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Preparation, Characterization and its Photocatalytic Performance
of Rare Earth Element Erbium Doped with TiO2 Material
Songtian Li 1, a, Guoxu He 1,b, Wei Ma 1,b, and Yanhua Liu 2,c
1Pingdingshan University, Pingdingshan, China
2Zhengzhou University, Zhengzhou, China
alisongtian@126.com, blst624@163.com, cst2008@pdsu.edu.cn
Keywords: Erbium-doped; TiO2; Photocatalysis Material; Preparation; Characterization
Abstract. In order to expand photoresponse range of TiO2, reduce energy consumption of
semiconductor material optical catalytic, certain amount of rare earth element Erbiun was doped
during preparation of anatase titanium dioxide to improve the light absorption and photocatalysis
efficiency. A series of rare earth element doped TiO2 material were prepared by sol-gel process, and
characterized by means of UV-vis diffuse reflectance spectra. UV-vis absorption verified that
doping of Er3+
enhanced absorptive capacity of catalyst in visible region. The photocatalytic
performance of anatase titanium dioxide and rare earth element Erbiun doped with TiO2 to basic
fuchsin were studied.
Introduction
Photocatalytic oxidation is an advanced oxidation technology. It was widely studied because it
could effectively oxidize many refractory organics in systems, until they were mineralized into
inorganic molecules and become non-toxic, decoloration and deodorization[1,2]. Many
semiconductor optical catalytic materials was studied, TiO2 was thought to be the best
semiconductor optical catalytic material so far. Because nano-TiO2 has many advantage such as
suitable band gap, better specific surface, strong photochemical stability, strong ability of oxidation
and deoxidization, non-toxic and low cost, it was widely used as photocatalyst. Studies showed that
when proper amount of metal or nonmetal were mixed into TiO2, absorption of light would be
improved, light efficiency and photolysis rate would be promoted [3,4]. In this study, rare earth
element Erbium was chosen as doping element. Doped TiO2 photocatalysts were prepared by
sol-gel process in order to expand photoresponse range of the product, to improve catalytic activity,
and to decompose organic more effectively.
Experiments
Major Experimental Instruments. 721 type spectrophotometer (The Ninth Sichuan Instruments
Factory), GHX-2 photochemistry reaction instrument (Yangzhou University Town Science and
Technology Limited Company), Electronic balance (Shanghai Balance Instruments Factory),
DF-101S heat-gathering constant temperature heating magnetic agitator (Henan Yuhua Instruments
Limited Company), DHG102 type electric blastdrying oven (Tianjin Huike Instruments and
Equipments Limited Company), KSY temperature controller (Wuhan Yahua Electric Stove Limited
Company), UV-2550 ultraviolet-visible spectrophotometer (SHIMADIU Company, Japan).
Advanced Materials Research Vol. 568 (2012) pp 380-383Online available since 2012/Sep/28 at www.scientific.net© (2012) Trans Tech Publications, Switzerlanddoi:10.4028/www.scientific.net/AMR.568.380
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP,www.ttp.net. (ID: 141.117.125.1, Ryerson University Lib, Toronto-26/05/14,19:45:30)
Test Method
Preparation of Material. 40 mL absolute alcohol was taken with dry measuring cylinder and
poured into 100 mL baker, 10 mL tetrabutyl titanate was taken with another dry measuring cylinder,
uniform mixed as solution A. Added 2.5 mL 0.1 mol/L Erbium Nitrate (Er(NO3)3·6H2O) solution,
proper amount of hydrochloric acid and distilled water into 40 mL absolute alcohol, after 30 min
fully stirring, that was solution B. Solution A was put in constant temperature (40℃) heating
magnetic agitator and stirred for 30 min. During continuous stirring, solution B was added in by
drop with glue dropper head. After dropping, continued stirring for 20min to form homogeneous
transparent gelation. Collosol was dried at 80℃ and porphyrized into powder. The powder was put
into muffle furnace and calcined at 500℃ for 5 h. Thus Erbium doped catalyst molar ratio 0.5%
Er3+
-TiO2 was got. 1.0% Er3+
-TiO2, 1.5% Er3+
-TiO2, 2.0% Er3+
-TiO2 were produced through the
same method. And also pure TiO2 was produced through the same method just there was no Erbium
Nitrate solution added.
