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We provide a novel strategy to eliminate the epoxy group from the basal plane of graphene platelets. Given that the current reduction methods are unsatisfactory to clean the epoxides or sometimes cause undesirable structure deformations, the proposed strategy restores the original hexagonal carbon network without creating other new defects. To the best of our knowledge, the electric field mediated graphene oxide (GO) reduction has not yet been systematically investigated. The capability would permit the improvement of existing GO reduction methods and assist in the fabrication of high-quality graphitic materials. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Abstract A novel reduced graphene oxide/poly(1,5-dihydroxynaphthalene)/TiO 2 (RGO/PDHN/TiO 2) ternary nanocomposite conducting polymer is electrochemically synthesized on gold electrodes for supercapacitor applications. The RGO/PDHN/TiO 2 nanocomposite polymer film is characterized by field-emission scanning electron microscopy (FESEM), Fourier transform infrared spectra (FT-IR), and energy dispersive X-ray spectrometry (EDX) and X-ray diffraction (XRD). The electrochemical performance of the nanocomposite polymer-modified electrode in 1.0 M HClO 4 is investigated by various electrochemical methods such as cyclic voltammetry (CV), galvanostatic charge-discharge, and electrochemical impedance spectroscopy (EIS). The RGO/PDHN/TiO 2 nanocomposite polymer film in a three-electrode system exhibits a large specific capacitance of 556 F g−1 in comparison with those obtained using RGO/PDHN (432 F g−1) and PDHN (223 F g−1) at a current density of 2.4 A g−1. Simultaneous usage of the electrical double layer capacitance (EDLC) of RGO with the pseudocapacitive behavior of PDHN and TiO 2 results in the large specific capacitance in RGO/PDHN/TiO 2. The electrochemical self-stabilities of RGO/PDHN/TiO 2 , RGO/PDHN, and PDHN polymer films are investigated by continuous cycling between −0.20–0.45 V. The RGO/PDHN/TiO 2 nanocomposite yields longer self-stability than that of other polymers after 1700 cycles and maintains about 74% of the initial capacitance values. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • MOFs-deriver N-doped CoC x /FeCo@C/rGO was synthesized as a catalyst for ORR. • The ORR activity of N-doped CoC x /FeCo@C/rGO was higher than that of the Pt/C. • The OER activity of N-doped CoC x /FeCo@C/rGO was higher than that of the RuO 2. • The synergistic effect of CoC x /FeCo and N-doped carbon results in the activity. Abstract Metal-organic framework derived materials have a great promise as non-precious metal-based electrocatalysts for large-scale applications of energy storage and transition devices with low-cost and high efficiency. Here, we report a high performance core-shell-structured nitrogen-doped CoC x /FeCo@C/reduced graphene oxide (rGO) hybrid, which is derived from Fe-doped Co 3 [Co(CN) 6 ] 2 MOFs, as bifunctional catalysts for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Structure characterizations show that the carbon shell of CoC x /FeCo and graphene support are bonded to each other, which offer a large surface area and stable anchoring sites for the CoC x /FeCo. Electrochemical tests show that N-doped CoC x /FeCo@C/rGO hybrid exhibits superior onset potential (1.0183 V vs RHE), half-wave potential (0.9653 V vs RHE), peak current intensity (0.9233 mA/cm−2) and long-term durability for ORR than those of Pt/C (onset potential, half-wave potential and peak current intensity are 1.0174 V and 0.9213 V, 0.8233 mA/cm−2, respectively) in 0.1 M KOH electrolyte. The overpotential of the hybrid for OER is only ∼390 mV at a current intensity of 10 mA/cm−2, which is close to that of the RuO 2. The excellent electrocatalytic properties of this hybrid make it a great potential to be substitute for precious-based catalysts for ORR and OER in fuel cells and water splitting. [ABSTRACT FROM AUTHOR]

