1. Au/TiO2
Nanopar/cle
Surface
Chemistry
Steven
P.
Burrows
Morris
Research
Group
30
April
2012
*
*
No
marital
jewelry
or
family
heirlooms
harmed
in
the
conduct
of
this
research.
2. Nanopar/cles:
The
Scale
• Nanopar'cles
range
from
~3
to
50
x
10-‐9m
diameter
(smaller
than
a
virus).
• Crystalline
material
on
this
size
scale
begins
to
assume
molecular
proper'es.
• Electron
behavior
within
nanopar'cles
“between
bands
and
bonds”2
2
2 x 10-6 m 2 x 10-8 m Degussa P25
0.25 x 10-8 m
Au 'Decoration'
0.04 x 10-8 m
1Bacteria Virus Nanoparticles
1Archives
of
Histology
and
Cytology,
2007
vol.
70
(1)
pp.
43-‐49
2Applied
Spectroscopy,
2006
vol.
56
(1)
pp.
16A-‐27A
Valence
Band
Conduction
Band
Egap
HOMO -
LUMO
Gap
Egap
Bulk
Semiconductor Nanoparticle Molecule
Energy
3. Applica/ons:
Present
and
An/cipated
• Hydrogen
Fuel
Produc'on
(Water
SpliTng)
• Hydrogen
Fuel
Storage
• Photovoltaic
Cells
• Building
Materials
Coa'ngs
(e.g.
Self-‐Cleaning
Windows)
• An'bacterial
Coa'ngs
• An'-‐Cancer
Therapies
• Pollu'on
Detec'on,
Control,
and
Remedia'on
• Industrial
Process
Catalysts
• Detec'on
and
Decomposi'on
of
Chemical
Warfare
Agents
(CWAs)
3
4. Research
Objec/ves
• Develop
understanding
of
size
and
loading
effects
for
Au/TiO2
nanopar'cle
catalysts.
• Inves'gate
structural
effects
on
catalyst
performance:
‘decorated’
vs.
aerogel
oxide
supports.
• Maximize
cataly'c
ac'vity.
• Develop
understanding
of
reac'on
mechanism
through
fundamental
catalyst
studies.
4
6. Laser
Vaporiza/on
(LV)
Nanopar/cles
• Sintered
tablet
of
metal
oxide
vaporized
with
CO2
laser.
• Vaporized
oxide
condenses
in
gas-‐phase
to
form
nanopar'cles.
• Nanopar'cles
accrete
on
sheet
metal
surface.
• Nanopar'cle
size
controlled
through
chamber
pressure
and
chamber
geometry.
6
7. Examples
of
LV
Produced
TiO2
7
P
=
1
Torr
O2
P
=
100
Torr
O2
9. CeO2
Rela/ve
CO
Oxida/on
Ac/vity
9
300 400 500 600 700 800
-1
0
1
2
3
4
5
6
7
CO2
PeaksArea(2280-2395cm
-1
)
Temperature / K
Blank
No. 1
No. 2
No. 3
No. 4
No. 5
No. 6
No. 7
No. 8
No. 9
CeO2
Nanoparticle Repeatability Study
He
+
O2
+
CO
Temperature
Control System
(100 ~ 675 K)
Catalyst Sample
Screening Tube
He
+
O2
+
CO
+
CO2
IR
Gas
Cell
FTIR Detection
Activity Screening Apparatus
Repeatability
Study
10. CO
Screening
Method
Valida/on
10
100
90
80
70
60
50
40
30
20
10
0
COConversion/%
700600500400300200100
Temperature / K
SPB_069 CeO2 CO Oxidation
Dual Flow Cell Calculations
10
the fluorite structure with a calculated lattice parameter of 5.416
Å, and the other phase still of fluorite structure with a contracted
lattice parameter of 5.403 Å, attributed to a solid solution
between gold and ceria. The closeness of the ionic radii of Ce4+
and Au3+, 0.97 and 0.85 Å, respectively,41 would indeed allow
for the formation of a composite Ce1-xAuxO2-δ (where δ takes
into account the charge balance).25,26 The XRD pattern of the
CP sample calcined at 673 K is shown in Figure 4. Differently
from the DP sample, and as expected from the high-temperature
treatment, this profile reveals the Au (111) and the Au (200)
reflection peaks of metallic gold along with the peaks related
to the CeO2 phase with a certain degree of amorphism. It is
worth mentioning that the further calcinations of the CP sample
at 673 K aimed to form the solid solution, with a modified
fluorite structure of ceria, which appeared to be amorphous after
the 393 K treatment. Moreover, for the purpose of this study,
the attainment of just ionic gold species by the DP method
followed by the mild treatment in air at 393 K fulfilled our
original objective.
