Density functional theory study on FeTi+ catalytic dehydrogenation of methylcyclohexane

Liquid organic hydrogen carriers （LOHCs） have emerged as a promising technology for hydrogen storage and transportation， featuring high safety， facile handling， and good recyclability under ambient conditions. Among them， methylcyclohexane （MCH） has attracted considerable attention due to its high hydrogen content， stability， and well-established hydrogenation/dehydrogenation cycle. These advantages render LOHCs a potential solution for large-scale， low-cost， and long-distance hydrogen delivery in future energy systems. In this study， the reaction mechanism of methylcyclohexane （MCH） dehydrogenation catalyzed by the FeTi⁺ bimetallic cation was investigated using density functional theory （DFT）. The PBE0 functional， combined with DFT-D3 dispersion correction， was employed to improve computational accuracy. The geometries of intermediates and transition states were optimized， and the corresponding energy profiles were obtained on both the doublet and sextet potential energy surfaces. The results reveal that the dehydrogenation process follows distinct pathways depending on the spin state. On the doublet surface， the removal of the second hydrogen molecule is identified as the rate-determining step， and the overall reaction is exothermic （-1.77 kcal/mol）. In contrast， on the sextet surface， the final hydrogen elimination step is rate-determining， with a slightly endothermic overall reaction （+0.16 kcal/mol）. To gain deeper insight into the catalytic mechanism， wavefunction-based analyses， including density of states （DOS） and natural population analysis （NPA）， were conducted to elucidate the electronic structure and charge redistribution during the reaction. These results provide detailed mechanistic understanding of spin-state-dependent MCH dehydrogenation over FeTi⁺， and offers theoretical guidance for the rational design of efficient bimetallic catalysts in LOHC-based hydrogen storage technologies.