Elevating hydrogen production efficiency in dark fermentation: The role of cobalt-doped magnetite nanoparticles with sugarcane molasses

This study investigates the enhancement of hydrogen production from sugarcane molasses through dark fermentation using magnetite nanoparticles (Fe₃O₄ NPs) and cobalt-doped magnetite nanoparticles (Co–Fe₃O₄ NPs). Hybrid nanoparticles are included to boost hydrogen yield towards the theoretical maximum. Fe₃O₄ and Co–Fe₃O₄ NPs are synthesized and characterized via hydrothermal methods. At an optimal dose of 300 mg/L, Co–Fe₃O₄ NPs increase hydrogen yield by 41.78 % and productivity by 46.13 % compared to the control. Metabolite analysis shows that acetate and butyrate pathways dominate hydrogen evolution. Co–Fe₃O₄ NPs enhance microbial growth and improve COD removal efficiency, achieving a maximum reduction of 53.30 %. Kinetic modeling with Gompertz and modified Logistic models aligns well with experimental data, indicating reduced lag phases and higher production rates. The results demonstrate that cobalt doping effectively boosts the performance of Fe₃O₄ NPs, offering a promising approach for maximizing hydrogen yield in biomass-based fermentation systems.