Photocatalysis Experimental Method. 20 mg/L basic fuchsin solution prepared to be degraded
was put into reaction bulb, A fair rare earth element Er doped TiO2 powder was added in. Under the
visible irradiation, the distance between the solution level and tube. After a certain time irradiation,
analysis and determination were proceeded. Absorbance of basic fuchsin solution was determined
with 721 type spectrophotometer. When maximum wavelength in visible light region was less than
540 nm, absorbance was determined. decoloration rate could be calculated according to absorbance
variation of the sample. The computational formula was:
decoloration rate (%) = (A0-Ai ) / A0×100%
In the formula: A0 was absorbance before reaction, Ai was absorbance after reaction.
Results and Discussion
Testing of Absorption Spectrum. Proper amount of TiO2 and Er3+
-TiO2 powder was detected with
UV-visible spectrophotometer, the absorption spectrogram was drawn. Fig. 1 was UV-visible light
absorption spectrogram of pure TiO2 and Er3+
-TiO2 powder. From Fig. 2, we could see that: there
was no absorbance of pure TiO2 in visible light, in 400-700 nm scope, absorbance of Er3+
-TiO2 was
strong and had three absorption peaks which were at 490 nm,523 nm and 654 nm. They were
separately attributed to 4f electron of Er transiting from ground state 4I15/2 to
4F7/2,
2H11/2 and
4F9/2.
400 450 500 550 600 650 700
0.04
0.05
0.06
0.07
0.08
0.01
0.02
0.03
0.04
0.05
0.06
Abso
rb v
alue
wavelength/nm
undoped
doped
Fig. 1 DRS of TiO2 and Er3+
-TiO2
Effects of Temperature. According to the experimental method, photocatalysis experiment was
conducted under different reaction temperature, absorbance was determined by timing sampling and
the decoloration rate was calculated. Results were shown as Fig. 2.
Advanced Materials Research Vol. 568 381
From Fig. 2, we could see that: temperature had some influence on the reaction efficiency. In
experiment, the decoloration rate of substrate improved with the raising of temperature. Properly
raising temperature could benefit the reaction process. In practical use, temperature controlling
could be ignored because photocatalysis experiment above-mentioned could be conducted under
normal temperature.
Effects of doping amount of rare earth element Er. At the other conditions remain unchanged,
photocatalysis experiments were conducted, absorbance was determined by timing sampling and the
optical absorption curves were drawn. Results were shown as Fig. 3.
From Fig. 3 we could see that: doping amount of rare earth element Er had significant effect on
catalytic performance. Doping of element Er improved TiO2 capacity to product high mars free
radical. If too much was doped, a lot of free redical in system could product side effects and went
against with catalytic performance of the catalyst. At the same time, if the concentration of Er3 was
too low, hydroxyl radicals could not be produced easily, so ·OH production amount and rate were
also small. Only when proper amount of rare earth element Er was doped with TiO2, enough ·OH
oxidation organic substances could be produced, catalytic activity was high. In this article, rare
earth element Er doping mole rate was 1.5%.
0 30 60 90 120 150 1800
5
10
15
20
25
Rat
io o
f co
lor
rem
oval
(%
)
Time (min)
20℃ 25℃ 30℃
0 30 60 90 120 150 1800
5
10
15
20
25
Rat
io o
f co
lor
rem
ov
al (
%)
Time (min)
1.0%
1.5%
2.0%
Fig. 2 The influence of temperature Fig. 3 The influence of catalyst’s quality
Effects of Concentration of Substrate. According to the experimental method, different basic
fuchsin solution concentrations were adjusted, its absorbance was determined every 30 min, the
decoloration rate was calculated. That sustained for 180 min. Results were shown as Fig. 4.
