Electrocatalytic Reduction Of Carbon Dioxide In Organic Composite Electrolyte

CO₂ is an abundant and cheap carbon resource.Converting CO₂ into value-added chemicals and liquid fuel,promote carbon resources recycle,it is extremely pay attention to the important scientific problems of chemical industry.In present work,we intends to use propylene carbonate（PC）/tetrabutyl ammonium perchlorate（TBAP）as the organic electrolyte with two-compartment electrolysis cell for CO₂ reduction,and Au,Ag,Zn and Ag₂S electrode were used as cathode respectively,The results are as follows:（1）We have analysised the water effect to conductivity,viscosity,CO₂ solubility of organic medium.The experiment results showed that the presence of water in PC/TBAP has a positive effect on the performance of the electrolyte,such as increasing the conductivity,decreasing the viscosity and improving the CO₂ solubility.The electrochemical reduction of CO₂ to CO was also studied in the PC/TBAP electrolyte which containing 6.8%water,the Faradic efficiency reaches 89%and the current density reaches 9.18 mA·cm^-2.During the long term electrolysis process,no deactivation has been found on the surface of Au electrode.（2）In 0.1mol/L PC/TBAP,the electro-reduction of CO₂ was carried out on Au,Ag and Zn electrodes,and the initial potential of Zn was higher than that of Ag,which was lower than Au.After 4 hours of electrolysis,in PC/TBAP solution,of formic acid was measured,and no formic acid was found on the Ag and Au electrodes.Add 6.8%H₂O in PC/TBAP/solution,the onset potential is shift positively and current density of Zn,Ag and Au increased significantly.The X-ray characterization showed that the Zn electrode was not toxic and the electrochemical reaction was stable.（3）We developed a new electrode material to further increase the current density,electro-reduction of CO₂ on Ag₂S electrode.After four hours electrolysis,the current density stabled 6.63 mA/cm²（-2.3V vs.Fc/Fc⁺）.The Faradic efficiency of CO formation reached 92%.Due to the presence of residual water,the cathode H₂ was generated,and the Faradic efficiency of H₂ formation is 8%.In PC/TBAP/H₂O/6.8wt%,the Faradic efficiency of CO and H₂ are 85%and 13%respectively,and the value is maintained until the end of the reaction.These results showed that Ag₂S nanoparticles were evenly distributed on the surface of Ag electrode after electro-oxidation.This nanostructure not only increases the electrode surface,but also promotes the CO₂ reduction reaction.Therefore,the current density is increased obviously,and the onset potential is shift positively.