Facet-dependent adsorption energy landscapes of the MoO3 precursor on γ-Al2O3: Possible implications for MoS2-based hydrodesulfurization catalysts

The morphology and dispersion of supported MoS 2 active phases play a central role in determining the performance of hydrotreating (HDT) catalysts. Although γ - Al 2 O 3 is the most widely used support, the role of surface crystallography in governing the initial adsorption of MoO 3 precursors remains poorly understood. Here, density functional theory (DFT) calculations were used to systematically map the adsorption energy landscape of MoO 3 on the dehydroxylated (001) and fully hydroxylated (110) surfaces of γ -alumina while examining their structural and electronic properties. On the dehydroxylated (001) facet, MoO 3 adsorbs through a localized bidentate interaction with coordinatively unsaturated sites. Its relatively flat energy landscape provides multiple energetically accessible configurations, allowing broad precursor distribution across the surface. In contrast, the hydroxylated (110) facet presents a much more restrictive adsorption environment, where the dense hydroxyl overlayer confines adsorption to a limited number of well-defined minima. Charge density difference (CDD) analysis reveals that these sites are stabilized by a four-point interaction network consisting of one coordinate bond and three hydrogen bonds. The distinct adsorption landscapes of the two facets suggest markedly different precursor distributions, with potential implications for subsequent agglomeration. These findings provide atomistic insights into the facet-dependent adsorption behavior of MoO 3 on γ - Al 2 O 3 , highlighting the role of surface crystallography in governing the initial adsorption behavior of the MoO 3 precursor and providing theoretical guidance for the rational design of more efficient HDT catalysts.