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Dimer saddle point searches to determine the reactivity of formate on Cu(111)

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Abstract.
We used the dimer saddle point searching method with density functional theory calculations to study
the reactivity of formate (HCOO) on the Cu(111) surface. We identified possible reaction paths for the
HCOO decomposition (or synthesis) and hydrogenation in the presence of a co-adsorbed H atom without
assuming their final states. Starting from the most stable bidentate HCOO adsorption configuration, we
calculated the pre-exponential factors and reaction rates of the identified HCOO reaction and diffusion
paths using harmonic transition state theory. In agreement with previous experimental and theoretical
studies, we found that HCOO was formed by gaseous CO2 and adsorbed H through the Eley–Rideal
(ER) mechanism. The activation barriers for direct HCOO synthesis from CO via the ER and Langmuir–
Hinshelwood (LH) mechanisms were 1.44 and 2.45 eV, respectively, suggesting that the reaction pathways
CO or CO(g) + OH ↔ HCOO were unfavorable on the Cu(111) surface. The decomposition of HCOO to
HCO + O was much slower than its reverse recombination. This indicated that the reaction pathway
from HCOO to HCO also was unlikely. On the other hand, the reaction route for HCOO hydrogenation to
H2COO in the presence of a co-adsorbed H atom had an activation energy of 1.24 eV, suggesting that
HCOO hydrogenation was competitive with HCOO decomposition via the ER mechanism with a barrier of
1.30 eV. Except for two fast HCOO diffusion processes, our results showed that HCOO ↔ CO2(g) + H and
HCOO + H ↔ H2COO were the dominant reaction pathways on the Cu(111) surface.

Keywords:
Reactivity
Density functional theory
Dimer method
Cu(111)
Formate

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Informasi Detail

Judul Seri

Journal of Catalysis

No. Panggil

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Penerbit

London : Elsevier Inc.., 2008

Deskripsi Fisik

Journal of Catalysis 258 (2008) 44–51

Bahasa

English

ISBN/ISSN

00219517

Klasifikasi

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Tipe Isi

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Tipe Media

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Tipe Pembawa

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Edisi

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Subjek

KIMIA

Info Detail Spesifik

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Pernyataan Tanggungjawab

agus

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