Conversion of CO2 to Formic Acid Using a Solid-State Electrolyte Device at Different Voltages

Abstract

A potential environmentally beneficial method to reduce greenhouse gas emissions is the electrochemical conversion of CO₂ to useful products like formic acid. However, a number of challenges must be addressed in order to synthesize formic acid at high concentrations. One of them is the generation of formate mixtures in conventional liquid reactors, which requires extensive purification processes to generate pure formic acid. A three-compartment reactor that introduces a solid-state electrolyte (SSE) between the anode and cathode has been developed to solve this issue. Numerous factors, such as the flow rates at which liquid and gas are utilized, have an impact on the reactor's performance. In this investigation, pure CO₂ gas was used with flow rates of 0.05 to 0.15 lpm entering the anode and 0.035–0.095 lpm of deionized water (DI) entering the cathode compartment at different voltages (2,98 V and 4,42 V). The results of this study demonstrate that a higher CO₂ gas flow rate increased Faraday Efficiency (FE), as did the rise in DI flow rate. Furthermore, the inclination of HCOOH concentration was related to the increasing CO₂ flowrate, but it declined along with the rise of DI flow rate. This trend was similar for the two voltages used in this experiment, but the reactor’s performance at 4,42 V was slightly better than its performance at 2,98 V. The highest formic acid concentration that could be produced in this experiment was 3.3% with a CO2 gas flow rate of 0.15 lpm and a DI water flow rate of 0.035 lpm.