In Table 3, the results in terms of the main binding energies,
Au 4f7/2, O 1s, of Au/Ce atomic ratio and gold loading, as
obtained from the XPS quantitative analyses, are reported for
the differently prepared samples. For all samples, no extra peaks
due to impurities were observed. In consideration of the
decreased activity of the 3AuCe(DP) with aging and after the
catalytic reaction, the XPS results of this sample at different
stages of its life, referred to as “as prepared”, “aged”, and
“used”, are listed in the table. Because no such changes in
activity were observed with the samples prepared by the other
two techniques, no distinction between different stages of the
Figure 1. CO conversion % as a function of temperature for the
different catalysts.
TABLE 1: Temperature in Correspondence of the 100%
Conversion of CO
catalyst T100% (K)
3AuCe(DP)393K 301
3AuCe(DP)1monthaged 373
3AuCe(SMAD)298K 427
10AuCe(CP)673K 473
ceria 723
TABLE 2: Average Ceria Crystallite Size, dCeO2, and Au
Particle Size, dAu, As Obtained from XRD Analyses of the
Different Catalysts (Values Are Quoted with an Uncertainty
Ceria-Supported Gold Catalysts J. Phys. Chem. B, Vol. 109, No. 7, 2005 2823
tober2,2009|http://pubs.acs.org
2005|doi:10.1021/jp045928i
Plot
Inset:
Venezia,
A.
M.
et
al.
Journal
of
Physical
Chemistry
B
2005,
109,
2821-‐2827.
• Samples
run
on
glass
wool
in
glass
bulb
screening
tube.
• Par'cles
condi'oned
and
200
∘C
for
~
30
minutes.
• Note
my
CeO2
achieves
50%
CO
conversion
at
~640K.
• Venezia
CeO2
achieves
50%
CO
conversion
at
~550K.
11. Degussa
TiO2
With/Without
Au
11
200 300 400 500 600 700 800
-2
0
2
4
6
8
10
12
14
16
18
20
22
CO2
PeaksArea(2280-2395cm
-1
)
Temperature / K
Blank
P25 TiO2
P25 TiO2
/ Au
Degussa P25 TiO2
with Solution Precipitated Au
Ti O Ti O Ti
Au
C O C OO
O O
12. Mul/ple
Au
Deposi/ons
Reactor
12
12
F
A
N
F
A
N
Heated Sand Bath
Air-cooled reflux
condenser tubes
Aluminum
air duct
tube
Air FlowAir Flow
Stirrer Motors
Note the removeable top and sliding air ducts for connection to the condenser duct.
Urea
Hydrolysis
Gold
Deposi/on
CO(NH2)2(aq)
+
3H2O(l)
→
CO2(g)
+
2NH4OH(aq)
pH
3
at
30∘C
to
pH
8
at
T
~
80∘C
HAuCl4(aq)
+
4NH4OH(aq)→
Au(OH)3(s)
+
4NH4Cl(aq)
+
H2O(l)
• Reac'on
vessels
are
heated
to
approximately
80
C
to
ini'ate
pH
shii
to
precipitate
Au(OH)3.
• Solu'ons
are
s'rred
for
approximately
20
hours
to
allow
‘Ostwald
Ripening’
par'cles.
• Reac'ons
conducted
under
low-‐light
condi'ons
to
block
uncontrolled
photo-‐reduc'on
of
Au3+.
• Gold
loading
%
determined
through
atomic
emission
spectroscopy
(ICP).
