Thermally triggered surface reconstruction enables self-protective layer for enhanced charge transfer in CdIn2S4 photoelectrode

Regulating bulk carrier separation and surface reaction kinetics is critical for effective photoelectrochemical water splitting. Here, we simultaneously address these challenges by constructing a heterojunction through in situ thermal reconstruction of CdIn 2 S 4 , which generates an amorphous InO x passivation layer to stabilize the surface while Ru single-atom sites accelerate hole injection. This dual modification synergistically enhances charge separation and interfacial kinetics, yielding an applied bias photon-to-current efficiency (ABPE) of 2.11 % at 0.45 V and a photocurrent density of 4.56 mA cm −2 at 1.23 V vs. RHE. Combined theoretical and experimental analyses reveal that the InO x layer suppresses recombination, while Ru single atoms lower the energy barrier for oxygen evolution reaction by modifying rate-determining steps. This work demonstrates surface reconstruction as a versatile route to optimize both stability and catalytic activity in metal sulfide photoanodes.