Bimetallic ZnCo-MOF derived porous Ir-doped cobalt oxides for water oxidation with improved activity and stability

Abstract

The slow reaction kinetics of the oxygen evolution reaction (OER) significantly impedes the advancement of overall water splitting for practical energy conversion and storage. Transition metal oxides have emerged as competitive alternatives to noble metal-based OER catalysts because of their adaptable composition, tunable electronic structure, and abundant availability. Here, we present a porous bimetallic zinc/cobalt oxide derived from a metal–organic framework (MOF) that is modified by a base-etching process, followed by further iridium loading. The resulting electrocatalyst, Ir-pZCO, exhibited satisfactory OER performance in alkaline conditions, attributed to its high concentration of oxygen vacancies and large specific surface area. Specifically, it demonstrated a small overpotential of 304 mV at 10 mA cm⁻² and a Tafel slope of 63.9 mV dec⁻¹, and maintained a decent current retention of 94.8% over 10 hours. This enhanced OER activity stems from the in situ formed oxygen vacancies and Ir introduction, supported by density functional theory calculations. This study offers a novel approach for the rational design and facile fabrication of porous MOF derivatives with abundant oxygen vacancies as well as metal-doping for desired electrochemical properties.