UK-China Forum on Nanostructure for Water
11-13 November 2010, The University of Hong Kong
Assembled Hollow Metal Oxide Nanostructures
for Water Treatment
Junbai Li
Institute of Chemistry, Beijing
CAS Key Lab of Colloid and Interface Science
Chinese Academy of Sciences
Metal Oxide Nanomaterials
Features
Large surface area
Various modification
Rich valence states
Diversity of electronic structure
TiO2(B) nanofibers with a shell of anatase nanocrystals-an efficient
photocatalyst structure
Zhao, J. C. et al. J. Am. Chem. Soc. 2009, 131, 17885
Photocatalytic degradation of RB by
Photo-inactivating E. coli by
TiO2 hollow spheres
TiO2 nanorods
A
C
B
Li, X. Y., Xie, Y., et al.
Inorg. Chem. 2006, 45, 3493
Joo, J., Kwon, S. G., et al.
J. Phys. Chem. B 2005, 109, 15297
MnO2 nanorods degrading methyl blue
Zhang, W. X., Yang, Z. H. et al. Catal. Commun. 2006, 7, 408
6
Controlled Preparation of MnO2 Hierarchical Hollow
Nanostructures
MnSO4
KMnO4
HCl
NH4HCO3
C2H6O
MnCO3
MnCO3@MnO2
MnO2
Fei, J. B., Li, J. B. et al, Adv. Mater. 2008, 20, 452
7
MnCO3 crystalline as precursor
MnCO3
MnO2
SAED
Hollow MnO2 sphere with hierarchical structure
8
The relevant chemical reaction
ΔGo = - 99.0 kJ/mol
XRD patterns: (a) MnCO3 crystals; (b) MnO2 hierarchical hollow nanostructures;
(c) the remained core after selective removal of the shell.
9
MnO2 hierarchical hollow nanostructures
MnCO3
MnCO3@MnO2
MnO2
10
Kirkendall effect
11
Hierarchical Nanostructures
easier separation and
recycle compared with
common nanoparticles
retaining high specific
surface area and high
catalytic activity
effectively preventing further
aggregation
unblocked mass transferring
12
Different treating time by KMnO4 a) 2; b) 6; c)10 min; and
d) remove the core of MnCO3 with HCl
13
Controlled thickness of MnO2 shells
0.01:1
0.02:1
0.04:1
0.1:1
MKMnO4 : MMnCO3
Wall thickness increasing
14
Controllable 3D self-assembly by limited
diffusion growth
MnSO4
KMnO4
NH4HCO3
HCl
C2H6O
(NH4)2SO4
MnCO3
MnCO3@MnO2
MnO2
15
MnCO3 microcubes
MnO2 hollow microcubes
Single MnO2 microcube
16
The surface structure of MnO
2
Adsorption of Congo red to MnO2 shells
3.0
1
b
0 min
5 min
10 min
20 min
30 min
2.5
2.0
1.5
3
1.0
0.5
0.0
1.0
2
400
500
Wavelength (nm)
0.6
b Commercial Fe2O 3 NPs
0.4
MnO 2 as-prepared
e f
d
c
0.2
4 5
300
a Commercial MnO 2
0.8
C/Co
Absorbance
3.5
0.0
600
Uv-vis spectra curve:
Congo red(100mg//L, 20mL), MnO2
(0.03g)
0
20
40
60
80
Time (min)
100
120
Adsorption curve, e-f regenerated
MnO2 particles
17
Wastewater treatment
Absorption of Congo red, the capacity is about 60 mg/g.
18
19
Controlled Assembly of Conductive Polymers with
Hollow Hierarchical Nanostructures
MnO2
MnO2 +4H+ +2e
Polymers
Mn2++2H2O (E o =1.2 V)
Fei, J. B., Li, J. B., et al. ACS Nano 2009, 3, 3714
Monomer
pyrrole
Polymerization
Potential
0.6～
～0.8V
thiophene
0.7～
～1.8V
aniline
～0.8V
1,2-diaminobenzene
～0.9V
o-aminophenol
～0.7V
……
……
C4H5N+MnO2 +H+
PPY+Mn2++ H2O
Summary
Hierarchical hollow MnO2 nanostructure with
intricate and well-controlled 3D morphologies
have been assembled by combining the
Kirkendall effect with removable crystalline
template;
MnO2 superstructures at a micro- and
nanoscale showed a good ability to remove
organic pollutant in waste water;
This approach will find wide acceptance and
use in the field of template-directed
nanostructure synthesis.
23
Acknowledgements
Co-workers:
Dr. Qiang He
Dr. Yue Cui
Dr. Jinbo Fei
Dr. Xuehai Yan
Dr. Yang Yang
Chinese Academy of Sciences (CAS)
National Nature Science Foundation of China (NNSFC)
Ministry of Science and Technology of China (MOST)
Max Planck Society (MPG)
EU FP6 Project-Active Biometics
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Financial Supports: