The Preparation Of ZnIn₂S₄-based Photocatalyst For Selective Oxidation Of Benzyl Alcohol

Benzaldehyde,as the main organic intermediate for synthesis,plays an important role in industrial applications.Traditional synthesis processes of benzaldehyde,not only consume large energy but also produce harmful substances to environment.Therefore,the development of a green,mild and efficient synthesis technology is extremely urgent.Currently,semiconductor photocatalytic technology as a green,moderate and highly efficient technology has been one of the hot topics because it can use solar energy directly to catalyze and oxidize benzyl alcohol to benzaldehyde.As a semiconductor responsive to the visible light,ZnIn2S4 has gained much attention due to its suitable band position and chemical stability.However,ZnIn2S4 prepared by traditional methods is inclined to agglomerate and possesses less catalytic active site,which leads to lower photocatalytic activity and inhibits its further applications in photocatalytic fields.In this paper,several strategies were applied to address these problems.Supporters with large specific surface were introduced firstly to increase high dispersity of ZnIn2S4 so as to create more catalytic active sites efficiently.In order to further enhance its photocatalytic activity,graphene with high electron mobility was coupled with ZnIn2S4 to improve migration rate of photon-generated carrier of ZnIn2S4.The details are summarized briefly as follows:(1)Due to highly specific surface area and large porosity,MOFs(UiO-66)was introduced to produce composite photocatalysts ZnIn2S4/UiO-66 by a hydrothermal method.Selective oxidation of benzyl alcohol was chosen as probe reaction to investigate the activities of photocatalysts under visible light(?>420 nm).The results show that UiO-66 can efficiently inhibit the aggregation of ZnIn2S4 and increase its dispersity,which can provide more catalytic sites of ZnIn2S4.Meanwhile,the large surface areas of the samples benefit the adsorption of benzyl alcohol.Therefore,the activities of the photocatalysts ZnIn2S4/UiO-66 can be highly improved.(2)Using UiO-66 as a template,a nanocomposite ZnIn2S4/ZrO2 was successfully prepared by the hydrothermal method in the present of hydrazine hydrate.Compared with ZnIn2S4/UiO-66,ZnIn2S4/ZrO2 has a higher photocatalytic activity for selective oxidation of benzyl alcohol.It can be ascribed to the following reasons:firstly,the in-situ transformation of UiO-66 to ZrO2 maintains a larger specific surface area of catalyst and high dispersity of ZnIn2S4 nanosheets;secondly,the resultant ZrO2 may creates more unique Lewis acid and Bronsted acid sites than UiO-66 further improves the adsorption of benzyl alcohol on ZnIn2S4/ZrO2.In addition,we introduce graphene with high electronic mobility to construct RGO-ZnIn2S4/ZrO2 ternary composite structure.It exhibits an enhanced photocatalytic activity compared with ZnIn2S4/ZrO2,which ascribe to that graphene can promote separation and transfer of photogenerated charge carriers.