Preparation of Mesoporous Titania Photocatalyst for Water Treatment

ApplicationXingdong Wang1, David R.G.Mitchell2, Patrick Hartley1 and Rachel A. Caruso1,3

1 CMSE, CSIRO Material Science and Engineering, 2 Australia Center for Microscopy and Microanalysis, The University of Sydney, 3 PFPC, School of Chemistry, The University of Melbourne

My background

Environmental pollution remediation ---principle of photocatalysis

http://www.mchnanosolutions.com/whatis.html

High recombination rate of e-/h+ pairs (~90%) Inactive under visible light (wide band gap---3.2 eV for anatase TiO2)

Outline of Porous TiO2 Project---Environmental pollution remediation

Enhancing photocatalytic (PC) activity UV light: decrease charge recombination (e-/h+) Visible light: narrow TiO2 band gap

Crystal properties Surface properties Porosity Band gap …

X. D. Wang, R. A. Caruso, J. Mater. Chem. 2011, 21, 20.

Control Material properties

X. Chen, S. S. Mao, Chem. Rev., 2007, 107, 2891.

Composition Crystal phase Morphology

Preparation of TiO2

Synthesis of porous TiO2 materials

Composition Composition and Crystal phase

Morphology: beads Morphology: fibre

X .D. Wang, G.I. N. Waterhouse, D. R. G. Mitchell, K. Prince, R. A. Caruso, submitted

X. D. Wang, M. Blackford, K. Prince, R. A. Caruso, submitted

X. D. Wang, L. Cao, D.H. Chen, R. A. Caruso, in preparation

Ongoing project: collaboration with J. choi, Y.

B. Truong, and L.Kyratzis

UV light PC increase: Noble metal deposition decrease recombination of e-/h+

Crystal phase & Boron doping: band gap Noble metal deposition: Visible light PC: increased

400 nm

TiCl3

Hydrolysis & condensation

NaOH

AmorphousTiO2

Washing

Solvothermal: 160°C, 16h

Crystallized TiO2

NaOH (mol) 0.041 0.054 0.059 0.068 0.070 0.073 0.076

Solution pH 0.25 0.56 0.80 7.92 7.98 9.67 11.58

Synthesis scheme

Surface area

0

50

100

150

200

250

300

0.25 0.56 0.80 7.92 7.98 11.58 P25

pH during the synthesis

Su

rfac

e ar

ea (

m2 g

-1)

Pore size distribution

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 20 40 60 80 100 120 140 160Pore diameter (nm)

dV

/dlo

gD

(cm

3/g

) 0.250.567.927.9811.58

-0.1

0.4

0.9

1.4

0 5 10 15 20

Morphology-SEM

0.25

7.98

11.58

Morphology and porosity -TEM

0.25 11.587.98

5 15 25 35 45 55 65 75 85

2 theta (degree)

Inte

ns

ity

(a.

u.)

0.25

0.80

7.92

7.98

9.67

11.58

Crystal phase

Anatase

Rutile

Titanate

Acid condition: rutile phaseNeutral condition: anatase phase (slight brookite)Alkaline condition: titanate phase

8Å

Surface hydroxyl groups (FT-IR)

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

1000150020002500300035004000

Wavenumber (cm-1)

abs

(a.

u.)

0.250.807.929.6711.58

Ti-OH

Ti…H2O

Diffuse UV-Vis and band gap

0

10

20

30

40

50

60

70

80

90

100

200 300 400 500 600 700 800

Wavelength (nm)

Ref

lect

ance

(%

)

P25 0.25 7.98 11.58

Diffuse UV-vis and Band gap

0

1

2

3

4

5

6

7

8

9

10

2.5 3 3.5 4

E (eV)

(F(r

)E)1

/2

11.587.987.929.670.560.25 pH9.67: 3.25 eV

pH11.58: 3.22 eV

pH7.98: 3.15 eV

pH0.56: 2.98 eV

pH7.92: 3.13 eV

pH0.25: 3.00 eV

pH 0.25 0.56 7.92 7.98 9.67 11.58 P25

Bg (eV) 3.00 2.98 3.13 3.15 3.25 3.22 3.10

Adsorption test

Test conditions: 100 ppmIn the dark: shaking overnight (pH 5.10)

0

10

20

30

40

50

60

70

80

90

100

0.25 0.8 7.92 7.98 9.67 11.58 P25 AC

Ad

sorp

tio

n o

f M

B (

pp

m)

Set up: 500 Watt Hg(Xe) lamp with band pass visible light filter (420-650 nm) Methylene blue (MB) as a probe molecule RSD< 3%

Photocatalysis reaction

Photocatalytic activity

Test conditions: 12.5 ppm of MBVisible light: 120 min at pH 5.10

pH

40

50

60

70

80

90

100

0 20 40 60 80 100 120

Degradation time (min)

C/C

0 *

100%

0.250.807.927.989.67P2511.58

Conclusions

• Solvothermal treatment produced high surface area TiO2.

• The material properties are pH dependant.

• The porous TiO2 prepared at pH 7.98 showed highest adsorption capacity.

• The maximum photocatalytic activity was for the sample prepared at pH 11.58.

Acknowledgements

• My supervisor (Dr Rachel Caruso) & group members • Internal collaborations (Dr Patrick Hartley and Darryl Wells)• Synchrotron PD teams (Dr Qinfen Gu, Justin Kimpton & Kia

Wallwork )• Dr Nathan Webster for help with synchrotron data analysis

CSIRO Materials Science and EngineeringDr Xingdong Wang

Ph: +61 3 9545 2689Email: xingdong.wang@csiro.auWeb: www.csiro.au/cmse

CSIRO Materials Science and EngineeringDr Rachel Caruso OCE Science leader | Advanced Porous Materials Ph: +61 3 9545 7960Email: rachel.caruso@csiro.auWeb: www.csiro.au/cmse