Studies On The Reduction Of CO₂ Based On Photo Thermochemical Cycle Enhanced By Photo Reaction

Fossil fuels have been used at an ever increasing pace as the main energy sources,and the use of fossil fuels is accompanied by significant anthropogenic CO2 emissions,leading to adverse changes in the global environment.Since solar energy is a theoretically unlimited energy source,solar-powered CO2 conversion has been considered as a promising solution to the global climate change and energy shortages.The photo thermochemical cycle decomposition of CO2 using solar energy proposed by our group is a promising solar energy utilization means.The design and manufacture of a photocatalytic system with high conversion efficiency is still a huge challenge.This thesis attempts to enhance the photo reaction of the catalyst to improve the efficiency of the conversion of CO2 based on photo thermochemical cycle.SrTiO3 and Au doped SrTiO3 perovskite compounds were prepared in this thesis.The experimental results show that SrTiO3 has the capability of decomposing CO2 by photo thermochemical cycle,with an average CO yield of 2.06 ?mol·g-1h-1 and an energy efficiency of 0.21%.The ability of CO2 decomposition of Au doped SrTiO3 was enhanced,of which 1.5wt%Au-SrTiO3 showed the highest CO yield of 14.46 ?mol g·-1·h-1.Au doped SrTiO3 expanded the optical absorption,inhibited electron-hole pairs recombination,Au SPR effect also enhanced the photo thermochemical reaction.CdS/TiO2 nano-composite system was constructed for photo thermochemical cycle.The composite system enhanced the ability of the photo thermochemical cycle to decompose CO2 with an average CO yield of 5.60 ?mol·g-1·h-1.XRD result showed that there are two different crystal compounds in the complex.We can clearly see the composite CdS and TiO2 on HRTEM pattern,which is consistent with the XRD characterization.XPS result showed that the corresponding states of the elements in the CdS/TiO2 composite system are in the expected states.The nanocomposite system increases the light response range and improves the carriers separation efficiency,thereby improving the efficiency of the photo thermochemical cycle.Cu-loaded TiO2 nanocomposite was prepared by photo-deposition for photo thermochemical cycle.Cu-supported TiO2 can promote the ability of TiO2 to decompose CO2.The catalyst prepared by this method possesses small metal particles and can effectively improve the dispersibility and utilization of the metal.The result of XPS showed that TiO2 produced more oxygen vacancies after light irradiation and provided more active sites for the second thermal reaction.The CO yield of Cu-TiO2 was 13 times that of P25 type TiO2.This is attributed to the activation of CO2 by Cu and the increase of carrier separation rate.