Mechanism On Photocatalytic Degradation Of Acid Dyes By Ag Modified TiO₂ Films Doped With N

Titanium dioxide is an excellent semiconductor photocatalyst,which plays an important role in the field of wastewater pollution control.It has the characteristics of stable chemical properties,high activity and low preparation cost.However,TiO₂ also has a wide band gap,can only respond to ultraviolet light,and has high recombination rate of electrons and holes excited by light,which limits the application of TiO₂.In this paper,TiO₂ films were modified to obtain better photocatalytic performance through the synergistic effect of Ag modification and N doping.Anatase titanium dioxide with good structural properties was prepared by magnetron sputtering,the substrate temperature was 300°C,the oxygen-argon ratio was 3:1,and the sputtering pressure was 0.7 Pa.On this basis,Ag modification was carried out.The effects of Ag-modified TiO₂ on the structure,morphology and light absorption properties of the films were studied.The results showed that Ag was deposited on the surface of TiO₂ film,the absorption edge was all red-shifted,and the forbidden band width was narrowed.The photocatalytic experiment results show that after 63 minutes of high-pressure mercury lamp irradiation,the sputtering power of Ag was 5 W,and the sputtering time was 50 s.The photocatalytic degradation of acid dyes in the film had the highest degradation rate of 64.1%.Ag deposited on the surface acted as an electron receiver,and the captured photogenerated electrons had strong mobility,forming a Schottky energy barrier near the interface,inhibiting the recombination of electrons and holes,and promoting the reaction.N-doped TiO₂ films were prepared by magnetron sputtering,and the effects of N-doping on the structure and properties of the films were studied.After N doped,the film was pure anatase phase,and the absorption edge of the film was blue-shifted.When the N₂ inlet flow rate was 2 sccm and the sputtering pressure was 0.78 Pa,the degradation rate of photocatalytic degradation of acid dyes was 66.6%.Doped N existed in TiO₂ in substituted form,which caused the diffraction angle to shift to the right,the lattice constant to become smaller,improving the degradation efficiency of TiO₂.Ag-modified N-doped TiO₂ films were prepared by magnetron sputtering,showing a single anatase structure.The absorption spectrum of the film was red-shifted and the energy band gap reduced after Ag and N compounded.The photocatalytic degradation of methyl orange was carried out by Ag/N-TiO₂,it was found that Ag-modified N doping could improve the efficiency of acid dye degradation in the film,and the degradation rate reached 84.03%.The Ag/N-TiO₂ was cyclically used to degrade methyl orange dye,and the photocatalytic activity of the film decreased after 3 cycles.The film was placed under a high-pressure mercury lamp for 1 h to allow the self-cleaning properties of titanium dioxide to clean up the intermediate products attached to the surface,and finally the photocatalytic activity of the film was restored.The mechanism of photocatalytic degradation of methyl orange was analyzed,and it was found that the Ag/N-TiO₂ film mainly rely on photocatalytic degradation to remove dye molecules.The first-order kinetic equation was used for fitting,and it was found that the photocatalytic degradation process conformed to the first-order kinetic model,indicating that the dye concentration controlled the reaction rate.