In Situ Photoelectrochemical Chelation Programs Defect-Resilient Coordination Microenvironments for Enhanced Water Oxidation.

Abstract

Deep-level defects function as non-radiative recombination centers that throttle oxygen evolution reaction (OER) kinetics. Conventionally, static and pre-deposited passivation layers often fail during operation, disconnecting defect suppression from the creation and sustained maintenance of catalytically competent sites. Here, we address this limitation with a photoelectrochemically-driven microenvironment strategy that selectively manipulates the first coordination shell of surface Zn on ZnIn₂S₄. Under the in situ photoelectrochemical chelation process, hydroxyethylidene diphosphonic acid writes robust Zn-O-P motifs that subtly distort the Zn-S framework and convert deep traps into shallow states, thereby accelerating charge transfer while suppressing recombination. Density functional theory suggests that Zn-O-P lowers the OER overpotential and switches the rate-determining step from O^*→OOH^* to OOH^*→O₂ via stabilized ^*OOH intermediates. The optimized photoanode delivers a photocurrent density of 5.38 mA cm^-2 at 1.23 V_RHE, surpassing previously reported ZnIn₂S₄-based photoanodes. By unifying in situ deep-trap management and active site construction along a single chemical pathway, this work establishes a modular and general route for dynamic defect engineering and active site reconfiguration, advancing defect-tolerant innovations in energy conversion and storage.