Electronic Structure Regulation Of Copper-based Catalysts And Their Electrocatalytic CO₂ Reduction Mechanis

With the increase in carbon dioxide（CO₂）emissions,global warming and energy shortage are becoming more serious.Electrochemical CO₂ reduction,which converts carbon dioxide into value-added chemicals and fuels by using renewable electricity,is an effective strategy to mitigate this situation and has become a frontier research in energy conversion and carbon-neutral development.Despite this,the activation process for CO₂ requires high energy due to the high thermodynamic stability and low electron affinities of CO₂ molecules.As a result,the current emphasis of research in this field is on the development of electrochemical CO₂ reduction catalysts with high catalytic activity.Copper-based catalysts have received a lot of interest because of their inexpensive price,abundant availability and adaptability in generating several types of hydrocarbons from CO₂.Unfortunately,the hydrogen evolution（HER）process’s practical applicability is constrained by its large overpotential,low product selectivity and severe side effects.As a consequence,more research needs to be done on the practical optimization and modification strategy of Cu-based catalysts.This paper,based on the metal-support interaction,bimetal synergistic effect and vacancy engineering to achieve the electronic structure regulation of copper-based catalysts,and explore their electrocatalytic carbon dioxide reduction performance.The correlation between the structure of the catalyst and its activity and selectivity was investigated by combining structural characterization and density functional theory（DFT）calculations,and the mechanism of the reaction of the catalyst was explained.Specific research contents are as follows:（1）The regulated surface electronic states of CuNi nanoparticles through metal-support interaction for enhanced electrocatalytic CO₂ reduction to ethanol were investigated.Carbon-encapsulated copper-nickel bimetallic nanoparticles anchored on nitrogen-doped nanoporous graphene（CuNi@C/N-np G）have been synthesized by the chemical vapor deposition（CVD）and atomic layer deposition（ALD）method.Excellent electrocatalytic CO₂ reduction performance has been demonstrated,with Faraday efficiency of ethanol exceeding 60%in a wide potential window of 600 m V.The Faraday efficiency（FE）,selectivity and cathode energy efficiency（CEE）of ethanol over the CuNi@C/N-np G catalyst at the optimum potential of-0.78 V vs.reversible hydrogen electrode（RHE）reached 84%,96.6%and 47.6%,respectively.In combination with the theoretical calculations,the strong metal-support interaction（Ni-N-C）can effectively regulate the electronic structure of CuNi@C/N-np G surface,promote the electron transfer and stabilize the active site(Cu⁰-Cu^δ+)on the catalyst surface,thus improving the electrocatalytic performance of CO₂ reduction.（2）The electronic structure of Cu-In metallic sulfide was regulated by sulfur vacancy to investigate its electrocatalytic CO₂ reduction mechanism.The introduction of vacancy can change the local coordination environment and electronic structure of the active site,as well as adjust the adsorption energy of the intermediates to improve the catalytic activity and selectivity of the catalyst by enhancing the intrinsic activity.Copper indium metallic sulfide with sulfur vacancy（V_S-Cu In S₂）was synthesized via a simple hydrothermal way,and its electrocatalytic CO₂ performance was measured.The FE of carbon product is 92%and the current density is 59.1 m A cm^-2 at-1.18 V vs.RHE.The experimental outcomes display that the existence of sulfur vacancy makes the catalyst surface rich in electrons,which is conducive to the adsorption and activation of CO₂,effectively inhibits the hydrogen evolution side reaction,and further improves the catalytic reaction kinetics.