Preparation Of HY Zeolite-loaded ZnS And CdS By Layer-by-layer Method And Photocatalytic Property For H₂Production

The technology of catalytic decomposition hydrogen sulfide （H₂S） can reduce theharmful gas emission, and at the same time, it can produce a kind of pollution-freeenergy （H₂）. It has became a hot spot of research and development in photocatalyticfield. Both ZnS and CdS have a good optical performance. They play an importantposition in the field of photocatalysts. Because of pure ZnS existing high resistancewhich leads to its Optical properties is not stable. The pure CdS has prone tophotochemial corrosion and low photocatalytic efficiency.In view of the above questions, combining the special structure properties ofHY-zeolite particles with the advantage of layer by layer self-assembly （L-B-L）technology, loaded-ZnS and loaded-CdS were prepared and we got multilayer systemfor photocatalysts. We optimized the process conditions for experiment and choseNH₂CSNH₂as S^2-source, Zn（AC）₂as Zn²⁺source, Cd（NO₃）₂as Cd²⁺source, theroasting temperature （T） under N₂protection was500℃. we prepared thephotocatalysts of HY/（ZnS）_n、HY/（CdS）_nand HY/（ZnS/CdS）_n. Through the methods ofUV-Vis diffuse reflective spectrum, XRD, XPS, SEM-EDS, PL etc in samples structureand chemical properties characterization and the experiments of photocatalyticproduction of hydrogen to research the photocatalysis activity.The results of characterization showed that the basic skeleton of HY-zeolite wasnot changed after the loaded of ZnS and CdS on surface. HY-zeolite belonged to a kindof inert materials for light. The strength of light absorption for the photocatalysts ofHY/（ZnS）_n、 HY/（CdS）_nand HY/（ZnS/CdS）_nwas increased as the increase ofloaded-layers n between ultraviolet and visible light. The thickness of photocatalystsfilms can be controled through the layer by layer technology in certain conditions. Thesingle loaded-ZnS on surface of HY-zeolite was cubic crystal, structure of fiber bar andthe wavelength of edge-absorbed was340nm. The single loaded-CdS showed six crystaltype, structure of flak and the wavelength of edge-absorbed was510nm. When ZnS andCdS were loaded at the same time, Zn_xCd_1-xS maybe formed.The experiments of photocatalytic production of H₂showed that both the amoutand the average velocity of HY/（ZnS）_n、HY/（CdS）_nand HY/（ZnS/CdS）_nfor H₂production were increased as the increase of loaded-layers n, and the photocatalystsshowed a relatively stable catalytic properties. The velocity of HY/（ZnS）₆for H₂ production can reach as high as18.4mmol/（h·g·cat.）; HY/（CdS）₆can reach12.9mmol/（h·g·cat.）; HY/（ZnS/CdS）₄can reach17.3mmol/（h·g·cat.）. In the sameloaded-layer n, the relation of velocity of HY/（ZnS）_n、HY/（CdS）_nand HY/（ZnS/CdS）_nfor H₂production is: HY/（ZnS/CdS）_n> HY/（ZnS）> HY/（CdS）_n, HY/（ZnS/CdS）_nshowed better catalytic activity.