LAUSR

The efficient production of hydrogen via acidic water electrolysis is hampered by the sluggish kinetics of the oxygen evolution reaction (OER) and the scarcity of robust bifunctional catalysts. Iridium-based materials have been recognized as promising active sites; however, the atomic utilization should be maximized, and the stability requires further enhancement. This work introduces a support-intensified catalyst design that features covalent Ir-P-Mo linkages for achieving robust water dissociation. Theoretical calculations reveal that the Ir─P─Mo bond enhances hydrogen evolution reaction (HER) activity by optimizing hydrogen adsorption, while the Ir─O─Mo bond is more favorable for OER. Guided by this principle, a catalyst with coexisting Ir-O-Mo and Ir-P-Mo linkages is rationally synthesized, which exhibits exceptional bifunctional performance in acid solution, including low overpotentials of 33 mV for HER and 249 mV for OER at 10 mA cm-2. When configured in a symmetrical two-electrode electrolyzer, it requires only 1.501 V to reach 10 mA cm-2 and demonstrates remarkable stability for 250 h with minimal voltage degradation. This work verifies the critical role of interfacial bond engineering in developing efficient and durable iridium-based electrocatalysts for practical acidic water splitting.