Remarkable Mass Activities for the Oxygen Evolution Reaction at Iridium Oxide Nanocatalysts Dispersed on Tin Oxides for Polymer Electrolyte Membrane Water Electrolysis

In order to reduce the amount of noble metal catalysts for the oxygen evolution reaction (OER) in polymer electrolyte membrane water electrolysis (PEMWE) while maintaining high efficiency, we synthesized new catalysts: IrO x nanoparticles dispersed on Nb-SnO 2 and Ta-SnO 2 supports with fused-aggregate structures. IrO x nanoparticles with a uniform size of ca. 2 nm were highly dispersed on these supports. The OER activities were evaluated by linear sweep voltammetry (LSV) in 0.1 M HClO 4 at 80°C using a channel flow electrode cell. The IrO x /Ta-SnO 2 catalysts exhibited an apparent mass activity ( MA ) of 15 A mg Ir −1 for the OER at 1.5 V vs. RHE, which was 32 times higher than that of a conventional catalyst (mixture of Pt black and IrO 2 powders). This suggests a possible reduction of the loading of the noble metal anode catalyst to a level as low as 0.1 mg cm −2 at a voltage efficiency of 90% at 1 A cm −2 .