Investigations On The Modulation Of Reaction Pathway For CO₂ Hydrogenation Via Surface And Interface Design

With the rapid development of the world economy,greenhouse gases such as carbon dioxide（CO₂）are discharged into the atmosphere,causing serious greenhouse effect and extreme climate problems.The use of highly efficient catalysts to catalyze the conversion of carbon dioxide not only reduces atmospheric CO₂ concentration,but also produces high value-added chemicals.Due to the complex reaction network of CO₂conversion and the diversity of reaction intermediates,the by-products are produced,while the selectivity of target reaction products is low.In addition,the identification of the active sites and the reaction pathway are of great significance for the rational design of heterogeneous catalysts.In this paper,a series of highly selective CO₂ hydrogenation catalysts were designed and synthesized by adjusting the metal-support interaction and adsorbate-mediated treatments,which can change the surface/interface structure and electronic properties of the catalysts,tune the adsorption of the intermediates and adjust reaction pathway.Aiming to solve the problem of unclear structure-activity relationship in the synthesis of C₁ products for CO₂ hydrogenation,surfaces with different crystal plane orientations were designed to regulate the interplay between the surface structure and CO₂ hydrogenation.Co₃O₄ with morphology-dependent crystallographic surfaces presents different reducibility and formation energy of oxygen vacancies,resulting in different steady-state structures and C₁ product selectivity.Focusing on the unclear electronic function of the binary oxide catalytic system in the CO₂ hydrogenation to methanol,an oxide interface with electron transport phenomenon was designed.This paper describes the observation of the strong electronic interaction between In₂O₃ and monoclinic ZrO₂ support by quasi-in-situ XPS experiments combined with theoretical studies,which leads to support-dependent methanol selectivity.The concept of the electronic interaction between an oxide and a support provides guidelines to develop hydrogenation catalysts.In view of the complicated reaction pathway of ethanol production and the low yield of ethanol,high density hydroxyl groups are introduced onto the surface of the support by hydrothermal method.The Rh Fe Li/TiO₂ catalyst prepared via hydrothermal treatment shows superior ethanol yield for CO₂hydrogenation.In situ infrared characterization proved that the high-density hydroxyl group promoted the cleavage of C-O bond and formation of ethanol.The study of the role of surface hydroxyl groups provides an effective way to design high-efficiency ethanol synthesis catalysts.Based on the difficulty of the dimerization step in the synthesis of oxalic acid,the thickness of CoO nanosheets with（111）crystal planes exposed was adjusted to regulate the Co electron density and the conversion of intermediates.With the aid of polar solvents,CoO nanosheets with a thickness of 4 nm achieved oxalic acid selectivity of 80%.This work focuses on the relationship between the surface/interface structure and the product selectivity and establishes the construction method of specific surface/interface.Thus,the adsorption properties of intermediates and reaction pathway were modulated.CO₂ hydrogenation reaction activity and target product selectivity were promoted.This work provides theoretical guidance for breaking through the bottleneck of CO₂ catalytic conversion.