Study On Hydrogen Production Performance And Charge Transfer Of CdS/WO_3-x Photocatalyst Introducing Oxygen Vacancy And Quantum Dots

Using photocatalytic technology to produce hydrogen energy to solve the problem of energy crisis has long been a focus of human concern.Semiconductor catalyst CdS stands out among many semiconductors used in photocatalytic hydrogen production due to its high efficiency in light energy utilization and excellent reduction ability.However,rapid electron hole recombination and severe photocorrosion lead to low catalytic efficiency of CdS,hindering its further development.WO_3-x was used to compound with CdS to form CdS/WO₃-based composite photocatalyst to improve the catalytic performance of CdS due to its non-toxicity,light resistance and good stability.Although CdS/WO₃ has been studied in photocatalytic hydrogen production of water splitting,it has low catalytic performance in the absence of cocatalyst and poor stability.Oxygen vacancy,as a kind of oxygen defect,has the ability to adjust the band gap of catalyst and broaden its light absorption range.Surface oxygen vacancy can also provide active sites for catalysts.Oxygen vacancy WO_3-x can be constructed by introducing oxygen vacancy into WO₃.CdS quantum dots?CdS QDs? have attractive optical properties,optical stability and chemical stability.The separation and transfer path of photogenerated carrier between two semiconductors will affect the redox capacity of the complex and the photocatalytic performance.Therefore,the main work of this paper is to introduce quantum dots and oxygen vacancy to improve the photocatalytic activity and stability of CdS/WO₃-based composite,and to study its photogenerated carrier transfer mechanism.Which will provide an idea for the preparation of high catalytic activity and great stability catalysts.In this paper,CdS/WO_3-x catalyst with oxygen vacancy was firstly prepared,and its photocatalytic hydrogen production performance and stability were studied.The transfer path of photogenerated carriers between CdS and WO_3-x was further explored by loading Mo S₂as a catalyst.Secondly,the CdS/WO_3-x-based catalyst with oxygen vacancy was further modified by introducing CdS quantum dot,and the mechanism of charge transfer was further explored through photocatalytic degradation experiments,so as to clarify the reasons for the improvement of photocatalytic hydrogen production performance and stability.The overall contents and conclusions of the study are as follows:?1?Study on preparation,photocatalytic hydrogen production performance and charge transfer mechanism of Z-scheme CdS/WO_3-x photocatalyst with oxygen vacancy:Firstly,WO_3-x nanosheet with oxygen defect was prepared by normal temperature method;Then,microwave-assisted hydrothermal method was used to construct Z-scheme structure CdS/WO_3-xby WO_3-xnanosheet load on CdS nanospheres.Z-scheme Mo S₂-CdS/WO_3-x catalyst was prepared by adding molybdenum source to the precursor of CdS.Oxygen vacancy facilitated the separation and transfer of photogenerated carriers of CdS/WO_3-xcatalyst.The results showed that the hydrogen production rates of Z-scheme structure CdS/WO_3-xand MoS₂-CdS/WO_3-x catalysts with oxygen defects were 1879.0?mol g^-1h^-1 and 2163.1?mol g^-1h^-1,respectively.Which was 3.6 times and 4.2 times that of CdS alone(519.1?mol g^-1h^-1).This is because the Z-scheme structure formed between CdS and WO_3-x and the oxygen vacancy jointly promoted the improvement of the catalytic performance of CdS/WO_3-x.The Mo S₂cocatalyst further proved that the optical carriers between CdS and WO_3-x were separated and transferred in Z-scheme structure.?2?Study on preparation,photocatalytic hydrogen production performance and charge transfer mechanism of type-? CdS/WO_3-x photocatalyst with oxygen vacancy and quantum dot:Firstly,WO_3-x nanosheets with oxygen defects were prepared by normal temperature method.Then the CdS quantum dot was loaded on WO_3-xnanosheet to construct the type-? structure CdS/WO_3-x catalyst by stirring at room temperature.Oxygen-vacancy WO_3-x enhanced the optical trapping ability of CdS/WO_3-x composite when CdS quantum dots improve the stability of CdS/WO_3-xcomposite.The results showed that the hydrogen production rate of CdS/WO_3-xwith oxygen vacancy and quantum dot regulation was 6545.3?mol g^-1h^-1,which was 54.1 times that of CdS alone(121.0?mol g^-1h^-1).That is because the type-II structure formed between CdS and WO_3-x and,oxygen vacancy and quantum dots jointly promoted the improvement of the catalytic performance of CdS/WO_3-x.The CdS/WO_3-x composite still maintained effective photocatalytic activity after 8 cycles of hydrogen production experiments,as a result of the action of CdS quantum dots.The photogenerated carriers between CdS and WO_3-x were further separated and transferred by type-? structure which was proved through photocatalytic degradation acid Orange ? experiment.