Role of Metal-Oxide\nInterfaces in Methanol Decomposition:\nReaction of Methanol on CeO<sub>2</sub>/Ag(111) Inverse Model Catalysts

Metal-oxide interfaces play a critical role in catalytic\nprocesses,\nsuch as methanol adsorption and decomposition reactions. In this work,\nwe investigated methanol reactions on the inverse model CeO<sub>2</sub>/Ag(111) catalyst surfaces, i.e., submonolayer CeO<sub>2</sub> films\non Ag(111), under ultrahigh vacuum (UHV) conditions to specially address\nthe role of CeO<sub>2</sub>–Ag interface in the catalytic methanol\ndecomposition reactions. Using scanning tunneling microscopy (STM),\nlow-energy electron diffraction (LEED), and synchrotron radiation\nphotoemission spectroscopy (SRPES), we found that, at the submonolayer\nceria coverages, the CeO<sub>2</sub> nanoislands exhibit a hexagonal\nCeO<sub>2</sub>(111) lattice with fully oxidized Ce<sup>4+</sup> on\nAg(111). At higher ceria coverages, multilayer ceria nanoislands form\non the Ag(111) surface instead of a well-ordered film. A combination\nof temperature-programmed desorption (TPD) and SRPES reveals that\nmethanol adsorbs dissociatively on the CeO<sub>2</sub>/Ag(111) surfaces\nat 110 K, resulting in the formation of methoxy groups. These methoxy\ngroups subsequently decompose via two pathways: (i) interaction with\nlattice oxygen to produce formate species at 230 K, which then decompose\nto CO, and (ii) direct dehydrogenation of methoxy to formaldehyde.\nNotably, the surface with submonolayer CeO<sub>2</sub> film on Ag(111)\ndemonstrates low-temperature reactivity (440 K) for methoxy dehydrogenation\nto formaldehyde, which occurs at a much lower temperature, compared\nto the surface of multilayer CeO<sub>2</sub> on Ag(111) surface (530\nK). This finding emphasizes that the CeO<sub>2</sub>–Ag(111)\ninterfaces provide unique active sites for methoxy dehydrogenation\nreactions.