Design And Synthesis Of Ni-based And Cu-based Catalysts And Their Applications In Electrocatalytic Reduction Of Carbon Dioxide

The production of fuels or high-value chemicals from carbon dioxide（CO₂）has dual significance in terms of environmental protection and comprehensive utilization of carbon resources.The electrochemical CO₂ reduction reaction（CO₂RR）for the production of high-value chemicals and fuels has great potential for practical applications and has attracted widespread attention both domestically and abroad.The design and preparation of efficient catalysts are the key issues for the industrial implementation of CO₂RR.In this thesis,we prepared multicomponent Ni-based and Cu-based catalysts and developed various methods for efficient CO₂RR to produce carbon monoxide（CO）and multicarbon(C₂₊)products.The main research content and innovative points are as follows:（1）A mass production for N-doped nickel single-atom catalysts（SACs）SA-Ni/NC-x（x represents the calcination temperature,°C）was achieved by using a hydrogen-bonded organic frameworks（HOFs）as the precursor,and applied to electrochemical CO₂RR for CO production.Results showed that SA-Ni/NC-900exhibited an ultrathin 2D sheet morphology with uniform distribution of Ni atoms in the form of Ni-N₃ coordination.SA-Ni/NC-900 achieved a high Faradaic efficiency of CO(FE_CO)of 95.6%with a partial current density of 19.6 m A cm^-2 at-1.0 V vs reversible hydrogen electrode（RHE）in 0.1 M KCl aqueous solution,and maintained stability for at least 24 hours.It was revealed that the abundant Ni-N₃ active sites in SA-Ni/NC-900 facilitated CO₂ activation to form*CO intermediates,promoting efficient CO₂ conversion to CO.Moreover,the method of preparing SACs from HOF precursor simplified the preparation process,offering a new approach for the synthesis of SACs in CO₂RR.（2）Pb-doped Cu-based bimetallic heterojunction catalyst,PANI-Cu Pb-x（x represents the electrodeposition time,min）,was successfully prepared by anchoring the metal elements in polyaniline（PANI）using a stepwise electrodeposition method for electrocatalytic CO₂RR to produce C₂₊products.Characterization results showed that the Cu dispersed atomicly on the CP.The PANI-Cu Pb-2 catalyst exhibited a high FE_C2+of 81.5%at-1.2 V（vs.RHE）and a partial current density of 15.4 m A cm^-2 in a 0.1 M Cs I aqueous solution.Further studies showed that the introduction of Pb could lower the Gibbs free energy（ΔG）in the electrocatalytic CO₂RR process,thereby suppressing the occurrence of the hydrogen evolution reaction（HER）and promoting the efficient conversion of CO₂ to C₂₊products.（3）In-doped Cu-based bimetallic catalysts were prepared by in-situ electrodeposition Cu_xIn_y-CP（x and y stand for concentrations of Cu and In ions in the electrolytes during electrodeposition,and CP denotes carbon paper）,and the catalysts were used for CO₂RR to produce C₂₊products.Characterization results showed that In was highly dispersed on the surface of the Cu particles.The study found that the Cu_0.1In_0.1-CP exhibited a FE_C2+of 80.1%at-1.2 V（vs.RHE）and a current density of30.2 m A cm^-2 in a 0.1 M Cs I aqueous solution.This work demonstrates that In doping can reduceΔG_*COOH to suppress HER and promote highly selective production of C₂₊products in CO₂RR.（4）P-doped Cu-based catalysts were prepared by regulating the P content using an in-situ electrodeposition method and applied for CO₂RR to produce C₂ products.The characterization results indicated that both Cu and P were uniformly distributed in the catalyst,and P doping could affect the Cu lattice structure.The electrocatalytic performance test showed that the FE_C2 could reach 80.4%at-1.2 V（vs.RHE）and a current density of 40.4 m A cm^-2 in a 0.1 M Cs I aqueous solution.Density functional theory（DFT）studies showed that P doping improved the electronic structure of the Cu-based catalyst and promoted proton transfer during the catalytic reaction,leading to the reduction of theΔG of hydrogen-containing intermediates formation process and promoting C-C coupling.