrocatalysts for Li–O2 batteries.

Ternary spinel MFe2O4 (M = Co, Ni) nanoparticles coated on multi-walled carbon nanotubes (MFe2O4/CNTs) were prepared via a simple hydrothermal method. Owing to their favorable structures and desirable bi-functional oxygen reduction and evolution activities, the resulting MFe2O4/CNT (M = Co, Ni) composites as electrocatalysts for the cathodes deliver better electrochemical performance during the discharge and charge processes compared with that of the pure carbon of ketjen black (KB). The good performance can be attributed to the excellent catalytic activity of highly dispersed MFe2O4 (M = Co, Ni) nanoparticles and facile electron transport by supporting CNTs. This preliminary result manifests that the ternary spinel MFe2O4/CNT (M = Co, Ni) composites are promising cathode electrocatalysts for non-aqueous Li–O2 batteries.

Designing an effective microstructural cathode combined with a highly efficient catalyst is essential for improving the electrochemical performance of Li-O2 batteries (LOBs), especially for long-term cycling. We present a nickel foam-supported composite of Pt nanoparticles (NPs) coated on self-standing carbon nanotubes (CNTs) as a binder-free cathode for LOBs. The assembled LOBs can afford excellent electrochemical performance with a reversible capacity of 4050 mAh/g tested at 20 mA/g and superior cyclability for 80 cycles with a limited capacity of 1500 mAh/g achieved at a high current density of 400 mA/g. The capacity corresponds to a high energy density of ∼3000 Wh/kg. The improved performance should be attributed to the excellent catalytic activity of highly dispersed Pt NPs, facile electron transport via loose CNTs connected to the nickel foam current collector, and fast O2 diffusion through the porous Pt/CNTs networks. In addition, some new insights from impedance analysis have been proposed to explain the enhanced mechanism of LOBs.Keywords: electrochemical performance; Li-O2 batteries; Pt/CNTs-NF cathodes; synergistic effect

•The prepared AC-PtCu–4/C has higher density of surface defects.•The AC-PtCu–4/C has higher mass and surface activity for ethanol oxidation.•The AC-PtCu–4/C can enhance the C–C bond cleavage of ethanol to generate CO2.•The chemical dealloying is suitable to prepare highly active Pt-based catalysts.•The electrochemical dealloying results in large size and aggregation of particles.The Pt–Cu alloy/C (AC-PtCu-4/C) with uniform nanoparticles and high density of surface defects was synthesized by the microwave-polyol technique following acid-treatment. The AC-PtCu-4/C contained much higher density of surface defects than did the commercial Pt/C. Electrochemical characterization demonstrated that the AC-PtCu-4/C exhibited mass activity and surface activity 4.8 and 3.9 times higher than those of Pt/C for ethanol oxidation. Moreover, the AC-PtCu-4/C can enhance the C–C bond cleavage of ethanol to generate CO2 2.47 times more than that of Pt/C under the same conditions, as evidenced by in situ FTIR reflection spectroscopy.The AC-PtCu-4/C contained much higher density of surface defects than did the commercial Pt/C. Electrochemical characterization demonstrated that the AC-PtCu-4/C exhibited mass activity and surface activity 4.8 and 3.9 times higher than those of Pt/C for ethanol oxidation. Moreover, the AC-PtCu-4/C can enhance the C–C bond cleavage of ethanol to generate CO2 2.47 times more than that of Pt/C under the same conditions, as evidenced by in situ FTIR reflection spectroscopy.

A novel single-walled carbon nanohorn–sulfur composite with high sulfur content up to 76% was synthesized via a straightforward melt-infusion strategy. The composite exhibits excellent electrochemical performance with a high capacity of 693 mA h g−1 retained after 100 cycles at a high rate of 1.6 A g−1.

