Formate production from CO2 electroreduction in a salinity-gradient energy intensified microbial electrochemical system

Abstract

The electricity production of microbial electrochemical system can be substantially strengthened by coupling with a reverse electrodialysis stack which extracts energy from salinity gradient, therefore provides a possible way for value-added products in cathode without external energy input. Here, a microbial reverse-electrodialysis CO2 reduction cell (MRECC) was developed and successfully utilized to drive CO2-to-formate conversion on a Bi/Cu cathode. Results confirmed the optimal anodic COD load and cathodic CO2 flow rate to be 1 g NaAc L−1 and 10 mL min−1. MRECC could yielded 143.5 ± 8.1 mg L−1 of formate with total energy efficiency of 4.6 ± 0.9% and coulombic efficiency of 46.4 ± 2.4%. Increasing or decreasing anode or cathode load impaired MRECC performance from economic and environmental viabilities. MRECC provided a promising platform for simultaneous CO2 reduction and value-added chemicals production by using sustainable energy from wastewaters.