Ultrafine IrRu Nanoparticles toward Efficient Oxygen Evolution Reaction in Acidic Media

Proton exchange membrane water electrolyzers (PEMWEs) are capable of mass-producing green hydrogen with renewable and wave-trough electricity, but confront the challenge of the lack of advanced electrocatalysts to accelerate sluggish oxygen evolution reaction (OER). Herein, we report the synthesis of ultrafine IrRu alloy nanoparticles (1.6 ± 0.3 nm) by coprecipitation of IrCl3, RuCl3, and HCOONa in water to allow Ir3+ and Ru3+ to be well dispersed and enclosed in the matrix of crystalline HCOONa, followed by heat treatment of HCOONa to reduce Ir3+ and Ru3+. Remarkably, the overpotential of IrRu toward acidic OER at 10 mA cm–2 is merely 230 and 194 mV at 51 and 204 μgIrRu cm–2, respectively. The high electrochemically active surface area (ECSA) of 577.1 m2 g–1 and high specific activity (SA) of 22.7 μA cm–2 at 1.45 V vs RHE would contribute to the exceptional OER activity. In addition, the electron transfer from Ir to Ru in IrRu should significantly boost the OER activity according to X-ray photoelectron spectroscopy (XPS). IrRu also shows an excellent stability during 10 h of a chronopotentiometry (CP) test at 10 mA cm–2. Eventually, the high OER activity of IrRu was verified in a PEMWE.