With varied applications across a number of fields, ceria-based materials are the focus of intense study. The suitability of ceria as a heterogeneous catalyst support due to its excellent oxygen storage and release characteristics is well-known. In particular, gold nanoparticles supported on ceria have displayed high catalytic activity towards the low temperature water-gas-shift reaction.1 In this work we describe the preparation and characterisation of model systems employed to study such catalysts. To overcome the charging problems resulting from the application of electron-based spectroscopy and microscopy to insulating materials such as ceria, we form ultrathin epitaxial films of CeO2-x(111) on a number of conducting substrates including Pt(111), 2,3 Rh(111),4 and Re(0001).5 These films have varying thickness from 0.6 - 2 nm and consist of discrete oxide islands with lateral dimensions ranging from 20 - 200 nm.            To characterise the morphology and oxidation state of these films we have employed a combination of techniques including scanning tunnelling microscopy (STM), low energy electron microscopy (LEEM) and synchrotron-based x-ray photoemission electron microscopy (XPEEM). The growth and structure of the ceria films have been followed in-situ with bright- and dark-field LEEM. We have analysed the defect structure of the CeO2-x(111) surface using atomically-resolved STM imaging and identified oxygen vacancy structures which may play important roles in their reactivity. High-resolution XPEEM imaging using resonant photoemission of Ce 4f has permitted us to interrogate the local oxidation state of individual ceria islands. The adsorption of gold clusters ranging in size from single atoms to ~5nm diameter nanoparticles has been investigated with STM and their chemical state probed using XPEEM imaging of the Au 4f. Shifts to higher binding energies are observed for gold supported on the ceria with the magnitude of the shift inversely related to the size of the gold clusters.  (1)      Fu, Q.; Saltsburg, H.; Flytzani-Stephanopoulos, M. Science 2003 , 301, 935-938.(2)      Grinter, D. C.; Ithnin, R.; Pang, C. L.; Thornton, G. J. Phys. Chem. C 2010 , 114, 17036�17041.(3)      Matharu, J.; Cabailh, G.; Lindsay, R.; Pang, C. L.; Grinter, D. C.; Sk�la, T.; Thornton, G. Surf. Sci. 2011 , 605, 1062�1066.(4)      Grinter, D. C. Manuscript in Preparation.(5)       Grinter, D. C.; Yim, C. M.; Pang, C. L.; Santos, B.; Mentes, T. O.; Locatelli, A.; Thornton, G. J. Phys. Chem. C 2013 , 117, 16509-16514.

Characterising a model catalyst system for the water-gas-shift reaction: Gold supported on ultrathin ceria

247th National Meeting (2014)

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