Interfacial Sites Engineering Minimizes Anodic Energy Loss Through Accelerated Deprotonation for High-Efficiency...

Achieving efficient solar-to-hydrogen (STH) conversion is essential for renewable energy storage, yet solar-driven water splitting remains fundamentally limited by energy losses associated with the anodic oxygen evolution reaction (OER). Herein, we deliberately combine Ir species with a NiFe model electrocatalyst to construct asymmetric Ir-O-Ni interfacial sites that optimize anodic reaction energetics. In situ spectroscopic analyses combined with theoretical calculations reveal that, in contrast to pristine NiFe operating via the conventional adsorbate evolution mechanism, the Ir-O-Ni interfacial sites directly participate in OER by lowering the *OOH deprotonation barrier and facilitating rapid proton transfer under alkaline conditions. Meanwhile, strong Ir-O orbital coupling stabilizes O-containing intermediates, thereby reducing the O-O bond formation barrier from 3.21 eV in pristine NiFe to 1.40 eV in NiFe-Ir. Consequently, NiFe-Ir delivers a low overpotential of 300 mV at a high current density of 500 mA cm^-2, corresponding to a 43.3% reduction in energy consumption compared to NiFe (430 mV). Importantly, the substantially reduced anodic energy dissipation translates directly into enhanced device-level performance, enabling the integrated photovoltaic-electrolyzer system to achieve an exceptional STH conversion efficiency of 19.7%. These results underscore interfacial engineering as a powerful and generalizable strategy for advancing practical solar water-splitting technologies.