Electrochemical Etching Switches Electrocatalytic Oxygen Evolution Pathway of IrOx/Y2O3 from Adsorbate Evolution Mechanism to Lattice‐Oxygen‐Mediated Mechanism

Abstract Oxygen evolution reaction (OER) plays key roles in electrochemical energy conversion devices. Recent advances have demonstrated that OER catalysts through lattice oxygen‐mediated mechanism (LOM) can bypass the scaling relation‐induced limitations on those catalysts through adsorbate evolution mechanism (AEM). Among various catalysts, IrO x , the most promising OER catalyst, suffers from low activities for its AEM pathway. Here, it is demonstrated that a pre‐electrochemical acidic etching treatments on the hybrids of IrO x and Y 2 O 3 (IrO x /Y 2 O 3 ) switch the AEM‐dominated OER pathway to LOM‐dominated one in alkali electrolyte, delivering a high performance with a low overpotential of 223 mV at 10 mA cm −2 and a long‐term stability. Mechanism investigations suggest that the pre‐electrochemical etching treatments create more oxygen vacancies in catalysts due to the dissolution of yttrium and then provide highly active surface lattice oxygen for participating OER, thereby enabling the LOM‐dominated pathway and resulting in a significantly increased OER activity in basic electrolyte.