Directed Charge Transfer‐Driven Efficient Photocatalytic Hydrogen Production in Dual S‐Scheme WS ₂ /Co ₉ S ₈ /ZnCdS Heterojunction

ABSTRACT ZnCdS‐based photocatalysts exhibit great potential for solar‐driven hydrogen (H ₂ ) evolution due to their tunable bandgaps and visible‐light absorption. Nevertheless, rapid charge recombination and structural instability hinder their practical implementation. To overcome these challenges, this work proposes a dual S‐scheme heterojunction design strategy utilizing polyoxometalates (POMs) as precursors to precisely control the heterojunction interfacial coupling. A dual S‐scheme WS ₂ /Co ₉ S ₈ /ZnCdS system was synthesized via a precursor‐guided sulfidation process, using K ₇ [Co ₂ W ₁₁ O ₄₀ H ₂ ]·15H ₂ O (Co ₂ W ₁₁ ) POM clusters as dual‐source templates. This approach enables the simultaneous achievement of tight interfacial coupling and a simplified single‐interface architecture. The charge transfer mechanism within the heterojunction was systematically investigated through analyses of the Fermi level, band structure, ultrafast timescale femtosecond transient absorption (fs‐TAS), time‐resolved photoluminescence (TRPL), in situ x‐ray photoelectron spectroscopy (XPS), and synchrotron radiation. The dual S‐scheme heterojunction not only expands the light absorption range of ZnCdS but also promotes efficient charge migration and separation. Under visible‐light irradiation ( λ ≥ 420 nm), this dual S‐scheme heterojunction exhibits remarkable stability and achieves a hydrogen evolution rate of up to 15.66 mmol g ⁻¹ h ⁻¹ , surpassing most reported noble metal‐free ZnCdS‐based photocatalysts. This research provides a robust methodology for developing dual S‐scheme heterojunctions that enhance photocatalytic hydrogen evolution efficiency.