15. Au
Deposi/on
with
Aerogel
TiO2
15
Au
Deposi'on
on
Oxide
Par'cles
Aerogel
Deposi'on
of
Oxide
on
Au
TiO2
TiO2
TiO2TiO2
TiO2
TiO2
TiO2
TiO2
Solution
Au(OH)3
Deposition
Au Particle
Reductive
Activation TiO2
TiO2
TiO2
TiO2
TiO2
TiO2
TiO2
TiO2
TiO2
TiO2
TiO2
TiO2
Au Particle
Preparation
Thiolate
Coating
Application
Sol-Gel
Application
of TiO2
Sintering Removal
of Thiolates and
TiO2 Crystallization
16. Why
This
Difference
MaZers
16
Thermal
migra'on
occurs
at
300
~
400
∘C
and
is
promoted
by
Cl-‐
contamina'on.
TiO2
Au
Decoration
(Active)
Au Aggregate
(Low Activity or Inactive)
Thermal
Migration
TiO2
TiO2
TiO2
TiO2
TiO2
TiO2
Au nanoparticles 'locked down' by
3-dimensional stabilization through
multiple Au - TiO2 interfaces.
2-Dimensional Au -TiO2 Au - Aerogel TiO2
17. Decorated
vs.
Aerogel
Au/TiO2
17
17
100
90
80
70
60
50
40
30
20
10
0
COConversion/%
400350300250200150100
Temperature / K
Decorated vs. Aerogel
Au/TiO2 Nanoparticles
Decorated Run A
Decorated Run B
Aerogel
19. High
Vacuum
Chamber
Apparatus
19
LN2 Cooled MCT
FTIR Detector
Interfacing
Optics
Nexus 470 FTIR
Pressure
Sensor
RGAQuadrupole
MassSpectrometer
View Port
Dosing
Jets
19
(Top
View
-‐
Not
to
Scale)
Sample
Mount
To Vacuum
Pass-Through
and
High-Current
Power Supply
Blank (Empty)
Sample 1
Sample 2
Tungsten Mesh
Copper
Mesh
Clamps
K-Thermocouple
(Welded to Mesh)
10-‐7
~
10-‐8
Torr
Pneumatic
Gate Valve
Manual
Gate Valve
Chamber
Pump
Pump
Pressure
Sensor
Pressure
Sensor
( Side View )
20. TiO2
Thermal
O2
Condi/oning
20
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
∆Absorbance
4000 3500 3000 2500 2000 1500 1000
Wavenumber / cm
-1
• Following
60
minutes
of
O2
treatment
at
673
K,
the
sample
is
cooled
slowly
to
300
K
and
the
O2
is
evacuated.
• Nega've
deflec'ons
in
spectrum
are
the
result
of
adsorbate
losses.
Au
/
Aerogel
TiO2
(Post-‐Treatment)
Aerogel
TiO2
(Post
Treatment)
Free
-‐OH
forma'on
Organics
Loss
H2O
Loss
Carbonates
Loss
21. 21
• Range
of
energies
observed
in
mid-‐IR
range
span
approximately
0.45
eV.
• Distribu'on
of
CB
electrons
governed
by
Fermi
probability
func'on
• Changes
in
CB
electron
popula'on
and
intraband
transi'ons
observed
as
broad
shii
in
infrared
baseline
absorbance.
IR
Spectroscopy
of
Electrons…
?
400 cm-1 / 0.05 eV
4000 cm-1
/ 0.5 eV
Ti 3+
shallow trap state
conduction band
0.3~0.4eV
FTIR spectrum
energy range
3.0 ~ 3.1 eV
conduction band
valence band
0.3 ~ 0.4 eV
Ti 3+
shallow trap state
FTIR spectrum
energy range
Egap
0.20
0.15
0.10
0.05
0.00
∆Absorbance
4000 3500 3000 2500 2000 1500 1000
Wavenumbers / cm
-1
313 K
673 K
f (E) =
1
1+ Exp
E − EF
kBT
⎡
⎣
⎢
⎤
⎦
⎥
22. Atomic
Hydrogen
n-‐Doping
22
sociation on supported Au particles in the 2-3 nm diameter
ge has been studied at 295 K. It has been found that the
O2 is a sensitive detector for spillover-H atoms, where trapped
ctrons in shallow trap states near the bottom of the conduction
ure 8. Schematic diagram of the hydrogen spillover process,
cting electrons into shallow trap states near the bottom of the
duction band. The trapped electrons are then excited by IR photons
the conduction band where they are highly delocalized, producing
oad IR absorbance in the range 4000-1000 cm-1
.
