Multivalence-State Tungsten Species Facilitated Iridium Loading for Robust Acidic Water Oxidation

The development of the proton exchange membrane water electrolyzer (PEMWE) is still limited by the prohibitive cost and scarcity of iridium (Ir)-based oxygen evolution reaction (OER) catalyst. This work presents a novel catalyst synthesized by precursor-atomization and rapid joule-heating method, successfully doping iridium atoms into polyvalent tungsten blends (W⁰, W⁵⁺, W⁶⁺) based on titanium substrate. The vacancy engineering of unsaturated tungsten oxide (W⁵⁺, W⁶⁺) reconstructs the electronic structure of the catalyst surface, which resulting in the low-valence state iridium species, avoiding excessive oxidation of iridium and accelerating the catalytic kinetics. Meanwhile, metallic tungsten (W⁰) improves the conductivity of catalyst and guarantees the stable existence of oxygen vacancy. The TiIrWO_x possesses excellent performance in acidic OER catalysis, requiring overpotential of only 181 mV to drive 10.0 mA cm^-2, and exhibiting a high mass activity of 753 A g_Ir ^-1 at an overpotential of 300 mV. The membrane electrode assembly (MEA) with TiIrWO_x as anode electrocatalyst can reduce the Ir consumption amount by >60% compared to commercial IrO₂, and it can operated over 120 h at a current density of 1.0 A cm^-2.