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N-doped hollow carbon nanospheres (NHCS) with mesoporous carbon shells is selected as nanoreactors and encapsulated with few-layered MoS2 nanosheets to monitor its electrochemical properties and structural conversion in long-term cycling. Mesoporous walls of NHCS can facilitate electrolyte penetration and provide conductive shells for superior mass diffusion and charge transfer. When serving as SIB anodes, MoS2@NHCS has a capacity value of 371 mAh g-1 at 1 A g-1 with a capacity retention of 94.9% after 100 cycles which is higher than powder form MoS2 and is among the highest values of earlier reported MoS2 electrodes. The origin of gradual capacity decay of MoS2@NHCS anodes in-between 50 to 150 cycles has been investigated. Transmission electron microscopy and ex-situ X-ray diffraction have shown significant morphology change of space-confined MoS2 and the production of MoO3 together with oxygen-deficient MoOx after continuous charge/discharge test. After long-term cycle test of MoS2@NHCS, the ratios of Mo6+ and Mo5+ increased significantly with the decreasing of Mo4+ ratio, while the sulfur from MoS2 transformed from S2− to SO42−. This work highlight the phase transformation and composition change of MoS2 for MoS2-based anode in long-duration charge/discharge tests.

Na3V2(PO4)3 (NVP) is one of the most promising cathode materials for sodium-ion batteries because of its stability, safety, and high reversible capacity. However, the sluggish Na-ion diffusion and poor electronic conductivity of NVP often hinder electrochemical performance, thus requiring compositing with carbon materials, such as graphene to improve the material. In this work, the effect of doping species of graphene on the electrochemical performance of NVP/graphene composites was systematically investigated and vigorously compared. 3D porous NVP fabricated by sol-gel method with 3 nm of carbon coating layers was deposited on graphene sheets with different surface functionalities (GO, N-rGO and P-rGO). NVP/N-rGO composites have low charge transfer resistance and high Na+ diffusion coefficient than that of NVP powder, NVP/P-rGO, and NVP/GO, which delivered a specific capacity of 113.9 mAh g−1 at 0.5C with a capacity retention up to 88.42% after 5000 cycles at 20 C. The superior sodium storage performance derives from the pyridinic and pyrrolic N doping in graphene, which triggers defective and active site numbers but maintains moderate graphitization to accelerate the Na+ and electron transportation. This work was supported by the National Natural Science Foundation of China (Grant No. 51502135), and Primary Research & Developement Plan of Jiangsu Province (BE2016183). The authors are grateful to Prof. Xia Hui, Nanjing University of Science & Technology for access to equipment. The authors are grateful to Prof. Jianmin Ma and Dr Zengxi Wei for discussion and theoretical calculation of NVP capacity.

A hierarchically structured free-standing V2O5/vertically aligned carbon nanotube/graphene foam (V2O5-VA-CNTs/GF) coated by PEDOT was designed. Instead of forming a thick coating layer around, the V2O5 nanobelts disperse uniformly among the CNTs forest without severe aggregations. The PEDOT-V2O5-VA-CNTs/GF delivered a reversible capacity of 296.8 mAh g−1 at 1C, and has capacity retention of 113.3 mAh g−1 at 5C after 1000 cycles. First principles calculations indicate the addition of VA-CNTs to V2O5 electrode could improve the electronic conductivity and facilitate Li-ion adsorption, which lead to the outstanding Li-ion storage and conversion behaviour.

In the last decade, Li-O2 batteries have been a research focus due to its ultrahigh energy density as chemical power sources and being rechargeable through oxygen reduction and evolution reactions. Besides catalyzing the oxygen reduction and evolution, the rationally designed air-cathode to accommodate the insoluble discharge products and allow efficient transfer of reactants is critical for Li-O2 batteries. To date, the development of a wide variety of electrocatalyst has driven the application-directed research in Li-O2 batteries. This review provides a comprehensive overview of the O2-electrodes for Li-O2 batteries, with an emphasis on the O2-electrodes synthesis, working mechanism, and overall performance evaluation. The aim of this review is to afford a better understanding of Li-O2 cathodes and to provide guidelines for researchers to design and construct high-performance, easy-to-use cathodes for Li-O2 batteries.

