Electrochemical conversion of CO2 to formic acid using a Sn based cathode: Combined effect of temperature and pressure

Abstract

Electrochemical conversion of CO2 in the aqueous electrolyte into value-added chemicals is considered one of the most promising strategies to valorize waste-CO2. In the last decade, high attention was focused on the electro- chemical synthesis of formic acid (FA) via CO2 reduction using Sn cathodes. To improve the final concentration of FA in aqueous electrolytes, several approaches, including the utilization of different technologies (i.e. pressurized CO2 reactor, a gas diffusion electrode, divided cell etc...) and different operative conditions (i.e. pH, current densities, temperature, mixing rate, etc...) were investigated in detail. To date, the effect of temperature (T) on the electrochemical conversion of CO2 into FA under pressurized undivided cells is still unexplored. Hence, in this work, the simultaneous effect of CO2 pressure (PCO2 ) (1 ÷ 3 bar) and T (3 ÷ 60 ◦C) on the electrochemical synthesis of FA in an aqueous electrolyte using a Sn cathode was studied in detail. It was found that the adoption of low T and high PCO2 values allows to work at high current densities (j) by achieving high final concentrations of FA ([FA]) and good relative faradaic efficiency (FEFA). As an example, a quite high final [FA] of approximately 360 mM coupled with a FEFA higher than 50% was reached in an aqueous electrolyte by working at T of 10◦C, j of− 75 mAcm−2 and PCO2 of 30 bar.