J. Phys. Chem. C, Vol. 111, No. 7, 2007 2963
D.
Panayotov
and
J.
T.
Yates.
J
Phys
Chem
C,
2007
vol.
111
(7)
pp.
2959-‐2964
• Molecular
hydrogen
adsorbed
onto
Au
nanopar'cles
dissociates
into
surface-‐
adsorbed
atomic
hydrogen.
• Spillover
of
atomic
hydrogen
onto
the
TiO2
support
surface
causes
popula'on
of
shallow
trap
states
with
addi'onal
electrons.
• The
remaining
proton
(electron
hole)
diffuses
into
the
TiO2
bulk.
• Shallow-‐trapped
electrons
are
thermally
or
IR
excited
into
the
TiO2
conduc'on
band
where
they
are
detected
by
IR.
• Removal
of
gaseous
H2
pressure
reverses
this
process.
23. Au/TiO2
n-‐Doping
(293
K)
23
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00
∆Absorbance
4000 3500 3000 2500 2000 1500 1000
Wavenumber / cm
-1
170
minutes
H2
exposure
• Sample
chamber
sealed
and
pressurized
to
1.4
Torr
with
high-‐purity
H2.
• Growth
of
peaks
at
1100
and
1600
cm-‐1
apributed
to
accumula'on
of
bicarbonate
and
molecular
water
from
methoxy
surface
treatment
decomposi'on.
• Nega've
peak
at
3700
cm-‐1
apributed
to
loss
of
free
-‐OH
due
to
adsorp'on
of
CO2
decomposi'on
product.
• H-‐bonded
-‐OH
growth
from
3600
-‐
3500
cm-‐1
noted.
24. Au/TiO2
n-‐Doping
(293
K)
24
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00
∆Absorbance
4000 3500 3000 2500 2000 1500 1000
Wavenumber / cm
-1
50
minutes
evacua'on
• Following
H2
exposure,
sample
chamber
gate
valves
opened
and
pump
down
to
~
1
x
10-‐8
Torr
started.
• Diffusion
of
protons
from
TiO2
bulk
and
TiO2
conduc'on
band
electrons
result
in
reforma'on
of
H2.
• Loss
of
TiO2
conduc'on
band
electrons
results
in
broad
drop
of
baseline
absorbance.
• Accumulated
methoxy
residue
decomposi'on
products
remain
on
surface.
25. Au/TiO2
n-‐Doping
(250
K)
25
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00
∆Absorbance
4000 3500 3000 2500 2000 1500 1000
Wavenumber / cm
-1
• Similar
baseline
absorbance
effects
noted
when
the
sample
temperature
was
lowered
to
250
K
during
H2
exposure
and
pump
off
removal.
• Because
this
experiment
followed
the
293
K
exposure,
further
methoxy
decomposi'on
products
accumulate
on
the
par'cle
surfaces.
90
minutes
H2
exposure
26. Au/TiO2
n-‐Doping
(250
K)
26
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00
∆Absorbance
4000 3500 3000 2500 2000 1500 1000
Wavenumber / cm
-1
• Similar
baseline
absorbance
effects
noted
when
the
sample
temperature
was
lowered
to
250
K
during
H2
exposure
and
pump
off
removal.
• Because
this
experiment
followed
the
293
K
exposure,
further
methoxy
decomposi'on
products
accumulate
on
the
par'cle
surfaces.
40
minutes
evacua'on
27. Propene
Chemistry
on
Au/TiO2
27
• Propene
has
been
observed
to
convert
to
acrolein
and
propenal
as
intermediates
during
complete
oxida'on.1,2
• Propene
reported
to
undergo
hydrogena'on
or
oxida'on
in
the
presence
of
Au/TiO2
nanopar'cles.3
• Hydrogena'on
selec'vity
reported
for
Au
>
4.5
nm
and
oxida'on
for
smaller
Au
nanopar'cles.4
• Propene
oxide
produc'on
of
commercial
interest
due
to
applica'on
as
a
polymer
feedstock.
