| Semiconductor materials can convert light energy into chemical energy under the irradiation of visible light.Spinel CuFe2O4 has ferromagnetism,and it is easy to synthesize,it has low cost and high mechanical strength.Compared with titanium dioxide,it has a narrower band gap,so it has received extensive attention.However,the photo-generated electron-hole recombination rate in CuFe2O4 material is relatively high,which limits the improvement of its photocatalytic performance.In this paper,doping,oxygen vacancies,construction of heterojunctions and other modification methods are used to change the surface and interface structure of the material to improve the serious problem of photo-generated electron-hole recombination in CuFe2O4 materials.The main content of this article is as follows(1)The zinc-doped CuFe2O4-3D material was prepared,and the specific surface area of the material was increased by the ammonia-assisted sol-gel method.The performance of the material in the photocatalyst reaction to selectively synthesize benzyl acetate was tested.After Zn doping,the oxygen vacancies brought by doping reduce the recombination rate of electron holes in the material.The photocurrent of pure CuFe2O4 is about 7.62?A·cm-2,while The photocurrent of CuFe2O4-Zno0.5 is five times that of the pure sample,which is about 30.45?A·cm-2.DFT calculations show that the adsorption energy of the intermediate product acetone on the Zn-doped CuFe2O4 surface is greater than the adsorption energy on the CuFe2O4 surface,so Zn doping is more conducive to the conversion of the intermediate product acetone,thereby increasing the selectivity of benzyl acetate.(2)CuFe2O4 was reduced by NaBH4 to prepare CuFe2O4 rich in oxygen vacancies and used for photocatalytic synthesis of cinnamamide.After introducing oxygen vacancies,the material exhibits significant light absorption intensity under 400-700 nm wavelength light.With the introduction of oxygen vacancies,the photocurrent value of CFO-400 has reached 8.5 times that of CuFe2O4.It can be seen from XPS that oxygen vacancies significantly reduce the valence states of Fe and Cu on the surface of the material,and the surface Fe? concentration reaches 90.92%.The existence of oxygen vacancy defects was proved by PL spectroscopy,and the oxygen vacancies were found through NH3-TPD to reduce the concentration of Bronsted acid and Lewis acid on the surface of the material,thereby reducing the generation of by-products in the coupling reaction.At the same time,oxygen vacancies capturing light generation.to inhibited the recombination of photo-generated charges,and finally increased the selectivity of CuFe2O4 for photocatalytic synthesis of cinnamamide from 50.93%to 98.56%.(3)Sulphur-doped spinel-type CuFe2O4 core-shell structure photocatalysts were prepared by a solvothermal method.XPS showed that the introduction of sulphur ions led to the generation of a large number of oxygen vacancies,with the surface oxygen vacancy concentration increasing from 11.34%to 52.56%.The photocurrent of the material reached 35.42 ?A·cm-2 after sulphur doping,which is nearly five times higher than that before doping(7.06?A·cm-2).The electrochemical impedance spectrum shows that the charge transfer resistance is significantly reduced by sulphur doping,with the Css value gradually increasing from 3.6524×10-6 F without doping to 5.524×10-5 F for CZFO-2-2.The Css value represents the surface state capacitance of the material,with higher Css values representing a higher number of trapped photogenerated carriers,which is more favourable for charge transfer.Therefore,low concentration of sulphur doping has better photochemical properties. |
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