The boron doped carbon nanomaterials that include in-plane B–C bonds at the local structure are considered as an efficient electrocatalyst for oxygen reduction reaction (ORR). However, a fundamental understanding about the electrocatalytic activity of out-of-plane B–C bonds remains unclear. Herein, we synthesize a boron nanosheet/reduced graphene oxide (B@rGO) heterostructure, where out-of-plane B–C chemical bonds are formed at the heterointerfaces, greatly improving the ORR activity. As verified by the combined experimental analyses and theoretical calculations, the ORR activity is boosted because the out-of-plane B–C chemical bonds contribute to the cleavage of O–O bond of O 2 * intermediate. The B@rGO heterostructure composite exhibits much higher ORR activity than those of respective boron and rGO nanosheets as demonstrated by half-wave potential, Tafel slope, electron transfer number, and electrochemical active area, achieving better durability and methanol tolerance than the commercial 20 wt% Pt/C catalyst. In this context, primary Zn–air battery, using the as-synthesized B@rGO heterostructure composite as metal-free electrocatalyst, delivers high peak power density of 131 mW cm−2 and specific capacity of 639.3 mAh g Zn −1. • Boron nanosheet/reduced graphene oxide heterostructure is constructed. • The out-of-plane B–C chemical bonds are formed at the heterointerfaces. • The ORR activity is boosted by the out-of-plane B–C bonds. • B@rGO heterostructure achieves high ORR activity and durability. • The Zn–air battery delivers a high power density of 131 mW cm−2. [ABSTRACT FROM AUTHOR]

• Few-layered ReSe 2 nanoflakes are vertically arranged on rGO. • Mechanism of vertical growth of ReSe 2 on rGO is clarified by DFT calculation. • Plentiful exposed edges/corners on ReSe 2 facilitate the generation of active sites for electrocatalysis. • Improved electrical conductivity and electrochemical stability of ReSe 2 are realized after hybrid with rGO. • Prominent HER performance is measured with a low overpotential and small Tafel slope. Hydrogen evolution reaction (HER) by water splitting has made a significant contribution to producing large amounts of hydrogen gas as the next generation fuel. Development of highly efficient, economically viable, and electrochemically stable HER electrocatalysts has accordingly become a prerequisite for practical implementation of large scale water electrolysis. Mono/few-layered transition metal dichalcogenide (TMD) based HER-electrocatalysts have recently garnered great interest due to their diverse tunable electrochemical properties. However, they still face intrinsic limitations such as self-aggregation, rare active sites, high electrical resistance, and long-term electrochemical instability. To tackle these challenges, we designed and synthesized a novel electrocatalyst comprising active site-rich rhenium diselenide (ReSe 2) nanoflakes perpendicularly anchored on a reduced graphene oxide (rGO) nanosheet support via a facile one-step hydrothermal synthesis. The rGO support provides a growing platform for few-layered ReSe 2 nanoflakes while facilitating plentiful exposure of edge/corner sites of ReSe 2 , highly desirable for maximizing the catalytic activity of ReSe 2 @rGO. The synthesized ReSe 2 @rGO exhibits a low overpotential of 145.3 mV at a current density of 10 mA·cm−2 with a Tafel slope of 40.7 mV·dec−1 for the HER process due to the synergistic combination of high surface density of unsaturated coordination sites, remarkably accelerated electron transfer, and enhanced electrochemical stability. This outcome suggests using structurally regulated hybridization of TMDs and graphene as a platform toolkit for developing high performance HER catalysts. [ABSTRACT FROM AUTHOR]

