Electronic structure regulation in medium-entropy CoNiFeSe enabling efficient and durable oxygen evolution electrocatalysis

Developing highly efficient and durable electrocatalysts for the oxygen evolution reaction (OER) holds great promise in revolutionizing the sustainable energy-conversion technologies, which greatly rely on the surface electronic structures. However, constructing catalytically active medium-entropy materials encounters great challenges due to the complex composition and the unsolved electronic structure-performance relationship. In this study, medium-entropy metal selenide (CoFeNiSe) with a cumulus-like architecture is fabricated through the selenylation of trimetallic hydroxide precursors. The medium-entropy CoFeNiSe manifests outstanding electrocatalytic OER activity and kinetics, that is, a low overpotential of 268 mV at 10 mA cm^-2 and a Tafel slope of 53.33 mV dec^-1 in 1 M KOH, outperforming the entropy-poor binary CoFeSe and CoNiSe, as well as its unary CoSe counterparts. It has been found experimentally and theoretically that the effective modulations of the valency and the d-band center at an optimal level regulate the adsorption/desorption ability of reaction intermediates via multimetallic electron interactions. This work provides valuable insight into the electronic structure regulation in entropy-rich materials, shedding light on the development of current green energy conversion technologies.