Preparation,Modification And Photocatalytic Performance Of La₂Sn₂O₇-based Photocatalyst

Photocatalytic technology,which can evolve hydrogen from decomposition water and produce hydrocarbon fuels from reducing CO2 using solar energy,has great prospect in the new energy development.The key of the conversion of solar energy into chemical energy lies in efficient photocatalytic materials,while the traditional TiO2-based photocatalyst with such defects as low quantum efficiency and poor solar energy utilization,which limit the practical application of photocatalytic technology.Therefore,it has been to be a hot topic to develop novel photocatalysts with high efficiency and stability for photocatalysis research.This thesis has carried out the study on the preparation,modification and photocatalytic performance of La2Sn2O7-based photocatalyst.Three photocatalysts were prepared,such as the La2Sn2O7,the RGO/La2Sn2O7 composite and the Pt/La2Sn2O7 composite photocatalyst.In the methanol-solution system,the photocatalytic hydrogen evolution performance of the La2Sn2O7 and RGO/La2Sn2O7 samples were investigated,and the performance of photocatalytic C02 reduction of-La2Sn2O7 and Pt/La2Sn2O7 were explored by using the full spectrum xenon lamp to simulate the sunlight.The structure of samples were characterized,the possible causes of its photocatalytic properties were discussed.Come to a conclusion as follows:(1)The 500 nm La2Sn2O7 nanosphere was prepared by the hydrothermal method.The prepared La2Sn2O7 sample,with cubic phase,13.6 nm grain size,and 256 nm the light absorption band edge,Showed the same photocatalyic activity for the H2 evolution as P25-TiO2.(2)RGO/La2Sn2O7 composite was synthesized by two-step hydrothermal method,When the amount of RGO is 1wt%,RGO/La2Sn2O7 showed the highest activity,which is 2.7 times higher as that of the pure La2Sn2O7.And the RGO/La2Sn2O7 shows transient photocurrent enhancement,decrease of impedance,the fluorescence decreases.It proves that the RGO effectively promote the photoproduction electron and holes separation,improving the activity of photocatalytic hydrogen production.(3)Pt/La2Sn2O7 composite was systhesised by NaBH4 reduction H2PtCl6 method.The La2Sn2O7 sampls after chemical platinum modification can selectively photocatalytic CO2 reduction into methane under simulated sunlight.Under the same condition,the activity of Pt/La2Sn2O7 is 14 times higher as that the activity of commercial anatase.The pure La2Sn2O7 shows the activity of decomposition of H2O,not CO2 reduction.After the modification by platinum nanoparticles,the capture of CO2 adsorption was increased,improving the ability of the transmission electron.The Pt effectively extended the life of the photogenerate carrier,so as to improve the selectivity of photocatalytic reduction of CO2.