Surface hydroxyl dependent adsorption of ruthenium on SiO2(0 0 1) – Understanding metal–support interaction

Highlight • Ru adsorption mechanism regulated by OH concentration of silica surface was computed. • Ru adsorption prefers surface O-H oxidative addition on the hydroxylated surface. • Stable configuration of adsorbed Ru atoms after H2 desorption depends on surface hydroxyls. • Singly adsorbed Ru atom has the highest stability on the partially hydroxylated surface. • Metal-support interaction affects the dynamic process of particles dispersion and deactivation. To understand the metal–support interaction of oxide supported transition metal catalysts, we computed the adsorption structures and energies of ruthenium on the idealized SiO2(0 0 1) surfaces with full (OH, 100%), partial (OH, 50%) surface hydroxyl and without surface hydroxyl (OH, 0%) at different ruthenium loading. On the fully (up to 9Ru) and partially (up to 6Ru) hydroxylated surfaces, ruthenium adsorption prefers surface O-H oxidative addition and forms regularly distributed Ru(H)2 species. After the reductive and re-combinative desorption of H2, the adsorbed ruthenium atoms prefer structures with aggregated 2Ru dimeric units on the fully hydroxylated surface, while structures of remote and dispersed singly adsorbed Ru atoms on the partially hydroxylated surface. On the hydroxyl free surface (up to 6Ru), the adsorbed ruthenium atoms prefer three-dimensional aggregated structures, which become more stable with the increase of ruthenium loading. This indicates the surface hydroxyl dependent ruthenium adsorption on SiO2 (0 0 1), and this finding is important for understanding the structure, stability and activity of silica supported ruthenium catalysts and catalysis.