•Pt nanoparticles are well dispersed on single-walled carbon nanotubes (SWCNTs).•Pt nanoparticles have narrow size distribution.•The Pt/SWCNTs has larger electrochemical surface area than the commercial Pt/C.•The Pt/SWCNTs is highly active for methanol and ethanol oxidation.Both narrow size and highly homogeneous distribution of Pt nanoparticles (NPs) are achieved on single-walled carbon nanotubes functionalized by carboxylic groups using ethylene glycol as reducing agents. Transmission electron microscope images show that the Pt NPs have an average particle size of about 2.1 nm and are homogeneously dispersed on the surface of SWCNTs. The electrochemical measurements show the resulting Pt NPs on SWCNTs (Pt/SWCNTs) exhibit competitively catalytic activity for methanol and ethanol electro-oxidation compared to Pt NPs on carbon black (Pt/C). The peak current density of Pt/SWCNTs for methanol and ethanol oxidation is 3.8 and 2.3 times higher than that of Pt/C. The most striking merit of the Pt/SWCNTs is its much better anti-poisoning ability than the Pt/C. The significantly improved performance is ascribed to more anchoring sites of SWCNTs, which improve the dispersion of Pt NPs and increase the utilization of Pt. The proposed synthesis route provides a facile, feasible and effective method for developing highly efficient electro-catalysts.Highly dispersed Pt nanoparticles on single-walled carbon nanotubes (SWCNTs) were synthesized (Pt/SWCNTs). The Pt/SWCNTs has larger electrochemical surface area and higher catalytic activity toward the oxidation of methanol and ethanol compared with the commercial Pt/C (Pt/C). The reason may be due to that functionalized SWCNTs with carboxylic groups result in both narrow size and highly homogeneous distribution of Pt NPs on SWCNTs, which makes more Pt atoms be utilized for the oxidation of methanol and ethanol.

Li2MnSiO4 possesses a high theoretical capacity of 332 mA h g−1 as a lithium battery cathode, but it suffered from rapid capacity fading due to the structural instability and manganese dissolution during cycles. Herein, we developed a unique reduced graphene oxide (RGO)@Li2MnSiO4@C composite as a cathode material for lithium ion batteries. Under the double protection from RGO and carbon coating, Li2MnSiO4 demonstrated outstanding electrochemical performance with a high capacity of 290 mA h g−1 at 0.05 C, and a long cycling life up to 700 cycles at 1 C.

Development of inexpensive and sustainable cathode catalysts that can efficiently catalyze the oxygen reduction reaction (ORR) is of significance in practical application of fuel cells. Herein we report the synthesis of sulfur and nitrogen dual-doped, ordered mesoporous carbon (SN-OMCs), which shows outstanding ORR electrocatalytic properties. The material was synthesized from a surface-templating process of ferrocene within the channel walls of SBA-15 mesoporous silica by carbonization, followed by in situ heteroatomic doping with sulfur- and nitrogen-containing vapors. After etching away the metal and silica template, the resulting material features distinctive bimodal mesoporous carbon frameworks with high nitrogen Brunauer–Emmett–Teller specific surface area (of up to ∼1100 m2/g) and uniform distribution of sulfur and nitrogen dopants. When employed as a noble-metal-free electrocatalyst for the ORR, such SN-OMC shows a remarkable electrocatalytic activity; improved durability and better resistance toward methanol crossover in oxygen reduction can be observed. More importantly, it performs a low onset voltage and an efficient nearly complete four-electron ORR process very similar to the observations in commercial 20 wt % Pt/C catalyst. In addition, we also found that the textural mesostructure of the catalyst has superseded the chemically bonded dopants to be the key factor in controlling the ORR performance.Keywords: doped carbons; electrocatalyst; fuel cells; mesoporous; non-precious-metal catalyst; ORR;

