Study On Construction And Properties Of CuSe Based Heterojunction Catalysts

With the research and development of photocatalysis technology,how to study a kind of efficient catalyst which can be applied in the fields of photocatalysis,photochemistry and electrochemistry has become the focus.Compared with traditional metal oxides and metal sulfides,metal selenides have been widely studied due to their narrow band gap,low internal resistance and large specific surface area.As the focus of this study,CuSe has a narrow band gap and low internal resistance.In related studies,CuSe has also shown good performance in photocatalytic degradation,electrocatalysis,photoelectric chemistry and other aspects.The innovative point of this study is to propose the construction of novel CuSe/Zn Se double heterojunction catalyst,CuSe/FeSe₂Z-type heterojunction catalyst and Cu_2-xSe/FeSe₂Z-type heterojunction catalyst with polyvalent states.None of these systems has been studied and this study proves that these three systems have their own advantages for improving the performance of photocatalysis,photochemistry and electrocatalysis.These systems first adopt efficient 2D/0D and 2D/1D structures.2D materials are very suitable for the base structure,and one-dimensional or zero-dimensional materials are loaded on the surface to construct heterojunctions.This structure increases the contact area of the two materials,better separates the photogenerated electrons and holes of the two different materials,and further improves the transport efficiency of the carriers.Secondly,materials with more suitable energy band matching are selected to construct better heterojunction types.The research content of this paper is mainly as follows:（1）0D Zn Se nanoparticles were loaded on（001）surface of 2D CuSe nanosheets to construct 2D/0D CuSe/Zn Se heterojunction catalyst.The double heterojunction structure allows the photogenerated electrons and holes to be separated to different locations to achieve higher carrier transport efficiency.The experimental results show that the CuSe/Zn Se catalyst has high photochemical and electrochemical properties,and the photocatalytic degradation performance is also improved.Under the optimal loading ratio,the electrocatalytic performance of the heterojunction catalyst increased by 4.67 times,the photochemical performance increased by 7 times,and the degradation rate of methylene blue increased by 1.26 times.（2）2D/1D CuSe/FeSe₂Z-type heterojunction catalyst was constructed by loading1D FeSe₂nanorods on 2D CuSe nanosheets.The multi-dimensional structure can increase the contact area and enhance the efficiency of carrier transport.The Z-type heterojunction structure makes the hole and electron can be separated better and retain higher redox activity.Under the optimum composite ratio,the photoelectrochemical performance of the heterojunction catalyst is 4.99 times higher,the degradation rate of levofloxacin is 8.37 times higher,and the degradation rate of methylene blue is 6.06times higher.（3）A multivalent Cu_2-xSe/FeSe₂Z-type heterojunction catalyst was constructed by loading zero-dimensional Cu_2-xSe nanoparticles on one-dimensional FeSe₂nanorods.The formation of Z-type heterojunction structure improves the redox capacity,the multivalent heterojunction improves the catalytic activity,and the appropriate multi-dimensional structure improves the carrier transport capacity.The photocatalytic and photoelectrochemical performance of Cu_2-xSe is 1.34 times and3.65 times of that of Cu_2-xSe,respectively,and the electrocatalytic performance is improved by 1.35 times under the optimum composite ratio.The advantages of these three parts of the work are briefly summarized.For photocatalytic degradation performance,CuSe/FeSe₂reached the optimum.Because CuSe/FeSe₂catalyst forms Z-type heterojunction structure and has the generation of superoxide radical,the carrier transport efficiency is further improved,and the existence of superoxide radical is more effective for the degradation of antibiotics and dyes.The electrocatalytic performance of CuSe/Zn Se is relatively better.Because the Zn Se nanoparticles have a larger surface area,they form a closer contact with the CuSe nanosheets,making it easier for electrons to be transported through the catalyst.In addition,close contact can provide more active sites,resulting in significantly reduced resistance and thus improved electrocatalytic performance.For photoelectric chemical performance,the three heterojunction catalysts have good improvement compared with the single catalyst.The formation of heterojunction can significantly improve the efficiency of photogenerated carrier separation.Cu_2-xSe has narrow band gap,excellent light absorption capacity,good photostability and high electrical conductivity.In addition,because Cu in Cu_2-xSe contains multiple valence states Cu¹⁺and Cu²⁺,different valence states may be transformed in the photoelectric chemical reaction,which increases the possibility of reaction and leads to its relatively better photoelectric chemical performance.In general,the photoelectric chemical properties of Cu_2-xSe/FeSe₂ are improved better.