Fabrication And Photocatalytic Performance Of Oxygen-defected CdWO₄/CdS And WO_x/TiO₂ Heterojunctions

At present,energy shortage and environmental pollution have become the major threats to the sustainable development of human being.The development of photocatalytic technology is expected to achieve the efficient use of solar energy to address the energy and environmental crisis.The integration of heterojunction engineering and defect engineering,which have been proved to be effective strategies,can provide new ideas for designing novel efficient photocatalyst.In this work,we constructed oxygen-defected CdWO₄/CdS and WO_x/TiO₂ heterojunctions to discussed the effect of oxygen defects on light absorption and charge transfer.O_xygen-defected CdWO₄/CdS composites were synthesized by solvothermal method using W18O₄9 as precursor and the composition and morphology of the composites change along with the Cd dosage.The presence of NH4+ and CH3COO-,produced during synthetic process,play a vital role on the formation of CdWO₄.Meanwhile,benefited from the reductive environment of synthetic solution,oxygen vacancies in W18O₄9 precursor are well retained.Thus,oxygen-defected CdWO₄ forms in composite and greatly promotes the visible light harvesting ability.O_xygen-defected CdWO₄/CdS composites show enhanced activity and superior stability for photocatalytic hydrogen evolution.Loading Pt cocatalyst can further improve the activity and stability.The contrast experiment demonstrates that the synergic effect of the composite is caused by oxygen vacancies and the well-built interface can facilitate the charge transfer.Photoelectrochemical test manifests the effective separation of photo-induced charge carriers and fast interfacial charge transfer,which can be attributed to heterojunction and oxygen vacancies.Radical-trapping experiments along with in-situ Pt photodeposition further prove that the charge transfer and separation follow Z-scheme mechanism.This work highlights the critical role of defects in the formation of direct Z-scheme composite.We decorated WO₃ nanodots on TiO₂ via solvothermal method,and then WO_x nanodots decorated TiO₂ were obtained by hydrogen-treatment.The amount of nanodots can be adjusted by varying the dosage of WCl6 precursor.When the dosage of WCl6 solution is 2 mL,the obtained sample shows higher activity on phenol photo-degradation.And compared with WO₃/TiO₂,the hydrogen-treated samples shows superior activity.The UV-Vis DRS and PL spectra demonstrate the introduction of oxygen vacancies can not only promote the light absorption of composite but also enhance the charge separation efficiency.