| Environment pollution and energy sources shortage have become two significant problems for hunman to solve at present. Therefore, one important objective of a extensive number of chemical researchers is to develop a kind of high-efficiency technology used to replace the energy-intensive process that is harmful to the surroundings. Introducing the photo-catalysis technology which could make use of sunlight directly to the organic chemistry, that is to say, the appearance and application of photo-catalysis selective oxidation system tremendously meet the demands for save energy sources and reduce environment pollution. In the above system, the conditions needed in the reaction are much wilder than that in the conventional organic reaction, and meanwhile, it also avoids the usage of some toxic and caustic strong oxidants. As a result, the method, photocatalysis selective oxidation, has ever been honored as one of the most promising green chemical-synthesis technology.In this article, solvothermal method was used to fabricate a series of hexagonal phase ZnIn2S4, Carbon doped ZnIn2S4 and cubic phase ZnIn2S4 compounds with special morphologies. The physical properties of the samples were characterized by the X-ray diffraction (XRD), N2 adsorption-desorption, field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and so on. The photocatalytic activities of the as-prepared ZnIn2S4 samples were evaluated mainly by selective oxidation of benzyl alcohol to benzaldehyde as a probe reaction to benzaldehyde under mild conditions. Using liquid chromatography to investigate concentration of product and calculate the conversion, productivity and selectivity. By utilizing the technologies of electron spin resonance (ESR), photoluminescence spectra (PL), electrochemistry and a variety of radical scavengers etc to detect the active species during the selective oxidation of benzyl alcohol process and further discuss the relationship between the configuration and efficiency of the catalysts and at the same time, also discuss the photo-catalysis reaction mechanism on the basis of above results.The main research results obtained from the present research were as follows:(1) under the visible light irradiation, the ZnIn2S4 samples were prepared at 160℃ for 24h in ethanol exhibited photocatalytic activity than ZnIn2S4 sample synthesized in deionized water. (2) The experiment parameters in the fabrication course such as reaction time, temperature, solvents, sulfur sources have great influence on the catalysts’ activities. (3) Carbon doped ZnIn2S4 nanocomposites prepared by using glucose as the salt precursor could enhance the photocatalytic activity effectively, among which the activity comes to maximum value with 30 mg glucose addition. (4) The outcomes showed that cubic phase ZnIn2S4 samples fabricated through hydrothermal process at 120℃ for 10h have a bit influence on the catalysts’ physical-chemical properties when re-treatment on different time. And besides, the experiment of selective oxidation activity towards benzyl alcohol to benzaldehyde demonstrated that re-treatment could effectively enhance the catalysts’ photocatalytic activities among which activity was the best when after-treatment for 18h. (5) It is proved that O2- is the major active species by adding different active species scavenger and electron spin resonance (ESR) etc, and the possible mechanism of photocatalytic selective oxidation of benzyl alcohol to benzaldehyde over ZnIn2S4 samples was also proposed preliminarily. (6) It is proved effectively that ZnIn2S4 samples possessed nice stability, and meanwhile, ZnIn2S4 also presented some photocatalysis selective oxidation activities on other aromatic alcohols.The innovation of this article was as follows:(1) it is the first time to use hexagonal ZnIn2S4, Carbon doped ZnIn2S4 and cubic ZnIn2S4 as visible light photocatalyst for selective oxidation of benzyl alcohol, which extended the application of ZnIn2S4 in the field of photocatalysis. (2) A possible mechanism for photocatalytic selective oxidation of benzyl alcohol over ZnIn2S4 samples is proposed according to a series of techniques such as adding different active species scavenger and the electron spin resonance (ESR). |
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