Coaxial MWNTs@MnO2 confined in conducting polypyrrole (PPy) has been synthesized through an in situ polymerization of pyrrole monomers in the presence of prepared MWNTs@MnO2. As an anode in lithium batteries (LIBs), the obtained MWNTs@MnO2@PPy shows a high reversible capacity of 530 mA h g−1 tested at 1000 mA g−1 even after 300 cycles and an excellent rate performance. The superior electrochemical performance of the nanocable MWNTs@MnO2@PPy is associated with a synergistic effect of the MWNT matrix and the highly conducting PPy coating layer. This nanocable configuration not only facilitates electron conduction but also maintains the structural integrity of active materials. In addition, an analysis of the AC impedance spectroscopy and the corresponding hypothesis for DC impedance confirm that such configuration can effectively enhance the charge-transfer efficiency and the lithium diffusion coefficient. Thus, PPy modification supplied a promising route to obtain manganese oxide based anode in order to achieve high-performance LIBs.Composites of MWNTs@MnO2 coated by PPy are synthesized via a facile method to improve the electrochemical performance.

Self-standing papers of N-doped carbon nanofibers loaded with SnCu–SnOx materials have been integratively prepared by electrospinning and directly used as anodes for lithium ion batteries. These anodes afford an excellent electrochemical performance with a reversible capacity of 470 mA h g−1 tested at 200 mA g−1 after 100 cycles.

Positively-charged single-walled carbon nanotubes (SWNTs) induced by physically encapsulated phosphorus demonstrate a little-promoted oxygen reduction reaction (ORR) electrocatalytic activity as compared with the empty SWNTs, including ORR current once increased at low potential and bare ORR-overpotential improvement. It implied that the substitutional doped P in hexagonal carbon framework should be the active center responsible for the excellent ORR activity concerning the P-doped carbon nanostructures reported recently.

•A modified Hummers' method was employed for cutting carbon nanotubes (CNT) short.•Many oxygen functional groups were meanwhile introduced in the short CNTs.•The short and oxygen-contained CNTs had good Li-ion performance as anode materials.An easy chemically cutting process, modified Hummers' method, was proposed to treat multi-walled carbon nanotubes, successfully cutting pristine long, entangled carbon nanotubes into hydrosoluble pieces, mostly less than 200 nm. This short, chemically oxidized carbon nanotube was then applied as an anode material for lithium-ion batteries. The as-prepared material possessed higher reversible capacity and coulombic efficiency. The intrinsic factors were explored by X-ray photoelectron spectroscopy and cyclic voltammetry.

In this report, a novel MWNT@Li2FeSiO4 coaxial nanocable was designed and used as a superior cathode material for lithium ion batteries. The shell Li2FeSiO4 delivered excellent rate performance with a high capacity of 180 mA h g−1 which remained after 120 cycles at 1 C.

A nanoflaky MnO2–graphene sheet (GS) hybrid material was mixed with a new binder, sodium alginate, and investigated as a cathode for lithium ion batteries. The MnO2 growing on the GS afforded an unprecedented high capacity of ∼230 mA h g−1 at a large current density of 200 mA g−1, even after more than 150 cycles.

Iron (II) phthalocyanine coated on single-walled carbon nanotubes was synthesized as a non-noble electrocatalyst for the oxygen reduction reaction (ORR). The composite exhibited higher activity than the commercial Pt/C catalyst, and excellent anti-crossover effect for methanol oxidation in the ORR.

Ferrocene-encapsulated single-walled carbon nanotubes (Fc@SWCNTs) uniformly coated with Fe2O3 (Fe2O3/Fc@SWCNTs) were synthesized and investigated as an anode material for lithium-ion batteries. The anode delivered a reversible capacity of ∼460 mA h g−1 after more than 600 cycles, even when measured at 1300 mA g−1, indicating the longest cycling performance for Fe2O3 anodes ever reported.

Nanocomposites of spinel LiMn2O4 and carbon nanotubes (CNTs) were in-situ prepared via a simple hydrothermal method by using MnO2/CNT and LiOH as reaction agent. The obtained composites demonstrated a homogenous dispersing of CNTs and LiMn2O4 nanocrystals, which combined both the advantages of the good crystallinity of LiMn2O4 and the excellent electron conductivity of CNTs. The LiMn2O4/CNT nanocomposites showed a good rate behavior and an excellent cycling retention for lithium ion batteries. A reversible discharge capacity of 115 mAh g− 1 at 1 C discharge rate based on the weight of LiMn2O4 was obtained. The good capacity retention nearly to 100% upon 100 cycles indicated that the LiMn2O4/CNT nanocomposites could act as promising cathode materials for lithium ion batteries.LiMn2O4/CNT nanocomposites with excellent electrochemical performance were prepared for lithium ion batteries via a hydrothermal method.Highlights► LiMn2O4/CNT nanocomposites were synthesized by a simple hydrothermal method. ► It combined both advantages of LiMn2O4 nanocrystals and the CNTs networks. ► It showed excellent electrochemical performance for lithium ion batteries.

