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A facile and green microbial method to produce graphite oxide nanosheets and nanoparticles is described. The obtained graphite oxide nanosheets have few layers with 0.7-1.5 nm height and 50-300 nm size. The carbon nanoparticles possess the size of 20-60 nm and the height of 2-4 nm.

Abstract: The large‐scale, low‐cost preparation of Pt‐based catalysts with high activity and durability for the methanol oxidation reaction is still challenging. The key to achieving this aim is finding suitable supporting materials. In this paper, N‐doped carbon nanofibrous networks are prepared by annealing a gel containing two inexpensive and ecofriendly precursors, that is, bacterial cellulose and urea, for the loading of Pt nanoparticles. An undoped analogue is also prepared for comparison. Meanwhile, the effect of the annealing temperature on the performance of the catalysts is evaluated. The results show that the N doping and higher annealing temperature can improve the electron conductivity of the catalyst and provide more active sites for the loading of ultrafine Pt nanoparticles with a narrow size distribution. The best catalyst exhibits a remarkably high electrocatalytic activity (627 mA mg−1), excellent poison tolerance, and high durability. This work demonstrates an ideal Pt supporting material for the methanol oxidation reaction. [ABSTRACT FROM AUTHOR]

Tin-based metal oxides usually suffer from severe capacity fading resulting from aggregation and considerable volume variation during the charge/discharge process in lithium ion batteries. In this work, a novel nanocomposite (MTO/N-RGO) of hollow amorphous MnSnO 3 (MTO) nanoparticles and nitrogen-doped reduced graphene oxide (N-RGO) has been designed and synthesized by a two-step method. Firstly, the nitrogen-doped graphene nanocomposite (MTO/N-RGO-P) with MnSn(OH) 6 crystal nanoparticles was synthesized by a facile solvothermal method. Subsequently, the MTO/N-RGO nanocomposite was obtained through the post heat treatment of MTO/N-RGO-P. The designed heterostructure and well-combination of the hollow amorphous MTO and N-RGO matrix can accelerate the ionic and electronic transport, and simultaneously accommodate the aggregation and volume variation of MTO nanoparticles during the lithiation–delithiation cycles. The as-prepared hybrid of MTO and N-RGO (MTO/N-RGO) exhibits a high reversible capacity of 707 mAh g −1 after 110 cycles at 200 mA g −1 , superior rate capability, and long-term cyclic life with high capacity of 610 mAh g −1 over 1000 cycles at 400 mA g −1 . Superior capacity retention of 97.3% over 1000 cycles was obtained. This work opens new opportunities to fabricate the high-performance electrode materials with heterostructure for lithium storage systems, especially for novel multi-metal oxide based nanocomposites with high cycling stability. [ABSTRACT FROM AUTHOR]

We have successfully prepared poly (3,4-ethylenedioxythiophene) (PEDOT)/N-doped reduced graphene oxide (N-rGO) by electrodeposition, post-reduction, and doping N atoms with a microorganism (as a green reagent) to modify PEDOT and resolve the exfoliation and fragmentation problems of pristine PEDOT. This modification greatly improves the electrochemical properties of PEDOT, showing great potential for a bio-electrode coating material, which should have excellent electrochemical properties, stability and biocompatibility. The as-prepared PEDOT/N-rGO shows lower impedance, and higher capacitive performance and cyclical stability than pristine PEDOT due to the doping of N-rGO. An MTT assay demonstrates this modified PEDOT has good adhesion, cell viability and proliferation, similar to pristine PEDOT. This indicates that the modification process does not restrain the good biocompatibility of pristine PEDOT, which results from the doping of highly biocompatible N-rGO by this green method. The wrinkled structure, residual oxygen containing functional groups and dopant N atoms of N-rGO lead to the formation of a fluctuating surface and an increase in the hydrophilicity of PEDOT, which increase the specific surface area and cell adhesion in cell culture, respectively. Consequently, this modified PEDOT improves the electrochemical properties, and resolves the exfoliation and fragmentation problems of pristine PEDOT, while still retaining the high biocompatibility of pristine PEDOT, which is promising for a bio-electrode coating material. [ABSTRACT FROM AUTHOR]

