Fabrication Of The Novel Efficient Photocatalytic System With The Synergistic Effect Of Facets And Cocatalysts

The reactivity of the photocatalyst is definitely affected by the surface atomic structures which determine the adsorption of reactant molecules,surface transfer of photoexcited electrons and the desorption of products.And the surface atomic arrangement and coordination vary with different orientations of the crystal facets.The higher exposure ratio of high active facets is favorable for the photocatalytic reactions.This indicates that the photocatalyst with the exposure of high-energy facets could be a kind of promising semiconductor photocatalysts.Therefore,the exploitation of photocatalysts with high-energy facets has recently attracted considerable attention.However,this kind of photocatalysts only increases the active site and strengthens the interaction between the photocatalyst and the reactant.The recombination of the photoexcited electrons and holes has not been restricted effectively.Based on the theory of semiconductor photocatalysis,choosing the suitable cocatalysts such as Pt,Au,Ag to deposit on the high energy facets of photocatalysts can solve this problem with the synergistic effects of facets and cocatalysts,and finally enchance the photoactivity of the photocatalysts.In the present thesis,Bi2W06,BiOBr and W03 nanosheets with the exposure of(001)facets have been synthesized by a soft-chemical method.And then,the photocatalytic system with the synergistic effects of cocatalyst and facet was constructed through the deposition of the cocatalysts(Au,Ag and Pt)on the surface of these nanosheets.The crystal structure,photoelectric property and morphology of the as-prepared samples were characterized by XRD,UV-Vis DRS,SEM and TEM in detail.The photocatalytic activities of as-prepared samples were evaluated by the selective oxidation of benzyl alcohol and degradation of organic dyes.The main results and conclusions obtained from the present research are as follows:(1)Pt and Au were successfully deposited on(001)facets of BiOBr through a simple photodeposition method for the first time,respectively.The conversion rate of benzyl alcohol by the modified BiOBr was higher than the pristine BiOBr.This could be ascribed to the synergistic effects of cocatalyst and facet which can improve the separation efficiency of photoexcited electrons and holes.The controlled experimentsshowed that ·O2-and photoexcited electron played a major role in the selective photocatalytic oxidation of benzyl alcohol.(2)Pt-loaded Bi2W06 with the exposure(001)facets has been successfully prepared for the first time,which displayed much higher photocatalytic activitiy for both selective oxidation of benzyl alcohol and degradation of organic dyes compared with the pristine Bi2WO6.It suggested that the separation and migration efficiency of photoexcited electrons and holes on the(001)facets of Bi2WO6 were improved by platinum modification effectively.(3)A catalytic system with the synergistic effects of cocatalyst and facet has been constructed by loading Pt,Au and Ag on(001)facets of W03 for the first time,respectively.The system shows higher photocatalytic degradation of organic dyes than the pristine one.Notably,Pt modified samples show the highest photocatalytic activity.The original results of this study are as follows:A catalytic system with the synergistic effects of cocatalyst and facet has been successfully constructed by loading cocatalysts(Pt,Au,etc.)on the(001)facets of Bi2WO6,BiOBr and WO3 for the first time,respectively.And they are explored for the selective oxidation of benzyl alcohol and the decomposition of the organic pollutants.The results show that the obtained photocatalysts exhibit excellent photocatalytic activity and stability.After that,the possible photocatalytic mechanism has also been illustrated.