Concentrations of Substrate directly affect decolorizing effect of the catalyst. When the
concentration was too high, catalyst was not enough to play effective function and the treatment
effect was not satisfying. When the concentration was too low, catalyst could not play effective
function also. In this article, 20 mg/L basic fuchsin was chosen as research object.
Contrast Experiment of the Decoloring effect of Pure Er and Er3+
-TiO2. Basic experimental
conditions: Doping rate 1.5% TiO2 doped with 0.3 g Er, pure TiO2, temperature was 25℃, under
visible light, basic fuchsin solution concentration was 20 mg/L. According to the experimental
method, absorbance was determined.
From Fig. 5 we could see that: doping with rare earth element Er directly affected decolorizing
effect of the substrate. That is to say, doping or not directly affected catalytic activity of the catalyst.
Decoloring effect to basic fuchsin of TiO2 doped with Er was much better than that of pure TiO2.
Doping with Er could improve catalytic activity of TiO2, the decoloration rate to basic fuchsin of
Er3+
- TiO2 system doping rate 1.5% could be enhanced 4.4 times. As time going, the result could be
better.
382 Advanced Research on Civil Engineering and Material Engineering
0 30 60 90 120 150 1800
5
10
15
20
25
Rat
ion
of
colo
r re
mo
val
(%)
Time/min
10mg/L
20mg/L
30mg/L
0 30 60 90 120 150 1800
5
10
15
20
25
Rat
ion o
f co
lor
rem
oval
(%)
Time (min)
undopt
dopet
Fig. 4 The influence of solution concentration Fig. 5 The decoloring effect of doped Er and
undoped Er
Conclusion
(1) Er3+
-TiO2 photocatalyst (mole rate was 1.0%, 1.5%, 2.0%) prepared by sol-gel process.
UV-vis results showed that TiO2 photocatalyst doped with Er3+
expanded the photoresponse range
of the material. Strong absorption was produced under visible light, these would benefit
photocatalytic reaction in visible light range. Thus the light utilization ratio was improved and
energy consumption was reduced.
(2) Experimental results showed that: under visible light, decoloring ability to basic fuchsin of
TiO2 doped with Er was much better than pure TiO2, the decoloration rate was enhanced 4.4 times
in 180 min.
(3) Doping with rare earth element Er could enhance light absorption ability of the catalyst in
visible light regional. But doping amount of Er had a proper range. In this experiment, when the
temperature was 25℃, TiO2 doping rate was 1.5%, basic fuchsin solution concentration was 20
mg/L, the decoloring effect was satisfying.
Acknowledgment
This work was financially supported by the Natural Science Foundation of He’nan Province
(0624720029,102102310298), the Fund for Academic and Technical Leader of Pingdingshan
University(2011) and the Doctor Research Funds of Pingdingshan University.
References
[1] K.Q. Wu, Y.D. Xie, J.C. Zhao, et al. J. of Molecular Catalysis A: Chemical, Vol. 144(2004),
p.77–84.
[2] L. Yunho, L. Changha, Y. Jeyong. Chemosphere, Vol. 51(2003), p.963-971.
[3] Y.H. Zhang, H.X. Zhang, Y.X. Xu, et al. J. of Solid State Chemistry,Vol. 177(2004),
p.3490-3498.
[4] S.Q. Peng, F.L. Li, Y.X. Li, et al. J. of Functional Materials. Vol. 37(2006), p.1663-1666.
Advanced Materials Research Vol. 568 383
Advanced Research on Civil Engineering and Material Engineering 10.4028/www.scientific.net/AMR.568 Preparation, Characterization and its Photocatalytic Performance of Rare Earth Element Erbium
Doped with TiO2 Material 10.4028/www.scientific.net/AMR.568.380
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