Fabrication Of Carbon Nanotube Aerogel-supported Pb Nanoparticles And Its Application To Electrochemical Reduction Of CO₂

Carbon dioxide is a non-toxic,inexpensive and abundant carbon source.In recent years,the electrochemical reduction of CO₂ into valuable chemicals has attracted much attention.For example,it can be converted to CO,CH₄,C₂H₄,CH₃OH,HCOOH,HCOO^-,etc.under mild conditions,which Can reduce the greenhouse effect and achieve carbon cycle.Currently,many metals or metal oxides act as electrocatalysts to electrochemically reduce CO₂ to HCOOH.some metals such as Sn,Pb,In,Pd and Bi have high selectivity when electrochemically reducing CO₂ to formic acid as a catalyst,Plus it has a high hydrogen evolution overpotential,so it is widely used.Carbon nanotube aerogels have excellent mechanical properties,large specific surface area and good electrical conductivity,so they are used in many fields widely.If it is combined with a metal or metal oxide,it will have far-reaching research significance.In this study,we prepared that a 3D layered porous carbon nanotube aerogel supported Pb catalyst?Pb/CNT-Agls?on carbon paper electrodes?Pb/CNT-Agls/CP?for the efficient and stable electrochemical reduction of CO2 to formate in KHCO3 aqueous solution.Compared with Pb/CNTs prepared by ordinary calcined Pb nanoparticles and drying method,the microstructure,specific surface area,electrochemical impedance and catalytic performance of the catalyst are obviously superior to those of the other two catalysts.It is indicated that the preparation of the catalyst by lyophilization is the best method.The activity was optimized to obtain a calcination temperature of 500 during the preparation of the catalyst,a calcination time of 4 h and a catalyst with a Pb addition of 0.2 M to achieve the best catalytic activity.The prepared Pb/CNT-Agls catalyst was made of carbon paper as a substrate to prepare Pb/CNT-Agls/CP for electrochemical reduction of CO₂.Linear sweep voltammetry testing of the electrode showed that the electrode has good reducing activity and corrective reduction potential for CO2.Effects of concentration of KHCO3,potential and temperature were investigated.The results indicated the best catalytic activity can be obtained at-1.7V vs.Ag/AgCl in 0.5M KHCO₃ electrolyte at 5?,with 84.6%current efficiency of formic acid.Tafel experiments were conducted on Pb/CNT-Agls/CP electrode,which revealed that the rate-determining step was same on both electrodes,which was one initial electron transfer to CO₂ to form a surface adsorbed CO₂·^-?ads?.The reusability of the electrode was investigated.It was found that the current density decreased after repeated use of the electrode,but no new substance formation or other impurities were adsorbed on the electrode surface.The reason for the slight decrease in current density and Faraday efficiency was further verified,and the electrode prepared by us was further proved to be reusable.