Nickel–cobalt oxide nanoparticles as superior electrocatalysts for enhanced coupling hydrogen evolution and selective ethanol oxidation reaction

Abstract

The selective oxidation of organic small molecules not only promotes cathodic hydrogen production, but also acts as an alternative reaction to the anodic oxygen evolution reaction of electrolytic water, producing value-added products at the anode. In this context, a bimetallic Ni–Co based oxide with a controllable ratio is prepared, acting as a high-performance electrocatalyst for the coupling reaction between the ethanol oxidation reaction (EOR) and the hydrogen evolution reaction (HER). The optimal Ni_0.67Co_0.33O_x nanoparticle (NP) anodic electrode, with Pt wire as the cathode, achieved a current density of 126 mA cm⁻² at a fixed potential of 1.6 V (versus RHE) and an ethanol-to-acetate Faraday efficiency of 85.74%. Additionally, the anodic EOR can be coupled with the hydrogen evolution reaction on the Co₃O₄-based cathode, only requiring a cell voltage of 1.6 V to generate a current density up to 145 mA cm⁻². Further density functional theory (DFT) calculations suggest that moderate doping of Co atoms helps to reduce the total energy barrier of the dehydrogenation reaction and the energy of the rate-limiting step. Our study provides insightful findings for enhanced hydrogen production with electrochemical conversion into acetate from ethanol in alkaline media.