Direct Z-scheme composite of CdS and oxygen-defected CdWO₄: An efficient visible-light-driven photocatalyst for hydrogen evolution

Direct Z-scheme photocatalyst, which enables efficient charge separation and retains high redox ability, is promising material for visible-light-driven hydrogen evolution. Here we developed a one-step solvothermal method to fabricate direct Z-scheme CdS/CdWO₄ composite via treating W₁₈O₄₉ with CH₃CSNH₂ and Cd(CH₃COO)₂. By controlling the dosage of Cd(CH₃COO)₂, CdS nanoparticles decorated CdWO₄ nanowires (CS-2) is synthesized. UV-vis DRS and XPS spectra demonstrate that the CdWO₄ possesses a large amount of oxygen vacancies, which help to form ohmic contact and broaden light absorption. Compared with CdS, CS-2 Exhibits 18 times higher visible-light H₂ evolution activity using lactic acid as sacrificial agent and shows 7.8-fold higher photocurrent density. Moreover, photoelectrochemical test manifests the efficient separation of the photo-induced charge carriers. Radical-trapping experiments along with in-situ Pt photodeposition further prove that the charge transfer and separation follows Z-scheme mechanism. This work highlights the critical role of defects in the formation of direct Z-scheme composite.