The use of CeO2-based materials in catalysis has attracted considerable attention in recent years. Ceria has shown great potential as a novel reducible oxide support with unique oxygen storage capacity (OSC) [1]. Ceria can accommodate a large number of oxygen vacancies and the oxidation states of the Ce cation can be switched readily between Ce+3 and Ce+4 depending on the ambient conditions. Hence ceria can actively participate in redox chemical reactions.

 

The formation of well-ordered, flat CeO2 films is required in order to minimize substrate effects in surface chemistry of ceria. An earlier successful approach to this problem involved growth of ceria films on Ru(0001) [2]. More recently, CeO2(111) was grown on a Cu(111) substrate [3]. High activity of ceria-based model catalysts was demonstrated on the inverse catalyst [4, 5] with ceria nanoparticles supported on noble metal substrates. Overall, there is still little known about the mechanism for the growth of ceria film on metal surfaces, its structure and stoichiometry.

 

In the present work the growth of thin ceria films on Cu(111) has been investigated in-situ by means of low-energy electron microscopy (LEEM). Ce was deposited from an e-beam evaporator onto Cu(111) under O2 atmosphere (5x10-7 Torr). Real-time observation of the film growth revealed that at relatively high substrate temperature (above 800K) flat, highly crystalline, epitaxial CeOx(111) film has been formed. In this presentation we will discuss in detail the mechanism of the nucleation and growth, and the atomistic structure of the CeOx film on Cu(111) under varying growth conditions and Cu(111) oxidation state.

 

[1] A. Trovarelli, Catalysis by Ceria and Related Metals, Imperial College Press, London, 2002.

[2] D. R. Mullins, P. V. Radulovic, S. H. Overbury, Surf. Sci. 429, 186 (1999).

[3] V. Matolin, J. Libra, I. Matolinova, V. Nehasil, L. Sedlacek, F. Sutara, Appl. Surf. Sci. 254, 153 (2007).

[4] J. A. Rodriguez, S. Ma, P. Liu, J. Hrbek, J. Evans, and M. Pérez, Science, 318, 1757 (2007).

[5] J. A. Rodriguez, J. Hrbek, Surf. Sci., 604, 241 (2010).

 

 

 

 The authors are thankful to the US Department of Energy (Chemical Sciences Division, contract no. DE-AC02-98CH10886) for financial support. Research carried out in part at the Center for Functional Nanomaterials, Brookhaven National Laboratory, which is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under contract no. DE-AC02-98CH10886.