High-rate biohydrogen production in single-chamber microbial electrolysis cell using iron-sulfide modified biocathode

Microbial electrolysis cells (MEC) can produce hydrogen (H₂) at a low energy expense, but the H₂ production rate is often limited by poor microbe-electrode interaction. This study aimed to enhance the interaction of microbes with a cathode electrode modified with an iron-sulfide (FeS) catalyst in MECs to achieve an efficient H₂ evolution reaction (HER) and to investigate performance at different substrate concentrations, ranging from 1 to 3 g/L of glucose. The electrochemical analysis revealed FeS, a highly active catalyst for HER, surpassing the performance of a 10% platinum (Pt-C)-modified cathode. At 2 g/L glucose, MECs with a FeS-modified cathode (MEC-FeS) produced H₂ at the highest yield of 7.01 mol H₂/mol glucose, and the H₂ production rate was 1.96 ± 0.09 m³/m³·d. The control operations of MEC with a pristine cathode and dark fermentation resulted in a reduced H₂ yield of 5.83 ± 0.49 mol H₂/mol glucose and 2.12 ± 0.12 mol H₂/mol glucose, respectively. Moreover, the MEC-FeS achieved a high energy efficiency of 78 ± 5% compared to the MEC without catalyst (60 ± 5%) and the dark fermentation (24 ± 1%). This study suggests that utilizing FeS as a cathode catalyst in MECs can ensure high-rate hydrogen generation with optimal substrate concentration, paving the way for efficient upscaling and field application.