Perovskite Materials For Photocatalytic Reduction Of CO₂ Based On E_g Orbital Electron Theory

The rapid development of industries has been accompanied by increasing concentrations of atmospheric pollutants.The energy crisis and increasing anthropogenic emissions of Greenhouse gases are widely recognized as two of the primary causes of global environmental problems.To this end,it is an urgent task to solve this problem.The use of sustainable/green energy?e.g.solar energy?to convert carbon dioxide into hydrocarbon fuels to achieve a green cycle of carbon is an extremely important technical route to solve this problem.It not only solves the problem of environmental pollution,but also has a new application prospect from the angle of energy.The main conclusions can be summarized as follows:?1?In this paper,the perovskite material is studied.First,the adjacent transition metal is doped in the B-site,and the LaFeO₃-LaCoO₃-LaNiO₃ ternary system is constructed.The photo-thermal catalytic activity of its crystal structure,grain size,pore size and material self-band structure and the e_g orbital electron are tested.The results of the experiment show that under the condition of 350^?C vis-light,the total yield of CH₄ and CH₃OH is 586.20,20.83 umol g^-1,respectively,and 4.3,2.3 and 3.0 times are respectively increased with respect to the pure material LaFeO₃,LaCoO₃,LaNiO₃,which is not doped in B-site,The methanol is increased by5.4,2.8 and 3.8 times,respectively,and the conversion rate of the methane is up to 96.57%.Further systematic analysis of the ORR electrocatalytic properties of the ternary system shows that the variation of the photocatalytic properties of the ternary system is consistent with that of the ORR electrocatalytic activity.It is concluded that the material design of photocatalytic materials may be based on the design principle of e_g orbital electron number 1 in ORR catalytic materials.?2?The ternary system of LaMnO₃-LaCoO₃-LaNiO₃ was constructed by selecting Mn,Co,Ni with e_g of 1 in typical transition metal elements,and the relationship between photothermal coupling catalytic performance and electron number of e_g orbitals was further studied.The crystal structure,the grain size,the size of the pore size and the energy band structure of the material and the e_g orbital electron are characterized,and the catalytic activity of the material is studied.In that study,after the Fe is replaced with Mn ion,the e_g orbital electron is reduced and close to 1,the e_g anti-bond electron is better combined with the surface of the catalyst,and the catalytic effect is the best.In the same catalytic case,LaMn_0.6Ni_0.4O₃,after 6 hours of visible light irradiation,the total yield of methane 1081.32 and 25.73 umol g^-1,for LaMnO₃,LaNiO₃,LaCoO₃,LaFeO₃ without any doping,The methane is increased by 2.07,4.17,5.58 and 8.0times,respectively,and the methanol is increased by 3.1,3.45,4.65 and 6.68 times,respectively,and the conversion rate of methane is 97.68%.By analyzing the data of Ni-Co-Mn ternary system,it is found that the electron number of e_g orbitals can be maintained near 1 when B-site doping reaches a certain proportion,and the catalytic activity is the highest.?3?In the end,we focus on the effect of specific surface area on the catalytic effect,and we use kit-6 as the hard template to increase the specific surface area of the sample.The photo-thermal catalytic performance is explored by increasing specific surface area.The experimental results show that although the specific surface area has been increased,the catalytic effect has not been significantly improved.Therefore,as far as the photocatalytic efficiency of the materials is concerned,it is more effective to obtain the specific number of e_g electrons by reasonable material design than to increase the specific surface area.In summary,when the B-site is doped with the adjacent transition metal element,the crystal structure of the material itself changes so as to influence the catalytic effect,and through the above experiment,we find that the effect is optimal when the manganese is doped.We use photothermal coupling to reduce CO₂.At the same time,combined with the light energy and the heat energy,the CO₂ is reduced to the hydrocarbon fuel such as methane,whether in the energy or the environment,it has certain application value.