Transcript 下載/瀏覽

Photocatalytic behavior of TiO2 thin
films prepared by sol–gel process
Ki Hyun Yoon a,b,c,∗, Jung Sok Noha, Chul Han Kwon a,b, Mamoun Muhammedc
a Department of Ceramic Engineering, Yonsei University, 134 Shinchon-dong, Seodaemoon-ku, Seoul 120-749, Republic of Korea
b Research Center, TIOZ Co. Ltd., 775-4 Wonsi-dong, Ansan, Kyunggi-Do, Republic of Korea
c Division of Materials Chemistry, Royal Institute of Technology, SE-10044 Stockholm, Sweden
Received 24 December 2004; received in revised form 23 May 2005; accepted 1 June 2005
報告學生：周暐祥
報告日期：2009/12/02
1
Introduction (1/3)

Titania has been widely used and explored as a photocatalytic
material since it is nontoxic, chemical stable, inexpensive, and
has favorable optoelectronic property.

Titanium dioxide possesses three different crystal structures:
rutile (tetragonal), anatase (tetragonal) and brookite
(orthorhombic).

The advantages of the sol–gel method are: good homogeneity,
ease of composition control, and low processing temperature,
and films are easily anchored on the substrate.
2
Introduction (2/3)

The strong oxidative potential of the positive holes oxidizes
water to create hydroxyl radicals. It can also oxidize oxygen or
organic materials directly.
3
Introduction (3/3)

TiO2 solutions were prepared using alkoxide sol–gel process
with and without AcAc and their physical and chemical
properties were investigated.

The thin films using these two different solutions were spincoated on the glass substrates and their comparison was made
in terms of the photocatalytic decomposition rate using
methylene blue solution.
4
Experimental drugs

Titanium isopropoxide (異丙氧基鈦)
(Ti[OCH(CH3)2]4) (precursor)

Isopropyl alcohol (solvent)

AcAc:Acetylacetonate (乙醯丙酮) (chelating agent)

HNO3
5
Experimental procedure
TIP
TIP + IPA
IPA + AcAc
Stirring (10 min.)
Stirring (30 min.)
H2O + HNO3
Dropping (30 min.)
H2O + HNO3 dropping
Stirring (80℃, 8hr)
Stirring (90 min.)
TiO2 sol without AcAc
TiO2 sol with AcAc
6
Results and Discussion
1380cm-1
1640cm-1
3400cm-1
500cm-1
7
XRD pattern : without AcAc
8
XRD pattern : with AcAc
9
Resultant of XRD

The addition of AcAc as a chelating agent to titanium
isopropoxide leads to much less reactive
titanium(acetylacetonate).

During heat treatment, pyrolysis may induce the formation of
the metastable anatase phase and converts the anatase phase to
the rutile phase at 500 ℃.
10
Photocatalytic decomposition rate
11
Comparison of photocatalytic
decomposition rates (1/2)
12
Comparison of photocatalytic
decomposition rates (2/2)

Upon illumination of UV light for 120 min, the photocatalytic
decomposition rate of the specimen without using AcAc
exceeded that of the specimen using AcAc by 10 %.

This difference can be explained in terms of the surface area.
13
Surface roughness
14
Structure

The hydrolysis between alkoxides and H2O is incomplete.
→ The monomers of (OH)x-Ti(OR)4−x form chain-like
structures.

The hydrolysis between alkoxides and H2O is complete.
→ the monomers of (OH)x-Ti(OR)4−x interact with each other
to establish a three-dimensional network structure.
15
Conclusion

TiO2 thin films prepared using AcAc showed the anatase
phase at 300 ℃ while the anatase phase from the TiO2 thin
films prepared without using AcAc began to form at 100 ℃.

Surface roughness ranged from 0.414 to 3.08 nm and from
3.72 to 5.35 nm for the TiO2 thin films with and without using
AcAc, respectively.

The photocatalytic decomposition activity exhibited a close
dependence on the formation of the anatase phase and the
surface roughness.
16
Thanks for your attention
17