Green Synthesis of Magnetite Nanoparticles and Catalytic Activity on Hydrogen Production

Abstract

In this study, magnetite (Fe₃O₄) nanoparticles were synthesized via a green route using Cucurbita pepo leaf extract as a bioreducing and capping agent and their catalytic efficacy in hydrogen production from aqueous formaldehyde under alkaline conditions was investigated. The biosynthesized Fe₃O₄ nanoparticles exhibited a strong UV-Vis absorption peak at 200-300 nm and characteristic Fe-O stretching vibrations in the FTIR spectrum, confirming successful nanoscale magnetite formation with biofunctional surface groups enhancing stability and catalytic activity. Hydrogen evolution experiments, performed through the downward displacement of water to ensure CO- and CO₂-free collection, revealed a 350-folds increase in hydrogen production rate from formaldehyde compared to the non-catalyzed system at 60 ºC. The hydrogen generation rate was directly proportional to catalyst loading, with a threefold increase in Fe₃O₄ quantity (0.005 g → 0.015 g) resulting in a substantial enhancement of H­₂ yield (from 30 → 48 mL h^–1). Mechanistic insights suggest a magnetite-facilitated Cannizzaro-type pathway, where formaldehyde and water each contribute a hydrogen atom to form molecular hydrogen, while sodium formate is generated as a recyclable byproduct. This green, low-temperature and CO-free hydrogen production process highlights the potential of biofunctionalized Fe₃O₄ nanoparticles as efficient and sustainable catalysts for on-demand hydrogen supply in proton exchange membrane fuel cells (PEMFCs) applications.