Redox mediators as cathode catalyst to boost the microbial electro-synthesis of biofuel product from carbon dioxide

Microbial electrosynthesis (MES) is a promising technology for carbon dioxide (CO2) sequestration to produce biofuel; however, its practical application is still a challenging due to lower biofuel production rates. This limitation can be alleviated by regulating the interfacial properties of biocathode. The present study investigates the feasibility of novel conducting polymer-based redox mediator modified electrodes to enhance the production of value-added chemicals. The redox mediators investigated in the study are neutral red (NR) and methyl viologen (MV), while polyaniline (PANI) was chosen as supporting conducting polymer. The electrochemical properties of MV-PANI and NR-PANI electrodes were investigated using cyclic voltammetry and electrochemical impedance spectroscopy. The results displayed an increase in biofuel production rates for modified electrodes with MV-PANI and NR-PANI electrodes showing respectively 1.3- and 1.1-times higher production of acetate respectively, as compared to plain Toray carbon paper electrodes. Furthermore, the coulombic efficiencies of acetic acid followed the trend: MV-PANI (74.15 ± 5%) > NR-PANI (64.20 ± 5%) > TCP (52.40 ± 5%). The improved performance of modified electrodes compared to plain carbon paper electrode could be attributed to increased extracellular electron transfer, reduced internal resistance of the system and enriched biofilm formation on the modified cathode.