Fe2O3 nanoparticles have been synthesized on the surface of an iron mesh current collector via a simple thermal oxidation progress within 6 min. Without any further treatment, this calcinated iron mesh current collector can be used directly as binder-free anode for lithium ion batteries. Electrochemical tests show the obtained Fe2O3 anode a good rate behavior and an excellent cycling retention. After 200 cycles, this binder-free Fe2O3 anode still can afford a discharge capacity of 1050 mAh g− 1 at the current density of 200 mA g− 1. The improvements of these electrochemical properties are attributed to the improved electron conductivity provided by the iron mesh current collector.Highlights► This paper developed a simple calcination route to prepare Fe2O3 anode within 6 min. ► Fe2O3 nanoparticles were synthesized by thermal oxidation of Fe current collector. ► This binder-free Fe2O3 anode performs excellent cycleability and rate performance. ► This Fe2O3 anode shows a high capacity of 1050 mAh g− 1 after 100 cycles.

In this report, we designed a novel SWNTs@SnO2@PPy coaxial nanocable as superior anode material for the first time. The nanosized SnO2 particles (2–3 nm) were uniformly distributed between one dimension SWNTs core and PPy shell, as confirmed by XRD, SEM, and TEM characterizations. As an anode material for lithium ion batteries, this composite delivered a high capacity of 823 mAh g–1 at 150 mA g–1 after 100 cycles. Even at a high rate of 3000 mA g–1, a reversible capacity of 480 mAh g–1 still remained. Furthermore, the SnO2 in this composite exhibited a large capacity of 1486 mAh g–1 as well as good capacity retention of 95% over 100 cycles. This result indicated the completely reversible reaction between Li4.4Sn and SnO2, greatly improving the theoretical capacity of SnO2 from 782 to 1493 mAh g–1.

A simple method for the preparation of highly dispersive Pt atoms on the surface of RuNi nanoparticles is developed by the deposition of Pt on single-walled carbon nanotube supported RuNi nanoparticles. The anodic peak current density of the nanocomposite is 8.0 times higher than that of Pt/C for ethanol oxidation, and it has a significantly lower onset potential than Pt/C for ethanol oxidation.

In this article, a simple route for modifying the morphology and lithium storage performance of iron oxide composites has been developed by using Ni2+ or Co2+ to substitute Fe3+. The as-prepared MFe2O4 (M = Ni, Co) nanoparticles (∼5 nm) were uniformly distributed on the surface of the carbon substrates. When evaluated as anode materials for lithium ion batteries, these composites showed high specific capacity, excellent cycling performance and rate capabilities. For example, the CoFe2O4/graphene sheets composite delivered a high reversible capacity of 950 mA h g−1, even higher than the theoretical value, as well as excellent cycling performance.

A novel composite of Fe2O3 and single-walled carbon nanohorns (SWCNHs) was firstly developed via a simple hydrothermal method. As an anode material for lithium ion batteries, a Fe2O3/SWCNHs composite shows excellent rate performance and cycle stability, even at a high current density of 1000 mA g−1.

Ferrocene-encapsulated single-walled carbon nanotubes (Fc@SWNTs) are developed as carriers for attaching SnO2. When Fc@SWNTs coated with SnO2 nanoparticles were used as anode material in lithium ion batteries, the reversible capacity remained over 900 mA h g−1 after 40 cycles, much higher than other carbon nanomaterials.

