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Polypyrrole-grafted nitrogen-doped graphene (PPY-g-NGE) was successfully synthesized by simultaneous modification of graphene through nitrogen doping and polymeric grafting, and used for the detection of paraquat (PQ). The chemical structure, morphology and interaction of the obtained PPY-g-NGE were verified by Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. The PPY-g-NGE modified glassy carbon electrode (GCE) was fabricated to investigate its electrochemical behavior and sensitive detection of PQ by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). It was found that the novel PPY-g-NGE modified GCE exhibited excellent electrochemical performance and electrocatalytic activity to the redox reaction of PQ, with comparison to NGE and non-grafted composite of PPY-NGE. The two reduction DPV peaks of PQ at −0.60 V and −1.00 V were significantly enhanced at the PPY-g-NGE modified electrode. Under the optimized condition, the reduction peak currents of PQ at the PPY-g-NGE modified electrode were linear over the concentration range from 5.00 × 10 −8 to 2.00 × 10 −6 M with detection limits of 41 nM and 58 nM for Peak 1 and Peak 2, respectively. Besides the good sensitivity, the sensor also exhibited fine stability and strong anti-interference ability due to the well-combination and synergistic effect of polypyrrole and nitrogen doped graphene. [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]

Highlights: [•] Graphene/SnO2/PEDOT composites were obtained via one-pot synthesis method. [•] No obvious capacitance loss was found for the composite at 1Ag−1 after 5000 cycles in 1M H2SO4. [•] The composites present the enhanced capacitance and energy density in both acidic and neutral electrolytes. [ABSTRACT FROM AUTHOR]

Highlights: [•] CoMoO4/Graphene composites were prepared via one-step hydrothermal method. [•] The composites have high surface/body ratios and large electroactive regions. [•] The composites present better electrochemical properties than pure-CoMoO4. [•] The composite achieves a capacitance of 394.5Fg−1 at 1mVs−1. [ABSTRACT FROM AUTHOR]

Abstract: A novel poly(3,4-ethylenedioxy-thiophene) (PEDOT)/graphene oxide (GO) hybrid film was directly electrodeposited on a glassy carbon electrode. The SEM and TEM images of the as-obtained film revealed that PEDOT grew well on the surface of GO sheets with high affinity. The chemical structure of the composite was characterized by FT-IR, and the result conformed the formation of PEDOT doped by GO, leading to the enhanced electrochemical performance of the modified electrode. The composite modified electrode was utilized as an electrochemical sensor for the simultaneous detection of hydroquinone (HQ) and catechol (CT). It showed well electrocatalytic activity toward the redox of HQ and CT. Under the optimized condition, the response peak currents of the modified electrodes were linear over ranges from 2.5 to 200μM for HQ and from 2 to 400μM for CT. The sensor also exhibited good sensitivity with the detection limit of 1.6μM for both HQ and CT, and good stability. This study provides a new kind of composite modified electrode for electrochemical sensors. [Copyright &y& Elsevier]

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]

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]