Preparation Of Niobium And Tantalum Potassium Salt Catalysts For Photocatalytic Reduction Of CO₂

In current,with the rapid development of economy,the burning of bio-energy,fossil fuel have contributed to a sharp increase of carbon dioxide concentration.Therefore,environmental pollution and the shortage of energy have been attracted attention of worldwide.As a result of the emission of greenhouse gas of carbon dioxide,global warming has become a serious issue.Meanwhile,it has threatened human survival and development seriously.Thus,it is urgent to take measures to reduce the emission of carbon dioxide.Photocatalytic reduction of carbon dioxide simulates the photosynthesis of plants.Using solar energy conversion of carbon dioxide into fuels,which may promote the realization of the carbon cycle,alleviate the environmental issues and the shortage of fossil fuel.This dissertation has investigated a series of perovskite-type photocatalysts.The photocatalytic activities of the samples for reduction of carbon dioxide into methanol using isopropanol as sacrificial agent under UV light irradiation were investigated.Through investigating the photocatalytic activities of photocatalysts which has various morphologies using different preparation methods.The main contents are as following:1.A serious of different potassium tantalates are synthesized by hydrothermal method,and the influences of different hydrothermal temperature,hydrothermal time and potassium hydroxide concentration are investigated.The results show that pyrochlore and perovskite powders of potassium tantalate are successfully synthesized by 1 mmol Ta2O5 powder in 30 mL aqueous alkaline solutions containing 5mol/L KOH and 15 mol/L KOH then heated to 180℃ 12 h respectively.2.A given amount of nickel oxides loading various morphologies potassium tantalates are prepared by an impregnation method.Different effect of samples on the photocatalytic reduction of carbon dioxide are systematically studied.The results show that both of pyrochlore and perovskite powders of potassium tantalate loaded 2wt% NiO exhibit the highest reactivity with methanol formation rate is 1815.31 μmol/h/g_cat、1523.03 μmol/h/g_cat respectively.3.Zinc oxide quantum dots are prepared by a low-hydrothermal method,and the influences of different hydrothermal temperature,hydrothermal time and the photocatalytic activities are invested.The results show that ZnO quantum dots were prepared at 120℃ heated 2 h exhibit the best photocatalytic performance with methanol formation rate is 1128.86 μmol/h/g_cat.4.Secondary hydrothermal method is used to prepare the sheet potassium niobates with perovskite-type.We take niobium pentoxide and potassium hydroxide as precursors,and expore reaction condictions how to influence the samples morphology.The main reaction condictions are as following: different hydrothermal temperature,hydrothermal time,potassium hydroxide concentration and reaction pH.The results show that reaction pH is the most important key factor,the sheet potassium niobates are successfully synthesized only when the reaction pH between 5-6.The the best photocatalytic performance with methanol formation rate is 1257.21 μmol/h/g_cat.5.Zinc oxide quantum dots loading the sheet potassium niobates are prepared by a secondary hydrothermal method.Different effect of samples on the photocatalytic reduction of carbon dioxide are systematically studied.The results show that the best photocatalytic performance with methanol formation rate is 1539.77 μmol/h/g_cat when 2 wt% ZnO quantum dots loaded.Through a series of studies confirmed that potassium tantalate and potassium niobate are the potential of photocatalytic materials in terms of their excellent self-characteristics and high photocatalytic activities.