Ionic liquid-mediated electrochemical CO2 reduction in a microbial electrolysis cell

Abstract

High external voltage requirement is the main hinder for electrochemical CO2 reduction. To solve this problem, an ionic liquid, 1-ethyl-3-methylimidazolium tetrafluoroborate, mediated electrochemical CO2 reduction was coupled with a Shewanella oneidensis MR-1 catalyzed anodic oxidation in a microbial electrolysis cell (MEC). In the MEC mode, the electrochemical CO2 reduction was triggered at −0.1V. The CO2 reduction rate increased as the external voltage decreased from −0.1 to −0.5V. From the aspect of CO2 reduction selectivity, −0.4V was the optimized external voltage. The low initiation voltage offered the possibility of powering the MEC with a microbial fuel cell (MFC). Therefore, a MEC-MFC-coupled system was developed to electrochemically reduce CO2. The results indicated that an MFC producing the maximal power density of 18.5W/m2 could successfully power the CO2 reduction at a rate of 0.06mmol/m2h in the MEC. Although the reduction rate and selectivity were still needed to be improved, this work provides an idea of integrating ionic liquid catalyzed electrochemical CO2 reduction and bioelectrochemical systems and provides a possibility of electrochemically reducing CO2 in the absence of external electrical power input.