Modeling and simulation of microfluidic electrolytic cells for CO2 electro-reduction to formic acid: The influence of a Bi-Sn catalyst and ionic liquid electrolyte on cell performance

The concentration of CO 2 in the atmosphere has recently exceeded 420 ppm and continues to rise, mainly because of the combustion of fossil fuels, contributing significantly to climate change. CO 2 capture, utilization and storage has become recognized as a critical approach to reducing energy and industrial emissions. CO 2 utilization through the electrochemical reduction route is a novel alternative to CO 2 storage. Microfluidic electrolytic cells for CO 2 electro-reduction have recently gained traction due to reduced reactor fouling and flooding rates. However, there is still limited understanding of mass transport, electrochemical interactions, and simultaneous optimization of microfluidic cell performance metrics, such as current density, Faradaic efficiency, and CO 2 conversion. This study employed COMSOL Multiphysics 5.3a to develop a steady-state numerical 2D model of microfluidic cell for electroreduction of CO 2 to HCOOH and compared the optimized performance of 2 electrolytes. Specifically, this work examined the influence of [EMIM][BF 4 ] (1-ethyl-3-methyl imidazolium tetra-fluoroborate) and [EMIM][CF 3 COOCH 3 ] (1-ethyl-3-methylimidazolium tri-fluoroacetate) ionic liquid electrolytes on current density, Faradaic efficiency, and CO 2 conversion. The analysis showed that a 0.9:0.1 Bi-Sn catalyst weight ratio exhibited the highest CO 2 consumption per pass in the cathode gas channel. The model achieved a peak HCOOH current density of 183.8 mA cm −2 , Faradaic efficiency of 87% (average of 66%), and CO 2 conversion of 31.96% at −4 V compared to a standard hydrogen electrode in a microfluidic cell. Furthermore, parametric studies were conducted to determine the best input parameter for cell optimization. • Modeling CO 2 electro-reduction in microfluidic cells. • Studying catalyst and electrolyte influence on cell performance. • Identifying the limiting factors to cell performance. • A comparison between [EMIM][BF 4 ] and [EMIM][CF 3 COOCH 3 ] ionic liquid electrolyte.