Surface hydroxylation engineering to boost oxygen evolution reaction on IrO2/TiO2 for PEM water electrolyzer

Abstract

Dynamic evolutionary hypervalent Ir species (HVI) plays a decisive role in promoting the catalytic activity towards acidic oxygen evolution reaction (OER) on Ir-based electrocatalysts, but regulating the efficient formation of HVI remains a big challenge. Herein we propose surface hydroxylation engineering to accelerate the formation of HVI along the OER process on the OH-rich IrO/TiO electrocatalyst. In-situ/operando spectroscopies demonstrate that the high concentration OH ligand accelerates the formation of HVI. DFT calculation clarifies that the dynamically evolved HVI benefits to weakening the adsorption free energy and thus boosting the OER kinetics. Differential electrochemical mass spectrometry with O isotope labelling experiment further unveils that the OH ligand directly participates in the OER cycle, facilitating the rapid oxidation of Ir to Ir and the O-O bond formation. PEM water electrolyzer with the optimized IrO/TiO electrocatalyst delivers a low cell voltage of 1.787 V at 2 Acm with an inaccessible low Ir usage of ca. 0.08 g/kW, while maintaining a good stability over 350 h, with an estimated cost of US$0.88 kg of H, much lower than 2026 US-DOE target.