Impregnation of granular activated carbon with nickel or copper improves performance of microbial electrosynthesis

Microbial electrosynthesis (MES) utilizes renewable electricity to power microbial conversion of carbon dioxide into multi-carbon products. As the cathode electrodes serve both as source of reducing equivalents and provide surface area for biofilm growth, the electrode material plays a crucial role in MES. In this study, granular activated carbon (GAC) was impregnated with copper or nickel (5 wt%) and used as MES cathode. In abiotic runs, metal impregnated GAC resulted in higher current densities, on average up to 5.6 mA cm⁻³, compared to GAC without metal impregnation, up to 1.1 mA cm⁻³. In MES, metal impregnated GAC enhanced acetate production rates compared to control GAC, up to 241 mg/L d^-1. The differences were mostly affected by the mass percentage of the metal catalyst on GAC, while the oxidation state of the metal had no considerable effect. Overall, impregnating GAC with metals shows high potential for improving the MES performance.