Study On The Synthesis And Visible Light Catalytic Activity Of CuC₂O₄-based Composites

TiO₂ is widely used in the field of photocatalytic oxidation of various contaminants due to its high chemical stability,no toxicity and low price.ZnO nanometerial also has fine application prospect in the photocatalytic fields because of its high catalytic efficiency,low cost,non-toxic and stable structure.However,both TiO₂ and ZnO are wide bandgap semiconductors,which are only responsive to ultraviolet light that accounts for 5%of the sun’s total energy,limiting their application in actual production.In recent years,it has been suggested that the photoinduced interfacial charge transfer（IFCT）between two complexes can not only widen the optical absorption of the wide bandgap semiconductor into visible region,but also improve the photocatalytic efficiency of catalyst.Transition metal Cu,being an indispensable trace element in human body,is low toxicity and inexpensive.In addition,oxalate compounds are stable at room temperature,and oxygen atom in oxalate compounds is easy to form coordination bonds.So,based on photoinduced interfacial charge transfer effect between CuC₂O₄ and TiO₂ or ZnO semiconductor,a series of high-efficiency visible light catalsts have been prepared.Their photocatalytic mechanism has also been studied.In this paper CuC₂O₄-P25,CuC₂O₄-novel TiO₂ and CuC₂O₄-ZnO have been prepared by chemical precipitation method and characterized by XRD,DRS,TEM,and XPS.The visible light photocatalytic activity of catalysts was evaluated by monitoring the oxidation of propylene in an on-line analysis system equipped with a gas chromatograph（GC7900）to monitor the concentration change of C₃H₆.The photoinduced interfacial charge transfer between the valence band of semiconductor and CuC₂O₄ nanoparticles was investigated.The main contents are as follows:（1）Pure CuC₂O₄ are nearly inert in oxidizing propylene experiment under visible light illumination.But CuC₂O₄-P25 composites with different ratio showed apparent visible light activity for the degradation of propylene,and CuC₂O₄-P25（2.5:10）exhibited the highest activity with a steady propylene removal rate of 46.5%.The enhancement of photocatalytic activity of CuC₂O₄-P25 is mainly due to the IFCT effect from the valence band of the TiO₂ to CuC₂O₄ nanoparticles.In addition,after three cycles of photodegradation of propylene,the photocatalytic activity of CuC₂O₄-P25 remains unchanged.（2）The effect of the morphology on the visible light catalytic performance of CuC₂O₄-P25 was studied by changing raw material,system temperature and the concentration of reactant,which affects the particle size and morphology of CuC₂O₄.（3）Novel TiO₂ containing oxygen vacancy was obtained by calcining titanium titanate nanoplatelets at different temperature.Then by chemical deposition method,the series of CuC₂O₄-novel TiO₂ were prepared.The characterization of composites and photocatalytic experiments showed that the photocatalytic activity of as-prepared CuC₂O₄-novel TiO₂ is closely related to the specific surface area,the crystal phase and visible light absorption ability of catalysts.Visible light activity of CuC₂O₄-novel TiO₂ for the degradation of propylene is higher than that of anatase TiO₂,and the order of catalytic activity was CuC₂O₄:TiO₂（500°C）2.5:10（62%）>CuC₂O₄:TiO₂（400°C）2.5:10（58%）>CuC₂O₄:TiO₂（600°C）2.5:10（50%）>CuC₂O₄:TiO₂（300°C）2.5:10（25%）.On the one hand,oxygen vacancies facilitated visible light absorption of catalyst.On the other hand,CuC₂O₄ particles not only suppressed the recombination of photogenerated electron-hole pairs,but also induced the interfacial charge transfer effect between novel TiO₂ and CuC₂O₄.（4）CuC₂O₄-ZnO composites with different mass ratio have been prepared by chemical precipitation method.The propylene degradation experiment showed that the visible light photocatalytic activity of CuC₂O₄-ZnO was attributed to the photoinduced interfacial charge transfer effect（IFCT）between ZnO and CuC₂O₄ nanoparticles.