Transcript `TiO2`, GREEN CATALYST: CLEAN ENVIRONMENT
‘TiO
2
’, GREEN CATALYST: CLEAN ENVIRONMENT
1 st National Conference on Biotechnology & Microbiology Dr. Romana Khan Department of Environmental Sciences, COMSATS Institute of Information Technology, Abbottabad
Introduction
Photocatalysis - Need of the day
Photocatalysis
H 2 O CO 2 Chlorophyll Starch + O 2 Organic compound Organic Compound + H 2 O + O 2 Photocatalyst CO 2 + H 2 O
Photocatalytic Applications
Antimicrobial Effect
Antimicrobial Effect
Self-Cleaning Effect
Photocatalysts
TiO 2 – an Ideal Photocatalyst
Cheap and can be reused
High photo-chemical corrosive resistance
Strong oxidizing power
Photocatalysis takes place at ambient temperature
Atmospheric oxygen is used for the reaction
TiO 2 - Photocatalysis 3.12 eV (380 nm)
Redox potential of h + 1.
2.
3.
The redox potential for photogenerated h + is +2.53 V vs. the SHE After reaction with water, these h + can produce •OH Both h + and •OH are more positive compare to ozone
Photocatalytic Reactions TiO 2 + h h + + H 2 O O 2 + e O 2 - + H + HO 2 + HO 2 O 2 + HO 2 HO 2 - + H 2 O 2 + h H 2 O 2 + O 2 H 2 O 2 + e TiO 2 (e + h + ) OH + H + O 2 HO 2 H 2 O 2 + O 2 O 2 + HO 2 H 2 O 2 2 OH HO + OH + O 2 HO + OH -
Entail Physicochemical Properties of TiO 2 The applications of TiO 2 is a function of specific physicochemical properties like:
High Surface area
Small Crystalline Size
Anatase form of TiO 2
High crystallinity
Porous structure
Activation light source An appropriate synthetic procedure can provide TiO 2 with promising efficiency
Synthesis
of TiO 2 Powders Synthesis of TiO 2 powders Sulfate Method Chloride Method Specific Methods Sol-Gel Method
Hydrolysis
and Condensation
Sol-Gel
Technology
Visible-Light Active Photocatalyst TiO 2 – efficient photocatalyst under UV light Yet, need visible-light active photocatalyst for practical purpose Can be achieved by doping TiO 2 with nonmetals, transition metals and dyes Activity increases by loading a metal oxide Metal oxide reduces the chance of recombination of electrons & holes produced during photocatalytic reactions
Modification of TiO
2 e e TM-TiO 2 e TiO 2 NM-TiO 2 h + h + h +
Coating
Techniques A- Spin Coating Method
B- Dip Coating Method
C-Spray Coating Method
D- Sputtering Method Setting Substrates Vacuuming Coating / Discharging plasma Collecting Substrates
E- Plate Coating
An Acid-Base Catalyzed Sol-Gel Synthesis of TiO 2 Photocatalysts Ti(OBu) 4 + EtOH HCl + H 2 O + EtOH Stirring (12 h) Sol (pH 0.8) Stirring (12 h) Gel (pH 9.0 ) Drying (110 0 C, 12 h) Calcination NH 4 OH
Phase Structure and Thermal Stability
(f) (e) (d) (c) (b)
20 30 40
2
50 60 70 XRD patterns of TiO 2 samples; (a) as-dried, and calcined at (b) 350 o C, (c) 400 o C, (d) 500 o C, (e) 600 o C and (f) 800 o C.
(a)
80
Some Selected Properties of TiO
2
Powders
Catalyst Crystal Phase a Size of A(nm) b S BET (m 2 /g) c V(cm 3 /g) d D BJH (nm) e P-25 T-as dried T-350 A:R (75:25) A A T-400 A T-500 T-600 T-800 A A: R (98: 2) A: R (5:95) 25 4.3
9 11 18 29.6
45.5
50 331 102 83 63 27 1.9
0.21
0.18
0.16
0.12
0.08
0.007
2.4
5.2
5.2
8.1
12.5
3.4
Photocatalytic Efficiency
7 6 5 4 3 2 1 0 0 30 60 90 120 Time (min) 150 180 Catalytic degradation of toluene by different TiO 2 (a)Blank ( ■ )(b)TiO 2 – as-dried ( ● ); (c) P-25 ( ▲ samples; ); and TiO 2 (d) 350 o C ( ▼ ); (e) 400 o C ( ) (f) 500 o C ( ◄ ); (g) 600 calcined at o C ( ► ).
Photoreactor
Publications 1.
Romana Khan
, S.W. Kim, T.J. Kim, H.S. Lee –
A novel acid-base catalyzed sol-gel synthesis of
highly active mesoporous TiO 2 photocatalysts,
Bulletin of the Korean Chemical Society
, 28(11), 1951-1957 (2007).
2.
Romana Khan
, S.W. Kim, T.J. Kim – Synthesis and control of physical properties of titania nanoparticles as a function of synthetic parameters,
Journal of Nanoscience and Nanotechnology
, 8(9), 4738-4742 (2008).
3.
Romana Khan
, S.W. Kim, T.J. Kim, C.M. Nam – Comparative study of the photocatalytic performance of boron– iron co-doped and boron-doped TiO 2 nanoparticles,
Materials Chemistry and Physics,
112(1), 167-172 (2008).
4.
Romana Khan
, S.W. Kim, T.J. Kim, C.M. Nam – Comparative study of the photocatalytic performance of boron– iron co-doped and boron-doped TiO 2 nanoparticles,
Materials Chemistry and Physics,
112(1), 167-172 (2008).
5.
Romana Khan
, T.J. Kim – Preparation and application of visible-light responsive Ni-doped and SnO 2 -coupled TiO 2 nanocomposite photocatalysts,
Journal of Hazardous Materials
, 163(2-3), 1179-1184 (2009).