Magnetic nitrogen-doped activated carbon improved biohydrogen production

Low biological hydrogen (bioH₂) production due to non-optimal metabolic pathways occurs frequently. In this work, magnetic nitrogen-doped activated carbon (MNAC) was prepared and added into the inoculated sludge with glucose as substrate to enhance hydrogen (H₂) yield by mesophilic dark fermentation (DF). The highest H₂ yield appeared in 400 mg/L AC (252.8 mL/g glucose) and 600 mg/L MNAC group (304.8 mL/g glucose), which were 26.02% and 51.94% higher than that of 0 mg/L MNAC group (200.6 mL/g glucose). The addition of MNAC allowed for efficient enrichment of Firmicutes and Clostridium-sensu-stricto-1, accelerating the metabolic pathway shifted towards butyrate type. The Fe ions released by MNAC facilitated electron transfer and favored the reduction of ferredoxin (Fd), thereby obtaining more bioH₂. Finally, the generation of [Fe-Fe] hydrogenase and cellular components of H₂-producing microbes (HPM) during homeostasis was discussed to understand on the use of MNAC in DF system.