Genesis of MoS2 from model-Mo-oxide precursors supported on γ-alumina

The molecular-scale understanding of the genesis MoS2 phase from Mo-oxide precursors supported on alumina is highly challenging with a strong impact activation process heterogeneous industrial catalysts. By means density functional theory (DFT), we quantify free energies elementary steps involved in sulfo-reduction mechanisms Mo-trioxide oligomers and stability corresponding Mo-oxysulfide intermediates γ-alumina (1 0 0) surface. Gibbs energy profiles highlight characteristic chemical reactivity various oxygen sites O/S exchange mechanism reveal that interfacial atoms (Mo-O-Al) are most to be exchanged S. We quantitatively compare two main paths proposed experimentally: one involving Mo-trisulfide second only Mo-oxysulfide. While requires moderate energies, rate-determining correspond S- O-removal small MonO3n-xSx or MonS3n (n ≤ 3) oligomeric intermediates. To overcome these high steps, (MonS3n) fast diffusing surface species promote growth towards targeted phase. A reconstruction chain triangular Mo3S9 conformer also facilitates this transformation.