H2C
CH
CH3
H3C
CH2
CH3
O
H2C
CH
CH3
Propene
Propane
Propene
Oxide
H2C
CH
CH
O
H3C
CH2
CH
O
Acrolein
Propenal
1Surface
Science,
2009
vol.
603
(7)
pp.
1010-‐1017
2J
Phys
Chem,
1971
vol.
75
pp.
2914-‐2921
3Journal
of
Catalysis,
2012
vol.
285
(1)
pp.
324-‐327
4J.
Gaudet,
K.K.
Bando,
Z.
Song,
T.
Fujitani,
W.
Zhang,
D.S.
Su,
and
S
T
Oyama
28. Propene
and
H2
at
Au/TiO2
(123
K)
28
0.12
0.11
0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00
∆Absorbance
4000 3500 3000 2500 2000 1500 1000
Wavenumber / cm
-1
Reac/on
Condi/ons
• Nanopar'cles
exposed
to
H2
and
n-‐doped.
• Chamber
evacuated
following
H2
exposure.
• Chamber
pressurized
to
1
Torr
with
propene.
• Sample
Temperature
maintained
at
123
K.
5
min.
8
min.
13
min.
17
min.
Propene
on
Au
/
Aerogel
TiO2
(123
K)
29. Propene
and
H2
at
Au/TiO2
(123
K)
29
0.12
0.11
0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00
∆Absorbance
4000 3500 3000 2500 2000 1500 1000
Wavenumber / cm
-1
5
min.
8
min.
13
min.
17
min.
10
min
Propene
on
Aerogel
TiO2
(123
K)
Gas-‐Phase
Propene
Propene
Adsorbate
Peaks
υ(C=C)
at
1656,
1640
cm-‐1
δa(CH3)
at
1456
cm-‐1
Catalysis
Lepers,
2002
vol.
84
(3)
pp.
143-‐146
δa(CH3)
υ(C=C)
Propene
on
Au
/
Aerogel
TiO2
(123
K)
30. Propene
and
H2
at
Au/TiO2
(123
K)
30
0.12
0.11
0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00
∆Absorbance
4000 3500 3000 2500 2000 1500 1000
Wavenumber / cm
-1
δa(CH3)
υ(C=C)
5
min.
8
min.
13
min.
17
min.
Propene
on
Aerogel
TiO2
(123
K)
10
min
50
min
• Iden'fied
propene
adsorbate
modes
diminish
with
'me
on
both
TiO2
and
Au/
TiO2.
• CO
(ads)
and
CO2
(ads)
peaks
grow
on
both
TiO2
and
Au/TiO2
with
length
of
exposure.
• Peak
at
2163
cm-‐1
assigned
to
CO
on
ca'onic
gold
(Auδ+)
and
2080
cm-‐1
is
assigned
to
CO
on
anionic
gold
(Auδ-‐).
CO2(ads)
CO(ads)
CO(ads)
CO
Auδ+
CO
Auδ-‐
31. Propene
and
H2
at
Au/TiO2
(123
K)
31
0.12
0.11
0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00
∆Absorbance
4000 3500 3000 2500 2000 1500 1000
Wavenumber / cm
-1
5
min.
8
min.
13
min.
17
min.
Propene
on
Au
/
Aerogel
TiO2
(123
K)
Methyl
Hydrogen
Abstrac/on
from
Propene
Loss
of
methyl
bending
mode
at
1456
cm-‐1
and
methyl
stretches
from
2800
~
3200
cm-‐1
caused
by
loss
of
methyl
hydrogens.
J
Phys
Chem,
1971
vol.
75
pp.
2914-‐2921
Catalysis
Lepers,
2002
vol.
84
(3)
pp.
143-‐146
Propene
Allyl
Ca'on
H2C
C
H
C
H
H
H
H2C
C
H
CH2
+
H2C
C
H
CH2
+
H2O
Ti
O
Ti
O
Ti
Ti
O
Ti
O
Ti
OH
δa(CH3)
υa,s(CH3)
32. Propene
and
H2
at
Au/TiO2
(123
K)
32
0.12
0.11
0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00
∆Absorbance
4000 3500 3000 2500 2000 1500 1000
Wavenumber / cm
-1
5
min.
8
min.
