Study On Preparation Of Carbon Monoxide By Electrolysis Of Carbon Dioxide On Gold And Silver Electrode

Carbon dioxide (CO2) is regarded as the main greenhouse gas. Meanwhile, CO2 is an abundant and inexpensive carbon resource in nature. Conversion of CO2 into more valuable commodity chemicals and reduction of the consumption of fossil fuels is one of the effective methods to reduce CO2 in the atmosphere. This paper adopted the new type ion-exchange membrane electrolyzer, respectively in KHCO3 aqueous solution and in organic solvents of dimethyl sulfoxide (DMSO) and propylene carbonate (PC), to study the electrochemical reduction reaction of CO2 on the Au and Ag electrodes, and analyze the deactivation mechanism of the CO2 reduction on Ag electrode in detail, and further explore the electrochemical reduction behavior of CO2 in nonaqueous solution. The main research contents were summarized as following:(1) The electrochemical kinetics characteristics of CO2 reduction was firstly investigated using Cyclic voltammetry(CV), Tafel curve, Potentiostatic electrolysis and Gas chromatogram. It was found that CO2 can be reduced to CO in KHCO3 aqueous solution. The equilibrium potential were respectively -0.720V and -0.934V, and the exchange current density were 4.014×10-4A/cm2 and 3.011×10-4A/cm2. The Faradaic efficiencies of CO formation on Au and Ag electrodes reached respectively 84% and 67%.(2) The deactivation mechanism of the CO2 reduction on Ag electrode was further proved by Linear sweep curve, Tafel curve, Electrochemical impedance spectroscopy, Potentiostatic electrolysis and X-ray photoelectron spectroscopy(XPS). It was found that the black substance was adsorbed on the Ag electrode during the continuous CO2 electrochemical reduction reaction, resulting in equilibrium potential increasing, exchange current reducing, electron transfer resistance markedly rising up, current density and Faradaic efficiency decreasing. The results showed that graphite was the main components of the poisonous intermediate with very small amount of Zn.(3) The electrochemical reduction behavior of CO2 has been studied in nonaqueous solution by means of Cyclic voltammetric curve, Potentiostatic electrolysis, Electrochemical impedance test and Gas chromatography. Potentiostatic electrolysis curve. The results showed that the current density were respectively 3.2mA/cm2 and 4.5mA/cm2 in TBAP/DMSO and TBAP/PC electrolytes, meaning that the deactivation was not serious. Electrochemical impedance spectroscopy analysis results indicated that the reduction process was controlled by the charge transfer and diffusion process. The Faradaic efficiencies of CO formation reached respectively 87% and 89% at the beginning of the electrochemical reduction reaction in the above electrolytes. During 2h electrolysis, the Ag electrode maintained high activity for CO2 reduction, and the faradaic efficiency of CO formation remained greater than 81.3% in the TBAP/DMSO catholyte, while the faradaic efficiency of CO formation remained greater than 83% in the TBAP/PC catholyte.