Switching the Oxygen Evolution Reaction Mechanism through the Creation of Disordered NiOOH Induced by Electrochemical Reconstruction.

Abstract

The electrochemical reconstruction behavior of electrocatalysts during the oxygen evolution reaction (OER) is the key to determining their performance. Despite its critical role, precisely controlling and rationally guiding this reconstruction behavior remains an elusive challenge. Here, an efficient strategy is reported to manipulate the reconstruction behavior of nickel oxides by concurrently introducing amorphous structure and easily oxidizable elements (i.e., Mo⁶⁺). Specifically, the amorphous structure promotes the reconstruction at a low potential and the oxidative removal of Mo⁶⁺, enabling the generation of disordered NiOOH (d-NiOOH) with abundant defects. Notably, the d-NiOOH markedly enhances the Ni-O covalency and thus triggers the reaction mechanism transition from the adsorption evolution mechanism (AEM) to the lattice oxygen-mediated mechanism (LOM). As a result, the d-NiOOH displays excellent performance for the OER with an overpotential of 201 mV at 100 mA cm^-2, surpassing the ordered NiOOH (o-NiOOH, 286 mV). Remarkably, an anion exchange membrane water electrolyzer (AEMWE) assembled with a-NiMoO as the anodic catalyst can attain a large current density of 1 A cm^-2 at a small voltage of 1.79 V, outperforming most of the reported electrocatalysts.