Photocatalytic and catalytic routes for removal of pollutants
present in water and air
G. Magesh
CY04D012
1
Contents of the thesis
 Chapter 1: Introduction
 Chapter 2: Materials and methods
 Chapter 3: Characterization and photocatalytic activity of Ce modified
TiO2
 Chapter 4: Characterization and photocatalytic studies of carbon-TiO2
composites
 Chapter 5: Characterization, photocatalytic and electrochemical studies
of CdSnO3 and Cd2SnO4
 Chapter 6: Characterization and CO oxidation activity of Au/TiO2
2
Environmental pollution
 Environmental pollution is having a deadly effect on humans and ecosystems
 Water pollution is mostly due to pesticides, oil, sewage, dyes, and heavy metals
 Air pollution is mostly due to automobile and industrial exhaust
Photocatalysis

Photocatalysis - reaction assisted by photons in the presence of a catalyst

In photo catalysis - simultaneous oxidation and reduction

Light excites electrons from valence to conduction band - electrons and holes
3
Light induced excitation processes in a photo catalyst
Factors to be considered in a photocatalyst

Recombination of electrons and holes

Amount of visible light utilized (Bandgap)

Stability against photo-corrosion

Position of VB and CB
Objectives
 To use heterogeneous photocatalysts for degrading/oxidizing organic pollutants in
water effectively.
 To expand the range of radiation required in TiO2 for the photocatalytic redox
process to visible region.
 To increase adsorption capacity of photocatalyst towards organic pollutants.
 To investigate new materials with suitable properties for their photocatalytic activity
in visible light.
 To study new support materials for Au as catalyts for oxidation of CO.
4
Chapter - 3
Preparation, characterization and photocatalytic activity of Ce
modified TiO2
5
Cerium modified TiO2

TiO2 is a widely studied and applied photocatalyst because of its favorable
properties

Solar radiation contains only 7 % UV light & pure TiO2 inactive in sunlight

Various methods have been attempted to improve the visible light absorption
- dye sensitization, doping of metal/non-metallic ions
- coupling of two semiconductors

CeO2 having a bandgap of 2.8 eV will increase visible light activity by coupled
semiconductor mechanism

