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Adsorption of Methyl Acetoacetate at Ni{111}: Experiment and Theory

DOI: 10.1021/acs.jpcc.6b10023 DOI Help

Authors: Jorge Ontaneda (University of Reading) , Richard E. J. Nicklin (University of Reading) , Alix Cornish (University of Reading) , Alberto Roldan (Cardiff University) , Ricardo Grau-crespo (University of Reading) , Georg Held (University of Reading; Diamond Light Source)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: The Journal Of Physical Chemistry C

State: Published (Approved)
Published: November 2016

Abstract: The hydrogenation of methyl acetoacetate (MAA) over modified Ni catalysts is one of the most important and best studied reactions in heterogeneous enantioselective catalysis. Yet, very little molecular-level information is available on the adsorption complex of the reactant. Here, we report on a combined experimental and theoretical study of MAA adsorption on Ni{111}. XPS shows that the chemisorbed layer is stable up to 250 K; above 250 K, decomposition sets in. In ultra-high-vacuum conditions, multilayers grow below 150 K. DFT modeling predicts a deprotonated enol species with bidentate coordination on the flat Ni{111} surface. The presence of adatoms on the surface leads to stronger MAA adsorption in comparison with the flat surface, whereby the stabilization energy is high enough for MAA to drive the formation of adatom defects at Ni{111}, assuming the adatoms come from steps. Comparison of experimental XPS and NEXAFS data with theoretical modeling, however, identifies the bidentate deprotonated enol on the flat Ni{111} surface as the dominant species at 250 K, indicating that the formation of adatom adsorption complexes is kinetically hindered at low temperatures.

Subject Areas: Chemistry

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Added On: 28/11/2016 15:26

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