Density Functional Theory Investigation Of Rational Modeling Of Catalytic Surfaces Under Reaction Conditions

In the context of global energy crisis and environmental degradation,catalysts have become the key to synthesizing chemicals needed by human beings and realizing efficient energy conversion.Among them,the carbon dioxide（CO₂）hydrogenation reactions transform atmospheric CO₂ gas into the chemical products such as carbon monoxide,methane,methanol,ethanol and other fuels.In the past 30 years,the CO₂hydrogenation catalyst system has made great progress and achieved many promising results.However,the experimental and theoretical analysis of catalyst activity and selectivity is still unable to break through the pressure gap,so that the modeling of catalyst surfaces cannot truly reflect real reactivity sites under the catalytic conditions.This thesis,based on density functional theory（DFT）,established reasonable surface models for CoCu binary alloy catalysts in CO₂ hydrogenation,expounding the important factors restricting surface modeling under reaction conditions,preliminary reducing the gap between theoretical models and the actual reactive surfaces.Firstly,the material gap between the theoretical model and the actual catalytic surface is narrowed by considering surface segregation.It was found that the adsorption energy difference of adsorbents at different sites and segregation energy on the alloy surface presented a good linear relationship.Adsorption preference is a good surface structure descriptor,which can be used to rapidly predict the direction of adsorbent-induced segregation on alloy surface.Combined with the theory and experiment,it is revealed that Co segregation can improve the activation ability of CO₂ and the selectivity of methane.Further,the coverage effect is introduced to shorten the pressure gap between the model and the surface.By constructing thermodynamic surface phase diagram and CO₂ hydrogenation reaction network,the mechanism of easy generation of ethanol precursor under medium CO coverage was revealed:the surface with medium CO coverage could realize the balance of C-O broken bond and C-C coupling.It provides critical theoretical insights to design high-performance catalysts for alcohol production.