(569fx) Interaction of Water with Molybdenum Carbide Catalyst for Thermochemical Hydrogen Production

Transition metal carbides show comparative catalytic activity to noble metals and therefore have obtained significant attention for hydrogen production. However, their stability and interaction with water, as a potential carbon-free source of hydrogen, is not well understood. In this work, the activity and stability of unsupported α-MoC_1−x catalyst was assessed for thermochemically activating water for H₂ production.

A thorough understanding of the stability of this crystallographic phase, while activating water and producing hydrogen, is evaluated. In addition, a possible phase change from carbide to oxide (MoO_x) was also studied as water is a mild oxidant. Different isotopes of water were used (D₂O, H₂¹⁸O) to carefully follow the catalyst activity in the production of hydrogen (or deuterium) as well as carbon dioxide isotopes (molar mass: 44, 46, and 48). A series of ex-situ and in-situ characterization and analysis methods including XRD, TG/DSC (coupled with MS), FT-IR, Raman, and elemental analysis were carried out to better understand the behavior of the catalyst. Ethylene hydrogenation was also employed to probe potential changes in the nature and density of the active site, upon treatment under different hydrogen production conditions. The catalyst showed activity for producing hydrogen from water when different isotope combinations of gaseous water passed over the surface of the activated catalyst. Different cycles were carried out to study the stability of the catalyst. In addition, the adsorption energy of water along with the endothermic energy required for the steam-reforming of excess carbon was analyzed using simultaneous TG/DSC. Overall, the catalyst shows significant potential for production of hydrogen from water and also opens possibilities for the reforming of hydrocarbons.