An enriched electroactive homoacetogenic biocathode for the microbial electrosynthesis of acetate through carbon dioxide reduction

Abstract

In the direction of generating value added chemicals from carbon dioxide (CO₂) reduction through microbial electrosynthesis (MES), considering the crucial impact of the electrode material for the biofilm development and electron delivery, an attempt was made in this study to evaluate the efficiency of two different materials as biocathodes and their respective output in terms of electrosynthesis. The electrode material is a key component in the MES process. Several electrodes such as platinum, graphite foil, dimentionally stable anode (DSA) and graphite rod, and VITO-CoRE™ derived electrodes were tested for their suitability for ideal electrode combination in a three electrode cell setup. Bicarbonates (the dissolved form of CO₂) was reduced to acetate by a selectively developed biocathode under a mild applied cathodic potential of −400 mV (vs. SHE) in 500 mL of single chamber MES cells operating for more than four months. Among the two electrode combinations evaluated, VITO-CoRE™-PL (VC-IS, plastic inert support) as the cathode and VITO-CoRE™-SS (VC-SS, stainless steel metal support) as the counter electrode showed higher production (4127 mg L⁻¹) with a volumetric production rate of 0.569 kg per m³ per d than the graphite rod (1523 mg L⁻¹) with a volumetric production rate of 0.206 kg per m³ per d. Contrary to the production efficiencies, the coulombic efficiency was higher with the second electrode combination (40.43%) than the first electrode combination (29.91%). Carbon conversion efficiency to acetate was higher for VC-IS (90.6%) than the graphite rod (82.0%).