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

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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

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