The role of oxygen vacancies : triggering lattice oxygen oxidation mechanism in acidic OER

Abstract

Rational design of highly efficient, acid-stable electrodes for oxygen production is crucial in the development of proton exchange membrane (PEM) electrolyzers. Spinel oxides have recently been discovered as effective catalysts for oxygen evolution reaction (OER), owing to their moderate adsorption energy of reaction intermediates. In this study, we present our findings that the incorporation of oxygen vacancies (OV) into spinel oxides could enable a switch from the inefficient adsorbate evolution mechanism (AEM) to the highly efficient lattice-oxygen oxidation mechanism (LOM) for OER. We show that oxygen vacancies promote OER mechanism transitions in oxide electrocatalysts while maintaining stable catalytic performance. These results provide important insight into the role of elemental doping in regulating reaction pathways under acidic conditions. The representative Mn/Ru-Co3O4 catalyst can reach an impressive low overpotential of 230 mV to deliver a current density of 10 mA cm−2, which is ∼ 48 % lower than the pristine Co3O4. Theoretical calculations reveal OV around the active sites could lower the energy barrier in the rate-determining step and prevent the formation of *OOH species. As a result, this process disrupts the scaling relationship observed in traditional AEM mechanisms, leading to a substantial enhancement in overall catalytic activity. Graphical abstract: [Figure not available: see fulltext.]