Electrochemical Etching Switches Electrocatalytic Oxygen Evolution Pathway of IrO x /Y 2 O 3 from Adsorbate Evolution Mechanism to Lattice-Oxygen-Mediated Mechanism.

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.