Construction Of Copper-based Composite Catalysts And Their Performance In Electrocatalytic CO₂ Reduction

Utilizing electricity generated from renewable energy to convert CO₂ into valuable carbon-based compounds（CO,HCOOH,CH₄,C₂H₄,C₂H₅OH,etc.）is one of the most promising ways to solve environmental and energy problems.Developing advanced electrocatalysts is the key to achieving efficient CO₂ conversion.So far,numerous catalysts have been developed to enhance the selectivity and activity of electrocatalytic CO₂ reduction.Cu based catalysts have been extensively studied by researchers due to their low cost,diverse product types,and adjustable properties.However,copper-based electrocatalysts for electrocatalytic CO₂ reduction reaction（CO₂RR）still suffered from high overpotential,low activity and low selectivity of single products.To address the above problems,this work constructed three kinds of Cu-based composite electrocatalysts,which enhanced the activity of CO₂RR and improved the selectivity of a single product by creating more active sites and playing the synergistic catalytic role between the two components.The specific research content was as follows:1、The Cu_xO/Pb₃C₂O₇-Y nanosheet composite electrocatalysts（where x=0-2 and Y represents the ratio of Cu（CH₃COO）₂·H₂O and Pb（CH₃COO）₂·3H₂O）were successfully constructed using electrodeposition method and cyclic voltammetry conversion.Among them,Cu_xO/Pb₃C₂O₇-1 showed up to 97.2%selectivity for HCOOH,and Faraday efficiency of formic acid(FE_HCOOH)was greater than 90%at a wide potential window of 400 m V.Cu_xO/Pb₃C₂O₇-1 also exhibited excellent stability with stable operation at a current density of 14.38 m A cm^-2 for 20 h.The excellent performance in a wide potential window was due to the creation of more active site by Cu_xO and Pb₃C₂O₇ heterostructures,which enhanced the adsorption and activation of CO₂.The experimental results demonstrated that the synergistic effect between Cu_xO and Pb₃C₂O₇ accelerated the formation of*OCHO intermediates,enabling efficient CO₂RR reduction to produce HCOOH.2、Cu_x/CdCO₃electrocatalysts were successfully prepared by simple electrodeposition and cyclic voltammetry conversion（x denotes the molar ratio of Cu to the total metal ion concentration）.By adjusting the ratio of Cu²⁺and Cd²⁺metal ions,the Faraday efficiency of CO（FEco）in Cu_0.6/CdCO₃ exceeded 90%under a 700 m V wide potential window and highest value up to 97.9%at-0.90 V vs.RHE.The maximum CO current density reached 12.98 m A cm^-2.The excellent performance of Cu_0.6/CdCO₃ catalyst came from the reasonable regulation of OH^-generation and adsorption,thereby inhibiting HER.In addition,theoretical calculations have shown that the Cu_x/CdCO₃ catalyst reduced the energy barrier from*COOH to*CO intermediate,thereby achieving highly selective electrochemical reduction of CO₂ to CO under a wide potential window.3、Pinpoint CuAg_y-X（y indicates the amount of Ag NO₃ added and X indicates the soaking time）bimetallic electrocatalysts were successfully prepared by replacement reaction as well as electrochemical reduction method.The effect of composition on the CO₂RR performance of CuAg_y-X bimetallic catalysts was investigated by adjusting the amount of Ag NO₃ and the soaking time.Among them,CuAg₁₅₀-80 had the optimal electrochemical reduction performance of CO₂ to multi-carbon compounds(C₂₊),with Faraday efficiency of multi-carbon compounds(FE_C2+)reaching a maximum of 63%.The experimental results demonstrated that the excellent performance came from the synergistic catalytic effect between Cu and Ag bimetallic.Needle-tipped Ag acted as an active site for CO production and highly selective reduction of CO₂ to CO.Then,Cu adsorbed CO to Cu surface for C-C coupling reaction by virtue of its strong adsorption capacity for CO.In addition,in situ Raman spectroscopy demonstrated that the OH^-adsorbed on the Cu surface could further promote the C-C coupling ability of Cu.