Development of novel MnO₂ coated carbon felt cathode for microbial electroreduction of CO₂ to biofuels

Fabrication of superior and cost-effective cathodic materials is vital in manufacturing sustainable microbial electrolysis cells (MECs) for biofuels production. In the present study, a novel manganese dioxide (MnO₂) coated felt cathode (Mn/CF) has been developed for MECs using electrodeposition method via potentiostat. MnO₂ is considered to encourage exogenous electron exchange and, in this way, improves the reduction of carbon dioxide (CO₂). MnO₂, as a cathodic catalyst, enhances the rate of biofuel production, electron transfer, and significantly reduces the cost of MECs. A maximum stabilized current density of 3.70 ± 0.5 mA/m² was obtained in case of MnO₂-coated Mn/CF based MEC, which was more than double the non-coated carbon felt (CF) cathode (1.70 ± 0.5 mA/m²). The dual chamber Mn/CF-MEC achieved the highest production rate of acetic acid (37.9 mmol/L) that was significantly higher (43.0%) in comparison to the non-coated CF-MEC. The cyclic voltammograms further verified the substantial enhancement in the electron transfer between the MnO₂ coated cathode and microbes. The obtained results demonstrate that MnO₂ interacted electrochemically with microbial cells and enhanced the extracellular electron transfer, therefore validating its potential role in biofuel production. The MnO₂ coated CF further offered higher electrode surface area and better electron transfer efficiency, suggesting its applicability in the large-scale MECs.