The Study Of Selective Oxidation Of Aromatic Alcohols To Corresponding Aromatic Aldehydes With Narrow Band Gap Semiconductor Photocatalyst

A series of ternary chalcogenides, zinc indium sulphide(Zn In2S4), were synthesized by a simple hydrothermal/solvothermal method with different solvents.On this basis, Ni S/Zn In2S4 photocatalysts were prepared by refluxing wet chemistry method and microwave-assisted synthesis method. The structure, textural, and optical properties of the resulting materials were thoroughly characterized by several techniques, such as XRD, XPS, SEM, TEM, UV-Vis DRS et al. The photocatalytic performance of the as-synthesized samples was evaluated by selective oxidation of aromatic alcohols to aromatic aldehydes. The results show that Zn In2S4 catalysts prepared by different solvents show an excellent photocatalytic activity. Moreover,ZIS-Et OH sample(Zn In2S4 prepared in ethanol solvent) exhibits the highest photocatalytic activity among the screened samples. Through developing the mechanism of catalyst synthesis, it shows that the samples synthesized with different solvents lead to the differences of the microstructures and specific surface area of the samples, which results in the differences of the level of exposed {0001} crystal faces,thus affacting the photocatalytic performance toward the photocatalytic selective oxidation of aromatic alcohols to aromatic aldehydes. In our work, the HR-TEM analysis shows that the hexagonal Zn In2S4 has exposed {0001} crystal planes.Furthermore, the experiments of scavenger prove that photo-induced holes are the major active species during the photocatalytic process. Importantly, the exposed{0001} crystal faces of hexagonal Zn In2S4 are active crystal planes, it is mainly because the {0001} crystal faces can enrich photo-induced holes, which effectively suppresses the recombination of photogenerated electron-hole pairs. It speculation that the photocatalytic activity largely depends on the exposed {0001} crystal faces of Zn In2S4 sample. A possible photocatalyic mechanism toward the selective oxidation of benzyl alcohol to benzaldehyde is proposed. The study of Ni S/Zn In2S4 samples shows that, with the increase of Ni S, the photocatalytic activities for selective oxidation of aromatic alcohols to aromatic aldehydes improve. When the loading amount of Ni S is1.0 wt%(1.0 wt% Ni S/Zn In2S4), the highest photocatalysis activity is obtained. Resultsuggests that Ni S/Zn In2S4 can effectively suppress recombination of photo-induced electron-hole pairs, and enhances the cataliytic performance for photocatalytic selective oxidation of benzyl alcohol to benzaldehyde. In a word, the photocatalytic activities of Ni S/Zn In2S4 samples mainly depend on interaction both preparation methods of bulk catalyst between co-catalyst.