A ternary thin film electrode was created by coating manganese oxide onto a network composed of single-walled carbon nanotubes and single-walled carbon nanohorns. The electrode exhibited a porous structure, which is a promising architecture for supercapacitors applications. The maximum specific capacitances of 357 F/g for total electrode at 1 A/g were achieved in 0.1 M Na2SO4 aqueous solution.Keywords: MnO2; porous structure; supercapacitors; SWNH; SWNT; thin film;

A simple process was developed for increasing the semiconducting component of single-walled carbon nanotubes (SWCNTs) with narrowed diameter distribution through directly eliminating metallic SWCNTs and semiconducting SWCNTs (s-SWCNTs) with smaller diameters in transparent conducting films of SWCNTs. The process is based on the oxidation with diazonium reagents and air. The transparent films of s-SWCNTs obtained had high-purity and retained the original structure. The possible mechanism of the process is discussed.

Manganese dioxide (MnO2) nanoflakes were uniformly coated on multi-walled carbon nanotubes (MWNTs) by immersing MWNTs into an aqueous KMnO4 solution. Directly using the MnO2/MWNT composites (containing 40 wt.% MWNTs) as lithium-air battery electrodes enhances kinetics of the oxygen reduction and evolution reactions, thereby effectively improving energy efficiency and reversible capacity.Research highlights► MnO2 nanoflakes uniformly coated on MWNTs were studied as cathode materials in lithium-air batteries. ► MnO2/MWNTs deliver discharge capacity of 796 mAh/g(electrode). ► MnO2/MWNTs composites effectively improved energy efficiency and reversible capacity in lithium-air batteries.

A novel composite of SnO2 and single-walled carbon nanohorns (SWCNHs) has been synthesized via a simple wet chemical method. SnO2 nanoparticles (2–3 nm) were homogeneously distributed on the surface of spherical SWCNHs, as confirmed by transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. When evaluated as an anode material for lithium ion batteries, this SnO2/SWCNHs composite shows superior electrochemical performance with high capacity, excellent cyclic stability and good rate performance, owing to the intimate interaction between the SWCNH matrix and nanosized SnO2. It delivered a high capacity of 530 mAh g−1 even after 180 cycles under a current density of 500 mA g−1, which is better than most SnO2 composites.

Here, we investigated the lithium insertion/extraction mechanism in single-walled carbon nanotubes (SWNTs) based both on the empty SWNTs and filled SWNTs, including ferrocene-filled SWNTs (Fc@SWNTs) and C60-filled SWNTs (C60@SWNTs). SWNTs, C60@SWNTs and Fc@SWNTs were systematically investigated as anode materials for Li-ion batteries. The electrochemical performance of the C60@SWNT electrode was slightly better than that of the SWNTs, and the reversible capacity of Fc@SWNTs per unit weight was ∼1.7 times greater than that of the empty SWNTs due to its special tube internal structure. It was proved that the dominant reversible sites for lithium storage in empty SWNTs are the trigonal interstitial channels. Meanwhile, lithium can reversibly insert or extract the inner channels of the tubes after doping with ferrocene; the reversible capacity presented in the inner channels of Fc@SWNTs is about Li1.13C6.

By a simple helium arc-discharged method, we explored the suitable conditions for producing graphene sheets by regulating gas pressures and currents. Graphene sheets containing monolayer, bilayer and few layers were obtained. The as-obtained graphene sheets were verified by transmission electron microscopy (TEM), electron diffraction and scanning electron microscopy (SEM).

In this work, we analyzed the effect of the catalyst metals with various forms on the thermal-oxidative stability of single-walled carbon nanotubes (SWCNTs) by using thermogravimetric analysis (TGA), transmission electron microscopy (TEM), and electronic dispersive X-ray spectroscopy (EDX). The results indicate that the catalyst metal nanoparticles encapsulated inside multi-shelled graphite particles play a main role on destabilizing SWCNTs during their air oxidation. We also compared the thermal stability of SWCNTs in the cloth-like soot and the cotton-like soot produced by arc-discharge. The SWCNTs in the cotton-like soot are of higher thermal-oxidation stability than that in the cloth-like soot due to fewer multi-shelled graphite nanoparticles encapsulating metal nanoparticles.

