氧化铈纳米材料的形貌控制合成

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2.Shape-controlled synthesis
2.1 Crystallographic structure direct
Anion sensitive——Cl- vs NO3-
NO3selectively absorded on the {100} planes Cl- weak adsorption of on the surface
Teflon-lined stainless steel autoclave （180 ℃ 24h)
cooled at room temperature. evaporated at 180 ℃ overnight calcined at 500 ℃for 2h
ceria nanosphere
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2.3.1 Self-template synthesis
Calcined 30min Calcined 60min
2Ce3+ + 2OH-+ H2O2 = 2Ce(OH)2 2+ (aq) thus, the Ce(OH)2 2+ transfer into the solution. As the concentration of the Ce(OH)2 2+ increased, ceria can beformed easily under the following reaction: Ce(OH)2 2+ (aq) + 2OH-= CeO2(s) + 2H2O
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1.Introduction of CeO2
Energy for oxygen vacancies (111) >(110) >(100) catalytic activity (111) <(110) <(100)
(110) and (100) are more favourable in catalytic reactions.
2.Shape-controlled synthesis
2.2 Capping Reagent
d
• Compared with the OLA tails interdigitating at ~2.2 nm, the shorter interparticle spacing d of ~1.3-1.9 nm in the regular arrays excludes a simple surfactant-mediated self-assembly. • The large-sized nanocubes can also self-assemble into 3D NP arrays through the evaporation of a mixed solvent of toluene and ethanol. • The strong dipole-dipole interactions from the polar {200} surfaces are probably the driving force for self-assembly of the nanocubes because long-range van der Waals forces become difficult to control for NPs whose dimensions are beyond molecular length scales (d > 10 nm).
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2.Shape-controlled synthesis
Crystallographic Structure Direct
Formation mechanism
Capping Reagent Direct
various templates
Templates Direct Method
2.Shape-controlled synthesis
2.3.1 Self-template synthesis
Using initially formed bulk nanocrystal as templates to confine and direct the following crystal growth.
J. Phys. Chem. Lett., 2012, 3, 1517–1522.
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2.Shape-controlled synthesis
2.2 Capping Reagent Nano Array
(100)
Both shape and size of the ceria NPs could be tuned more conveniently by changing the concentration of the reactants, the amount of stabilizing agents (especially for oleic acid (OLA)), and the water/toluene ratio in the reaction system.
2.2 Capping Reagent CTAB assisted hydrothermal synthesis, controlled conversion and CO oxidati on properties of CeO2 nanoplates, nanotubes, and nanorods
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2.Shape-controlled synthesis
2.2 Capping Reagent
S. W. Yang, L. Gao,. J Am. Chem. Soc., 2006, 128 (29), pp 9330–9331
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why:bromate ions could not be selectively absorbed on certain planes
J. Phys. Chem. C 2008, 112, 17076–17080
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2.Shape-controlled synthesis
3
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Hale Waihona Puke Baidu
1.Introduction of CeO2
Cerium is the most abundant among the
rare earth elements, occupying about 0.0046 wt.% of the Earth ’s crust. Ceria are often used in solid oxide fuel cells (SOFCs ), catalysis, oxygen sensors, glass-polishing, ceramics, and ultraviolet absorbent.
Calcined 90min
Angew. Chem.,2012, 124, 2488–2492
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2.Shape-controlled synthesis
2.3.2 Soft template-directed synthesis
Surfactants are often used as soft templates. Ostwald ripening mechanism: which refers to the dissolution of small
J. Phys. Chem. C 2008, 112, 17076–17080
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2.Shape-controlled synthesis
2.1 Crystallographic structure direct
Replace NaNO3 with NaBrO3
crystals or sol particles and the redeposition of the dissolved species
on the surface of larger crystals of sol particles. To synthesize rods, spheres, plates, cubes, flowers, and octahedra. Common surfactants: PVP, PEG etc.
2.Shape-controlled synthesis
2.3.2 Soft template-directed synthesis
2mml Ce(NO3)36H2O
0.0086mml PVP
deiohylenenized water 10ml dietglycol 30ml ( stirring） Synthesis of ceria nanosphere
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2.Shape-controlled synthesis
2.3 Template Method
Self-template Soft template Hard template
Nanotube
Template
Hollow sphere Arrays
Large surface area and wide range of potential applications
2.Shape-controlled synthesis
2.3.2 Soft template-directed synthesis
The possible formation mechanism of ceria nanospheres can be explain: with the high reaction temperature, diethyleneglycol is partially converted to the compounds with acidic groups . At the same time, high temperature and pressure cause cerium salt to decompose to form tiny ceria particles, and the surface hydroxyl groups of ceria tiny particles reacted with acidic groups to form the polymer-like inorganic–organic compounds , which are the above mentioned the intermediates of ceria nanospheres. Subsequently, in view of the low energy point as mentioned in previous reports , the polymer-like inorganic– organic compounds are self-assembled as monodispersed nanospheres with the aid of PVP. After calcinations at a suitable temperature, the uniform and monodisperse ceria nanospheres, which are composed of tiny nanoparticles, are obtained.
Can be used to fabricate nanotube and other hollow structure.
The Ostwald ripening is referred to as a reasonable mechanism.
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2.Shape-controlled synthesis
LOGO
Shape-controlled synthesis of ceria nanomaterials
成员：翟明龙 贺剑桥 田章留 潘颖 纪晓娜 黄楚楚 何乐为 田彦锋 章也 陈小武
Contents
1
Introduction of CeO2
2
Shape-controlled synthesis Conclusion and outlook