The Ce3+\Ce4+ redox couple is expected to increase charge transfer. This will lead
to reduction in recombination
6
Preparation of cerium modified TiO2
Aq. NH3 (pH 12.7)
Titanium(IV) isopropoxide in
CH2Cl2 at 1.5 ml/min
Ammonium ceric nitrate in water
at 0.5 ml/min
Sol
Stirred 12 h
Washed, centrifuged
Dried
Calcined 600 oC, air 6 h
 0.25 %, 0.5 %, 1 %, 2 %, 3 %, 5 % and 9 % CeO2 modified TiO2, pure
TiO2 and pure CeO2 were prepared
7
XRD patterns
XRD patterns of the samples
X-ray diffraction patterns of CeO2-TiO2 samples (a) CeO2
(b) 9% CeO2-TiO2 (c) 5% CeO2-TiO2 (d) 3% CeO2-TiO2
(e) 2% CeO2-TiO2 (f) 1% CeO2-TiO2 (g) 0.5% CeO2-TiO2
(h) 0.25% CeO2-TiO2 (i) TiO2
 Peaks corresponding to CeO2 start to appear at 2.0 % CeO2 loading
8
TEM images of 3 % CeO2-TiO2
15
o
No. of particles
3 % Ce-TiO2 600 C
10
 Particle size ranges from 10 – 50 nm
 Maximum no. of particles are around 25 nm in
size
5
9
0
10
15
20
25
30
35
Particle size (nm)
40
45
SEM image of 3 % CeO2-TiO2
 Agglomerates of particles were observed in SEM
 EDAX confirms presence of Cerium
10
Diffuse reflectance UV-Visible spectra
TiO2
3.2
Absorbance (arb. unit)
0.25 % Ce-TiO2
0.50 % Ce-TiO2
2.00 % Ce-TiO2
3.00 % Ce-TiO2
5.00 % Ce-TiO2
9.00 % Ce-TiO2
CeO2
3.1
Bandgap (eV)
1.00 % Ce-TiO2
3.0
2.9
2.8
325
350
375
400
425
450
475
500
525
550
0
Wavelength (nm)
1
2
3
4
5
6
7
8
9
% Ce loading
 Red shift observed with CeO2-modified samples
 Increase in red shift with increase in % of CeO2
11
Reaction conditions for irradiation and dark studies
Photocatalytic reaction conditions
Amount of catalyst
: 100 mg
Duration
: 90 minutes
Methylene blue
: 80 ml of 20 ppm solution
Visible light source
: 400 W high pressure Hg lamp ( > 420 nm using filter)
UV light used
: Eight 8 W Hg lamps ( = 365 nm)
Analysis
: Measuring max of methylene blue at 662 nm by
UV-visible spectrophotometry
 Adsorption studies were carried out for the same duration without irradiation
12
Amount of MB adsorbed in dark
Catalyst
Amt adsorbed
(× 10-7 mol /
0.1 g catalyst)
TiO2
9.10
0.25 % CeO2-TiO2
8.34
0.50 % CeO2-TiO2
7.27
1.00 % CeO2-TiO2
6.53
2.00 % CeO2-TiO2
5.78
3.00 % CeO2-TiO2
5.46
5.00 % CeO2-TiO2
4.60
9.00 % CeO2-TiO2
4.18
CeO2
3.42
MB adsorbed ( 10-7 mol 0.1 g-1)
Amount of MB adsorbed in dark after 90 minutes of stirring
9
8
7
6
5
4
0
1
2
3
4
5
6
% CeO2 loading
7
8
9
 Adsorption of MB decreases with increase in CeO2 loading
 Pure CeO2 shows about 1/3 adsorption of TiO2
13
Visible
UV
Overall
Photocatalytic
(Overall-Dark)
Overall
Photocatalytic
(Overall-Dark)
TiO2
9.63
0.53
32.40
23.30
0.25 % CeO2TiO2
14.65
6.31
34.56
26.22
0.50 % CeO2TiO2
17.01
9.74
37.28
30.01
1.00 % CeO2TiO2
16.80
10.27
40.45
33.92
2.00 % CeO2TiO2
14.65
8.87
39.22
33.44
3.00 % CeO2TiO2
14.12
8.66
31.61
26.18
5.00 % CeO2TiO2
11.34
6.74
28.17
23.57
9.00 % CeO2TiO2
9.73
CeO2
8.66
36
34
UV light
32
30
-7
Amount degraded ( x 10-7 mol / 0.1 g catalyst)
28
26
24
22
5.55
5.24
26.83
5.18
22.65
1.76
0
1
2
3
4
5
6
7
8
9
% Ce loading
10
Visible
8
6
-7
MB degraded (x 10 mol / 0.1 g catalyst)
Catalyst
MB degraded (x 10 mol / 0.1 g catalyst)
Overall and photocatalytic decrease in MB under UV and visible
irradiation
4
2
0
0
1
2
3
4
5
6
7
8
9
% Ce loading
14
Calculation of band position
No considerable change in d-value for CeO2-TiO2 compared to pure TiO2
Electronegativity of TiO2, (TiO2) = [(Ti) 2(O)]1/3
where (TiO2), (Ti), and (O) are the electronegativities of TiO2, titanium, and oxygen
respectively
VB energy = Ionisation energy, IE(TiO2) = EVB(TiO2) = (TiO2) + ½ Eg
CB energy = Electron affinity, EA(TiO2) = ECB(TiO2) = (TiO2) – ½ Eg
ECB(TiO2) (in NHE) = ECB(TiO2) – 4.5 eV (in Absolute vacuum scale)
 Band positions of TiO2, CeO2 and Ce2O3 were calculated
15
Y. Xu, M.A.A. Schoonen, Am. Mineral., 85 (2000) 543
Mechanism in visible light
Bandgap, conduction and valence band energy positions of the various oxides
Semiconductor
Bandgap
(in eV)
ECB in NHE
(in eV)
EVB in NHE
(in eV)
TiO2
3.20
-0.29
2.91
CeO2
2.76
-0.32
2.44
Ce2O3
2.40
-0.47
1.93
16
G. Magesh, B. Viswanathan, R.P. Viswanath, T.K. Varadarajan, Ind. J. Chem. A, 48A (2009) 480
Summary
 CeO2-TiO2 prepared by co-precipitation method
 No new phase observed due to CeO2 loading
 On loading CeO2 red shift of upto 75 nm was observed in UV-visible spectrum
compared to TiO2
 CeO2-TiO2 composite shows higher activity in visible light and UV light
 CeO2 has conduction band position more negative than that of TiO2
 CeO2-TiO2- works in visible and UV light by coupled semiconductor mechanism
17
Chapter - 4
Preparation, characterization and photocatalytic studies of
carbon-TiO2 composites
18
Carbon-TiO2
Adsorption:
 Adsorption - important step in photocatalysis
 TiO2 has less adsorption capacity
Improving adsorption leads to
 Electron and hole transferred quickly to adsorbed compounds
 Leads to reduction in recombination
Improving adsorption:
One way of improving adsorption is carbon- TiO2 catalysts
 Carbon is a good adsorbent
 Carbon - conducting and improves charge transfer
Preparing carbon-TiO2
 Literature shows carbon prepared over TiO2 and TiO2 prepared over carbon
 Preparing TiO2 and carbon together is expected to have better activity
19
Preparation of carbon-TiO2
Sucrose + Titanium trichloride solution
Dissolved in water
Kept in oven at 150 °C for 15 h
Calcined at 300 °C for 4 h in air
Calcined at 300, 400, 500, and 600 °C in N2 for 6 h to vary the amount of carbon
XRD patterns
A
o
R
RA R
AA
A
TiO2 600 C
R
A
Intensity (a.u.)
Anatase JCPDS File No 21-1272
Rutile JCPDS File No 21-1276
AA
A
o
C-TiO2 600 C
o
C-TiO2 500 C
o
C-TiO2 400 C
XRD pattern of C-TiO2 calcined at 300 oC in
air; at various temperatures in N2
o
C-TiO2 300 C
20
30
40
50
60
2 Theta (Degrees)
70
80
20
SEM images
TEM images
21
C-TiO2 calcined at 300 oC air ; 600 oC N2
Raman spectra
Carbon
C-TiO2 calcined at 300 oC in air- at 600 oC in N2
Intensity (a.u.)
Intensity (a.u.)
Anatase
Eg(3)
Anatase
B1g
Anatase
A1g+B1g
400
600
800
1000
1200
1400
1600
1800
-1
Raman shift (cm )
Carbon
(D-band)
1350
400
600
800
1000
1200
1400
Carbon
(G-band)
1580
1600
 Prepared carbon graphitic in nature
1800
-1
Raman shift (cm )
Diffuse reflectance UV visible spectra
o
600 C N2
C-TiO2 calcined in air 300 oC ; in N2 different temperatures
o
300 C N2
o
Carbon-TiO2 shows no absorbance in visible
region

