Catalytic dehydrogenation onset of liquid organic hydrogen carrier, perhydro-dibenzyltoluene: The effect of Pd and Pt subsurface configurations

Perhydro-dibenzyltoluene (H18-DBT) is the hydrogen-rich form of the liquid organic hydrogen carrier (LOHC), dibenzyltoluene. The reversible catalytic hydrogenation and dehydrogenation of LOHCs has made them highly favored for safe storage of hydrogen. In this study, the catalytic dehydrogenation onset was estimated using the reaction energy needed for the dehydrogenation of the first cyclohexane ring of H18-DBT. Using density functional theory calculations with van der Waals corrections, we have calculated the adsorption energies for H18-DBT with and without abstracted H atoms on pristine Pt (1 1 0) and Pd (1 1 0) surfaces and their respective subsurface configurations. The surface slabs consisted of three layers with the two bottom layers forming the subsurface configurations. Adsorption of H18-DBT with and without abstracted H atoms was found to be energetically stable. Based on the calculated reaction energies, catalytic activity towards dehydrogenation highly favored instances where Pt formed the top surface layer than when Pd formed the top surface layer with Pt-Pd-Pd and Pt-Pd-Pt subsurface configurations yielding relatively similar catalytic activity as pristine Pt surface slab. This indicates that with alloying, it is possible to achieve similar catalytic properties as pristine Pt for the catalytic dehydrogenation of H18-DBT.