Reduced valence state of iridium supported on antimony doped tin oxide as a highly active and robust oxygen evolution reaction electrocatalyst for proton exchange membrane-based electrolysis

We use facile microwaves (MWs)-assisted polyol method to synthesize metallic Ir-nanoparticles (Ir-NPs) supported on antimony-doped tin oxide (ATO). Parameters such as Ir loading, reaction temperature and reaction time were optimized to achieve high electrocatalytic performance of oxygen evolution reaction (OER) activity and durability under the corrosive OER environment of acidic electrolyzers. Electrocatalysts with varying Ir loading between 10 and 40 wt% were synthesized at two different temperatures (140 °C and 160 °C) to compare morphology, Ir valence state, OER activity and stability. This analysis has revealed efficient electrocatalyst synthesis with a narrow size distribution and homogeneous dispersion over the support surface. An electron rich state of Ir, contributing to the electrocatalyst activity and stability, was achieved at the synthesis temperature of 160 °C. Among the as-synthesized electrocatalysts, one, named Ir/ATO.AT-40-160, has demonstrated high activity (449 ± 2.7 A gIr−1) and high AST stability (75.1% retained current), reaching respectively 1.5 and 2 times those of a state-of-the-art commercial electrocatalyst. The high catalytic activity and excellent stability can both be attributed to the depressed overoxidation of the active Ir due to the low valence state, appropriate composition, and highly dispersed Ir NPs over the support surface.