Work function-induced spontaneous built-in electric field in Ir/MoSe2 for efficient PEM water electrolysis

Bifunctional Ir catalysts for proton exchange membrane (PEM) water electrolysis offer transformative potential by streamlining electrolyzer while achieving efficient performance remains challenging due to the distinct conditions required for oxygen and hydrogen evolution reaction (OER and HER). Herein, we propose a theory-directed design of Ir-based bifunctional catalysts, Ir nanoparticles supported on mesoporous carbon spheres embedded with MoSe 2 (Ir/MoSe 2 @MCS), leveraging a work function (WF)-induced spontaneous built-in electric field to enhance catalytic performance. They demonstrate exceptional kinetics for both OER and HER, and potential application in the practical PEM electrolyzer, showcasing the effectiveness of this innovative approach. Low overpotentials of 252 mV for OER and 28 mV for HER to drive 10 mA cm –2 were observed, and the PEM electrolyzer showed the current density of 2 A cm –2 at 1.87 V and maintained stable activity at 1.65 V for over 30 h to deliver 1 A cm –2 . Density functional theory calculations reveal that the WF difference at Ir/MoSe 2 interface induces a spontaneous built-in electric field with asymmetric charge distributions, that modulate the electronic environment and d -band center of Ir promoting bifunctional active phase formation. This significantly lowers reaction barriers for water splitting by balancing intermediate adsorption, endowing the bifunctional activity.