Electrodeposited IrO2/Ti electrodes as durable and cost-effective anodes in high-temperature polymer-membrane-electrolyte water electrolyzers

Abstract

In this study, IrO2-coated Ti mesh (e-IrO2/Ti) is proposed to be an efficient and durable oxygen electrode for high-temperature polymer-membrane-electrolyte water electrolyzers (HT-PEMWEs). A thin IrO2 film of submicron thickness was uniformly coated onto a porous Ti mesh substrate by anodic electrodeposition. The electrodeposited IrO2 film plays the dual role of a catalyst layer for the oxygen evolution reaction (OER), and a corrosion-protection layer that prevents oxidation of the inner Ti. The e-IrO2/Ti exhibited high performance (0.97 A cm(-2) at 1.6 V) despite a low IrO2 loading (0.4 mg cm(-2)) in single-cell tests conducted at 120 degrees C, which is comparable to that of conventional electrodes with greater catalyst loadings (0.8-5 mg cm(-2)). Furthermore, corrosion polarization tests reveal that the IrO2 coating physically blocks exposure of the Ti diffusion layer, thereby reducing Ti corrosion by 82% in 0.5 M H2SO4 at 25 degrees C. The low degradation rate (1.5 mA cm(-2) h(-1) (0.11% h(-1))) obtained in aging experiments at 120 degrees C and 1.72 V (voltage efficiency of 85%) confirms the excellent stability of this electrode.