| Since photocatalysis can effectively use cheap pollution-free solar energy to solve the problem of environment and energy, semiconductor-based photocatalysis, as a kind of clean and environmental-friendly technology, has attracted increasingly widespread attention. In recent years, titanium dioxide has been considered as the most promising photocatalyst in photocatalysis field. However, the low utilization of sunlight and the quantum conversion efficiency have seriously restricted its large-scale application. Therefore, developing the special photocatalytic materials with wide spectral response and high quantum efficiency has been inspiring ever-increasing research interest in the field of efficient photocatalysis. It also has an important significance to the development of environmental science. CdS has been widely studied due to its suitable visible-light-response properties and strong reduction ability over its photogenerated electrons. Nonetheless, there are still several drawbacks that need to be circumvented in order to improve the photocatalytic activity of pure CdS, for instance, the high recombination rate of photoinduced electron-hole pairs over bulk CdS and photocorrosion of CdS. The introduction of graphene (GR) into the semiconductor martrix can significantly reduce the recombination rate of photoexcited electron-hole pairs and improve the photocatalytic activity due to its unique planar morphology, ultrahigh electron conductivity and mobility.In this paper, graphene-CdS nanocomposites photocatalysts have been fabricated. The crystal phase, morphology, photoresponse, specific surface area and electrochemical properties of the as-prepared photocatalysts are characterized by a series of techniques, including X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), UV-vis diffuse reflectance spectra (DRS), transmission electron microscopy (TEM), nitrogen adsorption-desorption, electrochemical analysis and photoluminescence spectra (PL). In addition, photocatalytic performance of these photocatalysts has been evaluated by photocatalytic water splitting, photocatalytic reduction of Cr (VI) and photocatalytic selective oxidation of benzyl alcohol to benzaldehyde under visible light irradiation (λ≥420 nm).The main results and conclusions obtained from the present research are as follows:(1) CdS-GR nanocomposites fabricated via a simple hydrothermal method exhibit excellent photocatalytic performance toward photocatalytic H2 production under the light irradiation, especially the photoactivity of CdS-5%GR nanocomposite is about 2 times higher than blank CdS. (2) To further improve the photoactivity of GR-CdS nanocomposites toward photocatalytic hydrogen evolution, the efficient low-temperature refluxing method has been utilized to fabricate GR-CdS nanocomposites. The results demonstrate that the GR-CdS hybrids exhibit 9 times higher photocatalytic performance toward photocatalytic H2 production under light irradiation as compared with bare CdS, (3) The solvothermal method has also been used to prepare GR-CdS composites. In particular, the photocatalytic performance of 5%GR-CdS sample is about 6 times higher than blank CdS toward selective oxidation reactions under visible light. (4) A facile hydrothermal approach is used to synthesize a series of Cu(X)-CdIn2S4 microspheres photocatalysts, which exhibit excellent photocatalytic performance toward photocatalytic reduction of Cr (Ⅵ) to Cr (Ⅲ).The innovations of this paper were as follows:(1) It is the first time to utilize such a in situ low-temperature method to prepare CdS-GR nanocomposites with superior photoactivity toward photocatalytic hydrogen generation. (2) The flower-like CdS nanospheres has been synthesized in a tailored manner. After combination with graghene, the GR-CdS nanospheres composite exhibits higher photocatalytic performance than other GR-CdS hybrid toward selective oxidation reactions under visible light irradiation. (3) It is the frist time to prepare a series of Cu-CdIn2S4 samples toward photocatalytic reduction of Cr (Ⅵ) under visible light irradiation. (4) The rational reaction mechanism toward various model reactions is proposed by some techniques of characterization. |
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