Electrocatalytic Reduction Of Carbon Dioxide In An N-methylpyrrolidone/tetrabutylammonium Perchlorate Electrolyte

The increasing accumulation of CO₂ in the atmosphere has caused global warming.But on the other hand,CO₂ is an abundant and sustainable carbon resource in the chemical industry.In recent years,considerable efforts have been devoted to explore an efficient method to convert CO₂ into liquid fuels and value-added chemicals.Electrochemical reduction of CO₂ into CO using renewable electricity is of interest because this method can decrease the concentration of CO₂,promote carbon recycle and reduce the environment pollution.N-methyl pyrrolidone is an excellent electrochemical solvent,and commonly used in CO₂ absorption due to its high solubility in the chemical industry.It also has a large negative electrochemical window,low volatility and high conductivity.Tetrabutylammonium perchlorate is a common supporting electrolyte in electrochemistry,which possesses favorable properties for CO₂ reduction,such as good thermal and chemical stability,low price and easy preparation.In this work,we have studied CO₂ reduction in N-methyl pyrrolidone/Tetrabutylammonium perchlorate in two-compartment electrolysis cell on Au,porous copper foam and silver coated copper electrodes respectively,the reaction mechanism has been discussed in details.The main research and conclusions are as follows:?1?Electrochemical reduction of CO₂ into CO has been studied on Au electrode.The results show that the CO₂ can be reduced to CO efficiently.The cathodic current density reached 6.6 mA·cm-2,and the highest faradaic efficiency for CO formation reached 93%.During long-term electrolysis experiments,no deactivation of the Au electrode was observed.?2?Because the gold electrode is very expensive,we tried to study the electrochemical reduction of CO₂ on porous copper foam electrode.The results show that the CO₂ can be reduced on porous copper foam electrode.The current density reached 3.5 mA·cm-2 during potentiostatic electrolysis and the faradaic efficiency for CO formation reached 87%.However,due to the low catalytic activity of porous copper foam electrode,the current density is smaller than that of the Au electrode.?3?In order to improve the current density of CO₂ reduction further,we attempted to add the catalytic active substance on porous copper foam electrode.Silver has good catalytic activity,although the performance is lower than that of gold.However,its price is relatively low,so it has great potential in the practical application.The silver was deposited on porous copper foam electrode to prepare silver coated copper electrode to study the electrochemical reduction of CO₂.The potentiostatic electrolysis was conducted on silver coated copper electrode and the current density is up to 4.2 mA ·cm-2.The gas chromatography result shows that the faradaic efficiency for CO formation reached 90%,and the electrochemical reduction can be stable for a long time.Carbon dioxide is a non-polar molecule,and has high solubility in organic solvent.Therefore,it would be beneficial to conduct CO₂ reduction in organic electrolyte.The main problems to be addressed are to improve current density and decrease over-potential in the future.