Sacrificial Leaching Enables Fe‐Rich Oxyhydroxide Reconstruction on In ₂ S ₃ Photoanode

ABSTRACT Photoelectrochemical (PEC) water splitting is often constrained by interfacial recombination and sluggish oxygen evolution, highlighting the importance of constructing efficient catalytic junctions on photoanodes. Here, we report that a brief PEC activation restructures a photodeposited NiFe oxyhydroxide layer on In 2 S 3 into a self‐optimized catalytic interface through sacrificial Ni leaching‐induced interfacial reconstruction. Activation triggers selective Ni leaching and simultaneous surface porosification, generating an amorphous FeOOH‐like overlayer that is intimately coupled to the sulfide surface. Spectroscopic, kinetic, and theoretical analyses indicate that reconstruction strengthens electronic coupling, suppresses carrier recombination, and lowers charge‐transfer resistance at both the semiconductor/cocatalyst and cocatalyst/electrolyte interfaces. Consequently, the activated photoanode delivers 9.58 mA cm −2 at 1.23 V versus reversible hydrogen electrode, placing its performance among the best reported for oxide and sulfide photoanodes under comparable conditions. Beyond performance enhancement, this work highlights operando interface reconstruction as a powerful route for transforming static cocatalyst contacts into dynamically optimized catalytic junctions, providing new insights for the design of high‐efficiency solar water oxidation systems.