No doping of carbon is taking place
Intensity (a.u.)

400 C N2
o
500 C N2
Pure TiO2
Carbon
300
400
500
600
Wavelength (nm)
700
800
22
Photocatalytic activity of C-TiO2 from TiCl3 and sucrose
Source
: 400 W Hg lamp
Pollutant : 80ml 50ppm methylene blue
Irradiation
: 90 min
Catalyst : 0.1 g
Absorbance at 662 nm was monitored by UV-visible spectroscopy
%C
% MB conc.
decrease
under
irradiation
% MB
conc.
decrease
in dark
%
Photocatalytic
(Irradiation –
Dark)
TiO2
600 oC
NA
34.0
13.0
21.0
C-TiO2
300 oC
5.4
88.0
41.3
46.7
C-TiO2
400 oC
3.0
87.7
31.8
55.9
C-TiO2
500 oC
2.1
74.5
26.8
47.7
C-TiO2
600 oC
1.4
72.7
23.8
48.9
55
50
% MB degradaion
Catalyst
45
40
35
30
25
0
1
2
3
% Carbon
4
5
 All C-TiO2 samples showed at least 25 % increase in activity than TiO2
23
Preparation of carbon-P25 TiO2
Sucrose + P25 TiO2
Dispersed in water
Kept in oven at 150 °C for 15h
Calcined at 360, 365, 370, 375 and 400 °C for 4 h in air
XRD pattern
Intensity (a.u.)
A
Anatase JCPDS File No 21-1272
Rutile JCPDS File No 21-1276
R
A
A
A
R
R
20
30
40
A
A
R
50
60
2 Theta (Degree)
AA
70
A
80
24
TEM images
Carbon – P25 TiO2 calcined at 370 oC
Diffuse reflectance UV-visible spectra
C-P25 TiO2 from sucrose calcined at different temps in
air with varying amounts of carbon
TiO2 from P25+Sucrose
o
C-TiO2-370 C N2
No shift in UV-visible absorption was
observed

