Multistage Electron Distribution Engineering of Iridium Oxide by Codoping W and Sn for Enhanced Acidic Water...

Developing efficient and robust anodic electrocatalysts to implement the proton-exchange membrane (PEM) electrolyzer is critical for hydrogen generation. Nevertheless, the only known applicable anode catalyst IrO_x in PEM electrolyzers still requires high overpotential due to the weak binding energy between oxygen intermediates and active sites, limiting its wide applications. Herein, a ternary Ir_0.7 W_0.2 Sn_0.1 O_x nanocatalyst synthesized through a sol-gel strategy, exhibits a low overpotential of 236 mV (10 mA cm^-2 _geo ) for thoxygen evolution reaction (OER), accompanied with robust durability over 220 h at 1 A cm^-2 _geo in 0.5 m H₂ SO₄ . Moreover, the optimized Ir_0.7 W_0.2 Sn_0.1 O_x delivers a prominent mass activity of 722.7 A g^-1 _Ir at 1.53 V (vs RHE), which is around 34 times higher compared with that of IrO_x . The mircrostructural analyses reveal that codoping of W and Sn stabilizes Ir with a valence state lower than 4+ through multistage charge redistribution, avoiding the overoxidation of Ir above 1.6 V versus RHE and enhancing the acidic OER performance. Additionally, density functional theory calculations reveal that codoping of W and Sn moves the d band center of Ir to the Fermi level, thus enhancing the binding energies of oxygen intermediates with Ir sites and decreasing the energy barrier toward acidic OER.