Preparation of Visible Light Response ZnIn2S4 Catalyst with S Vacancy and Its Selective Oxidation of HMF
A visible light response catalyst with abundant S vacancies,zinc indium sulfide(VS-ZIS),was prepared in situ by one-step method using thioacetamide as the sulfur source.The process of selective photocatalytic oxidation of 5-hydroxymethylfurfural(HMF)to 2,5-diformylfuran(DFF)over VS-ZIS was studied,and the mechanism of VS-ZIS photocatalytic selective oxidation of HMF to DFF was analyzed.The existence of S vacancies was confirmed by electron paramagnetic resonance(EPR).The optical properties and elemental composition of VS-ZIS were investigated by UV-vis diffuse reflectance spectroscopy(DRS)and XPS,and the surface morphology and crystal structure of the catalyst were observed using SEM and XRD.The results showed that ZnIn2S4 could be successfully synthesized by the one-step method.The catalyst exhibited a petal-like microsphere morphology,and the elements of Zn,In,and S were uniformly distributed.The visible light absorption range of the catalyst was 420-530 nm.The synthesis time did not has significantly effect on the crystal structure of ZnIn2S4,while the S vacancies in the catalyst could be controlled by adjusting the synthesis time.Among the samples of VS-ZIS-2 to VS-ZIS-10 prepared at 2-10 h,the sample VS-ZIS-6 obtainedat 6 h had abundant S vacancies.The VS-ZIS-6 prepared by heating at 80℃for 6 h showed the best performance for the selectiveoxidationof HMFunder theconditionsof areactiontimeof4 h,VS-ZIS-6/HMFmassratioof3.2,HMF concentration of 1.0 mmol/L,and air flow rate of 20 mL/min.The HMF conversion rate reached 95.4%,and the DFF yield was61.8%.The abundant S vacancies on the surface of VS-ZIS could promote the adsorption and activation of O2 on the catalyst surface,capturing photoinduced electrons to generate more O-2·,thereby enhancing the selective oxidation ability of the catalyst towards HMF.
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