Ultrathin Spinel‐Structured Nanosheets Rich in Oxygen Deficiencies for Enhanced Electrocatalytic Water Oxidation

TLDR

Electrochemical water splitting is a clean hydrogen production method, but its efficiency is limited by the sluggish oxygen evolution reaction. The study aims to design ultrathin spinel‑structured NiCo₂O₄ nanosheets with oxygen vacancies to enhance catalytic reactivity and provide a new route for advanced OER catalysts. The nanosheets were engineered to confine oxygen vacancies, and theoretical calculations show these vacancies lower H₂O adsorption energy, thereby improving OER efficiency. The resulting NiCo₂O₄ nanosheets achieved a current density of 285 mA cm⁻² at 0.8 V and an overpotential of 0.32 V, outperforming bulk counterparts and most non‑precious‑metal catalysts.

Abstract

Electrochemical water splitting is a clean technology for H2 fuels, but greatly hindered by the slow kinetics of the oxygen evolution reaction (OER). Herein, a series of spinel-structured nanosheets with oxygen deficiencies and ultrathin thicknesses were designed to increase the reactivity and the number of active sites of the catalysts, which were then taken as an excellent platform for promoting the water oxidation process. Theoretical investigations showed that the oxygen vacancies confined in the ultrathin nanosheet could lower the adsorption energy of H2O, leading to increased OER efficiency. As expected, the NiCo2O4 ultrathin nanosheets rich in oxygen vacancies exhibited a large current density of 285 mA cm(-2) at 0.8 V and a small overpotential of 0.32 V, both of which are superior to the corresponding values of bulk samples or samples with few oxygen deficiencies and even higher than those of most reported non-precious-metal catalysts. This work should provide a new pathway for the design of advanced OER catalysts.