Reaction of Water with Ce-Au(111) and CeOx/Au(111) Surfaces: Photoemission and STM Studies
This article reports photoemission and STM studies for the adsorption and dissociation of water on CeAu(1 1 1) alloys and CeO{sub x}/Au(1 1 1) surfaces. In general, the adsorption of water at 300 K on disordered Ce Au(1 1 1) alloys led to OH bond breaking and the formation of Ce(OH){sub x} species. Heating to 500 600 K induced the decomposition or disproportionation of the adsorbed OH groups, with the evolution of H{sub 2} and H{sub 2}O into gas phase and the formation of Ce{sub 2}O{sub 3} islands on the gold substrate. The intrinsic Ce {leftrightarrow} H{sub 2}O interactions were explored by depositing Ce atoms on water multilayers supported on Au(1 1 1). After adsorbing Ce on ice layers at 100 K, the admetal was oxidized immediately to yield Ce{sup 3+}. Heating to room temperature produced finger-like islands of Ce(OH){sub x} on the gold substrate. The hydroxyl groups dissociated upon additional heating to 500-600 K, leaving Ce{sub 2}O{sub 3} particles over the surface. On these systems, water was not able to fully oxidize Ce into CeO{sub 2} under UHV conditions. A complete Ce{sub 2}O{sub 3} {yields} CeO{sub 2} transformation was seen upon reaction with O{sub 2}. The particles of CeO{sub 2} dispersed on Au(1 1 1) did not interact with water at 300 K or higher temperatures. In this respect, they exhibited the same reactivity as does a periodic CeO{sub 2}(1 1 1) surface. On the other hand, the Ce{sub 2}O{sub 3}/Au(1 1 1) and CeO{sub 2-x}/Au(1 1 1) surfaces readily dissociated H{sub 2}O at 300 500 K. These systems showed an interesting reactivity for H{sub 2}O decomposition. Water decomposed into OH groups on Ce{sub 2}O{sub 3}/Au(1 1 1) or CeO{sub 2-x}/Au(1 1 1) without completely oxidizing Cd{sup 3+} into Ce{sup 4+}. Annealing over 500 K removed the hydroxyl groups leaving behind CeO{sub 2=x}/Au(1 1 1) surfaces. In other words, the activity of CeO{sub x}/Au(1 1 1) for water dissociation can be easily recovered. The behavior of gold ceria catalysts during the water gas shift reaction is discussed in light of these results.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source
- Sponsoring Organization:
- Doe - Office Of Science
- DOE Contract Number:
- DE-AC02-98CH10886
- OSTI ID:
- 930469
- Report Number(s):
- BNL-81221-2008-JA; SUSCAS; TRN: US200904%%548
- Journal Information:
- Surface Science, Vol. 601, Issue 12; ISSN 0039-6028
- Country of Publication:
- United States
- Language:
- English
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