Double Vacancy CdS / Bi ₁₉ Cl ₃ S

Rationally designing heterojunction photocatalysts with directional charge transfer characteristics remains a challenge. Herein, we report a novel 0D/1D dual‐vacancy CdS/Bi ₁₉ Cl ₃ S ₂₇ (denoted as CdS _v /BCS _v ) heterojunction photocatalyst with an inverted F‐scheme charge transfer mechanism via electrostatic self‐assembly. This unique charge transfer mechanism enables the optimized CdS _v /BCS _v ‐2 heterojunction to achieve a H ₂ production rate of 446.8 μmol h ⁻¹  g ⁻¹ , which is 3.6 times higher than that of pure CdS _v (123.3 μmol h ⁻¹  g ⁻¹ ) and 60.4 times higher than that of pure BCS _v (7.4 μmol h ⁻¹ g ⁻¹ ). Mechanistic investigations, incorporating in situ characterization and density functional theory (DFT) calculations, reveal that the enhanced activity originates from the formation of the CdS _v /BCS _v heterojunction, which promotes efficient photoelectron transfer from CdS _v to BCS _v . This work proposes an inverted F‐scheme charge transfer mechanism to enhance photocatalytic activity and provides a new strategy for constructing high performance dual‐defect composite photocatalysts for photocatalytic H ₂ evolution.