Magnetic nitrogen-doped activated carbon improved biohydrogen production.

Low biological hydrogen (bioH) 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 (H) yield by mesophilic dark fermentation (DF). The highest H 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 bioH. Finally, the generation of [Fe-Fe] hydrogenase and cellular components of H-producing microbes (HPM) during homeostasis was discussed to understand on the use of MNAC in DF system.