https://doi.org/10.1016/j.apenergy.2020.115292

Abstract

Regulating cathodic interface properties towards highly effective CH4 production from CO2 is of great importance for energy storage using microbial electro-synthesis (MES). Herein, the feasibility and mechanism of two typical redox mediators, neutral red (NR) and anthraquinone-2, 6-disulfonate (AQDS), were evaluated for the improvement of CH4 formation from CO2 reduction in mixed-culture biocathodes of MESs. Results showed that the CH4 formation rates of biocathodes after modification with NR and AQDS were 5.8 and 3.5 times higher than that of unaltered cathodes. Moreover, the coulombic efficiency of CH4 formation improved from 44.27 ± 4.01% of the control cathode to 64.30 ± 4.83% and 62.26 ± 2.87% after modification with NR and AQDS, respectively. Consequently, the energy efficiency of MESs after cathode modification with NR and AQDS increased to 58.33 ± 3.17% and 53.21 ± 4.11% compared to 38.20 ± 3.12% without modification. Such improvements were likely attributed to the enhanced extracellular electron transfer of microbes, the reduction in internal resistances and the enrichment of hydrogenotrophic methanogens in the mixed-culture biocathodes after modification with NR and AQDS. This study provides an alternative strategy to regulate cathodic interface in MESs for renewable energy storage and biomethane production from CO2.

Keywords

CO2; Redox mediators; Microbial electro-synthesis; CH4; Energy efficiency