Direct Z‐Scheme Zn _0.5 Cd _0.5 S/SrTiO ₃ Heterojunction for Accelerated Charge Separation and Photocatalytic H ₂ Generation

ABSTRACT Photocatalytic hydrogen (H 2 ) generation is regarded as a sustainable pathway to alleviate global energy demand; however, achieving high conversion efficiency remains a significant bottleneck. In this work, Zn 0.5 Cd 0.5 S/SrTiO 3 (ZCST) heterostructures were fabricated through a single‐step hydrothermal route. Structural analysis reveals that Zn 0.5 Cd 0.5 S (ZCS) nanospheres are homogeneously distributed on SrTiO 3 (STO) nanoplates, creating interfacial contact and increasing the number of exposed active sites. Among the synthesized photocatalysts, ZCST30 delivers the maximum H 2 production rate of 13.3 mmol·g −1 ·h −1 , exhibiting ∼ 416‐ and ∼ 8‐fold enhancements compared to pristine STO (0.03 mmol·g −1 ·h −1 ) and ZCS (1.6 mmol·g −1 ·h −1 ), respectively. Additionally, the optimized ZCST30 shows an approximately 8.4‐fold higher apparent quantum yield (AQY) compared to bare ZCS under 420 nm irradiation. Photocurrent measurements further show that ZCST30 achieves a current density of 5.64 µA/cm 2 , which is ∼12‐ and ∼6‐fold greater than those of STO and ZCS, respectively. This remarkable improvement originates from facilitated charge migration across the ZCS/STO interface, where the heterojunction generates an internal electric field that accelerates carrier separation while preventing recombination. Notably, time‐resolved fluorescence measurements show that ZCST30 exhibits the shortest average electron lifetime (1.426 ns), indicating faster electron extraction and participation in the reduction reaction. Combined with the band‐edge alignment obtained from Mott–Schottky and optical analysis, these results support the formation of a direct Z‐scheme charge‐transfer pathway within the ZCST heterostructure, enabling efficient separation and utilization of photogenerated carriers. Overall, this study provides valuable insights for the rational design of next‐generation high‐performance photocatalysts.