Preparation And Photocatalytic Performance Of Cu-Fe Bimetallic Compound/MXene Heterojunction

Photocatalysts utilize photogenerated charge carriers to convert solar energy into chemical energy,which contribute to green sustainable chemistry and solves energy and environmental problems.CuFe2O4 has certain applications in the field of photocatalysis,but it is still limited by the problems such as low photogenerated electron-hole separation rate,low transfer rate,high recombination rate,and few reactive sites.The band gap of CuFeS2 is narrower than that of CuFe2O4,which is more conducive to the separation of photogenerated electrons and holes under light,but the photogenerated carriers are easy to recombine and the material are prone to photocorrosion.In this paper,two-dimensional nanosheets MXene are used as carriers to construct heterojunctions.The internal electric field formed at the interface is conducive to the separation of photogenerated carriers,improving the conductivity and facilitating the transfer of photogenerated carriers.It also helps to disperse the loaded nanoparticles to prevent agglomeration,limit the size of the load and increase the surface active sites of the photocatalyst.By reducing the size of the photocatalyst,the band gap can be adjusted,and the construction of quantum dot heterojunction can increase the specific surface area of the material,so as to increase the active sites of the reaction,and finally achieve the purpose of improving the photocatalytic reaction performance.The main content of this article is as follows:(1)CuFe2O4/MXene heterojunction fabricated by loading CuFe2O4 nanoparticles on 2D MXene nanosheets by a facile hydrothermal method.By adjusting the loading of CuFe2O4 on MXene,the reactive sites are increased.Among them,the CuFe2O4/MXene photocatalyst with 20%loading has the best performance,and the photocurrent response increases from almost no to 2.1 μA·cm-2,and the electron transfer resistance in the impedance is significantly reduced under light,proving that the photogenerated charge separation efficiency is indeed improved.The energy band structure indicates that the photogenerated electrons are transferred from CuFe2O4 to MXene to form Z-scheme heterojunction,and the photogenerated holes remain in the valence band of CuFe2O4 to participate in the oxidation reaction.The heterojunction has excellent photocatalytic oxidation of benzyl alcohol to benzaldehyde with a selectivity and yield of more than 99%,much higher than other loaded CuFe2O4/MXene heterojunctions and pure samples,while the selectivity and yield of pure CuFe2O4 are only 35%and 21%,indicating that the loaded heterojunction has good photocatalytic performance for benzyl alcohol oxidation.(2)In order to further promote the separation of photogenerated carriers,based on the 0D/2D CuFe2O4/MXene heterojunction,CuFeS2 with a narrower band gap is selected as loading material,and the 0D/2D CuFeS2/MXene heterojunction is rapidly prepared by microwave method.CuFeS2 and MXene combined to form 0D/2D heterojunction,and the photocurrent increases from 0.7 μA·cm-2 to 4.2 μA·cm-2,which is 6 times higher than that of pure CuFeS2.It proved that the photogenerated charge separation efficiency is improved.The energy band structure indicates that the photogenerated electrons transfer from MXene to CuFeS2 to form Z-scheme heterojunction,and the photogenerated electrons remain in the conduction band of CuFeS2 to participate in the reduction reaction.By regulating the load quality of CuFeS2,it is found that the CuFeS2/MXene heterojunction with 25%loading reflects the highest photocatalytic nitrobenzene reduction performance,and the conversion and selectivity are more than 99%.It still shows excellent performance in hydrogen production by photolysis of water,which can reach 276.8 μmol g-1 h-1.(3)In order to reduce the particle size of the photocatalyst,change the band gap,and increase the contact area and reactive sites between the photocatalyst and the reactant,a small-sized 0D/0D CuFeS2/MXene quantum dot heterojunction is rapidly prepared by microwave method.CuFeS2 quantum dots are combined with MXene quantum dots to form 0D/0D heterojunction quantum dots.The photocurrent density increased from 0.7 μA·cm-2 to 1.3 μA·cm-2,and the electron transfer resistance in the impedance spectrum decreased significantly under light,which proved that the photogenerated charge separation efficiency is indeed improved.Compared with the pure sample,the specific surface area of the CuFeS2/MXene quantum dot heterojunction increased,which improve the adsorption capacity of the reactant,promote the contact with the reactant,and increase the reactive active sites.The quantum dot heterojunction exhibited excellent activity in the photocatalytic reduction of nitrobenzene and hydrogen production by photolysis of water.The yield of reduction of nitrobenzene to aniline is much higher than that of pure CuFeS2 and MXene,and the yield of hydrogen production from photolysis of water is as high as 3273 μmol g-1 h-1.