Enhancing biohydrogen production through microbial fermentation with the addition of nanometal ions

Hydrogen is considered a primitive yet efficient gas that changed the quest for biofuels. Nanotechnology is a game changer in broader science applications and shows perspective in biohydrogen production from algae sources. This review focuses on biohydrogen production from microalgae and examines various fermentative methodologies. The potential impact of nanosized metals on the yield is discussed. A survey on the importance of metal oxidation states is also presented. Furthermore, the significance of metal nanoparticles (MNPs) in photofermentation (PF) and dark fermentation (DF) is reviewed, and their immobilization techniques are examined. Additionally, investigations on the catalytic abilities of transition metals such as Ni, Co, and Fe, noble metals such as Ag and Au, and photosensitizing transition metal compounds such as TiO₂ and CdS are explored. Moreover, synergistic MNPs and their loading ratio importance are expressed. Furthermore, key points for choosing MNPs and targeting hydrogen yield in PF and DF conditions are emphasized. Conclusive strategies for continuous biohydrogen yield are also elaborated.