| Environmental pollution and the development and utilization of new energy are huge problems facing society today.The use of photocatalysts to photocatalytically degrade pollutants is currently an effective method.There are many clean energy sources that can be developed and utilized in nature.Solar energy is one of them.At present,the use of solar energy is mainly concentrated in the aspects of photochemistry,photoelectricity,and photothermal conversion.As a new type of semiconductor material,bismuth oxybromide has various preparation methods,small forbidden band width,special layered structure,visible light response,strong solar energy absorption and conversion,and has important applications in the field of solar energy conversion.At present,most of the preparation of bismuth oxybromide uses bismuth nitrate as the source of bismuth,and is concentrated in the field of photocatalysis.There is no systematic report on its research in the field of photothermal driven water evaporation.In response to the above problems,this article takes bismuth bromoxide as the research object,and launches the following research work:（1）Using high-purity bismuth powder as the bismuth source,bismuth oxybromide is prepared by hydrothermal method.XRD,SEM,TEM and other morphological component characterization analysis results show that the obtained powder is bismuth oxybromide with flaky structure.The prepared bismuth oxybromide powder is used for photocatalytic degradation of rhodamine B,and the photocatalytic effect of the sample is obvious.By changing the pH of the solution during the hydrothermal process,the BiOBr/Bi24O31Br10 composite powder was prepared.Compared with the pure BiOBr powder,the light absorption capacity and specific surface area of the BiOBr/Bi24O31Br10 composite powder were increased,and its photocatalytic ability was also enhanced.（2）Using sodium borohydride to reduce BiOBr,the photothermal-driven water evaporation performance of the reduced sample was studied.XRD,SEM,TEM and other morphological component characterization analysis results show that BiOBr nanosheets gradually transformed into metallic Bi nanosheets due to the reduction effect of Na BH4,and the nanosheets changed from a dense structure to a loose porous structure.The light-heat-driven water evaporation experiment results show that the Bi/BiOBr composite nanosheet powder obtained by 20 mg Na BH4 has the best light-heat-driven water evaporation performance,its water evaporation rate can reach 2.18 kg m-2 h-1under a single sunlight intensity,and good cycle stability.This is significantly better than the photothermal driven water evaporation performance of BiOBr and Bi nanoplate powders.Further analysis suggests that there are two reasons:on the one hand,the composite of metal Bi can enhance the light absorption performance of the powder;on the other hand,compared with BiOBr and Bi nanoplate powder,Bi/BiOBr composite nanoplate powder has a significant loose and porous structure.This loose porous structure is beneficial to capture sunlight and increase the water evaporation area,thereby helping to obtain excellent light-heat-driven water evaporation performance.The research in this thesis is helpful for the development of a new preparation method of BiOBr and provides a reference for the application of BiOBr in the field of solar thermal conversion. |
