Surface Regulation And Photocatalytic Activity Of Bismuth Oxyiodide Visible-light Photocatalysts

As a potential environmental pollution control technology,photocatalysis has attracted extensive interest of researchers.A large number of new photocatalytic materials were developed,and the properties of the original materials were further improved through modification.Among many photocatalytic materials,BiOI is a highly anisotropic layered semiconductor photocatalytic material with a narrow band gap?1.8 eV?and can absorb visible light within 650 nm.However,its photooxidation ability is weak and its photocatalytic activity is very limited.Therefore,it is necessary to regulate its surface structure and energy band structure to improve its photooxidation ability.In this paper,self-doping,morphology and surface structure regulation were used to modify the BiOI photocatalytic materials with enhanced photooxidation ability.Anion vacancy can regulate the band structure of the material.Through theoretical calculation,we found that the construction of iodine vacancy can obtain a higher BiOI valence band position and then obtain photogenerated holes with high oxidation capacity.Therefore,it is feasible to introduce iodine vacancy to regulate the BiOI valence band position.We used heat treatment to volatilize part of iodine to construct iodine vacancy defects in BiOI.Compared to BiOI nanosheets without iodine vacancy,iodine-deficient BiOI_1-x nanosheets have significantly enhanced photocurrent intensity and photocatalytic degradation activity of organic pollutants such as methyl orange?MO?and phenol.The results show that the construction of iodine vacancy has a broad prospect for improving the photocatalytic activity of BiOI nanosheets.On this basis,a further attempt was made to regulate iodine vacancy defects in BiOI nanosheets by one-step method.We selected glycerol as the organic solvent to synthesize iodine-deficient BiOI_1-x ultrathin nanosheets by solvent thermal method.In the process of synthesis,the hydroxyl group of glycerol combined with the structure of iodide ion,and then formed iodine vacancy on the surface of BiOI.The amount of iodine vacancy was controlled by temperature regulation,and the morphological structure was further regulated by the ratio of glycerol to water.The thickness of the iodine-deficient BiOI_1-x ultrathin nanosheets prepared by this method could be controlled at about 7 nm,and the iodine vacancy defects constructed by this method also improved the valence band position,which further confirmed that the construction of iodine vacancy could regulate the energy band structure of BiOI.Iodine-deficient BiOI_1-x ultrathin nanosheets showed great degradation activity of organic dyes and phenol in visible light.BiOI was prepared with glycerol and it was found that the solvent can change the morphology and surface structure of BiOI during the wet chemical synthesis of BiOI.Therefore,we continue to explore the influence of other organic solvents on the morphology of BiOI nanosheets,and find key functional groups that affect the surface structure of BiOI.A variety of organic solvents containing different hydroxyl groups and methyl groups were used to synthesize BiOI nanosheets,and the effects of solvents with different hydroxyl groups but same methyl groups on the BiOI nanosheets were compared.It is found that the number of hydroxyl groups can more effectively regulate the surface structure of BiOI nanosheets,and obtain better photocatalytic performance.However,the photocatalytic performance of BiOI prepared by organic solvents with the same hydroxyl group but different methyl groups was not significantly improved.Therefore,hydroxyl groups play a key role in the regulation of surface atomic structure of BiOI.