Theoretical
Study of the Adsorption/Dissociation Reactions
of Formic Acid on the α‑Al<sub>2</sub>O<sub>3</sub>(0001)
Surface
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Abstract
Formic
acid was used as the model of lauric acid to investigate
the microscopic mechanism of the anti-icing behavior and was checked
to find out if it can be catalyzed to produce H<sub>2</sub> for fuel
cells by the α-Al<sub>2</sub>O<sub>3</sub>(0001) 2 × 2
supercell slab model. The density functional theory with the all-electron
double numerical polarized basis sets was employed. The results show
that when it involves the carboxyl O and hydroxyl H atom the 1,2-dissociated
adsorbate is the most stable intermediate on the dry Al<sub>2</sub>O<sub>3</sub>(0001) surface and is energetic barrier free to form
the fairly stable ROCO- and HO-covered surface with the binding energy
of 59.5 kcal/mol, and this dissociation mode has the lowest energy
barrier of 14.9 kcal/mol to form the HOCO- and H<sub>2</sub>O-covered
surface after the surface is fully hydroxylated. The energetic barrier
of the HCOOH dehydrogenation and dehydration reactions on the alumina
surface decreased considerably from 65.3 to 30.6 kcal/mol and from
62.1 to 26.8 kcal/mol, respectively, in comparison with the gaseous
decomposition. The dissociated configuration of lauric acid was tested,
and it was found that it dissociated with free energy barrier through
1,2-hydrogen migration into the C<sub>11</sub>H<sub>23</sub>OCO- and
HO-covered surface with a binding energy of 60.7 kcal/mol. The present
theoretical work is useful to gain some new insights on the microscopic
interaction mechanism of the superhydrophobic alumina surface fabrication
procedure and on the heterogeneous catalysis reactions of the H<sub>2</sub> production