Evaluation of biocathode materials for microbial electrosynthesis of methane and acetate

This study compares carbon felt (CF), granular activated carbon (GAC), and a conductive acrylonitrile butadiene styrene (cABS) polymer cathodes for CH₄ and acetate production in a microbial electrosynthesis (MES) cell. At an applied voltage of 2.8 V and continuous CO₂ flow, the CF biocathode MES cell showed the highest CH₄ production rate of 1420 ± 225 mL V_c^-1 d^-1 (V_c = cathode volume), also producing acetate at a rate of 710 ± 110 mg V_c^-1 d^-1. The volumetric rates of acetate and CH₄ production decreased when using the GAC cathode (720 ± 94 mL V_c^-1 d^-1 and 236 ± 65 mg V_c^-1 d^-1, respectively). When the cABS cathode was used, the CH₄ production declined to 250 ± 35 mL V_c^-1 d^-1, while the acetate production increased to 1105 ± 130 mg V_c^-1 d^-1. The biocatalytic activity of cABS increased after in-situ electrodeposition of Ni and Fe, resulting in a current increase from 205 mA to 380 mA accompanied by increasing acetate and ethanol production (1405 mg V_c^-1 d^-1 and 240 mg V_c^-1 d^-1, respectively), while the CH₄ production decreased. The cABS cathode showed the highest specific (per surface area) activity for acetate and CH₄ production.