• Bi-functional magnetic GO adsorbents with ion selectivities were developed. • Magnetite nanoclusters were grown in-situ on GO oxygenous groups. • Crown ethers as ligands were covalently grafted via linkers on GO backbone. • Magnetic GO tethered with 12CE4 was highly effective and selective towards Li+. • Wide selection of CE decorated magnetic GOs were fabricated for various applications. Metal ions (Mn+) in water are considered as environmental pollutants, as industrial impurities or as potential secondary sources for valuable metals. Increasing generation of complex feed streams has raised the need for more specialized adsorbents that could preferentially capture the target Mn+. While graphene oxide (GO) is an effective adsorbent, its indiscriminate sequestration negatively affects its selectivity. To meet the growing demand for more Mn+-selective materials, GO adsorbents with dual features of ion recognition and magnetic responsiveness were developed. The bi-functional GOs were fabricated by in-situ nucleation of Fe 3 O 4 nanoclusters on GO oxygenous groups and by direct grafting of ethynylbenzene linkers on its backbone, which served as tethering sites for the macrocyclic crown ether (CEs) ligands with tunable Mn+ affinities (i.e. CE@Fe 3 O 4 -rGO). As proof-of-concept, 12CE4@Fe 3 O 4 -rGO was proven highly selective for Li+ capture, achieving α = 367–14,513 against Na+, K+, Mg2+, Ca2+ in seawater. Its Langmuir-type Li+ adsorption achieved nearly ~100% 12CE4 utilization (1.03 mmol g−1 CE loading). Its pseudo-second uptake rate demonstrated its rapid Li+ capture. 12CE4@Fe 3 O 4 -rGO is water-dispersible, magnetically retrievable, and recyclable with consistent Li+ uptake performance. By replacing the CEs with aza15CE5, aza18CE6 and dibenzo-24CE8, three more types of CE@Fe 3 O 4 -rGOs (1.24–1.71 mmol CE g−1) were successfully synthesized with varying affinities towards heavy metals, radionuclides and alkali metal ions. These findings highlight the versatility of the proposed technique in producing a wide selection of CE@Fe 3 O 4 -rGOs which can be used for selective Mn+ capture in various application for water decontamination, salts removal, and resource recovery. [ABSTRACT FROM AUTHOR]

This report describes the design and fabrication of reduced graphene oxide/polyindole/ γ -Al 2 O 3 (RGO/PIn/ γ -Al 2 O 3) ternary nanocomposite electrode materials for asymmetric supercapacitors. The nanocomposite was prepared by chronoamperometry on a gold electrode. Polyindole (PIn) and RGO/PIn were prepared electrochemically and their performances were compared with RGO/PIn/ γ -Al 2 O 3. The structures and morphologies of samples were characterized by FESEM, EDX, XRD and FT-IR. To get electrochemical charasteristics of the RGO/PIn/ γ -Al 2 O 3 electrode in a HClO 4 solution electrolyte Cyclic voltammetry (CV) technique, electrochemical impedance spectroscopy (EIS) and galvanostatic charging and discharging were carried out. The results show that RGO/PIn/ γ -Al 2 O 3 performed well with a specific capacitance of 308 F/g in comparison with PIn (93 F/g) and RGO/PIn (214 F/g). RGO as the negative and RGO/PIn/ γ -Al 2 O 3 as the positive electrode were used to fabricate an asymmetric supercapacitor. The asymmetric RGO/1.0 M HClO 4 /RGO/PIn/ γ -Al 2 O 3 supercapacitor can be cycled in a high voltage range of 0.0–1.4 V that displayed a high energy density of 10 Wh/kg at a 3880 W/kg power density and a specific capacitance of 38.46 F/g. Furthermore, after 5000 cycles, 83% of the RGO/PIn/ γ -Al 2 O 3 initial capacitance was maintained. Image 1 • A novel Au/RGO/PIn/ γ -Al 2 O 3 nanocomposite electrode material is fabricated. • The Au/RGO/PIn/ γ -Al 2 O 3 is used as supercapacitors. • The RGO/PIn/ γ -Al 2 O 3 show high Cs and excellent electrochemical performance. • An asymmetric supercapacitor (ASC) are fabricated using RGO/PIn/ γ -Al 2 O 3. • The ASC displays high Cs and retention of 83% after 5000 cycle. [ABSTRACT FROM AUTHOR]