Five kinds of nanocarbon materials (NCMs)—single-walled carbon nanotubes (SWNTs), C60@SWNTs (C60-peapod), multiwalled carbon nanotubes (MWNTs), graphite nanoflakes, and graphite nanoparticles containing some MWNTs—were systematically investigated as anode materials for Li ion batteries via scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and a variety of electrochemical testing techniques. Galvanostatic charge−discharge indicated that lithium storage capacity, Coulombic efficiency, and cyclability strongly depended on both the subtle structures and the subsequent treatments of NCMs. It was proved by cyclic voltammetry that lithium oxidation potentials increase with the increase of the length of lithium reversible insertion/extraction route. Raman spectroscopy revealed a mechanism of lithium insertion/extraction in SWNT and C60-peapod electrodes, suggesting that lithium can enter the inner space of the tubes, the trigonal interstitial channels of the bundles, and the intercalation site between adjacent tubes, and that the dominant reversible sites for lithium storage are the trigonal interstitial channels.

Phosphorus was successfully introduced into the channels of single-walled carbon nanotubes (SWNTs), forming phosphorus chains, which selectively modified the band structure of SWNTs with different diameters.

Is it possible to form few-layer graphene by direct merging single-walled carbon nanotubes (SWNTs), which are generally regarded as rolled single-layered graphene? In this study, we reported the structure transformation of SWNTs to few-layer graphene assisted by the encapsulated ferrocene molecules. High resolution transmission electron microscopy imaging and Raman spectra revealed that the transformation is quite sensitive to the diameters of the host SWNTs and also the annealing temperature. The encapsulated ferrocene molecules played a key role during the transformation.

A new SnO2-Fe2O3/SWCNTs (single-walled carbon nanotubes) ternary nanocomposite was first synthesized by a facile hydrothermal approach. SnO2 and Fe2O3 nanoparticles (NPs) were homogeneously located on the surface of SWCNTs, as confirmed by X-ray diffraction (XRD), transmission electron microscope (TEM) and energy dispersive X-ray spectroscopy (EDX). Due to the synergistic effect of different components, the as synthesized SnO2-Fe2O3/SWCNTs composite as an anode material for lithium-ion batteries exhibited excellent electrochemical performance with a high capacity of 692 mAh·g−1 which could be maintained after 50 cycles at 200 mA·g−1. Even at a high rate of 2000 mA·g−1, the capacity was still remained at 656 mAh·g−1.SnO2 and Fe2O3 nanoparticles homogeneously coated on the surface of single-walled carbon nanotubes exhibited excellent electrochemical performance when used as anode materials for lithium-ion batteries.Download full-size image

•An aptasensor based on DNA-cappeds-SWCNTs for detection of exosomes was proposed.•The s-SWCNTs that are rich in carboxyl groups and water solubility were synthesized.•The peroxidase activity of s-SWCNTs was improved and tuned by DNA.•The factors of peroxidase activity of DNA-capped s-SWCNTs were studied in detailed.Recently, many studies have shown the potential use of circulating exosomes as novel biomarkers for monitoring and predicting a number of complex diseases, including cancer. However, reliable and cost-effective detection of exosomes in routine clinical settings, still remain a difficult task, mainly due to the lack of adequately easy and fast assay platforms. Therefore, we demonstrate here the development of a visible and simple method for the detection of exosomes by integrating single-walled carbon nanotubes that being excellent water solubility (s-SWCNTs) and aptamer. Aptamers, specific to exosomes transmembrane protein CD63, are absorbed onto the surface of s-SWCNTs and improve the minic peroxidase activity of s-SWCNTs, which can efficiently catalyze H2O2-mediated oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) and lead to a change from colorless to blue in solution. However, after adding exosomes, the aptamers are bound with CD63, leaving from the surface of s-SWCNTs through conformational changes, which results the color of solution from deep to moderate, and this can be observed by the naked eye and monitored by UV–vis spectrometry. Under optimal conditions, the linear range of exosomes is estimated to be 1.84×106 to 2.21×107 particles/μL with a detection of limit (LOD) of 5.2×105 particles/μL. Consequently, a visible and simple approach detecting exosomes is successfully constructed. Moreover, this proposed colorimetric aptasensor can be universally applicable for the detection of other targets by simple change the aptamer.

