Importance of Surface IrOx in Stabilizing RuO2 for Oxygen Evolution

Abstract

The high precious metal loading and high overpotential of the oxygen evolution reaction (OER) prevents the widespread utilization of polymer electrolyte membrane (PEM) water electrolyzers. Herein we explore the OER activity and stability in acidic electrolyte of a combined IrO_x/RuO₂ system consisting of RuO₂ thin films with submonolayer (1, 2, and 4 Å) amounts of IrO_x deposited on top. Operando extended X-ray absorption fine structure (EXAFS) on the Ir L-3 edge revealed a rutile type IrO₂ structure with some Ir sites occupied by Ru, IrO_x being at the surface of the RuO₂ thin film. We monitor corrosion on IrO_x/RuO₂ thin films by combining electrochemical quartz crystal microbalance (EQCM) with inductively coupled mass spectrometry (ICP-MS). We elucidate the importance of submonolayer surface IrO_x in minimizing Ru dissolution. Our work shows that we can tune the surface properties of active OER catalysts, such as RuO₂, aiming to achieve higher electrocatalytic stability in PEM electrolyzers.