| In recent years,due to the rapid development of human society,the phenomenon of environmental pollution and energy shortage has become more and more serious.This has made mankind have to pay attention to the treatment of environmental pollution and the creation of new energy,so using solar energy to solve the two major problems of environment and energy is the best choice.Since 1972,Professor Fujishima and other researchers have found that the photocatalytic decomposition of water into hydrogen and oxygen on the n-type TiO2 electrode has led to rapid development of semiconductor photocatalysis technology.It has extensive research and application in the production of hydrogen by water,degradation of organic pollutants,etc.TiO2 semiconductor is the most ideal photocatalyst nowadays.Its chemical properties are more stable than other metal oxides at room temperature.Non-toxic and inexpensive are its advantage which has great efficiency in degrading pollutants.In addition,it can be recycled.However,the band gap of TiO2 is wider,it only absorbs in the ultraviolet region of sunlight,and hardly responds in the visible region.By controlling the synthesis conditions,we can obtain other crystal planes different from(101)planes such as(001),(100),(111),curved surface and so on.These aspects show higher photocatalytic activity.Compositing with narrow bandgap semiconductors is considered to be an effective way to improve the separation efficiency of photogenerated carriers and the visible light utilization of photocatalytic systems.Metal sulfides are also visible-light photocatalysts that can be studied at present.Some of these metal sulfides can improve their activity by compounding with titanium dioxide semiconductor materials because of their small band gap and certain absorption ability to visible light.In this paper,based on anatase TiO2 with(101)and(001),we constructed a composite material with double heterojunction structure with two-dimensional sulfides,and its photocatalytic performance was greatly improved.The main contents of this paper are divided into three parts:(1)Anatase TiO2 was prepared by controlling the exposure ratios of(101)and(001)surfaces with HF,and then was compounded with MoS2 through hydrothermal method.We compared the relationship between the exposure ratio and the enhancement ratio of different composite materials.The results show that an appropriate(001)exposure ratio rather than a higher exposure ratio produces the highest enhancement ratio for photocatalytic activity.The combination of MoS2 with TiO2 having(101)and(001)faces forms a double heterojunction.(2)Anatase TiO2 was prepared by controlling the exposure ratios of(101)and(001)surfaces with HF,and then was compounded with ZnS through hydrothermal method.Comparing with the original TiO2 nanosheets,the photocatalytic activity of TiO2/ZnS composites increased by 108%.As a comparison,P25 which the main exposed surface is(101)surface compound with ZnS.Under the optimum compound ratio,the photocatalytic activity of P25/ZnS is only 2%higher than that of P25.In general,TiO2 and ZnS are n type semiconductors.The photoelectrons in the ZnS conduction band can hardly enter the conduction band of TiO2.The combination of ZnS with TiO2 having(101)and(001)faces forms a double heterojunction.(3)Anatase TiO2 was prepared by controlling the exposure ratios of(101)and(001)surfaces with HF,and then was compounded with SnS2 through hydrothermal method.Comparing with the original TiO2 nanosheets,the photocatalytic activity of the TiO2/SnS2 composites increased by 47%.As a comparison,the photocatalyst with n-n single heterostructure was prepared by the composite of P25 which with(101)main exposure/SnSs.The photocatalytic activity of the composites decreased 31-43%,which was slightly lower than that of P25.The combination of SnS2 with TiO2 having(101)and(001)faces forms a double heterojunction. |
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