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

Ontaneda, Jorge, Nicklin, Richard E. J., Cornish, Alix, Roldan Martinez, Alberto ORCID: https://orcid.org/0000-0003-0353-9004, Grau-Crespo, Ricardo and Held, Georg 2016. Adsorption of Methyl Acetoacetate at Ni{111}: Experiment and Theory. Journal of Physical Chemistry C 120 (48) , pp. 27490-27499. 10.1021/acs.jpcc.6b10023

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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 modelling 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, identify 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.

Item Type:	Article
Date Type:	Published Online
Status:	Published
Schools:	Chemistry Advanced Research Computing @ Cardiff (ARCCA)
Subjects:	Q Science > QD Chemistry
Uncontrolled Keywords:	Ni{111}, methyl acetoacetate, XPS, DFT, nickel adatoms.
Publisher:	American Chemical Society
ISSN:	1932-7447
Funders:	EPSRC
Date of First Compliant Deposit:	18 January 2017
Date of Acceptance:	8 November 2016
Last Modified:	12 Nov 2023 00:52
URI:	https://orca.cardiff.ac.uk/id/eprint/97532

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