A simple and sensitive label-free electrochemical biosensor for nimodipine was fabricated by using nitrogen-doped graphene (NGE) modified electrode. The surface morphology and electron transfer behavior of the modified electrodes were studied by scanning electron microscopy and electrochemical impedance spectroscopy, respectively. The electrochemical behaviors of nimodipine at the modified electrodes were investigated by using cyclic voltammetry. On the basis of the excellent electrocatalytic activity of NGE, an obvious cathodic peak of nimodipine could be caused at the NGE modified glassy carbon electrode (GCE), moreover, the electrochemical signal was greatly enhanced compared with the undoped graphene modified GCE. Under the optimized conditions, the present sensor showed excellent performances for nimodipine detection including wide linear range of 0.02–3 μM, low detection limit (9.1 nM), good selectivity to the general coexisted interferences, etc. The proposed biosensor was also successfully applied to validate its capability for the analysis of nimodipine in tablets. The work would promote the potential application of NGE as an excellent material in fabricating electrochemical sensors for chemical or biochemical analysis. [ABSTRACT FROM AUTHOR]

Abstract: To improve the electrochemical properties of chemically synthesized graphene hybrids, nitrogen-doped (N-doped) graphene decorated with M(OH) x (M=FeO, Ni, Co) nanoparticles were fabricated by a one-pot method at a mild temperature (95°C). Urea plays an important role in the synthesis process; it not only acts as the reducing agent and doping agent for N-doped graphene, but also as a hydroxyl donor for the fabrication of metal hydroxides and oxide-hydroxide. With the help of N-doped graphene and urea, FeOOH nanorods, Co(OH)2 nanowires and flower-like Ni(OH)2 nanoparticles were grown on the graphene sheets. The N-doped graphene hybrids exhibited the significantly improved electrochemical performances compared to the undoped equivalents or the separate components. [Copyright &y& Elsevier]

Oxygen reduction reaction (ORR) plays a key role in the application of fuel cells. Here, we used shaddock peel to fabricate a set of N, P dual-doped hierarchical porous carbons, abbreviated as NPSPs, where the carbons were carbonized, activated and dual-doped via a simple one-step pyrolyzation. Contrast results indicate the contents of pyridinic-N, graphitic-N and P–C species increase with the rising of temperatures, and the temperature also affects the degree of graphitization, surface area, morphology, thus influences the ORR performance. More importantly, the NPSP-900 demonstrates an outstanding ORR activity with a comparable half-wave potential (0.83 V vs. RHE) and higher current density with respect to commercial Pt/C, following 4e transfer pathway. Our work illustrates that NPSP-900 is a promising cathode for fuel cells because of its simple preparation, waste utilization, excellent ORR performance, good methanol tolerance and superior stability. Image 1 • One-step pyrolysis can accomplish carbonization, activation and N,P-dual doping. • NPSPs own hierarchical porous structures with high BET surface areas. • Higher temperature can enhance ORR activities with improved doping N/P species. • NPSP-900 owns a close ORR activity compared with Pt/C, following 4e transfer way. • NPSP-900 shows a remarkable methanol tolerance and superior stability. [ABSTRACT FROM AUTHOR]

Abstract Oxygen reduction reaction (ORR) and Lithium storage both play the key roles in energy conversion and storage devices. Here, we report a honeycomb-like nitrogen-doped carbon derived from enteromorpha algae (N-EA), using a one-step pyrolysis process at only 600 °C to simultaneously achieve doping, carbonization and activation. After anchoring CoFe 2 O 4 on N-EA, CoFe 2 O 4 /N-EA, not only inherits the high surface area, porous structure, active nitrogen species from N-EA, but also benefits from the active sites and high theoretical specific capacity of Li storage from CoFe 2 O 4. The synergistic effect makes CoFe 2 O 4 /N-EA an alternative catalyst to commercial Pt/C for ORR with superior activity and stability. Moreover, CoFe 2 O 4 /N-EA exhibits a remarkable cycle performance with a 100% capacity retention (∼900 mAh g−1) after 500 cycles at 0.5 A g−1. Green preparation, waste utilization, good ORR performance and Li storage property of CoFe 2 O 4 /N-EA could make it a promising candidate for fuel cells and LIBs. [ABSTRACT FROM AUTHOR]

