Interfacial electronic reconstruction of cobalt oxide-iridium oxide heterojunctions for efficient and durable acidic oxygen evolution.

The oxygen evolution reaction (OER) under acidic operating conditions is still a major limitation for proton exchange membrane water electrolysis (PEMWE) due to its intrinsically sluggish reaction kinetics. Herein, we report an in situ constructed Co3O4-IrO2 heterojunction catalyst with abundant interfacial sites, where strong interfacial electronic reconstruction is established to regulate the local electronic configuration of catalytic centers for enhanced acidic OER performance. The intimate coupling between Co3O4 and IrO2 induces pronounced interfacial electronic reconstruction accompanied by directional charge redistribution, thereby optimizing the electronic structure of Ir active sites, regulating oxygen intermediate adsorption, and promoting accelerated OER kinetics. Consequently, an overpotential of only 243 mV at 10 mA cm-2 and a Tafel slope of 47.58 mV dec-1 are achieved for the optimized Co3O4-IrO2 catalyst. Moreover, it maintains stable operation for 1000 h with negligible performance degradation. In PEMWE, the Co3O4-IrO2 achieves a low cell voltage of 1.64 V at 1.0 A cm-2 and demonstrates outstanding operational stability over 800 h. Theoretical and experimental results reveal that the interfacial electronic reconstruction originates from strong Co3O4-IrO2 electronic coupling, which tailors the electronic states of active Ir centers, optimizes oxygen-containing intermediate adsorption, and facilitates the O* → OOH* transformation by lowering the associated kinetic barrier, resulting in improved OER kinetics. Our findings highlight the role of interfacial electronic reconstruction in designing efficient and robust acidic OER catalysts.