Sulfur Vacancy‐Rich ZnS/ZnCdS S‐Scheme Heterojunction for Efficient Photocatalytic Hydrogen Evolution Under Visible‐Light Irradiation

S‐scheme heterojunction has demonstrated simultaneously extended light absorption and efficient charge separation while preserving strong redox potentials for excellent photocatalytic performance, yet the synergistic mechanism of defect‐induced visible‐light utilization and interfacial charge transfer in S‐scheme systems remains poorly explored. Herein, a sulfur vacancy‐rich ZnS/ZnCdS S‐scheme heterostructure, with Zn/(Zn+Cd) ratio ≈0.7, is rationally constructed via a facile cation‐exchange strategy, and demonstrates exceptional hydrogen‐evolution rate of 59.71 mmol h −1 g −1 under visible‐light irradiation ( λ ≥ 420 nm), which is 426.5 times as that of pristine ZnS and 7 times that of ZnCdS, with an apparent quantum yield (AQY) of 54.84% at 420 nm, surpassing most reported metal sulfide‐based photocatalysts. Notably, with the in‐situ introduction of NiS x cocatalyst, the AQY is further increased to 76.75%. Experimental and theoretical analyses reveal that the as‐prepared heterostructure not only effectively broadens the light absorption range of ZnS by introducing mid‐gap energy levels generated by sulfur vacancy (S v ), but also accelerates the interfacial charge separation of the S‐scheme heterostructure by acting as interfacial charge bridges via the as‐introduced intermediate energy level. This dual function substantially improves photon utilization and suppresses charge recombination, promising efficient visible‐light‐driven hydrogen evolution through the defect‐mediated interfacial engineering of S‐scheme heterostructures.