Synthesis Of CdS/g-C₃N₄ And Photocatalysis For Hydrogen Production

Cadmium sulfide(CdS), which is an important kind of visible-light-response semiconductor catalysts, is paid attention to in the field of photocatalytic hydrogen generation. The pure CdS is easily photocorroded leading to a decrease in its photocatalytic activity after a long period illumination. In order to solve this proplem, CdS/g-C3N4 was synthesized. The morphology and structure of photocatalysts were characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and UV-vis diffuse reflectance spectroscopy (UV-vis). Their photoactivity was evaluated by hydrogen evolution from aqueous solution containing lactic acid as a hole scavenger under visible light (λ≥ 420 nm) irradiation. Effects of the process of charge transfer, crystallinity, crystalline structure and crystalline morphology on photocatalytic hydrogen evolution were discussed in detail. This work was mainly composed of two parts:(1) CdS was synthesized by hydrothermal method. Effects of crystallinity, crystalline structure and crystalline morphology on photocatalytic hydrogen evolution were investigated. The XRD and TEM indicated that hydrothermal temperature had an impact on crystal phase and crystallinity of CdS photocatalyst. Moreover sulfur source had an influence on crystal phase, crystallinity and crystal morphology of CdS photocatalyst. In this section, the influential factors of platinum loaded method, the hydrothermal temperature, reaction time and sulfur source on photocatalytic hydrogen evolution were discussed in detail. The experimental results show that the hydrogen evolution amount for 5 h of the optimal Pt/CdS-CP-450 was 1298 μmol.(2) A variety of platinum deposited positions on the surface of CdS/g-C3N4 composite photocatalyst was synthesized by co-precipitation method, impregnation method, photodeposition method and grinding method. Effects of the process of charge transfer on photocatalytic hydrogen evolution were investigated. The XRD andTEM showed the interfacial contact between CdS and g-C3N4. The structure of CdS was not changed. The UV-vis indicated that the (g-C3N4-CdS-Pt)0.8-450 composite photocatalyst shows hybrid absorption features of g-C3N4 and CdS, which allows for more efficient utilization of the solar spectrum to create photogenerated electrons and holes. At the same time, the sample showed enhanced absorption in the range of 550～800 nm because the high temperature is conducive to the reduction of H2PtCl6.In this section, the influential factors of platinum deposited position, the mass ratio of g-C3N4 and CdS, calcination temperature and the sequence of stuffing on photocatalytic hydrogen evolution were discussed in detail. The experimental results show that the (g-C3N4-CdS-Pt)0.8-450 composite photocatalyst exhibit remarkably higher efficiency for photocatalytic hydrogen evolution under visible light irradiation. The amount of evolved hydrogen for 5 h is 1298 μmol in 10 vol% lactic acid solution.