Modulation Of Interfacial Sites Over Copper-Cerium Catalysts Toward Water-Gas Shift Reaction

The water-gas shift reaction is an important process in petrochemical and ammonia synthesis.Since the reaction is reversible and exothermic,higher CO conversions can only be achieved at low temperatures under the limitation of thermodynamic equilibrium,placing higher demands on the low-temperature activity of water-gas shift catalysts.Copper-cerium catalysts（Cu/CeO₂）have good low-temperature water-gas shift performance due to their excellent redox performance and unique electronic properties.The catalyst interface is the main site where electron transfer and catalytic reactions occur.Adjusting the interfacial sites of inverse Copper-cerium catalysts（CeO₂/Cu）is one of the key methods to enhance the low-temperature activity of water-gas shift reaction.This thesis utilises a’non-chemical’strategy of enhanced reactant micro-mixing and a’chemical’strategy of alkali metal modification to regulate the interfacial sites of inverse CeO₂/Cu catalysts,revealing the scientific rules of metal-support interactions and interfacial electron migration on water-gas shift activity.The scientific rules of the influence of metal-support interaction and interfacial electron migration on the activity of the water-gas shift reaction are revealed.The low-temperature performance of the water-gas shift reaction is improved,providing a theoretical basis and practical exploration for the design,synthesis and characterization of high-efficiency low-temperature water-gas shift catalysts.The main research results are listed as follows:（1）The Cu₂O nanocubes were efficiently prepared by using a rotating packed bed reactor with enhanced micro-mixing.The size of Cu₂O nanocubes was reduced from 158.0 nm to 57.8 nm compared with the conventional method,which significantly increased the specific surface area and defect content of Cu₂O nanocubes.The Cu₂O nanocubes were reduced to expose the most favourable Cu（100）crystalline surface for the water-gas shift,as CeO₂-Cu（100）interfacial sites were constructed.（2）CeO₂ loading was applied to Cu（100）surfaces prepared by different processes,and Ce³⁺-O-Cu⁺interfacial sites were demonstrated by XAFS.The results showed that CeO₂ loading elevates the Cu⁺content and confirms the electron migration pattern of Cu⁰+Ce⁴⁺→Cu⁺+Ce³⁺at the interfacial site.Meanwhile,the smaller particle size of Cu（100）prepared by high-gravity enhanced micro-mixing is more favourable to CeO₂ anchoring and dispersion,and the interfacial electron transfer is more obvious（i.e.stronger metal-support interaction）,and the low-temperature activity of the water-gas shift reaction is greatly enhanced,confirming the feasibility of a"non-chemical"strategy to regulate the interfacial sites of the enhanced reactant micro-mixing.The feasibility of a"non-chemical"strategy to regulate the interfacial sites of the catalyst by enhancing the micro-mixing of the reactants was confirmed.（3）The inverse CeO₂/Cu catalysts were modified with alkali metal K⁺and Na⁺to further modulate the electron transfer at the interfacial sites.The results showed that the alkali metal modification increased the Cu⁺content,where K⁺had a better electron-modulating effect than Na⁺,resulting in a significant increase in electron transfer at the interfacial sites of the CeO₂/Cu catalyst.The catalytic reaction results showed that the K⁺-modified CeO_2/Cu catalyst has efficient low-temperature water-gas shift performance with activation energy as low as 21.3 k J·mol^-1,enabling the activation and conversion of reactants at room temperature.