The hydrogenation of naphthalene to tetralin is an industrially important catalytic reaction for the value-added upgrading of polycyclic aromatic hydrocarbons and the production of clean fuels. Ni/MoS2-based catalysts have exhibited high performance in this selective hydrogenation; however, the intrinsic structure of their active sites remains ambiguous. By combining density functional theory calculations with microkinetic simulations, we reveal that the epitaxial NiS grown on the edge of pristine MoS2 along the sulfur-terminated zigzag orientation (NiS/MoS2-ZZS) exhibits the highest activity for naphthalene hydrogenation, which can be attributed to the presence of dual nickel atom pairs (Ni-Ni) at the edge. In contrast, the introduction of sulfur vacancies or the epitaxial growth of NiS along other orientations on MoS2 edges does not significantly enhance the hydrogenation activity. The adsorption energy of naphthalene is identified as a key descriptor enabling the establishment of the scaling relations for the energies of transition states and intermediates across a series of transition-metal sulfides epitaxially grown on the MoS2-ZZS edge. A volcano-type relationship is observed between the hydrogenation activity and the adsorption energy of naphthalene, and the edge of the NiS/MoS2-ZZS structure exhibits activity approaching the summit of this plot. Such a structure is also capable of reproducing the experimental selectivity. By comparing the hydrogenation activities to those over NiS and Ni surfaces, we further confirm that the high hydrogenation activity of Ni/MoS2-based catalysts originates from its specific edge structure. These computational findings pave the way for the rational design of MoS2-based catalysts via edge-modulated epitaxial growth.
HU et al. (Mon,) studied this question.