1. Sol-gel derived Mesoporous
Titanium Phosphate
Mayur Sundararajan and Gang Chen
Department of Physics and Astronomy
Ohio University
Athens OH
20th May 2015
2. Photocatalysis
Introduction
Chemical reaction induced by photoirradiation in the
presence of a photocatalyst.
Valence Band
Conduction Band
e-
e-
h+
Reactants
Reduce
Oxidize
Bandgap
Energy
Photocatalyst
TiO2 is the most
researched Photocatalyst
Properties of a Efficient Photocatalyst
•Suitable Bandgap(>1.23eV)
•Slow recombination
•High specific surface area
H2
Photocatalyst
Hydrogen Production by Water-splitting
3. Photocatalysis
TiO2 has a bandgap of ~ 3.2eV
Some of the Bandgap Manipulation methods used
Composite Materials , Doping , Metal Loading
We want to manipulate the bandgap by a physical method
Bandgap Manipulation
380 nm,3.2 eV 700 nm,1.77 eV
4. Bandgap Manipulation by Controlling Residual Strain
Mesoporous Glass – MCM-41
Hexagonal pore arrangement
Mesopores
Porewall
• Material with pores of size 2-50nm
Ex. Mesoporous Silica (MCM-41, SBA-15)
• Amorphous porewalls
• High Specific Surface Area
• High Porosity
• The pores may be ordered or disordered
0 100 200 300 400 500 600
0.19140
0.19145
0.19150
0.19155
0.19160
0.19165
0.19170
0.19175
SAXS_peak_position(Å-1)
WAXS_peak_position(Å-1)
Temperature(°C)
SAXS_peak_position(Å-1)
1.562
1.564
1.566
1.568
1.570
1.572
1.574
WAXS_peak_position(Å-1)
Along the pores
Expansion
Perpendicular
to the pores
Contraction
Inter-poredistance(Å-1)
Strainintheporewall(Å-1)
Anisotropic Thermal Expansion
Thermal Expansion mismatch
5. Hypothesis
We propose that this thermal annealing method
can modify the bandgap of a wide bandgap
amorphous material by controlling the strain
Why Titanium Phosphate?
Requirements
• Photocatalyst
• Bandgap comparable to TiO2
• Sol-gel synthesis(Mesoporous Possibility)
• Higher crystallization temperature(Amorphous)
8. Very few publications on Mesoporous Titanium Phosphate (2 papers)
Mesoporous Titanium Phosphate
Synthesis Method - Literature
9. 1 10
Intensity(arb.units)
q(nm-1
)
0hr
7hr
14hr
24hr
extr
Mesoporous Titanium Phosphate
Sol-gel Synthesis Method - Literature
• Synthesis was performed as batch processing
• SAXS data shows that the organic and inorganic component never formed
proper liquid crystal template
SAXS – sample synthesis – literature
Different stages of aging
SAXS – MCM-41
After Calcination
Small Angle X-ray Scattering(SAXS)
1 10
Intensity(arb.units)
q(nm-1
)
10. Mesoporous Titanium Phosphate
Modified Sol-gel Synthesis Method
H3PO4
1h Vigorous Stirring
Adjust pH - 3
Ti(OPr)4
Liquid Crystal Template begins to form
Condensation
And Cooperative
Assembly begins
48hrs
Further
Condensation
@60C
SDA removal
Calcination
Filtered
& Dried
CH3(CH2)17N(Br)(CH3) Octadecyltrimethylammoniumbromide
H3PO4 Phosphoric Acid
Ti(OPr)4 Titanium iso-Propoxide
B
A C
D
60C 60C 60C
Aging begins
11. Modified Synthesis Method
SAXS – Gel Formation Steps
1 10
Intensity(arb.units)
q(nm-1
)
SurfactantAfter Surfactant was dissolved
1 10
Intensity(arb.units)
q(nm-1
)
Surfactant + Phosphoric AcidAfter Phosphoric Acid was dissolved
1 10
Intensity(arb.units)
q(nm-1
)
Phos 1hrAfter 1hr of stirring
1 10
Intensity(arb.units)
q(nm-1
)
Ti addAfter Ti(OPr)4 was dissolved
A B
CD
12. Modified Synthesis Method
SAXS – Aging Process
The two peaks maybe considered 211 and 220 planes, which
correspond to pores having cubic order like MCM-48
211
220
Before template removal – Various stages of aging
1 10
Intensity(arb.units)
q(nm-1
)
0hr
11hr
34hr
48hr
13. Modified Synthesis Method
Surfactant Template Removal
After the 48hr aging, 2 different template removal methods were tried:
• Extraction: Acidified Ethanol – Upto 4hrs
• Calcination: Heating upto 550C at different rates
1 10
Intensity(arb.units)
q(nm-1
)
48hr
extraction
calcination
14. 1 10
Intensity(arb.units)
q(nm-1
)
Before Calcination
Direct Calcination
Calcination - N2
flow
Modified Synthesis Method
Surfactant Template Removal – N2 Flow
• The surfactant was removed by heating to 550C with flowing N2
gas.
