Self-assembled 3D flower-like perovskite PbTiO
3
nanostructures and their application in the catalytic
oxidation of CO†
Gang Xu,
*
Huiwen Bai, Xiaoqiang Huang, Wanbo He, Lingling Li, Ge Shen
and Gaorong Han
*
3D flower-like PbTiO
3
nanostructures self-assembled with (101) nanosheets have been realized by the
hydrothermal treatment of the mixture of the lead and titanium hydroxides under the effect of high KOH
concentration. The layered K
2
Ti
6
O
13
formed in situ under the effect of the high KOH concentration plays
an important role in the crystallization of the primary PbTiO
3
nanosheets and the further self-assembly
of the 3D flower-like perovskite PbTiO
3
nanostructures. The self-assembled 3D flower-like perovskite
PbTiO
3
nanostructures express good mesoporous structures and high specific surface area. In
consequence, the 3D flower-like perovskite PbTiO
3
nanostructures as supports show excellent ability to
enhance the catalytic activity of Pt. Over the Pt/PbTiO
3
nanoflowers, the CO instantaneously completely
converts to CO
2
at a very low temperature of ca. 107
C facilitating the catalytic purification of the
automotive exhaust produced in the cold-start period.
Introduction
Automotive exhaust, which is mainly composed of carbon
monoxide (CO), nitrogen oxides (NO
x
), unburned hydrocarbons
(CH
x
), and sulfur oxides (SO
x
), is one of the main generators of
air pollutants.
1–3
This problem is expected to be controlled by
catalytic purication, in which CO is oxidized to carbon dioxide
(CO
2
). To date, the automotive exhaust puried emission
indeed has been realized under the effect of the noble metal
three-way catalysts. However, the catalytic purication of the
automotive exhaust produced in the cold start period is still
difficult because of the catalytic converter's inability at low
temperatures.
4
Perovskite-based materials have been investigated, since the
1970s,
5
as promising automotive exhaust catalysts to replace the
existing noble metal-based catalysts due to their surface redox
properties, high bulk oxygen mobility and good thermal
stability.
6–8
Because the perovskite-based materials are generally
less active for hydrocarbon oxidation compared to noble metal
catalysts,
6,9,10
a lot of investigations are performed on the
perovskite-based materials as supports to enhance the catalytic
activity of the noble metal catalysts.
10–12
For example,
impregnating Pd over perovskite LaMnO
3
-based materials
produces active catalysts for methane combustion,
10,11
and Pt-
supported on the perovskite SrTiO
3
nanocuboid effectively
promotes the propane oxidation.
12
Lead titanate, PbTiO
3
,isa
typical perovskite oxide. Below about 490
C, PbTiO
3
has dis-
torted perovskite structures and consequently displays sponta-
neous polarization. In our recent experiment, it has been
demonstrated that when the Pt nanoparticles are supported
over the PbTiO
3
nanoplates, the catalytic activity is signi cantly
improved, allowing the complete catalytic oxidation of CO at a
very low temperature of about 100
C.
13
Moreover, the catalytic
oxidation of the carbon monoxide occurs at the surface of the
catalysts.
14,15
However, it is essential to prepare the PbTiO
3
catalyst carriers of high specic surface area for the instanta-
neous oxidation of the carbon monoxide involved in the auto-
motive exhaust, especially in the cold-start period.
Three-dimensional (3D) nanostructures have attracted
intensive attention because of their unique properties and
potential applications.
16–27
Generally, the 3D nanostructures are
self-assembled with primary building blocks, such as nano-
crystallites, nanorods and nanosheets, in a spontaneous
process. As the primary building blocks are nanosheets, the 3D
nanostructures traditionally express high specic surface area
and good mesoporous structures. Due to the high adsorption
ability, the 3D ower-like iron oxide nanostructures self-
assembled with nanosheets show an excellent ability to remove
heavy metal ions and other pollutants in water treatment.
19
Because the ultrathin primary nanosheets facilitate the fast Li
ion diffusion, and the effective accommodation of the large
volumetric change occurred during the discharge and charge
State Key Laboratory of Silicon Materials and Department of Materials Science and
Engineering, Zhejiang University, Hangzhou 310027, China. E-mail: msegxu@zju.
edu.cn; hgr@zju.edu.cn; Fax: +86-571-87952341; Tel: +86-57 1-87951649
† Electronic supplementary information (ESI) available: XRD patterns of the
samples obtained aer hydrothermal treatment for different time and the
STEM image, element Pb, Pt, O and Ti EDX map of the Pt/PbTiO
3
nanooweres.
See DOI: 10.1039/c4ta04667f
Cite this: J. Mater. Chem. A,2015,3,
547
Received 9th September 2014
Accepted 5th November 2014
DOI: 10.1039/c4ta04667f
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