Thermo-catalytic applications of two-dimensional metal carbides : (de)hydrogenation of liquid hydrogen carriers, CH₄ dry reforming, and CO₂ hydrogenation

Two-dimensional (2D) nanomaterials, with their ultra-thin structure of a single or a few atomic layers, exhibit unique physical and chemical properties. Despite limited research on their thermocatalytic applications, this thesis explores the potential of 2D metal carbides as promoters of thermo-catalysts for clean energy and greenhouse gas mitigation. Hydrogen storage and transportation presents challenges in utilizing H₂ as an energy source. Liquid organic hydrogen carriers (LOHCs) store and release H₂ through hydrogenation and dehydrogenation, but slow dehydrogenation kinetics hinder adoption. This study showed that adding 6.2 wt.% 2D-Mo2C to 1.3 wt.% Pt/Al₂O₃ significantly enhanced both hydrogenation and dehydrogenation of dibenzyltoluene (DBT) and perhydro-dibenzyl toluene (H18-DBT) in a semi-batch reactor. The modified catalyst remained stable over three cycles, with increased Pt particle size and electron density due to 2D-Mo₂C. Turn-over-frequency analysis showed a linear improvement with higher 2D-Mo₂C loading. A techno-economic analysis indicated that LOHC supply chain costs remain high because DBT has no use at the destination and must return for hydrogenation unlike NH₃ or CH₄ as H₂ carriers. Development of dry reforming of methane (DRM) technology is impeded by coke deposition and catalyst sintering due to high temperatures and carbon-rich reactants. This study reports that adding 1.1 wt.% 2D-Mo₂C to 13 wt.% Ni/γ-Al₂O₃ improved DRM activity by ~40% and enhanced stability by reducing coke formation. XRD and XPS analyses confirmed interactions between 2D-Mo₂C and Ni, forming NixMoy bulk phases and Ni-Mo-oxycarbide surface species. H₂ space-time yields were independent of CO₂ partial pressure and lower than CO yields, consistent with a reaction pathway involving CH₄ decomposition and reverse Boudoaurd reactions. Finally, CO₂ hydrogenation was studied over a 2D-Ti₃C₂ promoted Ni/Al₂O₃ catalyst in a plug flow reactor. Unlike 2D-Mo₂C, synthesized with hydrochloric acid and fluoride salts, 2D-Ti₃C₂ was synthesized using HF, introducing F, O, and OH termination groups. A 5 wt.% loading of 2D-Ti₃C₂ enhanced activity by 78%. The reaction showed zero-order dependence on CO₂ and 0.45 on H₂. The activation energy of the promoted catalyst was 45 kJ/mol, comparable to noble metal catalysts.