The Construction Of Nonmetal-metal Bicomponent Catalysts For Electrocatalytic CO₂ Reduction

Electrocatalytic reduction of CO₂（CO₂RR）can be operated under ambient temperature and pressure,and thus offers an ideal route towards carbon neutrality by converting renewable electricity into carbon-containing chemical feedstocks.For CO₂RR,CO₂-to-CO conversion is considered an ideal route towards carbon neutrality for practical applications.The most representative electrocatalysts are based on noble metals（such as Au）,which suffer from high cost.Recently,single atomic site catalysts（SACs）have shown excellent catalytic activities.However,the structurally simple SACs may not be ideal to activate the multiple molecules involved for CO₂RR.In the thesis,the double-atomic sites catalysts（DACs）and nanocatalysts containing nonmetal and metal component were prepared.Benefiting from the differences in size and electronegativity between nonmetal and metal,those catalysts displayed excellent catalytic activity and selectivity.The main content is as follows:1.Synthesis of tellurium（Te）/copper（Cu）heteronuclear diatomic catalysts and their electrocatalytic performance for CO₂ reduction.Metal organic framework compounds（ZIF-8）were coated on the surface of Te nanowires,and then Cu ions were introduced by the dual solvents method,and calcined at high temperature to generate ortho-site Te/Cu double-atomic sites catalysts.Synchrotron radiation shows that the synthesized diatomic has a Te N₂-Cu N₃ structure,and the CO Faradaic efficiency(FE_CO)of the catalyst is higher than 90%in the range of-0.55 to-0.85 V（vs.RHE）,and at-0.65 V,the FE_CO reaches 97%,stable operationed for 96 hours without obvious attenuation,showing good stability.DFT shows that Te/Cu diatoms can effectively reduce the energy barriers to*COOH and*CO desorption during CO₂RR process,and improve the catalytic activity.In the CO₂RR process,Cu sites activate H₂O molecules,Te sites activate CO₂ molecules,and diatomic sites play a synergistic role in the reaction.The research work reveals the synergistic catalytic mechanism of diatomic catalysts in the electrocatalytic CO₂ process,and provides a scheme for the preparation of efficient diatomic catalysts.2.Synthesis of sulfur（S）in situ doped Au nanoparticles and their electrocatalytic CO₂RR performance.The synthesized Au₂₅ nanoclusters were loaded onto the framework of ZIF-8,and then by high temperature pyrolysis,S in situ modified Au nanoparticles were synthesized,which were about 10 nm in size and uniformly supported on the carbon support.The ICP test shows that the Au content is only 0.4wt%,and the FE_CO of the catalyst exceeds 95%at-0.75 V（vs.RHE）,while the FE_CO of the Au catalyst without S modification is only 58%.Theoretical calculations show that S and Au construct a heteroatom interface,which modulates the electronic structure of the catalytic site,which can significantly reduce the energy barrier for the formation of intermediate*COOH,suppress the hydrogen evolution reaction,and improve FE_CO and catalytic activity.