Electrochemical reduction of CO2 in a mixed supercritical fluid

A mixture of 1,1,1,2-tetrafluoroethane (HFC 134a) and carbon dioxide is used as a medium for electrochemical study. The reduction of CO2 in the liquid and supercritical states was investigated on both Pt and Pb electrode surfaces. It was shown that there is a decrease in the reduction potential on both electrode materials in the supercritical state compared to the liquid. The reduction of CO2 on a Pt electrode is shown to have a high faradaic efficiency for oxalate production. This is discussed in terms of the adsorption of the CO2.- anion radical on the electrode surface.