Reported herein is a facile solution-processed substrate-independent approach for preparation of oriented coordination polymer (Co-BTA) thin-film electrodes for on-chip micro-supercapacitors (MSCs). The Co-BTA-MSCs exhibited excellent AC line-filtering performance with an extremely short resistance-capacitance constant, making it capable of replacing aluminum electrolytic capacitors for AC line-filtering applications.

Two-dimensional (2D) porous SiO 2 nanomesh obtained from mixed acid etching of vermiculite (VMT) was successfully used as a catalyst support for CO methanation. Compared with three-dimensional (3D) MCM-41, 2D VMT-SiO 2 provided a superior position for implantation of NiO species. Although NiO/VMT-SiO 2 has a total loading of 10 wt.% NiO as well as the NiO/MCM-41, the NiO particles on VMT-SiO 2 were observed to show a better dispersion as the of 3D MCM-41 channels were easily blocked by large NiO particles. Moreover, on the basis of the H 2 temperature-programming reduction results, NiO particles on VMT-SiO 2 were more easily reduced than those on MCM-41. These characteristics indicated that NiO/VMT-SiO 2 was significantly superior to NiO/MCM-41. The as-obtained NiO/VMT-SiO 2 exhibited a CO conversion of 85.9%, CH 4 selectivity of 78% at 450 °C, 0.1151 s −1 turn over frequency at 320 °C and a gas hourly space velocity of 20745 ml/g/h. All of which were much better than those measured for NiO/MCM-41. We believed that 2D VMT-SiO 2 as a new catalyst support open a prospect application of catalyst.

In this study, a free-standing electrochemical sensor based on 3D graphene foam (GF) with dense carbon nanotubes (CNTs) and gold nanoparticles (GNPs) was developed for the first time. The structure of this hybrid electrode (GF/CNTs/GNPs) was observed by scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS) and transmission electron microscopy (TEM), and its electrochemical properties was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The obtained sensor displayed outstanding electrocatalytic activity toward dopamine (DA) and uric acid (UA) compared with the commercial unmodified glass carbon electrode. Detection of DA and UA with the presented sensor yielded remarkable sensitivity of 12.72 μA μM − 1 cm − 2 and 3.36 μA μM − 1 cm − 2 , the low detection limits of 1.36 nM and 33.03 nM (S/N = 3), with wide linear range of 0.10–48 μM and 0.50–60 μM, respectively. Furthermore, quantification of DA in brain tissue and UA in human urine was realized and the results were found in good agreement with those obtained by using high performance liquid chromatography.

Si/C@NGs composite containing flake-shaped sub-micron sized silicon (Si) enwrapped by pyrolyzed carbon and natural graphite (NG) was successfully prepared by spray-drying-assisted self-assembly method and was systematically studied as an anode material for lithium-ion batteries. The as-prepared Si/C@NGs composite material has a loading amount of sub-micron sized silicon as low as 6.7 wt%. The Si/C@NGs composite has a hierarchical structure with Si/C embedded into natural graphite which further assembles into larger secondary particles of ∼20–50 μm. Compared with pure silicon, the as-synthesized Si/C@NGs composite has multi-layer carbon coating as well as voids to alleviate the structural changes of Si during charging/discharging, exhibits an initial efficiency of 82.8% and a capacity retention of 428.1 mA h g −1 (1524.0 mA h g −1 vs. Si) after 100 cycles at 0.1 A g −1 . The remarkable cycling performances, high initial cycle efficiency together with low-cost manufacturing process make Si/C@NGs composite appealing for commercial applications.