13
min.
17
min.
Propene
on
Au
/
Aerogel
TiO2
(123
K)
Resonance
Stabilized
Allyl
Ca/on
Reacts
with
TiO2
Bridge
Oxygens
Allyl
Ca'on
H2C
C
H
CH2
δ+
δ+
Ti
Ti
O
Ti
O
Ti
O
Ti
Ti
O
Ti3+
Ti3+
OH
O
H2C
C
H
C
H
Acrolein
υ(C=O)
at
1715
cm-‐1
is
assigned
to
acrolein
produced
from
allyl.
As
propene
is
converted
to
acrolein
this
peak
grows.
υ(C=O)
Acrolein
33. Propene
and
H2
at
Au/TiO2
(123
K)
33
0.12
0.11
0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00
∆Absorbance
4000 3500 3000 2500 2000 1500 1000
Wavenumber / cm
-1
5
min.
8
min.
13
min.
17
min.
Propene
on
Au
/
Aerogel
TiO2
(123
K)
Acrolein
Binds
at
Lewis
Acid
Sites
(Ti4+)
and
Reacts
with
Surface
-‐OH
Acrolein
Hydroxyla'on
of
the
TiO2
surface
by
water
reacts
with
acrolein
to
produce
propenal.
υ(C=O)
at
1682
cm-‐1
and
δa(CH3)
at
1349
cm-‐1
are
assigned
to
propenal.
Surface
Science,
2009
vol.
603
(7)
pp.
1010-‐1017
Propenal
Ti
O
Ti
O
Ti
H2C
C
H
C
O
H
Ti
O
Ti
O
Ti
O
CH2
H3C
C
H
OH
OH
O-‐
O-‐
H2O
υ(C=O)
Propenal
Acrolein
δa(CH3)
34. Propene
and
H2
at
Au/TiO2
(123
K)
34
0.12
0.11
0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00
∆Absorbance
4000 3500 3000 2500 2000 1500 1000
Wavenumber / cm
-1
5
min.
8
min.
13
min.
17
min.
Propene
on
Au
/
Aerogel
TiO2
(123
K)
Adsorbed
Propenal
Reacts
with
Ladce
Oxygen
to
Yield
CO
and
CO2
CO(g)
is
either
re-‐adsorbed
to
the
Au/TiO2
as
shown
earlier
or
spilled
over
onto
the
adjacent
TiO2
sample.
CO2(g)
also
either
adsorbs
to
the
Au/TiO2
as
carbonates
or
spills
over
to
the
TiO2
sample.
Propenal
Ti
O
Ti
O
Ti
O
CH2
H3C
C
H
Ti3+
Ti3+
Ti3+
CO
CO2
H2O
(Gaseous
and
Adsorbed)
CO(ads)
CO
Auδ+
CO
Auδ-‐
CO2(ads)
CO3
2-‐
(ads)
35. Summary
• A
variety
of
decorated
Au
/
Degussa
P25
TiO2
were
prepared,
with
some
catalysts
demonstra'ng
surprising
CO
oxida'on
ac'vity.
• CO
oxida'on
screening
suggested
Aerogel
oxide
supported
Au/TiO2
catalysts
are
less
ac've
than
their
decorated
counterparts.
• Aerogel
supported
Au
catalysts
s'll
demonstrate
high
ac'vity
for
H2
dissocia'on
and
propene
oxida'on.
35
36. Future
Work
• Further
experimenta'on
with
condi'ons
to
op'mize
decorated
Au/TiO2
catalysts.
• Study
condi'ons
(if
any)
that
can
cause
Aerogel
Au/TiO2
catalysts
to
selec'vely
epoxidize
propene.
• Beper
understand
mechanisms
for
propene
oxida'on
and
epoxida'on
on
both
decorated
and
Aerogel
Au/TiO2
catalysts.
36
37. Acknowledgements
• Prof.
John
R.
Morris
• Commipee
Members
– Prof.
Brian
M.
Tissue
– Prof.
Karen
J.
Brewer
– Prof.
Sungsool
Wi
• Kathy
Lowe
(Veterinary
School)
• Leslie
Owen
• Drs.
