Dealloying the Ir–P Bond Coordination to Strengthen d–p Orbital Affinity for Efficient Anion Exchange Membrane Water Electrolyzer

The d–p orbital hybridization of metal–based compounds can substantially impact their catalytic activity in water electrolysis. However, the metal-nonmetal chemical bond may in turn bring down the electrical conductivity and catalytic charge transfer, leading to an activity-kinetics trade-off. The co-effectuation of d–p hybridization and conductive metallic state is thus expectable to optimize the water-splitting electrocatalysis, but challengeable. Herein, we profile a P-doped Ir metallic (Ir-P) structure by dealloying the IrP₂ nanocrystals for the water electrolysis studies. Such a IrP₂→Ir-P dealloying is found to neighbour the Ir d-band and P p-band centers to strengthen the d–p orbital affinity, together with a decreased Ir-P coordination number. Resultantly, the catalyst actively delivers the hydrogen evolution reaction with ultralow overpotentials of 14, 25, and 64 mV at 10 mA cm⁻² in alkaline, acidic, and neutral media, respectively. It also puts forward the anion-exchange-membrane water electrolyzer with a low cell voltage of 1.65 V at 1 A cm⁻² under 60°C. The device further presents a durable operation with a small voltage decay of 0.132 µV h⁻¹ over 500 h at 0.5 A cm⁻². This work navigates a viable pathway to rationalize efficient water splitting catalysts through metal-nonmetal bond engineering.