Electrochemistry in the water-energy-climate nexus

Electrochemical conversion of CO2 into formic acid (FA) in an aqueous electrolyte is considered a promising strategy to valorise waste-CO2. Some studies, mainly performed using Sn cathodes, have shown that the performance of the process can be strongly improved using pressurized systems. On the other hand, other studies, usually carried out in non-pressurized systems, have indicated that the nature of the cathode can strongly affect the process. Hence, in this work, we have investigated the coupled effect of nature of the cathode and CO2 pressure (PCO2) on the electrochemical conversion of CO2 to FA. Four electrodes (Sn, Sn/C-NP, Bi, Bi/C-NP) have been used as model cathodes. The results obtained have shown that the increase of PCO2 enhances the production of FA and the faradic efficiency of the process (FEFA) for all tested cathodes. Moreover, it has been observed that nanoparticle-based cathodes provided better results for electrolyses carried out at 1 bar and high current density. Conversely, at relatively high PCO2, the effect of the nature of the cathode becomes less important and bulk Sn and Bi electrodes display very interesting results in terms of production of FA, FEFA and stability.