Abstract Sandwich-like ZIF-8 nanocrystal derived N-doped carbon decorated graphene sheets are developed through in-situ growth and followed by a thermal annealing treatment. The sandwich-like N-doped carbon decorated graphene sheets (NCGs) contain graphene substrate and the carbon nanoparticles with 30–50 nm in size. The sandwich-like NCGs generate a large specific surface area of 816.4 m2 g−1. With the high surface area and nitrogen doping, the as-fabricated NCGs as electrode materials for supercapacitor exhibit high specific capacitance of 225.0 F g−1 at 0.5 A g−1, an enhanced rate capability and excellent electrochemical stability with 96.8% retention after 10000 cycles even at 10 A g−1. The symmetry supercapacitor based on NCGs delivers an energy density of 12.7 Wh kg−1 at a specific power of 447 W kg−1. When the power density increases to 15126 W kg−1, the energy density can still keep 6.5 W h kg−1. Furthermore, the symmetry supercapacitor shows an excellent cycle stability with 96.6% capacitance retention at 2 A g−1 after 10000 cycles. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

A novel electrochemical sensor based on nitrogen doped graphene (NGE) and palygorskite (Pal) for the simultaneous detection of hydroquinone (HQ) and catechol (CT) has been proposed. Pal is particularly pointed out for its appreciable specific surface area and reactive-OH groups on its surface. Acid treatment Pal demonstrated better physico-chemical properties, which are propitious to electrochemical sensor construction. The introduction of NGE not only improved the poor conductivity of Pal but also served as an excellent adherent matrix. The modified electrode demonstrated the enhanced redox peak currents of HQ and CT with good discrimination. Under optimized conditions, the linear ranges for HQ and CT were 2–50 μM and 1–50 μM, with detection limit (LOD) of 0.8 μM and 0.13 μM, respectively. The result designates that the Pal/NGE composite promises to be a new eco-friendly modified material for sensor fabrication. [ABSTRACT FROM AUTHOR]

Poly(3-methylthiophene)/nitrogen doped graphene modified glassy carbon electrode (P3MT/NGE/GCE) was prepared through simple drop-casting of NGE, followed by the electrodeposition of P3MT film for sensitive electrochemical determination of trace amounts of pesticide phoxim. The morphology and structure of P3MT/NGE/GCE were characterized by scanning electron microscopy; the electrochemical behavior of P3MT/NGE/GCE was investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and chronocoulometry. The preparation conditions of modified electrode, the dropping amount of NGE and polymerization laps of P3MT, were optimized. Under the optimized conditions, the reduction peak current of cyclic voltammetric curve varied linearly with the concentration of phoxim over the two linear ranges of 0.02–0.2 μM and 0.2–2.0 μM, and the low detection limit was 6.4 nM according to lower linear range (S/N = 3). The sensor also exhibited excellent selectivity to phoxim over a wide range of possible interferents including ions, biomolecules, common environment pollutants and widely-used organophosphate pesticides. Moreover, the satisfactory practical feasibility of the sensor was evaluated by the environmental phoxim measurements. [ABSTRACT FROM AUTHOR]

Highlights: [•] PEDOT/NGE modified electrode was fabricated via CV method using nitrogen-doped graphene (NGE) coated GCE. [•] Highly reversible and well-separated redox couples of hydroquinone (HQ) and catechol (CT) were obtained at PEDOT/NGE/GCE. [•] A facile electrochemical sensor based on PEDOT/NGE/GCE was developed for simultaneous detection of HQ and CT. [Copyright &y& Elsevier]