Highly Active, Durable Dispersed Iridium Nanocatalysts for PEM Water Electrolyzers

Abstract

One of the primary challenges for proton exchange membrane (PEM) electrolyzers is the sluggish kinetics of the oxygen evolution reaction (OER) at the anode, which requires the use of precious metals or metal oxides, such as iridium (Ir) or iridium oxide (IrOx), as the OER catalyst. This study introduces a one-pot surfactant-free polyol reduction method to disperse iridium nanoparticles on a tungsten doped titanium oxide (WxTi1-xO2) support. The polyol reduction approach for the Ir/WxTi1-xO2 catalyst synthesis was systematically investigated to determine the influence of synthesis parameters on the catalysts’ physical properties, and its electrochemical activity and durability. The most promising synthesized catalyst with 38 wt% Ir (Ir38%/WxTi1-xO2) demonstrated five times higher mass activity than an Ir-black baseline (the industry standard catalyst) based on rotating-disk electrode (RDE) studies. When tested in a real water electrolyzer system, the synthesized catalyst enabled the Ir loading to be lowered by an order of magnitude while retaining a similar electrolyzer performance found for the baseline Ir-black catalyst. The Ir38%/WxTi1-xO2 catalyst also demonstrated remarkable stability, e.g., only small voltage (<20 mV) increase was observed during a 1200-hour durability test at a constant current density of 1500 mA/cm2.