Nano-capattery: Taming electron traffic for a 367% leap in biohydrogen surge through suppressing competing pathways in photo photo-fermentative system

Abstract: The electron flux diverts electrons from optimal hydrogen production pathways to competitive pathways, which overall reduces the efficiency of the photo fermentation hydrogen production (PFHP) system. For tackling electron flux and metabolic pathway regulation, a hybrid material (nano-capattery (NC)) was developed based on cobalt-iron-nitrogen doped biochar (Co-Fe-NBC). The NC possessed both the capacitor property (287.91 F/g) and battery-like charge storage 38.3 mC/g with the highest energy density of 159.95 mWh/g. These properties existed due to its Fe2+/Fe3+ and Co2+/Co3+ redox cycle ability, a highly porous surface (291.81 m2/g BET surface area) caused by the defects (AD/AG 3.13) and abundant oxygen vacancies (OVs) observed through electro paramagnetic resonance. During PFHP, there is an 85% reduction in propionic acid, a 65.3% record electron management efficiency, an improved 1.34 NAD+/NADH ratio, along with a 87% increase in dehydrogenase activity, confirming the superior role of NC in efficient regulation of the metabolic pathway and electron flux management. These exceptional properties of biochar-based NC raised the cumulative hydrogen production from 151.03 mL (control) to 589.54 mL, which was an enormous increase of 367%.