Designing, Fabrication And Photocatalytic Properties Of Cu₃SnS₄/TiO₂ Coaxial Heterojunction Films

Long-term use of traditional fossil fuels brought about by environmental pollution problems,the most affected and most common is the chemical pollution.Photocatalytic degradation technology is currently recognized as the most promising environmental management methods.Among the photocatalyst materials,titanium dioxide（TiO₂）is a promising solid-phase semiconductor photocatalyst material,and one-dimensional oriented TiO₂ nanotube arrays are considered to be ideal for thin film photocatalysts.However,due to its wide bandgap（3.2 eV）,the current research to overcome the problem is to broaden its light response range and improve the photon quantum efficiency;the second is to further improve its photocatalytic degradation of pollutants stability.Based on the review and analysis of the existing work,this paper puts forward the new ideas and new ways of material selection and structure design.“Based on the design,fabrication and photocatalytic properties of Cu₃SnS₄/TiO₂coaxial heterojunction film”for the research project system summed up the research period for the master’s degree.The main research contents and achievements are summarized as follows:1.The p-type ternary compound Cu₃SnS₄（CTS）with narrow band gap（0.8-1.7 eV）of high light absorption coefficient(10⁴-10⁵ cm^-1)was selected,the CTS nanoparticles and the glass-based CTS films were successfully prepared by one-step hydrothermal method and Sol-Gel self-assembled film-forming process.The results show that CTS nanoparticles have some photocatalytic degradation properties to methyl orange under simulated sunlight,and the surface wetting characteristics of CTS films are sensitive to annealing temperature and 500^oC annealed samples show super-hydrophilic and super-parent amphiphilic properties,stearic acid surface treatment can make the film into a hydrophobic lipophilic surface,stearic acid surface modification,CTS surface super-parental characteristics can be regenerated.The surface super-parent-hydrophobic lipophilic cycle wetting properties of CTS films are expected to be applied to the design and preparation of oil-water separation and complex environmental photovoltaic devices.2.A batch of ordered nanotubes（PhC-TiO₂）with a photonic crystal structure was successfully fabricated on the metal Ti foil by cyclic anodic oxidation.The correlation between the anodic oxidation process parameters and the structure of Ti O₂ photonic crystals was investigated,and the photocatalytic degradation characteristics of the series were studied.The results showed that the photocatalytic degradation efficiency of TiO₂ nanocrystalline nanotubes was better than that of traditional TiO₂ nanotube arrays(k=0.00508 min^-1)based on Bragg scattering and slow photon effect of photonic crystal structure(k=0.01022 min^-1).3.Based on the above research,a series of CTS/PhC-TiO₂ pn coaxial heterojunction thin film photocatalysts were prepared by in-situ self-assembled film-forming process.The results of their photocatalytic properties showed that not only CTS Which can broaden the spectral response range of CTS/TiO₂,and the p-n heterojunction interface can improve the separation efficiency of photo-generated electron-hole pairs,effectively inhibit the recombination of carriers and improve the photocatalytic degradation rate(simulated solar light for 120 min,The degradation rate of methyl orange was 82%and the degradation rate of k=0.01413 min^-1).Subsequently,in order to further improve its photocatalytic efficiency,the Ti³⁺self-doping treatment of PhC-TiO₂ was studied by NaBH₄ liquid phase reduction method to improve the transfer efficiency of photogenerated electrons in TiO₂.The effect of Ti³⁺doping on the photocatalytic activity of CTS/PhC-TiO₂ was investigated.It was found that the optimized CTS/Ti³⁺-PhC-TiO₂ under the same light condition（120 min）The degradation rate of base orange was 96.6%and the degradation rate was increased to k=0.02257 min^-1.