A nanoflaky MnO2–graphene sheet (GS) hybrid material was mixed with a new binder, sodium alginate, and investigated as a cathode for lithium ion batteries. The MnO2 growing on the GS afforded an unprecedented high capacity of ∼230 mA h g−1 at a large current density of 200 mA g−1, even after more than 150 cycles.

Designing an efficient catalyst is essential to improve the electrochemical performance for Li–O2 batteries. In this study, the novel composites of Fe/Fe3C carbon nanofibers (Fe/Fe3C–CNFs) were synthesized via a facile electrospinning method and used as cathode catalysts for Li–O2 batteries. Owing to their favorable structures and desirable bifunctional catalytic activities, the resulting cathodes with a Fe/Fe3C–CNF catalyst exhibited superior electrochemical performance with high specific capacity, good rate capability and cycle stability. It is revealed that the synergistic effect of the fast kinetics of electron transport provided by the CNF support and the high electro-catalytic activity provided by the Fe/Fe3C composites resulted in the excellent performance for Li–O2 batteries. The preliminary result manifests that the composites of Fe/Fe3C–CNFs are promising cathode electrocatalysts for Li–O2 batteries.

We artfully synthesized Pt defects and SnO2 on the surface of a carbon-supported Pt2SnCu nanoalloy (Pt2SnCu–O-A/C) by in situ surface oxidation and acid treatment. The Pt2SnCu–O-A/C modified in this way exhibits excellent electrocatalytic activities for the ethanol oxidation reaction (EOR) in comparison to the commercial Pt/C and PtRu/C. The surface activity and mass activity are, respectively, 3.1 and 4.3 times greater than those of Pt/C. The enhanced activity for ethanol oxidation is attributed to the synergistic catalytic effect of Pt defects and SnO2.

A novel composite of Fe2O3 and single-walled carbon nanohorns (SWCNHs) was firstly developed via a simple hydrothermal method. As an anode material for lithium ion batteries, a Fe2O3/SWCNHs composite shows excellent rate performance and cycle stability, even at a high current density of 1000 mA g−1.

Ferrocene-encapsulated single-walled carbon nanotubes (Fc@SWNTs) are developed as carriers for attaching SnO2. When Fc@SWNTs coated with SnO2 nanoparticles were used as anode material in lithium ion batteries, the reversible capacity remained over 900 mA h g−1 after 40 cycles, much higher than other carbon nanomaterials.

Porous cobalt–nitrogen-doped hollow graphene spheres were prepared by a template synthesis method. As a catalyst for the oxygen reduction reaction, they exhibit an excellent electrocatalytic activity, superior methanol tolerance and strong durability, not only in alkaline solution, but also in acidic solution. The unprecedented electrocatalytic performance of the catalyst is attributed to the well-defined morphology, high specific surface area (321 m2 g−1), large pore volume (1.8 cm3 g−1) and homogeneous distribution of cobalt–nitrogen active sites.

Hierarchically nanoporous N-doped carbon nanowires (N-CWs) were prepared by a novel space-confinement-induced assembly strategy, for which nitrogen-enriched pyrimidine and anodic aluminium oxide (AAO) template bearing metal oxides are employed as precursor and nanoscale channels, respectively, and the Fe/Co metal oxide not only blocks the AAO surface from the original surface-templating carbonization, but also introduces nanoporosity with acid etching. Thus-obtained carbon nanowires composed of N-doped graphene-like carbon nanosheets not only contain a high N content (up to ∼12%), but also possess a hierarchically meso/microporous structure (∼1.3 cm3 g−1) with high specific surface area (∼455 m2 g−1). This protocol allows for the simultaneous optimization of graphitization, porous structure and surface functionalization. As a result, the prepared N-CWs demonstrate an attractive electrocatalytic capability towards oxygen reduction reaction (ORR). Specifically, in addition to the improved kinetic current density and overpotential, the N-CWs prepared at 700 °C show the optimized ORR performance with an electron-transfer number of ∼4.0, which very close to that of a commercial Pt/C catalyst.