Zn–air batteries have attracted significant attention because of their high energy density, environmental friendliness, safety, and low cost. The air cathode of is one of the most expensive cell components and a key factor in determining the performance of Zn–air batteries. As a fuel, O2 availability to the air cathode is determined by the level of both its dissolution and diffusion in an electrolyte, whereby electrocatalysis happens in the three-phase interface where the catalyst, electrolyte, and O2 meet. Maximizing the performance of air cathodes by rational design of the catalyst structure is of significant importance. To date, various electrocatalysts, including heteroatom-doped carbon, transition metal nitrides/oxides/sulfides, and perovskite oxides, have been developed with outstanding oxygen reduction reaction and oxygen evolution activity. More and more researchers are trying to apply electrocatalysts into Zn–air battery prototypes. The aim of this review is to afford a better understanding of air cathodes and provide guidelines to the researchers for the design and construction of high-performance, easy-to-use cathodes for metal–air batteries.

In recent years, graphene has been considered as a potential “miracle material” that will revolutionize the Li-ion battery (LIB) field and bring a huge improvement in the performance of LIBs. However, despite the large number of publications every year, practical prototypes of graphene-based batteries are still few and no commercial products have entered large-scale production so far. In this review, we will start from a brief introduction of the working mechanism of LIBs, important concepts such as the solid–electrolyte interface (SEI), graphene and the production methods of graphene and graphene based composites followed by the review of graphene and graphene composites as electrode materials, highlighting the role graphene plays in the composite materials and the advantages and drawbacks of these materials. The previous sections laid the foundation of the focus of discussion, which is the application of graphene based materials in full cell prototypes, the difficulties they face and efforts to solve the various problems preventing the implementation of graphene based materials in practical commercial cells.

Contact interface between the active materials and the current collector is essential for electron transfer rate and the mechanical properties of an electrode. In this study, various types of contacts between the active material (graphene sheets) and the metal current collector are created through different fabrication methods, and their impacts to the electrochemical performance are investigated. Intimate “sheet contact” is observed between graphene sheets and Ni foam after KOH in situ activation, which is believed to facilitate the electron transfer. The anode that is tailored to have “sheet contact” delivers a reversible capacity of 1457 mAh g–1 at 0.1 C, which is higher than the electrode obtained by a commercial drop-casting method and comparable to most of the high-end graphene-based anodes. In addition, the anode delivers a high capacity of 173 mAh g–1 with a short charging time of 56 s, indicating its promising use as a high-rate LIB anode.

Electrocatalysts for the oxygen reduction reaction (ORR) play a crucial role in renewable-energy technologies, including metal-air batteries and fuel cells. However, development of novel catalysts with high activity and low cost remains a great challenge. Here, we present hierarchical MnO 2 /reduced graphene oxide (MnO 2 /rGO) hybrid nanosheets by using a facile method and study its electrocatalytic performance. Cyclic voltammograms, and rotating disk electrode and rotating ring/disk electrode measurements demonstrate that the hierarchical MnO 2 /rGO hybrid nanosheets exhibit excellent electrocatalytic activity for the ORR in an alkaline medium, as evidenced by their higher cathodic current density, more positive onset potential, lower H 2 O 2 yield, and higher electron transfer number compared to pure rGO. The excellent catalytic activity of the MnO 2 /rGO hybrid nanosheets highlights the importance of the synergetic chemical coupling effect between the ultrathin MnO 2 nanosheets and the graphene layer.

A new type of three-dimensional (3D) electrochemical sensor was prepared by combining carbon nanotubes on graphene foam (GF/CNT) with molecularly imprinted polymer (MIP), which affords simultaneous identification and quantification towards target compound. The hybrid sensor shows ultralow detection limit of 6.67 × 10−16 M (S/N = 3), wide range of 2 × 10−15 M to 1 × 10−12 M, and superb selectivity for dopamine (DA) detection. Keywords: Electrochemical sensor, Dopamine, Graphene network, Carbon nanotube, Molecularly imprinted polymer

