Reduced Graphene Oxide-NiO/Ni Nanomembranes as Oxygen Evolution Reaction Electrocatalysts

Abstract

There is great interest in using carbon materials in the anode as a scaffold for nanostructural water-splitting catalysts. Here the graphene oxide membrane was used as a scaffold to grow nickel oxide/nickel heterostructures under thermal annealing at different temperatures. The formation of reduced graphene oxide (RGO)-NiO/Ni heterostructure membranes was confirmed by structural characterization and thereby used as electrocatalysts for the oxygen evolution reaction (OER) in basic solution. The OER performance was optimized with the sample annealed at 500 • C, with a NiO/Ni core/shell structure, where the average NiO size was ∼6 nm. A Tafel slope of 81 mV/decade was measured for the sample, with a potential of ∼1.76 V to achieve a current density of 10 mA/cm 2 . In comparison with the three-dimensional (3D) RGO foam previously studied, the catalysts on RGO membranes show weaker OER performance, possibly due to less porous surfaces in a tightly packed layered structure, which may limit the access of electrolytes for ion transport and reaction. Our current study suggests that future work may need to focus on 3D RGO foam scaffolds for growth of efficient water-splitting nanocatalysts. Hydrogen from water electrolysis as an alternative fuel has attracted intense attention.1,2 To replace rare and expensive noble metal electrocatalysts for water-splitting reaction, one of the best strategies currently under development is using low-cost approaches to develop earth-abundant catalysts at the nanoscale (<10 nm), and enhance their dispersion and electrical conductivity on conductive supports with a large number of active sites on porous surfaces.3-8 Arrangement of two different materials into hybrids with synergistic effects to enhance water-splitting performance has also been actively pursued. 9The splitting of water by electrolysis involves two half reactions, the hydrogen evolution reaction (HER) for producing hydrogen at the cathode, and the oxygen evolution reaction (OER) for producing oxygen at the anode. As an important half-reaction for water splitting, OER has been intensely studied for long time. 10,11 In particular, Nibased compounds have been used as active OER electrocatalysts. [10][11][12] Recently, there has been renewed interest in Ni-based nanostructural materials that have presented promising OER performance in alkaline conditions with enhanced activity and stability. [6][7][8]12,13 There have been an increasing number of reports that carbon materials are used in the anode as a scaffold or support for nanostructural water-splitting catalysts in alkaline solution. The graphene-based carbon materials include carbon nanotubes, 6 reduced graphene oxide, 8,12,14,15 graphene shells, 16 and carbon fibers. 7,17 The anodes show excellent stability under the water splitting tests, though traditional use of carbon materials on the anode for electrolysis is limited because of the electrochemical oxidation of carbon.18 Our recent work 8 and others 3-7 has demonstrated that carbon-based scaffolds provide crucial morpho...

Synthesis and water oxidation electrocatalytic and electrochromic behaviours of mesoporous nickel oxide thin film electrodes

“…The Tafel slope (62 mV dec À1 ) of the electrode (m-NiO-10-450) is comparable to that of cobalt and nickel-based water oxidation electrocatalysts in the literature. [32][33][34][35][36][37] The overpotentials, extracted from the Tafel equation, are 288 and 350 mV at current densities of 1 and 10 mA cm À2 , which are quite consistent with the experimental values once the IR drop is subtracted from the experimental data.…”

Biomimetic Nanomembranes: An Overview

“…Instead of using a photocatalytic structure, an alternative approach is to use electrocatalyst nanomembranes [195]. Wang et al used nanomembranes with reduced graphene oxide combined with NiO/Ni.…”

Role of Specific N-Containing Active Sites in Interconnected Graphene Quantum Dots for the Enhanced Electrocatalytic Activity towards Oxygen Evolution Reaction

“…In order to understand the role of interconnection and doping in GQDs towards OER activity, the electrochemical performance of two analogous materials, namely, GQDs (without any inter‐connection, doping or functionalization), N‐GQDs (only N‐doping, without any interconnection) has been studied systematically along with C‐GQDs and RuO 2 . Conclusively, C–GQDs render a much better OER activity ( η 10 mAcm‐2 : 350 mV ) as compared to other two analogues, Cobalt Phosphide Polyhedron (η 10 mAcm‐2 : 400 mV), pristine carbon nanotube (η 10 mAcm‐2 : 430 mV) and RGO – NiO / Ni nano membrane (η 10 mAcm‐2 : 450 mV), and a comparable one with nickel sulfide system …”