• The flow may have made the removal of some carbon compounds
from the sample more efficient.
10 15 20 25
2000
4000
6000
TiPO4_550C
Intensity(arb.units)
q(nm-1)
The pore-wall is still amorphous
even after calcination @550C
After N2 flow calcination
SAXS
WAXS
16. Mesoporous Titanium Phosphate
Mesoporous - Nonporous
The difference in bandgap in the nonporous sample maybe due to defects in them
and/or relaxation of the residual strain.
3.97 eV
3.82 eV
UV vis Spectroscopy
1.5 2.0 2.5 3.0 3.5 4.0 4.5
a.E(arb.units)
Bandgap(eV)
Nonp_TiPO4
1.5 2.0 2.5 3.0 3.5 4.0 4.5
a.E(arb.units)
Bandgap(eV)
Meso_TiPO4
17. 1.5 2.0 2.5 3.0 3.5 4.0 4.5
a.E(arb.units)
Bandgap(eV)
Meso_TiPO4
_600C
1.5 2.0 2.5 3.0 3.5 4.0 4.5
a.E(arb.units)
Bandgap(eV)
Meso_TiPO4
_550C
Mesoporous Titanium Phosphate
Thermal Annealing
The bandgap change might be caused due to strain change in the amorphous network
due to annealing
4.12
4.02
UV vis Spectroscopy
18. Conclusion
• Mesoporous Titanium Phosphate was successfully
synthesized by a modified template-based sol-gel
method.
• Optical bandgap of mesoporous Titanium Phosphate is
larger than its nonporous form.
• Optical bandgap of mesoporous Titanium Phosphate can
be tuned by thermal annealing.
19. THANK YOU
Dr. G. Chen, Dr. M. E. Kordesch, C. A. Ihalawela, P. Jakkala
Department of Physics and Astronomy
Ohio University
Athens OH
This work was funded by NSF #0906825/1507670
Acknowledgement
References
1. Asim Bhaumik and Shinji Inagaki, J. Am. Chem. Soc (123), 691 (2001)
2. Nabanita Pal Mandipa Paul, Bharath Singh Rana, Anil Kumar Sinha and Asim Bhaumik, Catalysis Communication 10, 2041 (2009)
3. Deborah J. Jones, G. Aptel,a Markus Brandhorst, MeÂlanieJacquin, JoseÂJimeÂnezJimeÂnez, Antonio JimeÂnez-LoÂpez, Pedro Maireles-Torres, Ireneusz
Piwonski, Enrique RodrÂõguez-CastelloÂn, Jerzy Zajaca and Jacques RozieÁrea, J. Mater. Chem., 2000, 10, 1957-1963
4. Pal N, Bhaumik A, Soft templating strategies for the synthesis of mesoporous materials: Inorganic, organic–inorganic hybrid and purely organic solids, Adv Colloid
Interface Sci (2013)
5. J. Livage, P. Barboux, M.T. Vandenborre, C. Schmutz and F. Taulelle, Journal of Non-Crystalline Solids 147&148 (1992) 18-23
20. Mesoporous Synthesis Mechanism
Surfactant based Self Assembly
M(OR)4
OH
𝐻2 𝑂+
M
OH
𝐻2 𝑂+
𝑂−
OH
M
OH
𝑂−
Basic
Acidic
Metal Precursor
Condensation
with template
Surfactant
Micelle
Surfactant
Self-assembly
Liquid crystal
Template
Condensation
with metal
precursor
Template
Removal
Mesoporous material
Reference1Figure 2
Inorganic
Component
Organic
Component
Aging
21. Mesoporous TiPO4
Synthesis Method - Literature
