Semihydrogenation of Acetylene on the (010) Surface of GaPd2

Author(s)

M. Krajci, J. Hafner

Abstract

Ab-initio density-functional calculations have been used to investigate

the structure and stability of the (010) surfaces of the intermetallic

compound GaPd₂ and their activity and selectivity for the

catalytic semihydrogenation of acetylene to ethylene. The calculations

of the surface energies show that Ga-enrichment of the surface is

energetically favored under Ga-rich preparation conditions. The

bulk-terminated stoichiometric GaPd₂(010) surface is

catalytically active but does not exhibit the desired selectivity. The

high Pd concentration in the surface leads to the formation of Pd₃ triplets favoring a strong binding of ethylene and its further hydrogenation to ethyl. In contrast Ga-enriched GaPd₂(010)

surfaces provide an excellent selectivity for the formation of

ethylene. Selectivity increases with increasing number of Ga atoms in

the vicinity of the active Pd atoms. The atomistic scenarios for the

dissociative adsorption of hydrogen, the diffusion of atomic hydrogen,

and the hydrogenation reactions of acetylene to vinyl and further to

ethylene demonstrate that on the selective surfaces the catalytically

active centers are triangular configurations of one Pd and two Ga atoms

binding acetylene through di-σ bonds in Ga–Ga bridge sites. Ethylene, on

the other hand is only weakly π-bonded on top of the Pd atom such that

desorption is easier than further hydrogenation to ethyl. It is

remarkable that the atomic structure of one of the Ga-enriched GaPd₂(010) surfaces is very similar to that of the (001) surface of the Ga₃Pd₅

compound and to the structure of the (210) surface of GaPd. The

structural similarity of the surfaces results in comparable catalytic

properties. The comparison with the results for the semihydrogenation of

acetylene to ethylene on the (210) surfaces of GaPd and AlPd and on the

(100) surface of Al₁₃Co₄ suggests that the

concept of catalytically active centers consisting of

transition-metal–sp-bonded-metal complexes has general validity.

Organisation(s)

Computational Materials Physics

External organisation(s)

Slovenian Academy of Sciences and Arts

Journal

The Journal of Physical Chemistry Part C (Nanomaterials and Interfaces)

Volume

118

Pages

12285-12301

No. of pages

ISSN

1932-7447

DOI

https://doi.org/10.1021/jp5025075

Publication date

06-2014

Peer reviewed

Yes

Austrian Fields of Science 2012

103009 Solid state physics, 103015 Condensed matter, 103025 Quantum mechanics, 103036 Theoretical physics

Keywords

Portal url

https://ucrisportal.univie.ac.at/en/publications/semihydrogenation-of-acetylene-on-the-010-surface-of-gapd2(3ade7bef-9e57-4d5a-bd8f-495ff09fec6e).html