Descriptors of transition metal promoters on MoS2 nanocatalysts for hydrodesulfurization: binding energy of metal sulfides from first principles

Abstract

MoS₂-based catalysts have been used in the petroleum refinery industry for decades and it is of long-term interest to improve their catalytic efficiency in the hydrodesulfurization (HDS) process such as via edge promotion using transition metal (TM) atoms. To develop an effective descriptor for selecting appropriate TM promoters, here we report a comprehensive computational study of TM promotion effects on the catalytic activity of MoS₂ nanosheets with 26 TM elements, including ten 3d, eight 4d, and eight 5d elements, using sulfur-terminated hexagonal MoS₂ nanosheets. The binding energies between TM atoms and MoS₂ nanosheets without and with sulfur saturation and the formation energies of sulfur vacancies of the TM-promoted MoS₂ were studied to examine the possibility of edge promotion of TM atoms. The HDS activity of sulfur saturated TM-MoS₂ nanocatalysts is evaluated by modeling three consequent steps in an HDS process with a dibenzothiophene molecule. We studied the reaction energy for each step with respect to the binding energy (E_b ∼ 2.5–6.5 eV per atom) of binary TM sulfides and found that E_b can be an effective descriptor for selecting TM promoters to enhance the catalytic activity of MoS₂ nanocatalysts. That is, the E_b value of an ideal TM promoter should neither be extremely high nor extremely low with an ideal range of about 4–5 eV per atom. On the basis of this descriptor, several candidate TM promoters including 3d elements Mn, Cr, Co, Fe, Ni, and V, 4d element Ru, and 5d element Pt are proposed. This work is expected to provide an informative guide to design high-performance MoS₂-based nanocatalysts for HDS.