For a promising material surprisingly very few literature on Mesoporous
TiPO4 (2 papers)
1. Asim Bhaumik and Shinji Inagaki, J. Am. Chem. Soc (123), 691 (2001)
2. Nabanita Pal Mandipa Paul, Bharath Singh Rana, Anil Kumar Sinha and Asim Bhaumik, Catalysis Communication 10, 2041 (2009)
3. Deborah J. Jones, G. Aptel,a Markus Brandhorst, MeÂlanieJacquin, JoseÂJimeÂnezJimeÂnez, Antonio JimeÂnez-LoÂpez, Pedro Maireles-
Torres, Ireneusz Piwonski, Enrique RodrÂõguez-CastelloÂn, Jerzy Zajaca and Jacques RozieÁrea, J. Mater. Chem., 2000, 10, 1957-1963
4. Pal N, Bhaumik A, Soft templating strategies for the synthesis of mesoporous materials: Inorganic, organic–inorganic hybrid and purely
organic solids, Adv Colloid Interface Sci (2013)
5. J. Livage, P. Barboux, M.T. Vandenborre, C. Schmutz and F. Taulelle, Journal of Non-Crystalline Solids 147&148 (1992) 18-23
22. Mesoporous TiPO4
Structure Directing Agent
Metal Precursor
Phosphate Precursor
Nucleation
Cooperative
Assembly
Liquid crystal
Formation and Further
Condensation
Template
Removal
Synthesis Mechanism - Literature
23. • Ti-alkoxide precipitates with H3PO4 very rapidly
• High reactivity of transition metals leads to phase
separation between organic and inorganic components
• H3PO4 in H2O – does not undergo condensation readily
but forms phosphate with metals.
• Found to be extremely sensitive to Temperature, Time,
Pressure
Mesoporous TiPO4
Caveats
25. Nonporous & Mesoporous Silica Glass
1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8
Intensity(arb.units)
q(Å-1)
Bulk_Silica
MCM41
WAXS - First Sharp Diffraction Peak
change in FWHM indicates that the glass network is under stress
26. Mesoporous Silica Glass
Thermal Annealing
10 15 20 25
Intensity(arb.units)
q(nm-1
)
MCM41_600C
MCM41_650C
Change in the FWHM indicates that there is a change in the stress
in the glass network due to annealing
28. References
1. Asim Bhaumik and Shinji Inagaki, J. Am. Chem. Soc (123), 691 (2001)
2. Nabanita Pal Mandipa Paul, Bharath Singh Rana, Anil Kumar Sinha and
Asim Bhaumik, Catalysis Communication 10, 2041 (2009)
3. Deborah J. Jones, G. Aptel,a Markus Brandhorst, MeÂlanieJacquin,
JoseÂJimeÂnezJimeÂnez, Antonio JimeÂnez-LoÂpez, Pedro Maireles-
Torres, Ireneusz Piwonski, Enrique RodrÂõguez-CastelloÂn, Jerzy Zajaca
and Jacques RozieÁrea, J. Mater. Chem., 2000, 10, 1957-1963
4. Pal N, Bhaumik A, Soft templating strategies for the synthesis of
mesoporous materials: Inorganic, organic–inorganic hybrid and purely
organic solids, Adv Colloid Interface Sci (2013)
5. J. Livage, P. Barboux, M.T. Vandenborre, C. Schmutz and F. Taulelle,
Journal of Non-Crystalline Solids 147&148 (1992) 18-23
