Study On Photocatalytic Property And Modification Of BiFeO₃ Films Prepared By Magnetron Sputtering

Photocatalytic technology is one of the effective methods to utilize solar energy for organic matter pollution treatment.Traditional photocatalytic materials such as TiO2 can only respond to ultraviolet light due to its wide optical band gap,and the The quantum efficiency is low,so it is urgent to develop new photocatalytic materials to improve the utilization of solar energy.In recent years,the multiferroic material BiFeO3 is one of the candidate materials for a novel photocatalytic material because it has a unique ferroelectric,ferromagnetic energy,particularly a narrow optical bandgap.However,because BiFeO3 is difficult to prepare pure phase,the quantum efficiency is not high and the photogenic carrier is easy to compound,which greatly limits its application in the field of photocatalysis.Hence,BiFeO3 was selected as the research object of photocatalytic performance in this paper,through the control of the preparation process to explore the optimal preparation process parameters of BiFeO3.And in order to improve the light absorption ability and lower light carrier recombination rate,non-metallic N doping and compositing with TiO2 to form heterojunction structure were done in this work,thereby improving BiFeO3 photocatalytic performance of the materials.In this work,BiFeO3 films,N-BiFeO3 films and N-BiFeO3/N-TiO2 composite films were prepared by magnetron sputter technology.The effects of preparation process parameters,N doping and composite of N-TiO2 films on BiFeO3 film structure and optical and photocatalytic properties were investigated respectively.And established heterojunction photocatalytic mechanism of the composite films.The results show that:(1)The sputtering pressure,oxygen argon ratio and annealing temperature have great influence on the phase structure and optical and photocatalytic properties of BiFeO3 films.When the sputtering pressure was lower than lpa,the content of the films was relatively high,while the relative strength of the BiFeO3 diffraction peak decreased at 3Pa,so the optimal sputtering pressure in this paper was 2Pa;The oxygen argon ratio is more important to the structure and performance of the BiFeO3 film,and it can be used to reduce oxygen vacancy,reduce the production of the hybrid,and improve its performance.When the ratio of oxygen to argon was 1:4,the heterophase content was the least,and with high photocatalytic activity;Proper annealing temperature is the key to the preparation of BiFeO3 film,high temperature can induce Bi volatile and BiFeO3 decomposition.But it unable to crystallization when the temperature is too low.So the good control of annealing temperature on the preparation of BiFeO3 is particularly important.The best annealing temperature was 500? in this work.(2)The doping of N has no significant influence on the phase structure of BiFeO3 film,but it can cause the light absorption edge of BiFeO3 film to be redshifted,enlarge its light response range and reduce the optical band gap.On the other hand,moderate doping can reduce the composite rate of the photogenic carrier,thus it can improve the photocatalytic performance of BiFeO3 films.(3)When the N-BiFeO3 film was combined with N-TiO2 film,the heterostructure was formed due to the coupling of the band structure,so that the optical band gap of the composite film was reduced to a different degree compared with single-layer film,and the internal construction of the electric field accelerated the separation of the photogenic carrier,which improved the photocatalytic properties of the composite film at a certain extent.