Systematic screening of carbon-based anode materials for bioelectrochemical systems

BACKGROUND: The anode material of bioelectrochemical systems (BES) is crucial because its characteristics directly affect electron transfer from the bacteria to the anode. To assess its usefulness, each material must undergo evaluation under relevant operating conditions, as well as a complete electrochemical characterization. RESULTS: Five carbonaceous materials – carbon brush (CB), carbon granules (CG), thicker carbon felt (CF1), high-conductivity carbon felt (CF2), and high-active-area carbon felt (CF3) – anodes were tested in this work. The current generation with each anode material was studied, operating as a microbial fuel cell (MFC) and microbial electrolysis cell (MEC). Two MFC inoculation strategies were tested: (i) fixed 10 Ω external resistance (ER) and (ii) poised anode potential (PA) of 200 mV versus Ag/AgCl. Once reproducible cycles were obtained in MFC operation, CB yielded the highest maximum current density, amounting to 15.9 A m⁻². A slightly reduced start-up time was observed for each anode with PA than ER. When the anodes were transferred to MEC operation, the maximum hydrogen production rate of 1.04 m³ H₂ m⁻³ d⁻¹ was obtained for CB. CONCLUSION: This study helps in selecting anode material for BES, allowing a shortening of the start-up time and improving its performance using different inoculation strategies and anode materials. Among all the anode materials employed in this study, CB and CF3 electrodes presented the best overall performance.