Electronic Oxide-Metal\nStrong Interactions (EOMSI)\nLocalized at CeO<sub><i>x</i></sub>‑Ag Interface

Electronic oxide–metal strong interactions (EOMSI)\nrefer\nto the electronic oxide-metal interactions (EOMI) between oxide adlayers\nand underlying metal substrate that is strong enough to stabilize\nsupported oxide adlayers in a low-oxidation state, which individually\nis not stable under an ambient condition, from high temperature oxidation\nin air to a certain extent. Herein we report the deposition and electronic\nstructure of CeO<sub><i>x</i></sub> adlayers on capping\nligand-free cubic Ag nanocrystals, i.e., CeO<sub><i>x</i></sub>/Ag inverse catalysts. The EOMI occur via the charge transfer\nfrom Ag substrate to CeO<sub><i>x</i></sub> adlayers in\nthe CeO<sub><i>x</i></sub>/Ag inverse catalyst, and the\nEOMSI are observed in the CeO<sub><i>x</i></sub>/Ag inverse\ncatalyst with the average thickness of CeO<sub><i>x</i></sub> adlayers about 0.9 nm to exclusively form Ce<sub>2</sub>O<sub>3</sub> adlayers stable against oxidation at 400 °C. As the thickness\nof CeO<sub><i>x</i></sub> adlayers increases, ceria adlayers\nwith oxygen vacancies (CeO<sub>2–<i>x</i></sub>)\nemerge and grow in the CeO<sub><i>x</i></sub>/Ag inverse\ncatalysts, and the Ce<sup>3+</sup>/Ce<sup>4+</sup> ratio decreases.\nCatalytic performance of CeO<sub><i>x</i></sub>/Ag inverse\ncatalysts in the CO oxidation reaction is closely linked with the\nthickness and electronic structure of CeO<sub><i>x</i></sub> adlayers. These results demonstrate that the EOMSI and EOMI in the\noxide/metal inverse catalysts are localized at the oxide-metal interface\nand sensitively vary with the thickness of oxide adlayers, offering\na strategy of thickness engineering to tune electronic structures\nof oxide adlayers in oxide/metal inverse catalysts.