Constructing a medium-entropy spinel oxide FeNiMnO4/CeO2 heterojunction as a high-performance electrocatalyst for the oxygen evolution reaction

Abstract

Medium-entropy oxides are commonly employed as electrocatalysts for the oxygen evolution reaction (OER) in electrolysers aimed at producing sustainable hydrogen. However, their poor conductivity poses a significant obstacle to further enhancing their electrocatalytic activity. It is therefore imperative to develop stable and highly active non-precious metal electrocatalysts for the advancement of sustainable energy technologies. CeO₂ is incorporated into the FeNiMnO₄ medium-entropy spinel oxide system as an “electron pump” to facilitate electron transfer from FeNiMnO₄ to CeO₂. Benefiting from the heterogenous interface and medium-entropy system, the medium-entropy spinel oxide FeNiMnO₄/CeO₂ heterojunction electrocatalyst exhibits exceptional activity and stability for the alkaline OER. It requires an overpotential of 241 mV to reach the benchmark current density of 10 mA cm⁻² with a lower Tafel slope of 44.8 mV dec⁻¹. Theoretical calculations indicate that the incorporation of CeO₂ effectively lowers the barriers for the potential-determining steps in the OER, and optimizes the electronic structure to facilitate the OER process. The present study demonstrates that constructing medium-entropy heterojunction materials represents a crucial approach towards developing efficient and durable OER electrocatalysts.