Studies On Preparation And Photocatalytic Performance Of LaCoO₃ Photocatalyst By Doping

Environmental issues have become increasingly prominent at present. Especially the processing of organic pollutants has become one of the hottest spot of research. Photocatalytic reaction can directly convert solar into chemical energy, with which photocatalyst can degrade organic pollutants when they both are exposed in light. This provides an ideal way to solve the environmental pollution. So far, most photocatalytic materials are semiconductors with wide band gap, which only absorbs ultraviolet light and limits the utilization of solar energy. Perovskite oxides have been paid much attention from scholars because of its special structure and good photocatalytic properties. It has found that the range of spectral response can be expanded and the photocatalytic activity can be improved when the band gap of the photocatalyst is modified by doping or partly replacing on the basis of maintaining the basic structure unchanged. So LaCoO₃ was selected as the catalyst parent sample in this paper. The effects of doping Fe+3 and Cu2+ on the optical absorption characteristics were studied. The results were showed as follows:(1) Perovskite photocatalyst LaCoO₃ was prepared by citrate complexing method and characterized by XRD, BET, SEM, and UV-Vis absorbance technology. The effects of calcination temperature on the photocatalytic properties of LaCoO₃ were studied and the results showed that: 700℃was better for LaCoO₃ sample to formed a complete perovskite crystalline structure without impurities.(2) The photocatalytic activity of the catalyst was tested with degradation rate of methyl orange. The reaction conditions was optimized to increase the degradation rate. The results was with 400W high pressure mercury lamp as a light source (the main wavelength of 365 nm), 10 mg·L^-1 methyl orange solution, a volume of 50 mL, 0.1 g catalyst, 10 min adsorption equilibrium time and 60 min reaction time.(3) Photocatalyst LaCoO₃ was modified with metal ions Fe³⁺. The effects of amounts doped on the photocatalytic activity was studied by XRD,UV-vis and so no. The results showed that: Fe³⁺ doping made the adsorption edge of LaCoO₃ catalyst a red shift, expanded the scope of its absorption and improved the photocatalytic activity; When the Fe³⁺ doping amount reached 3%, the degradation rate of methyl orange was up to 75.16 %.(4) Photocatalyst LaCoO₃ was doped with metal ions Cu²⁺. The effects of Cu²⁺ amount doped on the photocatalytic activity was studied by XRD,UV-vis diffuse reflectance and other testing methods. The results showed that: Cu²⁺ doping made the adsorption edge of LaCoO₃ catalyst a red shift, expanded the scope of its absorption and improved the photocatalytic activity; When the Cu²⁺ doping amount reached 5 %, the degradation rate of methyl orange was up to 65.31 %.(5) Fe³⁺ and Cu²⁺ doping could make the adsorption edge of LaCoO₃ a red shift and improved the photocatalytic activity of the catalyst. However, the two metal ions have different valence band and electron configuration, they have different effects on the photocatalytic activity of LaCoO₃. Samples doped with Fe³⁺ have better performance and higher photocatalytic activity compared with Cu²⁺.