Study On The Performance Of Carbon Aerogel-based Gas Diffusion Electrode For CO₂ Catalytic Reduction

The excessive use of fossil fuels not only causes the energy crisis,but also releases a large amount of CO₂,causing many environmental problems.Electrochemical CO₂reduction reaction（ECO₂RR）using renewable energy sources such as wind energy,tidal energy and solar energy is an effective means of CO₂ emission reduction.It can effectively consume CO₂ and generate industrial products such as CO,CH₄,C₂H₄ and CH₃CH₂OH to alleviate the shortage of fossil raw materials.In recent years,carbon aerogel（CA）materials have been gradually used in ECO₂RR due to their designable physical and chemical structure,good mechanical stability and high conductivity.At present,the demand for gas diffusion electrodes（GDEs）is still to design high-performance CA-based catalysts and further clarify the influence mechanism of catalyst micro-nano scale structure on catalytic reaction.Therefore,the thesis aims to synthesize CA-based catalysts with low cost and high catalytic performance for ECO₂RR,and further explore the influence mechanism of CA-based catalyst structure on catalytic performance.1.N,P co-doped CA was prepared by using Konjac glucomannan（KGM）as CA precursor,melamine and phytic acid as N source and P source for ECO₂RR.The results show that P doping improves the electrocatalytic activity and selectivity of the catalyst,and NP-CA-900 obtained at 900°C has the best catalytic performance.At a current density of-18.8 m A cm^-2,the Faraday efficiency（FE,FE=73%）of C₂₊is about 1.92times that of NCA(FE_C2+=38%)without P addition.An appropriate amount of P doping leads to the reconstruction of the electron density of C,which is beneficial to the formation of C₂₊.In addition,the higher CO₂-C₂₊activity and selectivity may be attributed to the three-dimensional（3D）interconnected hierarchical porous structure of CA,which exposes more active sites and provides lower interfacial charge transfer resistance.2.Based on multi-physics finite element simulation,Cu Zn@KCA catalyst with superstructure was prepared by combining N-doped KGM-derived CA with Cu Zn-MOF for ECO₂RR.The Cu Zn@KCA-700 catalyst exhibits high ECO₂RR performance（Faraday efficiency of HCOOH reaches 75%at-1.0 V vs.RHE）.The finite element simulation and experimental results show that the improvement of ECO₂RR performance can be attributed to the superstructure of Cu Zn@KCA,which greatly accelerates the mass transfer rate in the reaction process.This chapter clarifies the influence mechanism of catalyst structure on reaction mass transfer and electron transport.The strategy of preparing 3D superstructure catalyst provides a feasible way to enhance the mass transfer of ECO₂RR.3.Cu Co-MOF was in situ grown on gelatin/agarose-derived CA to prepare Cu₁Co_x@NCA（x=1,4,8）catalysts for ECO₂RR.The effects of different Cu and Co ratios on product selectivity were investigated.The Cu₁Co₁@NCA catalyst tends to selectively generate CH₃COOH,while Cu₁Co₄@NCA shows good selectivity for HCOOH.The FE of the products is the highest at-0.8 V vs.RHE,reaching 38%and 48%,respectively,which is superior to other catalysts with Cu and Co ratios.The results showed that the synergistic effect between Cu and Co changed the adsorption capacity of the catalyst to the intermediates.With the decrease of Cu content,the product gradually changed from C₂₊product such as CH₃COOH to C1 product such as HCOOH.In addition,the high activity of Cu₁Co_x@NCA catalyst can be attributed to its large surface area,abundant Cu-Co active metal sites and N-doped hierarchical porous structure.