First Principles Study On Photothermal Catalytic Reduction Of CO₂ By Modified LDHs

The greenhouse effect caused by large emissions of carbon dioxide（CO₂）has seriously threatened the sustainable development of human society."Carbon peaking and carbon neutrality"has become one of the key tasks of the central economic work in 2021.Photocatalysis,which uses semiconductor catalysts and sunlight to convert CO₂ into useful carbon-based chemicals,can effectively reduce the concentration of CO₂ in the atmosphere,and is a current scientific frontier and hot issue.LDH has a tunable band gap structure,which is conducive to the improvement of electronic structure,and the hydroxyl group on its surface is easy to adsorb acidic gas CO₂,so it has received wide attention in the field of catalysis.In this paper,the performance of modified LDH for photocatalytic reduction of CO₂ and the selectivity of the products are investigated with the help of density functional theory as follows:（1）A perspective LDHs/Ti₃C₂O₂ design by DFT calculation for photocatalytic reduction of CO₂ to C₂ organicsThis paper designs a defective Zn Ti-LDHs/Ti₃C₂O₂ photocatalyst through density functional theory（DFT）calculation to improve selectivity of the C₂ products by enhancing adsorption activation of CO₂and C–C coupling reaction.The formation of Schottky junction greatly inhibit recombination of the photogenerated electron-hole pairs and increase the density of photogenerated electrons on the defective Zn Ti-LDHs/Ti₃C₂O₂ surface.Furthermore,the presence of surficial oxygen vacancies changes the adsorption state of CO₂ molecule and make more enriched electrons boost CO₂ adsorption and activation,especially lower the Gibbs free energy barrier for forming the*CO intermediate favored for reducing CO₂ to multi-electron products.Finally,the photocatalytic mechanism and reaction pathway of CO₂ reduction to C₂products on O-defect-rich Zn Ti-LDHs/Ti₃C₂O₂ are proposed.Our work provides a new strategy for designing photocatalyst to produce the high value-added C₂ products.（2）Mn-CeO₂/Zn Al-LDH heterojunction for efficient photothermal catalytic reduction of CO₂ to COA typy II type Mn-CeO₂/Zn Al-LDH heterostructure is constructed,and the structural stability of Mn-CeO₂/Zn Al-LDH is demonstrated to be significantly enhanced by the calculation of phonon spectra and electron transfer.The analysis of electronic properties shows that the narrow band gap Mn-CeO₂/Zn Al-LDH improves the separation efficiency of photogenerated carriers and expands the photoresponse range,thus enhancing the performance of photothermal catalytic reduction of CO₂.Molecular dynamics simulations at 600 K revealed that*CO is more easily desorbed from the Mn-CeO₂/Zn Al-LDH catalyst to form CO products,which greatly improved the yield and selectivity of CO.