POTENTIAL OF Ti-W-Zn MIXED METAL OXIDES FOR · PDF fileMicrosoft PowerPoint - Franklyn...
Transcript of POTENTIAL OF Ti-W-Zn MIXED METAL OXIDES FOR · PDF fileMicrosoft PowerPoint - Franklyn...
POTENTIAL OF Ti-W-Zn
MIXED METAL OXIDES FOR
PHOTOVOLTAIC AND
PHOTOCATALYTIC
APPLICATIONS
Dr Paul Franklyn
Dr S Durbach, L Hlekelele, R. Carnie
N Driver, Pfano, A Narrandes
Aims
� Synthesize a range of both ternary and quaternary mixed metal oxides of titanium, zinc and tungsten
� Characterise the samples
� Test each material for photocatalyticand photovoltaic applications
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Anatase
• Distorted Octahedra
• a=b = 3.7845 Ȧ• c=9.5143 Ȧ
• Band gap of 3.2 eV
• Large, open structure
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Mixed Metal Oxides
� Creating a single crystal structure◦ But with multiple metals in the structure
◦ Try not to disrupt the host crystal
◦ Add the metal ions after or during formation
� Ternary Oxides◦ Titanium-Tungsten oxide
◦ Titanium-Zinc oxide
� Quaternary Oxides◦ Titanium-Tungsten-Zinc oxide
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Why the interest?
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We want to remove this physical gap
and still reduce the bandgap
but yet maintain the redox suface
and keep the interior electrical behaviours
Our Approach
� Incorporation of tungsten/zinc ions into the anatase structure
� Titanium- 0.745Ȧ
� Tungsten- 0.740Ȧ
� Zinc- 0.740Ȧ
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The Results
� Titanium-Tungsten Mixed Metal Oxides
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0
500
1000
1500
2000
2500
0 20 40 60 80
Inte
nsi
ty (
A.U
)
2θ(°)
Ti60-W40
Ti70-W30
Ti80-W20
Ti90-W10
Ti95-W5
Distortion of unit cells
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c parameter
b parameter
� Calculation of b and c parameters
� Determined using PXRD 2θ (in radians)
� The calculated parameters are then
compared to the literature parameters
Distortion of the unit cells
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� Ti-W b parameter c parameter
� Ti-W-Zn
Ti95-W5
Ti90-W10
Ti80-W20
Ti60-W40
0
0,005
0,01
0,015
0,02
0,025
0,03
0,035
0 20 40 60 80 100
Dif
fere
nce
betw
een li
tera
ture
and
exp
eri
menta
l
Percentage of Titanium
Ti95-W5
Ti90-W10
Ti80-W20Ti60-W40
-0,18
-0,16
-0,14
-0,12
-0,1
-0,08
-0,06
-0,04
-0,02
0
0 20 40 60 80 100
Dif
fere
nc
e b
etw
ee
n l
ite
ratu
re a
nd
ex
pe
rim
en
tal
Percentage of Titanium
Ti70-W10-
Zn20(a-c)
Ti70-W20-
Zn10(a-c)
Ti50-W25-
Zn25(a-c)
Ti40-W30-
Zn30(a-c)
0
0,005
0,01
0,015
0,02
0,025
0,03
0,035
0 20 40 60 80
Dif
fere
nce
be
twe
en
lit
era
ture
an
d
exp
eri
me
nta
l
Percentage of titanium
Ti70-W10-
Zn20(a-c)
Ti70-W20-
Zn10(a-c)
Ti50-W25-
Zn25(a-c)
Ti40-W30-
Zn30(a-c)
-0,08
-0,07
-0,06
-0,05
-0,04
-0,03
-0,02
-0,01
0
0 10 20 30 40 50 60 70 80
Dif
fere
nce
be
twe
en
lit
era
ture
an
d
exp
eri
me
nta
l
Percentage of titanium
Testing the photocatlysts
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� The first sample
tested decomposed
20ml of water in 12
hours.
� When retested it only
decomposed 2ml
� Retested it did 5ml
� Other samples
showed similar
behaviour
In conclusion
� The synthesis of all the samples was confirmed - characterised using PXRD, TEM and EDS
� The testing of the catalysts was inconclusive◦ Reproducibility proved a problem
◦ Despite reproducible structural data
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Future Work
� The synthesis of clean, carbon free ternary and quaternary mixed metal oxides
� The set up of a more reliable testing system
� Exploring the complete phase diagram of composition and temperature
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Acknowledgements
� Pfano (vac student)
� Robyn Carnie (4th year)
� Lerato Hlekelele (PhD)
� Nicholas Driver (MSc)
� Ashvir Narrandes (PhD)
� National Research Foundation of South Africa for the grant, 87885◦ Any opinion, finding and conclusion or recommendation expressed in this material is that of the
author(s) and the NRF does not accept any liability in this regard.