In this work, non-precious metal catalysts (FeCoN) were loaded onto the surface of N-modified graphene (N-G), graphite and activated carbon during a simple yet effective chemical process. The oxygen reduction reaction (ORR) performance of the as-prepared catalysts with different pyrolysis temperatures were evaluated in 0.5 M H2SO4. The use of N-G at a pyrolysis temperature of 750 °C yielded the highest catalyst activity, while both the metal nitrides (MeN) and pyridinic N were demonstrated as the active center for the ORR. The pyridinic-N, which sits surrounding MeN works synergistically with metal nitrides to enhance the catalytic activity of the MeN/N-G composite. A maximum power density output of 130 mW cm−2 at 0.25 V was achieved in a membrane electrode assembly (MEA) using FeCoN-N-G as a cathode catalyst. The mechanism of the ORR at the catalyst and the nature of the active center are discussed.

Cobalt hydroxide nanowires network grown on nitrogen modified microwave exfoliated graphite oxide (NMEG) with a specific capacitance of 610 F/g is successfully synthesized by a chemical precipitation method. Asymmetric-type pseudocapacitors are fabricated with Co(OH) 2 /NMEG and polypyrrole (PPy)/rG-O applied as positive and negative electrodes respectively. The electrochemical properties of the electrodes in three electrode and two electrode systems are systematically investigated in 1 M KOH electrolyte. Various supercapacitor devices, such as rG-O//Co(OH) 2 /NMEG, NG//NG, rG-O//rG-O, and PPy/rG-O//PPy/rG-O are assembled with electrochemical performance evaluated by cyclic voltammetry and galvanostatic charge/discharge measurements. The Co(OH) 2 /NMEG//PPy/rG-O asymmetric supercapacitor cells can achieve a high cell voltage of 1.6 V and an energy density up to 24.9 Wh/kg with an active materials loading of ∼5 mg/cm 2 , significantly higher than that of rG-O//Co(OH) 2 /NMEG (19.3 Wh/kg), NG//NG (16.4 Wh/kg), rG-O//rG-O (15.3 Wh/kg) and PPy/rG-O//PPy/rG-O (9.4 Wh/kg) supercapacitor devices under the same measurement environment. The PPy/rG-O is a superior negative electrode to match cobalt/nickel oxides/hydroxides based positive electrodes for supercapacitor devices.

Compared with thermally exfoliated graphene oxide (TEGO) prepared at high temperature of 800 °C and a long time of 12 h, microwave exfoliated graphene oxide (MEGO) is successfully synthesized at 800 W for 2 min benefiting from “inert and instant heating” of microwave irradiation and employed to optimize electrochemical performance of LiFePO 4 . The as-obtained LiFePO 4 /MEGO exhibits overwhelming superiorities to LiFePO 4 /TEGO, particularly in high-rate performance. Although LiFePO 4 /MEGO delivers the similar specific capacity of 158.1 mAh · g −1 as well as the LiFePO 4 /TEGO at the rate of 0.1 C, the LiFePO 4 /MEGO performs smaller polarization of 53.3 mV resulting in better specific energy of 518.1 Wh · kg −1 and energy efficiency of 89.8%. Even at the high rate of 10 C and 20 C, the LiFePO 4 /MEGO delivers excellent specific energy of 300.3 Wh · kg −1 and 229.7 Wh · kg −1 (with corresponding specific capacity of 104.3 mAh · g −1 and 87.3 mAh · g −1 respectively), much better than those of the LiFePO 4 /TEGO. After 2000 cycles, the LiFePO 4 /MEGO still performs excellent rate capabilities with 91.2% and 83.8% retention respectively.

Increasing energy and power demands have continued to stimulate the development of new electrochemical energy storage devices. Supercapacitors, well-known energy storage systems characterized by a high power density and long cycle life, have experienced a rapid progress benefiting from fast advancements in electrode materials. However, for those conventional supercapacitors assembled through a thin film preparation technique, the conductive agent and polymer binder will inevitably account for a large amount of ‘dead volume’, which should be further diminished through a better design of the supercapacitor architecture. Here, we present a comprehensive review on recent research progress on the design of integrated electrode architectures, especially the binder-free nanoarray electrodes. By means of an integration of highly-ordered active nanomaterials and a current collector, the binder-free nanoarrays can provide a larger active surface area, faster electron-transport route, easier ion diffusion and superior structural stability, thus leading to a substantially improved cycling and rate performance. This work will narrow its focus on two independent aspects of binder-free architectures: the design of electrode materials and the construction of current collectors. In addition, we also discuss and review future research directions and the remaining challenges in materials development for advanced supercapacitors.