This shows absence of C doping
Intensity (a.u.)

o
C-TiO2-360 C N2
o
C-TiO2-365 C N2
o
C-TiO2-370 C N2
P25 TiO2
Carbon
300
400
500
600
Wavelength (nm)
700
25
800
Photocatalytic activity of C-TiO2 from sucrose and P25 TiO2
Source
: 400W Hg lamp
Pollutant : 80ml 50ppm Methylene blue
Irradiation
: 90 min
Catalyst : 0.1 g
Catalyst
%C
% MB conc.
decrease under
irradiation
% MB conc.
decrease in dark
%
Photocatalytic
(Irradiation –
Dark)
P25 400 oC air
NA
55.2
9.4
45.8
C-P25 365 oC
2.3
95.4
38.8
56.6
C-P25 370 oC
0.5
90.5
25.5
65.0
C-P25 375 oC
0.2
59.5
12.2
47.3
 Carbon-P25 TiO2 showed higher activity than P25 treated under similar
conditions
 Up to 20 % improvement in activity observed
26
Summary
Carbon and TiO2 were prepared together using sucrose and TiCl3
Carbon was prepared over commercial P25 TiO2
SEM and TEM images confirmed the existence of carbon and TiO2
together
Amount of carbon was varied by changing the calcination temperatures
Photocatalytic studies for the degradation of methylene blue showed that
carbon and TiO2 prepared together showed better activity than carbon
prepared over commercial TiO2
27
Chapter - 5
Preparation, characterization, photocatalytic and electrochemical studies
of CdSnO3 and Cd2SnO4
28
Choice of materials for new visible light photocatalysts
 Semiconductor valence band are composed of d-orbitals and p-orbitals
 Conduction band is composed of s-orbitals and p-orbitals
 Materials containing elements with completely filled d-orbitals (d10) have VB
edge at higher energy and hence small bandgap
13
Al
14
Si
15
P
28
Ni
29
Cu
30
Zn
31
Ga
32
Ge
33
As
46
Pd
47
Ag
48
Cd
49
In
50
Sn
51
Sb
78
Pt
79
Au
80
Hg
81
Tl
82
Pb
83
Bi
Elements whose compounds show small bandgap
Preparation of CdSnO3
Aqueous
SnCl4.5H2O
solution
Aq. 3CdSO4. 8H2O
solution
Added simultaneously
Aq. NaOH solution
Stirred overnight
Washed, dried, calcined 850 oC air 6 h
CdSnO3
30
Rhombohedral
(JCPDS no.
880287)
Intensity (a.u.)
XRD pattern of CdSnO3
20
30
40
50
60
70
80
90
2 Theta (Degree)
SEM images
31
 Absorbance starts 415 nm
 Bandgap 3.0 eV
Absorbance (a.u.)
Diffuse reflectance UV-visible spectrum
250
300
350
400
450
500
550
600
650
700
Wavelength (nm)
Photocatalytic decontamination of water
Catalyst
: 50 mg
Light source
: 480 W Hg lamp
Irradiation time
: 90 min
Model pollutant
: 50 ml 25 ppm p-chlorophenol
Visible light
:  > 420 nm (HOYA L-42 filter)
Catalyst
CdSnO3
% Degradation
UV-Visible
Visible
94.47
0.00
32
Preparation of Cd2SnO4
Aq. SnCl4.5H2O solution
Aq. NaOH solution
Mixed together
Sn(OH)4 precipitate
Washed till absence of ClDissolved in con. H2SO4
Mixed with aq. 3CdSO4 . 8H2O solution
Precipitated with NaOH
Precipitate washed till absence of SO42Dried calcined air 900 oC
Cd2SnO4
33
Orthorhombic
(JCPDS no.
801467)
Intensity (a.u.)
XRD pattern
20
30
40
50
60
70
80
90
2 Theta (Degrees)
SEM images of Cd2SnO4
34
Absorbance (a.u.)
Diffuse reflectance UV-visible spectrum
Absorbance starts at 532 nm
Bandgap : 2.3 eV
250
300
350
400
450
500
550
600
650
700
Wavelength (nm)
Photocatalytic decontamination of p-chlorophenol
Catalyst
: 50 mg
Light source
: 480 W Hg lamp
Irradiation time
: 90 min
Model pollutant
: 50 ml 25 ppm p-chlorophenol
Visible light
:  > 420 nm (HOYA L-42 filter)
Catalyst
Cd2SnO4
% Degradation
UV-Visible
Visible
75.81
24.94
35
Types of semiconductors suitable for water splitting
For H2 evolution
Conduction band potential - more negative than 0.00 V vs NHE
For O2 evolution
Valence band potential - more positive than +1.23 V vs NHE
-ve
P
o
t
e
n
t
i
a
l
Reduction (H+ /H2) 0.00 V
E
n
e
r
g
y
Oxidation (HO-/O2) +1.23 V
+ve
Band positions of various types of
semiconductors
36
Determination of band potential by Mott-Schottky plot
Impedance measurements
Coated on Ti plates using PVDF as binder
Frequency
: 0.01 – 10000 Hz
Reference electrode
: Ag/AgCl
Counter electrode
: Pt
Amplitude
: 0.005 V
Electrolyte
: 0.5 M Na2SO4
Potential range
: 0 V to 0.9 V
MS plot of CdSnO3

