Photo‐Driven Selective Sulfur Oxidation Enables Dual Modulation of Surface Reconstruction and Sulfate Anchoring for Enhanced Photoelectrochemical Properties

ABSTRACT This study presents a novel photo‐driven selective oxidation (PDSO) strategy for the synchronous modulation of surface structure and SO 4 2− group anchoring in In 2 S 3 /MgIn 2 S 4 (IS/MIS) heterostructure. Gradient sulfur vacancies were first engineered via hydrothermal synthesis and annealing to direct hole migration. Subsequently, a photo‐assisted chronoamperometric treatment was employed to selectively oxidize S 2− to SO 4 2− , which concurrently triggered Mg 2+ leaching and surface reconstruction. This dual modulation resulted in an over 200% expansion of the electrochemical active surface area and the effective anchoring of SO 4 2− species, which effectively promoted the participation of photogenerated holes in interface redox reactions via surface trap states. The optimized selective oxidation of rearranged‐S v IS/MIS (SO‐R‐IS/MIS) photoanode exhibited a remarkable 410 mV negative shift in onset potential (to 0.24 V vs. RHE) and delivered a photocurrent density of 7.8 mA cm −2 at 1.23 V vs. RHE. This work establishes a paradigm for precision surface engineering of photoanodes via photo‐driven selective reconstruction.