Oxygen vacancy-mediated high-entropy oxide electrocatalysts for efficient oxygen evolution reaction

Transition metal oxides hold great potential for water splitting due to their tunable electronic structures and abundant availability. However, their inherently poor electrical conductivity and limited catalytic activity hinder their practical implementation. Herein, high-entropy oxide (FeCoNiCrCuO) electrocatalysts featuring grain-like structure and oxygen vacancies-enriched surface were synthesized through an ultra-fast non-equilibrium high-temperature shock. The introduction of oxygen vacancies modulates the electronic structure and increases the carrier concentration, accelerating the rate-determining step of the oxygen evolution reactions and reducing the overpotential of oxygen evolution reactions. Consequently, the synthesized FeCoNiCrCuO electrocatalyst delivers a low overpotential of 256 mV at a current density of 10 mA·cm⁻² and a Tafel slope of 48.2 mV·dec⁻¹ in 1 M KOH, which is superior to samples lacking oxygen vacancies after annealing. This study presents an alternative approach to enhancing OER activity by employing a high-entropy oxide engineering strategy.