Preparation Of TiO₂-based Nanocomposite And Study On Its Photocatalytic Performance Of CO₂ Reduction

Energy crisis and environmental pollution are the two major problems facing mankind in the 21st century.The reduction of CO2 at room temperature through inorganic semiconductor photocatalysis technology can not only solve the greenhouse effect in the environment,but also alleviate the crisis of energy shortage.The core of inorganic semiconductor photocatalysis technology lies in the design and development of high-efficiency photocatalysts.Efficient photocatalysts not only require a high light response range,but also a high CO2 conversion rate.However,most of the existing photocatalysts with a single composition and structure have problems such as narrow spectral response range,poor quantum efficiency,and poor cycle stability.Based on the above problems,this study uses TiO2 as the base material,through element doping and the construction of semiconductor heterojunction methods to control the energy band structure and the separation of photogenerated charges,so as to design and prepare a high-efficiency carbon dioxide conversion photocatalyst.The main findings are as follows:1.Using Na2Ti3O7 nanobelt as the precursor,the Co3O4/Co-TiO2 heterojunction photocatalyst was successfully prepared by the ion exchange method.HRTEM showed that the Co304/Co-TiO2 heterojunction photocatalyst has a tight hetero interface,and the existence of the hetero interface can realize the effective separation of photogenerated electrons and holes.It was applied to the photocatalytic conversion experiment of carbon dioxide and water and found that the catalyst can efficiently convert carbon dioxide into carbon monoxide.The activity test results show that the Co3O4/Co-TiO2 heterojunction photocatalyst has a 10 times higher than that of pure TiO2 in CO generation rate and 6 times higher than that of pure Co3O4 in CH4 generation rate.A series of analysis tests show that the Z mechanism formed by the Co3O4/Co-TiO2 heterojunction photocatalyst is the main reason for the increase in the photocatalytic carbon dioxide activity.2.The In2O3/TiO2 heterojunction photocatalyst was prepared by a simple hydrothermal method at 180 ℃ for 12 hours.Under light conditions,the CO generation rate of In2O3/TiO2 heterojunction photocatalyst reaches 11.8 μmol g-1 h-1.Under these conditions,In2O3 has no photocatalytic activity,and the CO generation rate of TiO2 is 2.4μmol g-1 h-1.The photocurrent,AC impedance and other series of test results show that the formation of heterojunction inhibits the recombination of photogenerated electrons and holes,and promotes the transfer of charges between the interfaces.3.The Co3O4/In2O3/TiO2 ternary heterojunction was successfully synthesized through the combination of hydrothermal and ion exchange methods combined with the previous results.Due to the bidirectional light-induced charge interface migration mechanism,electrons and holes were effectively separated.Compared with the binary heterojunction of TiO2/In2O3 and TiO2/Co3O4,the ternary heterojunction of Co3O4/In2O3/TiO2 exhibits better photocatalytic carbon dioxide conversion performance,and the generation rate of CO reaches 30.1 μmol g-1 h-1,The generation rate of CH4 reached 12.7μmol g-1 h-1.A series of analysis tests show that the existence of heterogeneous structures greatly promotes the separation of photo-generated charges and realizes high-efficiency catalytic conversion of carbon dioxide.In short,this research designed a series of heterojunction photocatalysts with higher photocatalytic activity,which provides a new method for the design of high-efficiency heterojunction photocatalysts for constructing a new charge transfer mechanism,and also provides a new perspective on reducing CO2 with using photocatalysis for the interface charge transfer mechanism.