Flat band potential : 0.15 V vs Ag/AgCl
0.35 V vs NHE

Cannot evolve H2 and only O2 evolution
possible
MS plot of Cd2SnO4

Flat band potential : 0.23 V vs Ag/AgCl
0.43 V vs NHE

Cannot evolve H2 and only O2 evolution
possible
37
Photocatalytic water splitting studies
Hydrogen evolution reaction using CdSnO3 and Cd2SnO4
 Medium
: 35 ml Water-methanol (5:1 ratio)
 Catalyst
: 50 mg
 Light source
: 480 W Hg lamp
 No hydrogen evolution occurred in UV-visible and visible irradiation
38
Summary
 Rhombhohedral CdSnO3 and orthorhombic Cd2SnO4 were prepared by coprecipitation method
 Diffuse reflectance measurements showed bandgaps of 3.0 and 2.3 eV for
CdSnO3 and Cd2SnO4 respectively
 Photocatalytic p-chlorophenol degradation measurements showed both
catalyst were effective in UV-visible radiation
 Only Cd2SnO4 was found to be photoactive in visible radiation ( > 420 nm)
 Mott-schottky plots showed flat band potentials of 0.35 and 0.43 V (vs NHE)
for CdSnO3 and Cd2SnO4 respectively
 Water splitting studies showed no H2 evolution in accordance with
measured flat band potentials
39
Chapter - 6
Preparation, characterization and CO oxidation activity of
Au/TiO2
40
Carbon monoxide oxidation
 CO is a toxic gas from the partial combustion of fuel from Internal
Combustion Engines
 Oxidation to CO2 is one of the ways of removing CO
 Gold nanoparticles supported on TiO2 is a suitable catalyst
 TiO2 exists in different crystalline forms
 Mostly anatase and rutile were studied as supports
 Report shows brookite phase of TiO2 gives a higher activity than anatase
and rutile
W. Yan, B. Chen, S.M. Mahurin, S. Dai and S.H. Overbury, Chem. Commun., (2004) 1918.
41
Preparation of TiO2
TiO2 was prepared from TiCl4 and TiCl3 and were labeled as BRT4 and BRT3
respectively
Preparation of Au/TiO2 – sol deposition
40 ml HAuCl4 (5 millimoles) in
600 ml water
Heat 60 oC
32 ml 1 % sodium citrate + 8 ml 1 % tannin +
120 ml water. pH adjusted to 8 using 4 %
Na2CO3
Heat 60 oC
Both solutions mixed, stirred maintained at 60 oC for 30 mins
Pink colored gold sol
 Gold sol was deposited with the help of poly(diallyldimethylammonium chloride)
(PDDA)
 Calculated amount of gold loading – 2 wt %
 Gold loaded on BRT4, BRT3 and Degussa P25 TiO2
42
XRD analysis and surface area
Catalyst
XRD
Surface
area
(m2/g)
%
Anatase
%
Rutile
%
Brookite
BRT4
0
0
100
114
BRT3
55
0
45
197
P25
75
25
0
50
Gold estimation by ICP
Catalyst
% Au loading
based on ICP
Catalyst
Average size in nm
(No. of particles)
Au/BRT4-Sol
2.22
Au/BRT4-asprep
15.2 (56)
Au/P25-Sol
2.15
Au/BRT4-used
17.0 (167)
Au/BRT3-Sol
2.22
Au/P25-asprep
15.1 (59)
Au/P25-used
15.0 (149)
Particle size from TEM
43
TEM images of Au/TiO2 prepared by sol method

