SiO-Rh(111) Interface: Stability and Activation of Small Molecules

SiO₂ supported Rh-based catalysts have been extensively used in CO hydrogenation reactions. The incorporation of promoters into the Rh/SiO₂ catalyst modulates the charge on Rh, subsequently enhancing its activity and selectivity toward C₂ oxygenates. Despite this, the structural and electronic properties of the Rh-SiO interface have not been exhaustively explored. In this study, silicon was evaporated onto the Rh(111) surface, followed by annealing in O₂ to form ultrathin SiO films. The results indicate that SiO films grow on the Rh(111) surface in a layer-plus-island mode. The stabilities of the SiO-Rh interface in O₂ with an elevated pressure and vacuum annealing were examined. Both O₂ and CO can adsorb in the interface of SiO-Rh in elevated pressures. The binding energies of Si 2p and O 1s shift as oxygen is adsorbed in the interface. The results provide evidence for the activation of small molecules in the metal-oxide interface, and show a passivation effect of an oxide coated metal surface.