Magnetically enhanced electrochemical conversion of CO2 to formate: experimental studies

Abstract

The application of external magnetic fields in electrochemical processes has emerged as a promising strategy to enhance efficiency. Nevertheless, the use of magnetic fields in electrochemical CO2 reduction (ERCO2) has been scarcely explored. This study evaluates the impact of magnetic fields on ERCO2 to formate in a filter-press reactor, combining experimental analysis with magnetic field modeling to understand the performance enhancements achieved by placing magnets outside the electrochemical cell. Magnetic field modeling reveals that the positioning of magnets relative to the cathode surface significantly affects the field strength. For instance, placing a magnet near the anode generates a field strength of 20 mT on the GDE, while positioning two magnets at opposite ends of the cell increases the field to 400 mT. Experimentally, placing magnets near the cathode or at both ends of the cell boosts formate concentration by more than 20 %, achieving values of 4.4 g L−1 and 4.95 g L−1, respectively, with FEs approaching 100 %. These improvements are attributed to the magnetohydrodynamic (MHD) effect, which enhances mass transfer by inducing turbulence in the cathodic electrolyte. This effect is particularly important at low catholyte flow rates, leading to a more than 50 % increase in formate concentration, reaching up to 27.25 g L−1 at a flow rate of 0.07 mL min−1 cm−2. However, the application of magnetic fields also increases energy consumption due to the higher cell voltage requirements, as indicated by Tafel analysis. Despite this limitation, this study demonstrates the potential application of magnetic fields to enhance ERCO2 processes, paving the way for future research to further explore and optimize this promising strategy.