Harnessing lattice oxygens in a high-entropy perovskite oxide for enhanced oxygen evolution reaction

Abstract

The development of highly active and stable electrocatalysts for the oxygen evolution reaction (OER) is the main challenge in water electrolysis for green hydrogen production. Although Ru-based electrocatalysts have been in use for the past few decades, their stability in the reaction medium remains a major concern. Herein, a high-entropy simple perovskite oxide Ba_0.33Sr_0.67Co_0.33Ti_0.165Ru_0.165Sb_0.33O₃ (BSCTRS) is designed and synthesized by introducing Ru at 16.5 mol% B-site positions of Ba_0.33Sr_0.67Co_0.33Ti_0.33Sb_0.33O₃ (BSCTS) to achieve enhanced lattice oxygen participation. The BSCTRS perovskite electrocatalyst exhibits an OER overpotential similar to RuO₂ at 10 mA cm⁻² and a far superior OER overpotential (340 mV) compared to the benchmark RuO₂ at 100 mA cm⁻². Moreover, BSCTRS shows ∼20% lower Tafel slope and ∼120% higher TOF than Ba_0.33Sr_0.67Co_0.33Ti_0.33Sb_0.33O₃. This results in a significant enhancement of current density to 263 mA (at 1.58 V vs. RHE) for BSCTRS compared to only 99 mA for the parent BSCTS. The enhanced activity of the catalyst stems from optimal filling of e_g orbitals of the active metals and greater lattice oxygen participation. The work demonstrates the ability of high-entropy stabilized simple perovskite compositions with low concentrations of active noble metals to significantly enhance OER activity.