Electronic Oxide-Metal Strong Interactions (EOMSI) Localized at CeO_<i>x</i>-Ag Interface

Electronic oxide-metal strong interactions (EOMSI) refer to the electronic oxide-metal interactions (EOMI) between oxide adlayers and underlying metal substrate that is strong enough to stabilize supported oxide adlayers in a low-oxidation state, which individually is not stable under an ambient condition, from high temperature oxidation in air to a certain extent. Herein we report the deposition and electronic structure of CeO_<i>x</i> adlayers on capping ligand-free cubic Ag nanocrystals, i.e., CeO_<i>x</i>/Ag inverse catalysts. The EOMI occur via the charge transfer from Ag substrate to CeO_<i>x</i> adlayers in the CeO_<i>x</i>/Ag inverse catalyst, and the EOMSI are observed in the CeO_<i>x</i>/Ag inverse catalyst with the average thickness of CeO_<i>x</i> adlayers about 0.9 nm to exclusively form Ce₂O₃ adlayers stable against oxidation at 400 °C. As the thickness of CeO_<i>x</i> adlayers increases, ceria adlayers with oxygen vacancies (CeO_2-<i>x</i>) emerge and grow in the CeO_<i>x</i>/Ag inverse catalysts, and the Ce³⁺/Ce⁴⁺ ratio decreases. Catalytic performance of CeO_<i>x</i>/Ag inverse catalysts in the CO oxidation reaction is closely linked with the thickness and electronic structure of CeO_<i>x</i> adlayers. These results demonstrate that the EOMSI and EOMI in the oxide/metal inverse catalysts are localized at the oxide-metal interface and sensitively vary with the thickness of oxide adlayers, offering a strategy of thickness engineering to tune electronic structures of oxide adlayers in oxide/metal inverse catalysts.