Efficient Catalysts for Cyclohexane Dehydrogenation Synthesized by Mo-Promoted Growth of 3D Block Carbon Coupled with Mo₂C

Cyclohexane can serve as a good dihydrogen (H₂) carrier and a safer medium to store and transport H₂, as it is liquid under ambient conditions and it has a relatively high hydrogen density per unit volume (0.056 g(H₂)/cm³(Cy)_liq.). However, cyclohexane can release H₂ only with efficient cyclohexane dehydrogenation catalysts. Here, we report the synthesis of three-dimensional micron-sized block carbon-molybdenum carbide (BCMC) composite materials that can serve as noble-metal-free catalysts for cyclohexane dehydrogenation. The materials are synthesized by a facile hydrothermal synthetic route, and their structures and morphologies are characterized by various analytical techniques. The results show that the BCMCs, along with specific morphologies, form when a source of Mo is included in the precursor and that the sizes of the microparticles in them can be tailored by changing the relative amount of Mo used for their synthesis. The as-synthesized BCMC materials exhibit high catalytic activity for cyclohexane dehydrogenation while remaining stable and maintaining their catalytic activities during the reaction. The materials' catalytic activity increases as the amount of Mo used to make the materials is increased. This is further found to be because the BCMC materials containing higher amounts of ammonium molybdate or higher densities of Mo₂C provide substantially lower activation energies for the reaction. These materials can be expected to find industrial applications for catalytic production of H₂ from hydrocarbons.