Electroreduction of carbon dioxide to formic acid using a BiSn nanoparticle catalyst and an ionic liquid electrolyte

Abstract

Climate change and ocean acidification pose significant global challenges due to rising atmospheric CO2 levels, now nearing 424 ppm. Addressing this issue requires urgent solutions for CO2 mitigation. Electrochemical reduction of CO2 presents a promising pathway for CO2 conversion. Microfluidic electrolytic cells (MECs) offer advantages in mitigating reactor fouling and flooding. However, scaling up CO2 electroreduction to formic acid using MECs, particularly with 1-ethyl-3-methylimidazolium tetrafluoroborate [emim][BF4] as an ionic liquid electrolyte and Bi-Sn as a catalyst, remains underexplored. This study develops a scaled-up, steady-state numerical model for CO2 reduction to formic acid in MECs, employing a 70 % v/v [emim][BF4] electrolyte and a BiSn catalyst at a 0.9:0.1 ratio. Key findings include achieving a current density of 275.8 mA/cm², a Faradaic efficiency of 89 %, and a CO2 conversion rate of 39.6 % at –16 V. These results underline the ionic liquid’s high CO2 solubility and conductivity. The model was also scaled to an n-cell stack using COMSOL Multiphysics, revealing a 2.2 % relative error between unit cell and stack configurations. This study demonstrates the feasibility of scaling MECs for efficient CO2 reduction.