In this article, a simple route for modifying the morphology and lithium storage performance of iron oxide composites has been developed by using Ni2+ or Co2+ to substitute Fe3+. The as-prepared MFe2O4 (M = Ni, Co) nanoparticles (∼5 nm) were uniformly distributed on the surface of the carbon substrates. When evaluated as anode materials for lithium ion batteries, these composites showed high specific capacity, excellent cycling performance and rate capabilities. For example, the CoFe2O4/graphene sheets composite delivered a high reversible capacity of 950 mA h g−1, even higher than the theoretical value, as well as excellent cycling performance.

Iron (II) phthalocyanine coated on single-walled carbon nanotubes was synthesized as a non-noble electrocatalyst for the oxygen reduction reaction (ORR). The composite exhibited higher activity than the commercial Pt/C catalyst, and excellent anti-crossover effect for methanol oxidation in the ORR.

In this report, a novel MWNT@Li2FeSiO4 coaxial nanocable was designed and used as a superior cathode material for lithium ion batteries. The shell Li2FeSiO4 delivered excellent rate performance with a high capacity of 180 mA h g−1 which remained after 120 cycles at 1 C.

Li2MnSiO4 possesses a high theoretical capacity of 332 mA h g−1 as a lithium battery cathode, but it suffered from rapid capacity fading due to the structural instability and manganese dissolution during cycles. Herein, we developed a unique reduced graphene oxide (RGO)@Li2MnSiO4@C composite as a cathode material for lithium ion batteries. Under the double protection from RGO and carbon coating, Li2MnSiO4 demonstrated outstanding electrochemical performance with a high capacity of 290 mA h g−1 at 0.05 C, and a long cycling life up to 700 cycles at 1 C.

Ternary spinel MFe2O4 (M = Co, Ni) nanoparticles coated on multi-walled carbon nanotubes (MFe2O4/CNTs) were prepared via a simple hydrothermal method. Owing to their favorable structures and desirable bi-functional oxygen reduction and evolution activities, the resulting MFe2O4/CNT (M = Co, Ni) composites as electrocatalysts for the cathodes deliver better electrochemical performance during the discharge and charge processes compared with that of the pure carbon of ketjen black (KB). The good performance can be attributed to the excellent catalytic activity of highly dispersed MFe2O4 (M = Co, Ni) nanoparticles and facile electron transport by supporting CNTs. This preliminary result manifests that the ternary spinel MFe2O4/CNT (M = Co, Ni) composites are promising cathode electrocatalysts for non-aqueous Li–O2 batteries.

Due to the high cost of Pt-based materials used in the electrocatalysis of the oxygen reduction reaction (ORR), an alternative composed of non-precious metals is highly desirable. Herein a hybrid with cobalt monoxide nanocrystals spatially confined in holey N-doped carbon nanowires (CoO/NCWs) was synthesized via metal oxide assisted surface pitting of chemical vapor deposited carbon nitrogen nanowires and colloidal assembly. The catalyst consists of a Co2+ enriched surface and delivers a remarkably higher ORR electrocatalytic activity and stability than its surface smooth N-doped carbon nanotube supported counterpart, with a kinetically limited current density (30.3 mA cm−2 at 0.7 V) nearly three times that of the latter. It also outperformed the commercial Pt/C catalyst. As characterized by cyclic voltammetry and XPS, the enlarged interfacial area by spatially confined hybridization is believed to be responsible for the improved ORR performance, which might create more active catalytic sites for the ORR. We propose that in-depth consideration of interfacial construction is essential when designing carbon supported metal oxide catalysts for the ORR in alkaline media.