In this paper, using Ni 3 S 2 @MoS 2 as an example, we report the successful design and synthesis of a novel hybrid core/shell metal sulfides with a conductive Ni 3 S 2 core by a green, scalable and one-step solution strategy. When they are tested as supercapacitor electrodes, the Ni 3 S 2 @MoS 2 heterostructure exhibits about 2 times the capacitance (848 F g −1 ) compared to the pristine Ni 3 S 2 sample (425 F g −1 ), excellent rate capability (46.6% capacity retention at 20 A g −1 ) and outstanding cycling stability (91% retention after 2000 cycles). The enhancement is ascribed to the robust hierarchical core/shell structures which provide an increased reaction area and a close contact of electrolyte with the active material. In addition, a highly conductive 1D core material endows the quick transport of electrons along Ni 3 S 2 nanorods to Ni foam. It is prospected that such novel hybrids can offer great potential promise in large-scale energy storage device applications.

Transition metal nitrides (TMN)/N modified graphene (N-rG-O) composites are prepared by annealing of Metal n+ -EN (EN: ethylene diamine) chelate and G-O composite. Li-storage and cycling behavior of TMN/N-rG-O composite have been evaluated by galvanostatic discharge-charge and cyclic voltammetry in coin cells with Li-metal as counter electrode. FeN/N-rG-O, CoN/N-rG-O, FeCoN/N-rG-O, NiN/N-rG-O are prepared using this method, and all have shown pronounced cyclability and considerable high capacity value. Even a low loading of TMN (12.5% ±2.0%) on graphene can significantly improve the Li-ion storage capacity of graphene. For example, FeN/N-rG-O with FeN weight ratio of only 12.5% has an initial reversible capacity of 665 ± 10 mAhg −1 at a current density of 50 mA g −1 , and the capacity value further increase consistently to 698 ±10 mAhg −1 after 50 cycles. The excellent cyclability, low charge/discharge potentials (

Cost-effective synthesis of carbon nanospheres with a desirable mesoporous network for diversified energy storage applications remains a challenge. Herein, a direct templating strategy is developed to fabricate monodispersed N-doped mesoporous carbon nanospheres (NMCSs) with an average particle size of 100 nm, a pore diameter of 4 nm, and a specific area of 1093 m2 g-1 . Hexadecyl trimethyl ammonium bromide and tetraethyl orthosilicate not only play key roles in the evolution of mesopores but also guide the assembly of phenolic resins to generate carbon nanospheres. Benefiting from the high surface area and optimum mesopore structure, NMCSs deliver a large specific capacitance up to 433 F g-1 in 1 m H2 SO4 . The NMCS electrodes-based symmetric sandwich supercapacitor has an output voltage of 1.4 V in polyvinyl alcohol/H2 SO4 gel electrolyte and delivers an energy density of 10.9 Wh kg-1 at a power density of 14014.5 W kg-1 . Notably, NMCSs can be directly applied through the mask-assisted casting technique by a doctor blade to fabricate micro-supercapacitors. The micro-supercapacitors exhibit excellent mechanical flexibility, long-term stability, and reliable power output.

