Nanosized high entropy spinel oxide (FeCoNiCrMn)O as a highly active and ultra-stable electrocatalyst for the oxygen evolution reaction

High-entropy oxides (HEOs) with a multi-component single-phase structure are considered as promising electrocatalysts for the oxygen evolution reaction due to their good catalytic activity and tailorable electrochemical properties. Herein, a series of small-sized non-noble metal-based HEO nanoparticles composed of five transition metal elements of Fe, Co, Ni, Cr, and Mn are synthesized via a simple solvothermal strategy followed by different-temperature heat treatment. The HEO treated at 400 °C exhibits the best catalytic activity with an overpotential of 288 mV at a current density of 10 mA cm −2 and outstanding stability (potential change of only 1.3% after a 95 h OER test at 10 mA cm −2 ) in 1 M KOH electrolyte, outperforming the commercial RuO 2 electrocatalysts. The excellent catalytic performance, including the low overpotential, fast dynamics, and superb long-term durability, is mainly attributed to the advantages of the large number of active sites provided by ultra-small nanoparticles, the synergistic effect of various catalytically active metal elements, and the entropy stabilization effect. Therefore, this work enriches the selection of high-entropy oxide elements, provides an idea for solving the current problems of traditional methods, and develops a prospective material for OER catalysts. High-entropy oxides (HEOs) with a multi-component single-phase structure are considered as promising electrocatalysts for the oxygen evolution reaction due to their good catalytic activity and tailorable electrochemical properties.