Quantum Chemical Molecular Dynamics Study of the Water–Gas
Shift Reaction on a Pd/MgO(100) Catalyst Surface
Farouq Ahmed
Ryuji Miura
Nozomu Hatakeyama
Hiromitsu Takaba
Akira Miyamoto
Dennis R. Salahub
10.1021/jp310946x.s001
https://acs.figshare.com/articles/journal_contribution/Quantum_Chemical_Molecular_Dynamics_Study_of_the_Water_Gas_Shift_Reaction_on_a_Pd_MgO_100_Catalyst_Surface/2434453
The
water–gas shift (WGS) reaction on a Pd/MgO(100) catalyst
surface was studied using the tight binding-quantum chemical molecular
dynamics (TB-QCMD) method. Molecular adsorption of CO was observed.
In contrast, we observed that H<sub>2</sub>O adsorption occurs first
molecularly but the molecule then dissociates on the surface. The
resultant hydroxyl group reacts with preadsorbed CO to form an OCOH
intermediate and a single H atom. This process is relevant as the
initial hydroxylation step, and it is part of the catalyzed hydrolysis
mechanism. During the molecular dynamics simulation the OCOH intermediate
inverted into an H–CO<sub>2</sub> like molecule and finally
HCO<sub>2</sub> decomposed to CO<sub>2</sub> and H. Later on, the
resultant H interacts with the previously dissociated single H atom
(H released from the H–OH dissociation) and forms the WGS product
H–H molecule. It was observed that the CO<sub>2</sub> desorbed
from the supported Pd cluster while the H<sub>2</sub> molecule remains
attached to the Pd cluster during the simulation. The geometries and
dissociation energies of water molecules were obtained and the type
of adsorption assessed. Chemical changes, changes in electronic and
adsorption states, and structural changes were also investigated through
TB-QCMD calculations, which indicate that the metal-oxide interface
plays an essential role in the catalysis, helping in the dissociation
of water and the formation of the OCOH intermediate. The present study
indicates that the MgO(100) support has a strong interaction with
the Pd catalyst, which may cause an increase in Pd activity as well
as enhancement of the metal catalyst dispersion, hence, increasing
the rate of the WGS reaction. Furthermore, from the molecular dynamics
and electronic structure calculations, we have identified a number
of consequences for the interpretation and modeling of the WGS reaction.
2016-02-19 18:03:26
H 2O adsorption
dynamic
H atom
H 2 molecule
dissociation
WGS reaction
Pd cluster
OCOH
HCO
quantum Chemical Molecular Dynamics Study
CO 2 desorbed
metal catalyst dispersion