Study On The Controllable Synthesis Of Cu-based Materials And The Performance Of CO₂ Electrochemical Reduction

Since the industrial revolution,the excessive use of fossil energy has brought dual threats to global energy and the natural environment.As an effective method of energy transfer,CO₂electrochemical reduction can use the energy generated by renewable clean energy such as solar energy,wind energy,and tidal energy to convert CO₂into high value-added chemicals and fuels under mild conditions without secondary emissions.However,this reaction also faces many development bottlenecks,such as poor catalyst selectivity and stability,and low energy utilization.Therefore,electrochemical reduction research puts forward higher requirements for the selection and modification of catalytic materials.Cu-based catalysts can reduce CO₂to hydrocarbons and alcohol products,and have abundant reserves and low prices.However,when used as a catalyst alone,the overpotential of the reaction is relatively high,and the side reaction of hydrogen evolution is serious,resulting in poor product selectivity.Therefore,the introduction of another metal element into the Cu-based catalyst and the control of the microscopic morphology of polycrystalline copper provide a new research idea for the electro-reduction of CO₂.In this paper,a two-step solvothermal method was used to prepare Ag@Cu-MOF series catalysts and a pressurized hydrothermal synthesis method to prepare porous CuO series catalysts,and the electro-reduction performance of CO₂was explored.The specific research is as follows:1、A two-step solvothermal synthesis method was used to prepare Ag@Cu-MOF,and then the material was heat-treated at different temperatures in a N₂atmosphere.The study found that the CO selectivity is improved after the material is doped with Ag;Ag@Cu-MOF heat-treated at 250°C in a N₂atmosphere for 3h has the best ethylene selectivity at-1.2 V vs RHE,and FE_C2H4is 52.5%.This is because the incorporation of Ag retains the CO₂adsorption capacity of Cu-MOF,and the conductivity is also improved.The formed Cu Ag alloy generates alloy stress,which not only reduces the coverage rate of the adsorbed hydrogen on the electrode surface,but also facilitates the synergistic series catalysis of Ag and Cu active sites,thereby improving the selectivity of hydrocarbon products.2、The porous CuO series catalysts were synthesized by hydrothermal method under different pressures.The influence of the solvent ratio,reactant ratio,pressure and other conditions of the reaction system on the morphology of the synthesized material was systematically studied.Studies have found that under the conditions of water as solvent and CO₂pressure,basic copper carbonate nanoparticles are first generated,and then the nanoparticles are self-assembled to form a long strip structure,and finally baked under air conditions to obtain porous"biscuit-shaped"CuO.The electrochemical properties of the materials are evaluated by LSV,CV,EIS and other electrochemical methods,and the reduction performance is tested by constant potential electrolysis.The reduction products detected by gas chromatography and ¹H NMR are only CO and H₂.The well-developed pore structure of the elongated CuO prepared under the optimal conditions exposes more catalytic active sites,which is conducive to the diffusion of CO₂on the electrode surface and the mass transfer during the reaction.After electrochemical in-situ reduction,FE_COcan reach 88%at-1.1 V vs RHE.