Au particles on Au/BRT4 were
agglomerated after reaction

No change in size observed in
Au particles on Au/P25 after
reaction
44 (B)
TEM images of Au/TiO2 samples prepared by sol method (A) Au/BRT4-sol-asprepared
Au/BRT4-sol-after reaction (C) Au/P25-sol-asprepared and (D) Au/P25-sol-after reaction
CO oxidation activity results
100



Reaction mixture 35 ml/min of gas
flow (0.5 vol. % CO, 9.4 % O2, 51.9 %
He and 38.2 % Ar) and at a ramp
rate of 4 oC/min
Reaction performed before and
after calcination in O2
60 mg of catalyst calcined at 400 oC
in 20 % O2 in Ar for 1 h (10 oC /min
heating rate, 30 ml/min gas flow)
Products monitored online by mass
spectrometer
90
80
% CO conversion

70
60
50
40
P25 sol bef. calc
P25 sol aft. calc
BRT4 Sol bef.calc.
BRT4 Sol aft. calc.
BRT3 sol bef. calc
BRT3 sol aft. calc.
30
20
10
0
25
50
75
100
125
150
175
200
225
250
275
300
o
Temperature ( C)
CO oxidation activity of catalysts

100 % conversion is achieved at 100 oC, 200 oC and 220 oC for Au/P25, Au/BRT3 (anatase +
brookite) and Au/BRT4 (brookite) respectively

Activity of Au/P25 is retained after calcination whereas considerable decrease observed in
Au/BRT4 and a slight decrease in Au/BRT3
45
Preparation of Au/TiO2 by deposition-precipitation method
15 ml of 0.0254 M HAuCl4.3 H2O soln. + 10 ml water in a beaker
pH adjusted to 8 using 1 M KOH
Heated up to 60 oC with stirring
500 mg TiO2 added
Stirred at 60 oC for 2 h
Centrifuged 5000 RPM 10 mins
Washed & centrifuged 3 times in water and once in ethanol
Dried 60 oC for 12 h
Au/TiO2
Calculated gold loading – 2.2 wt %
Gold loaded on P25 and BRT4
46
W. Yan, B. Chen, S.M. Mahurin, S. Dai and S.H. Overbury, Chem. Commun., (2004) 1918.
CO oxidation activity of samples from DP method
100


Temperature programmed reaction
was performed with 27.5 ml/min of
gas flow (0.5 vol. % CO, 9.4 % O2,
51.9 % He and 38.2 % Ar) and at a
ramp rate of 5 oC/min
oC
30 mg of catalyst calcined at 400
in 20 % O2 in Ar for 1 h (10 oC/min
heating rate, 12.5 ml/min gas flow)
% CO conversion
90
80
70
60
BRT4-DP-BC
BRT4-DP-AC
P25-DP-BC
P25-DP-AC
50
40
BC - before calcination
AC - after calcination
30
50
100
150
200
250
300
Temperature (oC)
Important observations
 Au/Brookite shows higher activity in DP method
 Au/P25 shows higher activity in sol method
 Brookite shows considerable decrease in activity after calcination in both cases
47
Intensity (a.u.)
Anatase
101
20
30
40
P25 - asp
P25 used
Au - 311
60
70
80
No peaks corresponding to Au
were observed
Anatase 224
Anatase 215
Anatase 116
Anatase 220
Anatase 204
Anatase 105
Anatase 211
Rutile 220
Anatase 200
Rutile 111
Rutile 101
Anatase 004
50
2 Theta (Degrees)

Rutile 110
Brookite 421
Other phases of TiO2 not
observed after reaction
Brookite 321

Au - 200
Au (200) peak showed an
increase in intensity after
reaction
Brookite 102
Au - 111

BRT4-asp
BRT4-used
Brookite 211
Peaks corresponding to Au
were observed
Intensity (a.u.)

