AVS 62nd International Symposium & Exhibition
    Surface Science Tuesday Sessions
       Session SS+AS+EN-TuM

Paper SS+AS+EN-TuM2
Cerium Oxide-Induced Intercalation of Oxygen on Supported Graphene

Tuesday, October 20, 2015, 8:20 am, Room 113

Session: Mechanistic Insight of Surface Reactions: Catalysis, ALD, etc. - I
Presenter: Zbynek Novotny, Pacific Northwest National Laboratory
Authors: Z. Novotny, Pacific Northwest National Laboratory
F.P. Netzer, Karl-Franzens University, Austria
Z. Dohnalek, Pacific Northwest National Laboratory
Correspondent: Click to Email
Cerium oxide is an important catalytic material known for its ability to store and release oxygen, and as such, it has been used in a range of applications, both as an active catalyst and as a catalyst support. Using scanning tunneling microscopy and Auger electron spectroscopy, we investigated oxygen interactions with CeOx clusters on a complete graphene monolayer-covered Ru(0001) at elevated temperatures (550 – 700 K). Under oxidizing conditions (~10-7 Torr of O2), oxygen intercalation under the graphene layer is observed. Time dependent studies demonstrate that the intercalation starts in the vicinity of the CeOx clusters and extends until a completely intercalated layer is observed. Atomically resolved images further show that oxygen forms p(2×1) structure underneath the graphene monolayer. Temperature dependent studies yield an apparent kinetic barrier for the intercalation of 0.9 eV. This value correlates well with the theoretically determined value for the reduction of small CeO2 clusters reported previously. At higher temperatures, the intercalation is followed by a slower etching of the intercalated graphene (apparent barrier of 1.1 eV). The intercalated oxygen can also be released through the CeOx clusters by annealing in vacuum. In agreement with previous studies, no intercalation is observed on a complete graphene monolayer without CeOx clusters, even in the presence of a large number of point defects. These studies demonstrate that the easily reducible CeOx clusters act as intercalation gateways capable of efficiently delivering oxygen underneath the graphene layer.