Metal Single-atom Modified Cerium Oxide Photocatalyst And Selective Photocatalytic Carbon Dioxide Reduction

Energy and environment are the issues that have to be paid attention to in the sustainable development of human science and society.Carbon dioxide（CO₂）is the main emission of human activities and modern industry,and the use of fossil fuels as the main energy supply inevitably emits CO₂.But from another perspective,carbon dioxide is also a renewable carbon resource that can produce high value-added chemicals.Solar powered photocatalysis is a promising technology.Photocatalysis is a feasible and promising method to achieve this transformation,in which photocatalyst plays a key role.In this paper,the reaction mechanism of catalyst surface modification and regulation was studied.As the highest oxide of carbon,CO₂ itself cannot absorb light with wavelength between200 nm and 900 nm,which covers ultraviolet light and visible light in the solar spectrum.Therefore,CO₂ cannot be spontaneously activated under sunlight,so it needs to use other substances.The semiconductor photocatalyst is excited by light to form electron-hole pairs,and its redox ability can further activate the carbon dioxide adsorbed on the surface of the photocatalyst in the first step,destroying its stable linear triatomic structure and causing the linear molecules to bend and activate.In fact,the matching of semiconductor band-gap width and reduction potential greatly reduces the selection of catalysts for semiconductor photocatalytic reduction of carbon dioxide.However,this does not limit the exploration of researchers in the field of photocatalysis.Structural adjustment and surface modification of catalysts can also make unsuitable catalysts change valence band and conduction band position for photocatalytic reduction of carbon dioxide.Cerium（Ce O₂）has attracted much attention in the photocatalytic conversion of CO₂ due to its unique 4f electron distribution and abundant reserves in the Earth’s crust.However,CeO₂ can rapidly form phase and surface oxygen vacancy（V_Os）at low oxygen partial pressure,which is not conducive to the separation and migration of photogenic carriers.The presence of V_Os enriches the L-acid site on the catalyst surface and can effectively adsorb CO₂.In this paper,in the experiment of photocatalytic conversion of CO₂,the catalyst morphology was regulated to prepare the exposed surface with high reduction performance[110],and the surface V_Os of the exposed surface could be formed more easily.In this study,it is found that highly dispersed metal atoms stabilize the V_Os of Ce O₂by coordination method,and the synergistic effect of metal（M）and V_Os plays a crucial role in selective photocatalytic CO₂ conversion.The resulting M-O-Ce³⁺atomic interface promotes electron transfer from the Ce³⁺defect site to the M atom,thus improving the carrier separation efficiency and enhancing the photocatalytic activity.The photocatalytic reduction of CO₂ to methanol by Ce O₂ containing V_Os is highly selective,and the M-V_Os-Ce O₂ photocatalytic reduction tends to be more carbon species.The synergistic effect of Lewis pairs formed by Ag and V_Os not only promoted the adsorption and activation of CO₂ molecules,but also improved the selectivity of products.Under the synergistic action of M and V_Os,the key intermediates are stably preserved.This work provides an insight into the selective conversion of CO₂ to high value-added organics by surface conditioning of photocatalysts.