Co3O4 nanoparticles are grown on nitrogen modified microwave exfoliated graphite oxide (NMEG) with weight ratio controlled from 10% to 70%. Electrochemical performance reveals that the obtained Co3O4/NMEG composite as Li-ion battery anode exhibits improved cycle stability, excellent reversible capacity, high current rate performance, and reduced irreversible capacity loss in the initial cycle compared to pure Co3O4 without graphene or Co3O4 on thermally reduced graphene oxide (tRG-O). The 70%Co3O4/NMEG composite has initial irreversible capacity of 230 mAh g−1 (first cycle efficiency of 77%), and 910 mAh g−1 of capacity is retained after 100 cycles. The 70%Co3O4/tRG-O delivers a reversible capacity of 750±20 mAh g−1, and the irreversible capacity loss during the first cycle is 700±20 mAh g−1. Nitrogen functional groups in NMEG, especially pyridinic and pyrrolic N are advantageous for the Co3O4 growth. Furthermore, the N modification is effective in reducing the oxygen content of chemically prepared graphene and hence is good for Co3O4 dispersion and the amelioration of first cycle efficiency, demonstrating the potential of NMEG based composite as high performance Li-ion battery anode materials.

The synthesis of graphene in both high quality and quantity via economic ways is highly desirable and meaningful for practical applications. Here we report a simple, green and cost- effective multiple electrochemical exfoliation approach to high quality and high yield (nearly 50%) graphene flakes by using graphite rod from spent zinc–carbon as graphene source. The graphite rod (anode) and platinum (cathode) were placed vertically at bottom and top of the electrochemical cell, with protonic acid (i.e, H 2 SO 4 , H 3 PO 4 or H 2 C 2 O 4 ) aqueous solution as electrolyte. The vertical cell configuration enables multiple exfoliation process to improve both the quality and yield of graphene sheets from electrochemical exfoliation of graphite. After nitrogen doping, the exfoliated graphene flakes processes excellent electrocatalytic activity, stability and toxicity tolerance for oxygen reduction reaction in alkaline solution.

A series of functionalized graphene derived from graphite oxide (GO) and doped with polypyrrole (PPy) are prepared to systematically investigate the combined effect of surface functionalization and polymer hybridization on supercapacitor performance. Surface chemistry of graphene is found to be of significant importance to PPy growth and PPy/graphene electrochemical performance improvement. High specific capacitance has been achieved by N doped graphene/polypyrrole (NG–PPy) electrode with a value of 393.67 Fg −1 , which is larger than those of –NH 2 modified graphene/PPy (225.33 Fg −1 ), GO/PPy (165.25 Fg −1 ), reduced GO/PPy electrodes (150.00 Fg −1 ) under the same experimental conditions. Incorporation of N into the graphene network enhances electronic transfer efficiency and improved graphene surface wettability, therefore, largest synergistic effect is achieved on NG–PPy. Introduction of N doping to carbon material before the growth of conducting polymer is essential to prepare carbon/conducting polymer composites with high cycling stability and specific capacitance for supercapacitor application.

Multi-walled carbon nanotubes (MWCNTs) are functionalized with 2-pyrridone functional groups by wrapping poly(vinylpyrrolidone) polymers around it under high-powered sonication. The presence of 2-pyrridone functional groups facilitates the complexation of metal ions (Fe 3+ , Co 2+ ). The best oxygen reduction catalyst, MWCNT–FeCo, is synthesized by annealing poly(vinylpyrrolidone)/MWCNTs/Fe–Co complex in ammonia at 900 °C and exhibits nearly four-electron oxygen pathway ( n ∼3.8). X-ray diffraction pattern shows that low loading of metallic Fe nanoparticles (0.79 wt.%) and bimetallic FeCo nanoparticles (0.34 wt.%) is formed on the MWCNT–FeCo catalysts. X-ray photoelectron spectroscopy reveals that ∼1 at.% of nitrogen has been doped into MWCNT–FeCo catalysts.

