Chemistry Reference
In-Depth Information
layer and the outside wall of NTs. Therefore, CO oxidation by the lattice
oxygen on the single layer, the outside and inside wall of NTs into CO
2
totally release -0.92, -1.19 and -1.01 eV compared with gaseous CO and
clean V
2
O
5
system. The transition state in these three cases is nearly the
same, which is a bent CO
2
structure. The distance of the dissociated
O
surface
-C and O
out
-C is 1.91 (Fig. 30a) and 1.96 Å (Fig. 30b), respectively,
larger than the distance of the dissociated O
in
-C (1.80 Å in Fig. 30c).
Therefore, the confined environment is beneficial to CO
2
formation. This
effect is similar to O
2
adsorption on the confined inside wall of ZnO NTs,
which is much stronger than that on the outside one.
104
In fact, the
formation of CO
2
by the decomposition of carbonate is an important
reaction pathway for CO oxidation on a series of metal (for example
Au
141
) and metal oxide (for example CeO
2
and RuO
2
).
138,139,142
Our study
provides a solid evidence that the lattice oxygen of V
2
O
5
participates in
the CO oxidation, which is the first theoretical study to confirm a series of
experimental results that CO
3
species exist and CO reacts with the lattice
oxygen on V
2
O
5
catalyst.
6 Conclusions
Numerous computer simulations have been applied in many appli-
cations to avoid costly or dangerous experiments and elucidate chemical
reaction processes effectively. As novel catalysts or catalyst supports, the
highly-ordered nanosized channels of nanotubes provide fanscinating
confinement environment for catalysis. This chapter mainly provides our
recently simulated advances in the understanding of the physicochem-
ical properties of 1D carbon nanotubes and metal oxide nanotubes in-
cluding TiO
2
, ZnO and V
2
O
5
NTs. MD simulations are used to investigate
the melting and freezing of confined metals in CNTs; DFT calculations
are employed to investigate the formation, structural and electronic
properties, modifications and catalytic behaviors of those nanotubes.
The interactions between nanotubes and a variety of reactive species are
mainly disscussed in the aspects of adsorption site and geometry, ad-
sorption energies, charge transfer and electronic band structure, etc. Our
DFT calculations demonstrated the enhanced role of interfacial sites
between CNTs support and Pd ensemble in H
2
O
2
synthesis. The DFT
energy values combined with a thermodynamic model furnish a better
way to identify the electrocatalytic activity of prestine and doped TiO
2
nanotube arrays for water-splitting. The compared investigations on CO
oxidation into CO
2
by the lattice oxygen on the inside and ouside wall of
V
2
O
5
NTs and on the V
2
O
5
(010) single layer strongly demonstrate the
unusual catalytic property of nanotubes. However, simulated study on
the chemical reactions within the nanotubes is still in its infancy com-
pared to many-body experimental research. The complex multi-steps of
catalysis processes, the large size of nanotubes and the immaturity of
simulated methods make it dicult, time-consuming and energy-cost to
disclose the general principles governing the catalysis in nanotubes. Al-
though DFT simulations help to offer new highlights on how catalysis
reactions proceed in nanotubes at a microscopic level, there is a long way
