Hydrogen storage by electrochemical reduction of CO2

In the present paper experimental results to the electrochemical reduction of CO2 on porous gas diffusion electrodes in aqueous solutions and preliminary data on the reduction in liquid carbon dioxide are presented. Further some correlation between pseudocapacity of the electrodes and electrochemical activity are discussed. Experiments with gas diffusion electrodes activated by a perovskite type catalyst, La1.8Sr0.2CuO4, showed that at current densities of about 100-200 mA/cm(2) faradaic efficiencies up to 40% are achievable. The reduction of liquid carbon dioxide was investigated in a high pressure cell. Since liquid or supercritical carbon dioxide possesses no ionic conductivity experiments have been carried out with different compounds (e.g. nitroderivates and ammonium carbamates) added to liquid CO2. The ionic conductivity increased up to 10(-2) S/cm. Electrolysis experiments at 90 bar and 55 degrees C provide evidence that the reduction takes place, the main product being methane.