Molybdenum oxide-based catalyst towards better hydrogen production: effects of isothermal carburization

Hydrogen (H₂) represents a promising avenue for reducing carbon emissions in energy systems. However, achieving its widespread adoption requires more effective and scalable synthesis methods. Herein, we investigated the isothermal carburization process of the MoO₃ catalyst. This reaction was carried out at a constant temperature of 700 °C in a 60% CO/He stream, with hold reaction times varying (60-min, 90-min, and 120-min). This investigation was conducted using a micro-reactor Autochem with the aim of enhancing the yield of H₂. The study focused on evaluating the chemical reduction and carburization behavior of the MoO₃ catalyst through X-ray diffraction (XRD), transmission electron microscopy (TEM), and CHNS elemental analysis. The XRD analysis revealed the formation of carbides, Mo₂C, and MoO₂, serving as active sites for subsequent H₂ production in the thermochemical water splitting (TWS) process. The carburization at a 60-min hold time exhibited enhanced H₂ production, generating approximately ~ 6.60 µmol of H₂ with a yield of up to ~ 32.90% and a conversion rate of ~ 54.83%. This finding emphasizes the essential role played by the formation of carbides, particularly Mo₂C, in the carburization process, contributing significantly to the facilitation of H₂ production. These carbides serve as exceptionally active catalytic sites that actively promote the generation of hydrogen. This study underscores that the optimized duration of catalyst exposure is a key factor influencing the successful carburization of MoO₃ catalysts. This emphasizes how important carbide species are to increasing H₂ efficiency. Additionally, it is noted that carbon formation on the MoO₃ active sites can act as a potential poison to the catalysts, leading to rapid deactivation after prolonged exposure to the CO precursor.