Electrochemical reduction of carbon dioxide to formic acid at a tin cathode in divided and undivided cells: effect of carbon dioxide pressure and other operating parameters

The reduction of carbon dioxide to formic acid at a tin cathode was studied in both divided and undivided cells. In the first stage of the study, the effect of some operating parameters, including the working potential and the nature of the supporting electrolyte and of the cathode, on both the cathodic reduction of CO2 and the anodic oxidation of formic acid was investigated in a divided cell. In a second stage, the reduction of carbon dioxide was performed in an undivided cell with the aim of studying the effect on the generation of formic acid of various operating parameters such as current density, cathode to anode area ratio, mixing rate and nature of the anode and of the supporting electrolyte. A detailed investigation on the effect of the carbon dioxide pressure was also carried out. The utilization of relatively high CO2 pressures (15-30 bar) allowed to achieve high concentrations of formic acid (up to 0.46 mol L−1) working with high current density (up to 90 mA cm−2) and using cheap and simple undivided cell and electrodes.