Doping Shortens the Metal/Metal Distance and Promotes OH Coverage in Non-Noble Acidic Oxygen Evolution Reaction Catalysts

Abstract

Acidic water electrolysis enables the production of hydrogen for use as a chemical and as a fuel. The acidic environment hinders water electrolysis on non-noble catalysts, a result of the sluggish kinetics associated with the adsorbate evolution mechanism, reliant as it is on four concerted proton-electron transfer steps. Enabling a faster mechanism with non-noble catalysts will help to further advance acidic water electrolysis. Here, we report evidence that doping Ba cations into a Co₃O₄ framework to form Co_3-<i>x</i>Ba_<i>x</i>O₄ promotes the oxide path mechanism and simultaneously improves activity in acidic electrolytes. Co_3-<i>x</i>Ba_<i>x</i>O₄ catalysts reported herein exhibit an overpotential of 278 mV at 10 mA/cm² in 0.5 M H₂SO₄ electrolyte and are stable over 110 h of continuous water oxidation operation. We find that the incorporation of Ba cations shortens the Co-Co distance and promotes OH adsorption, findings we link to improved water oxidation in acidic electrolyte.