Program for New Century Excellent Talents in Fujian Province [X12103]; Natural Science Foundation of China [20701031]; Natural Science Foundation of Fujian Province of China [C0710045]

We present the electronic structure evolution from graphite oxide to thermally reduced graphite oxide. Most functional groups were removed by thermal reduction as indicated by high resolution X-ray photoelectron spectroscopy, and the electrical conductivity increased 6 orders compare with the precursor graphite oxide. X-ray absorption spectroscopy reveals that the thermally reduced graphite oxide shows several absorption peaks similar to those of pristine graphite, which were not observed in graphite oxide or chemically reduced graphite oxide. This indicates the better restoration of graphitic electronic conjugation by thermal reduction. Furthermore, the significant increased intensity of Raman 2D band of thermally reduced graphite oxide compared with graphite oxide also suggests the restoration of graphitic electronic structure (π orbital). These results provide useful information for fundamental understanding of the electronic structure of graphite oxide and thermally reduced graphite oxide.

Amine-modified carbon micro/sub-microtubes that encapsulate magnetite cores have been synthesized by decomposing a ferrocene/hexabromobenzene mixture in the presence of ammonia under solvothermal conditions at 250°C for 24 h in a one-step process. The as-prepared carbon microstructures (NH 2 -ME-CMTs) were 90-2000nm in diameter and from tens to hundreds of micrometers in length that could be tuned in various solvents. The surface of the carbon microtubes can be modified with amino groups by the synthetic process, as confirmed by infra-red (IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). Ammonia in the reaction system plays a key role in the formation of the microtube morphology and was the source of the surface functionalization groups. Fluorescent fluorescein isothiocyanate (FITC) was selected as a model compound and successively attached to the amino groups of the carbon microtubes. This result confirms the reactivity of the amino groups on the surface of the carbon microtubes. The inner magnetite cores were removed after immersion in 1 M HCl solution at room temperature over two months, and hollow carbon microtubes (NH 2 -H-CMTs) were obtained. The magnetite-encapsulated carbon microtubes and the hollow carbon microtubes were coated on gold electrodes to prepare carbon microtube-modified gold electrodes. The two electrodes have been used to investigate the oxidative properties of dopamine (DA) and ascorbic acid (AA). Different from the magnetite-encapsulated microtube-modified electrode, the hollow microtube-modified electrode can be utilized in the selective detection of DA in the presence of a large excess of AA. The electrochemical behaviour of DA and AA on the hollow carbon microtubes modified with amino groups is similar to that on carbon nanotubes. This result suggests that the one-step synthesis method will not change the electrochemical properties or break the backbone structure of the carbon microtubes.

Correction for ‘Recent advances in air electrodes for Zn–air batteries: electrocatalysis and structural design’ by Xiaoyi Cai et al., Mater. Horiz., 2017, 4, 945–976.

The increasing demand for graphene's industrial application requires a new route for its mass production with high quality. Here, we report a facile, green, highly efficient and cost effective method for preparing a large amount of high quality graphene flakes, which is by the repeated microwave assisted exfoliation of expandable graphite (EG). The successful exfoliation of graphite is realized through the intercalation and decomposition of eco-friendly chemicals with the assistance of a microwave source. The chemical morphology and electrocatalytic performance analyses reveal that the graphene flakes are of high quality with little degradation.

Different C–N bonding configurations in nitrogen (N) doped carbon materials have different electronic structures. Carbon materials doped with only one kind of C–N bonding configuration are an excellent platform for studying doping effects on the electronic structure and physical/chemical properties. Here we report synthesis of single layer graphene doped with pure pyridinic N by thermal chemical vapour deposition of hydrogen and ethylene on Cu foils in the presence of ammonia. By adjusting the flow rate of ammonia, the atomic ratio of N and C can be modulated from 0 to 16%. The domain like distribution of N incorporated in graphene was revealed by the imaging of Raman spectroscopy and time-of-flight secondary ion mass spectrometry. The ultraviolet photoemission spectroscopy investigation demonstrated that the pyridinic N efficiently changed the valence band structure of graphene, including the raising of density of π states near the Fermi level and the reduction of work function. Such pyridinic N doping in carbon materials was generally considered to be responsible for their oxygen reduction reaction (ORR) activity. The 2e reduction mechanism of ORR on our CNxgraphene revealed by rotating disk electrode voltammetry indicated that the pyridinic N may not be an effective promoter for ORR activity of carbon materials as previously expected.