Synergistic engineering of sulfur vacancies and Z-scheme heterojunction in CdS/MoS2 for unlocking enhanced charge dynamics in photocatalytic hydrogen evolution

S vacancies and Z-scheme heterojunction synergize in CdS/MoS 2  for visible-light H 2  evolution at 4464.5 μmol·g -1 ·h -1 . • S vacancies as e -  traps and active sites synergize with Z-scheme, boosting charge separation and surface reactivity. • DFT shows S vacancies enhance interfacial orbital hybridization and lower charge-transfer barrier, confirming Z-scheme. • Optimized composite shows 82% retention after 10 cycles, highlighting defect-heterojunction synergy’s practicality. The integration of defect engineering and heterojunction construction provides a promising strategy for photocatalytic hydrogen evolution. This work addresses the knowledge gap regarding their synergistic effect by constructing a Z-scheme heterojunction between sulfur vacancy-rich CdS (S V -CdS) and MoS 2 . The optimal composite achieved a remarkable hydrogen evolution rate of 4464.5 μmol g -1 h −1 under visible light, which is nearly sixfold enhancement compared to pristine S V -CdS. Mechanistic studies reveal that sulfur vacancies function dually. They act as electron traps to suppress charge recombination and as active sites to facilitate surface reactions. Meanwhile, the established Z-scheme charge transfer pathway, driven by the built-in electric field, enables directional electron migration to MoS 2 while preserving high redox potentials. First-principles calculations, including HSE06 hybrid functional calculations, corroborate these findings. They reveal that sulfur vacancies enhance orbital hybridization between CdS and MoS 2 , lowering the energy barrier for interfacial charge transfer. Additionally, the composite exhibits excellent stability, retaining ∼ 82% of its activity after 10 cycles. This work provides a fundamental insight and a design principle for developing efficient and stable photocatalysts through the combined application of defect and heterojunction engineering. Download: Download high-res image (112KB) Download: Download full-size image