Boosting the Microbial Electrosynthesis of Formate by Shewanella oneidensis MR-1 with an Ionic Liquid Cosolvent.

Microbial electrosynthesis (MES) is a rapidly growing technology at the forefront of sustainable chemistry, leveraging the ability of microorganisms to catalyze electrochemical reactions to synthesize valuable compounds from renewable energy sources. The reduction of CO2 is a major target application for MES, but research in this area has been stifled, especially with the use of direct electron transfer (DET)-based microbial systems. The major fundamental hurdle that needs to be overcome is the low efficiency of CO2 reduction largely attributed to minimal microbial access to CO2 owing to its low solubility in the electrolyte. With their tunable physical properties, ionic liquids present a potential solution to this challenge and have previously shown promise in facilitating efficient CO2 electroreduction by increasing the CO2 solubility. However, the use of ionic liquids in MES remains unexplored. In this study, we investigated the role of 1-ethyl-3-methylimidazolium acetate ([EMIM][Ac]) using Shewanella oneidensis MR-1 as a model DET strain. Electrochemical investigations demonstrated the ability of S. oneidensis MR-1 biocathodes to directly convert CO2 to formate with a faradaic efficiency of 34.5 ± 26.1%. The addition of [EMIM][Ac] to the system significantly increased cathodic current density and enhanced the faradaic efficiency to 94.5 ± 4.3% while concurrently amplifying the product yield from 34 ± 23 μM to 366 ± 34 μM. These findings demonstrate that ionic liquids can serve as efficient, biocompatible cosolvents for microbial electrochemical reduction of CO2 to value-added products, holding promise for more robust applications of MES.