The Computational Chemistry And Experimental Studv On Photo-Thermochemical Cvcle For CO₂ Reduction

Energy is always an important issue for the development of human society.Currently the main global energy consumption is still based on fossil fuel.The global warming and extreme weather caused by the heavy emission of CO₂,has attracted broad attention from all circles of the society in the world.Recently,a large number of innovative researches have 'been carried out on CO₂ capture and resource utilization in the world.The CO₂ reduction using solar energy is one of the popular issues.Our research group has established a novel photo,thermochemical cycle?PTC?to carry out the CO₂ reduction,making a decisively step towards comprehensive utilization of solar energy.At present,the PTC has made a breakthrough by using TiO₂ materials,but there are still some existing problems,such as the low CO production,low utilization of solar energy and so on.In this paper,the CO₂ decomposition on TiO₂ materials in PTC was carried out.First principle calculation related to the anatase?101?surface of TiO₂ and its modified materials was performed,to theoretically search and design the efficient modified catalyst for the photo-thermal catalytic reaction of PTC.According to the analysis of the structural stability,electronic structure and optical properties,it found that the Cu-doped TiO₂?101?has the smaller single and double oxygen vacancy formation energy,as well as narrower band gap.Also it introduced the impurity levels into the gap to become the interstitial state,which reduced the transition energy of photo electron.Meanwhile,the Cu doping would cause the red shift of the optical absorption spectrum,and perform well absorption in the visible range.Based on the calculation result,the 0.5%Gu-TiO₂ film was produced using a sol-gel method,and applied in the PTC experiment for CO₂ reduction,comparing with the blank group.The result showed that the yield of CO production was 3.81 times of that of undoped TiO₂.X-ray diffraction?XRD?,Scanning electron microscopy?SEM?,and transmission electron microscopy?TEM?were used to assess the structure and morphology of the catalyst.The characterization result showed that the particle size and the crystal shape of the original and cycled samples had no significant change,which performed a well catalytic cycling performance.With the investigation of X-ray photoelectron spectroscopy?XPS?,UV-VIS diffuse reflectance spectra?UV-VIS DRS?and photoluminescence?PL?,it found that the Cu doping could significantly improve the solar light absorption coefficient of the doped system,and prevent the recombination of photo-generated electrons and holes.It would produce more photo-generated holes to participate in the photochemical reaction and form more oxygen vacancies.As the active center of the PTC reaction,the oxygen vacancies would promote the CO₂ adsorption to CO production,which improved the efficiency of the overall PTC process.