Brookite
210 & 111
XRD pattern of Au/BRT4 and Au/P25 prepared by sol method
48
20
30
40
50
60
2 Theta (Degrees)
70
80
90
90
Summary
 Au supported on brookite and P25 TiO2 were prepared by deposition-precipitation
and sol deposition methods
 CO oxidation studies were carried out with the catalysts
 Au/P25 more active in sol deposition method
 Au/Brookite showed better activity in deposition-precipitation method
 Au/Brookite prepared by both methods showed decrease in activity after calcination
49
Conclusions
 CeO2-TiO2 showed redshift up to 75 nm and higher activity than TiO2 in visible light
and UV light. CeO2 has a conduction band position more negative than that of TiO2
and CeO2-TiO2 works in visible and UV light by coupled semiconductor mechanism.
 Carbon-TiO2 composites were prepared by two different methods namely
preparation of carbon and TiO2 together and preparation of carbon over
commercial P25 TiO2. Photocatalytic degradation of methylene blue experiments
showed that carbon and TiO2 prepared together showed better activity than carbon
prepared over commercial TiO2.
 Photocatalytic p-chlorophenol degradation studies showed that both Cd2SnO4 and
CdSnO3 were active in UV-visible radiation whereas, Cd2SnO4 alone was active in
visible radiation. Mott-Schottky plots showed that both CdSnO3 and Cd2SnO4 have
flat band potentials lower in energy than the H2 evolution potential. Photocatalytic
water splitting experiments showed no H2 evolution.
 Au supported on brookite and P25 TiO2 (Anatase+Rutile) were prepared by
deposition precipitation and sol deposition methods. Au/P25 was found to be more
active in sol deposition method whereas Au/brookite showed better activity in
deposition-precipitation method. Au/brookite prepared by both the methods
showed decrease in activity after calcination at higher temperature.
Acknowledgements
Grateful thanks are due to
 (Late) Prof. R.P. Viswanath
 Prof. T.K. Varadarajan
 Prof. B. Viswanathan
 The current and past Heads of Department of Chemistry
 The Doctoral committee members and faculty of the Department of Chemistry
 The supporting staff
 Colleagues and friends
 DST and CSIR for fellowships
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LIST OF PUBLICATIONS
REFEREED JOURNALS
Magesh, G., B. Viswanathan, R.P. Viswanath and T.K. Varadarajan (2009) Photocatalytic behavior of
CeO2-TiO2 system for the degradation of methylene blue. Indian J. Chem., Sec A, 48A, 480-488.
OTHER PUBLICATIONS
Magesh, G., B. Viswanathan, R.P. Viswanath and T.K. Varadarajan (2007) Photocatalytic routes for
chemicals. Photo/Electrochemistry & Photobiology in the Environment, Energy and Fuel, 321-357.
PRESENTATIONS IN SYMPOSIUM/CONFERENCE
Magesh, G., B. Viswanathan, R. P. Viswanath and T. K. Varadarajan, ‘Visible light photocatalytic activity of
Ce modified TiO2 nanoparticles for methylene blue decomposition’, International Conference on
Nanomaterials and its Applications (Poster presentation), February 4-6th 2007, NIT, Trichy, India.
Magesh, G., B. Viswanathan, T.K. Varadarajan and R.P. Viswanath, ‘CeO2-TiO2 system as visible light
photocatalyst for the degradation 4-chlorophenol’, Catworkshop-2008 (Poster Presentation), February 1820, 2008, IMMT, Bhubaneswar, India.
Magesh, G., T.K. Varadarajan and R.P. Viswanath, ‘Enhanced photocatalytic activity of carbon-TiO2
composites towards pollutant removal’, CATSYMP-19, (Poster presentation) January 18-21, 2009,
National Chemical Laboratory, Pune, India.
Magesh, G., B. Viswanathan, T.K. Varadarajan and R.P. Viswanath, ‘Cadmium stannates as
photocatalysts for decontamination of water’, Indo-Hungarian workshop on future frontiers in catalysis
(poster presentation) February 16-18, 2010, IIT Madras, Chennai, India.
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