Support-Intensified Ir─P/O─Mo Cooperative Linkages for Robust Acidic Water Dissociation

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.