Modulating the valence electronic structure using earth-abundant aluminum for high-performance acidic oxygen evolution reaction

Iridium oxide (IrO2) is the most widely used anode catalyst for a proton exchange membrane water electrolyzer (PEMWE). However, its high cost and poor intrinsic activity impede its practical application, which calls for the development of catalysts devoid of Ir or with minimal Ir content. Herein, we designed a facile synthetic route incorporating Al, a p-block metal, into RuO2 and RuIrOx for a durable PEMWE. Al dopants favorably modulate the valence electronic structure of Ru–O hybridized orbitals, which tunes the adsorption energy of oxygen intermediates, consequently promoting the formation of O–O bonds. The optimized Al-doped RuIrOx requires an overpotential of 178 mV at 10 mA cm−2 and maintains the high activity for over 300 h at 100 mA cm−2. In a PEMWE, a high current density of 4.1 A cm−2 at 2.0 V was achieved with negligible performance degradation at 1.0 A cm−2 for 60 h.