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Title: Investigation of trimethylacetic acid adsorption on stoichiometric and oxygen-deficient CeO2(111) surfaces

We studied the interactions between the carboxylate anchoring group from trimethylacetic acid (TMAA) and CeO2(111) surfaces as a function of oxygen stoichiometry using in-situ x-ray photoelectron spectroscopy (XPS). Stoichiometric CeO2(111) surface was obtained by annealing the thin film under 2.0x10-5 Torr of oxygen at ~550°C for 30 min. In order to reduce the CeO2(111) surface, the thin film was annealed in ~5.0x10-10 Torr vacuum at 550°C, 650°C, 750°C and 850°C for 30 min to progressively increase the oxygen defect concentration on the surface. The saturated TMAA coverage on CeO2(111) surface determined from XPS elemental composition is found to increase with increasing oxygen defect concentration. This is attributed to the increase of under-coordinated cerium sites on the surface with increase in the oxygen defect concentrations. Periodic density functional theory (DFT) calculations are in agreement with XPS results and indicate a stronger binding between carboxylate group from TMAA with oxygen deficient CeO2-δ(111) surface. In addition DFT calculations reveal that dissociative mode of carboxylate adsorption is more favored than the molecular state and that carboxylate moiety bind to CeO2(111) surface in a bidentate configuration.
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Journal Article
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Journal Name: Physical Chemistry Chemical Physics. PCCP, 18(23):15625-15631
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
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Country of Publication:
United States