Jeremy
Pietron
and
Debra
Rolison
(Naval
Research
Laboratories)
• Army
Research
Office
• Members
of
the
Morris
Research
Group
37
38. Acknowledgements
• Prof.
John
R.
Morris
• Commipee
Members
– Prof.
Brian
M.
Tissue
– Prof.
Karen
J.
Brewer
– Prof.
Sungsool
Wi
• Kathy
Lowe
(Veterinary
School)
• Leslie
Owen
• Drs.
Jeremy
Pietron
and
Debra
Rolison
(Naval
Research
Laboratories)
• Army
Research
Office
• Members
of
the
Morris
Research
Group
– Dr.
Dimitar
Panayotov
(a.k.a.
Mitko)
38
42. CO
Screening:
Linear
Flow
Tube
42
42
6 mm Soft Glass Tube Nanoparticle Film
Type K Thermocouple
1/4 - 1/8" OD
Steel Tube Union
Ceramic Coating
Nichrome
Heating
Element
Aluminum
Tube
Cast Aluminum Enclosure
Reactor Heater
Nanoparticle Screening Tube
• Mixture
of
7:1
molar
ra'o
O2:CO
passed
through
sample
tube.
• Sample
tube
temperature
varied
from
200
to
600K.
• IR
spectra
recorded
from
2600
~1800
cm-‐1.
• CO2
peaks
integrated
from
2395
-‐
2280
cm-‐1.
Examples
of
CO
Screening
Tubes
(Au/TiO2)
43. Sample
Stage
Posi/oning
Precision
43
43
0.25
0.20
0.15
0.10
0.05
0.00
∆Absorbance
4000 3000 2000 1000
Wavenumber / cm
-1
Z = 14.46 mm
10 Spectra
RSD = 0.27% @ 2602 cm
-1
Z = 23.42 mm
10 Spectra
RSD = 0.25% @ 2602 cm
-1
9.5% (w/w) Au / TiO2
3.4% (w/w) Au / TiO2
S 0
S 1
S 2
FTIR HeNe
Laser Reflection
Z = 0 mm
Z = 14.16 mm
Z = 23.42 mm
Z-AxisTranslation
44. Au
Deposi/on
in
Progress…
44
44
S'rrer
Motors
Reflux
Air
Cooling
Reac'on
Tubes
(6)
Heated
Sand
Bath
S'rrer
Controller
Thermocouple
Well
PTFE
S'r
Vane
45. Post
Au
Deposi/on
Processing
45
45
• Nanopar'cles
transferred
to
centrifuge
tubes.
• Centrifuge
and
rinse
un'l
AgNO3
test
shows
no
Cl-‐
present
(~8
rinses).
• Rinsed
nanopar'cles
air
dried.
• All
processing
opera'ons
must
be
conducted
under
darkroom
condi'ons.
• Au(OH)3
reduced
to
Au0
immediately
prior
to
use.
46. Au
Assay
by
Atomic
Spectroscopy
46
46
‘Wet’
Au(OH3)
on
TiO2
Reduced
Au0
on
TiO2
Au0
Dissolu'on
in
HNO3
/
HCl
Heated
Acid
Diges'on
of
Au0
ICP-‐AES
Analyses
47. 2-‐Channel
Gas
Flow
Cell
47
47
N2
Purged
Flexible
Op'cal
Paths
X-‐Y
Transla'on
Stage
M
M
M
He O2 CO
Vent 1
Vent 2
Needle
Valve
Micrometer
Needle
Valve
NeedleValve
Rotometer
Low-Flow
Rotometer
Gas Flow
Splitter
Gas Flow
Splitter
F
B
FTIR
2-Channel
Flow Cell
Catalyst Screening Tube
Vent 3
Total Flow
180 mL/min
Total Flow
28 mL/min
Gas
Mixing
/
SpliTng
Manifold
48. Screening
Tube
Temperature
Control
48
48
Catalyst
Screening
Tube
Heaters
Gas
Flow
Subambient
Temperatures
Enclosure
LN2
Fill
49. Bulb
-‐
Type
Screening
Tubes
49
49
K-Thermocouple
Junction
6 mm OD
Tubing
2 cm OD Bulb
Glass Wool
Packing
Gas Expansion Zone
• Original
screening
tubes
were
‘wet-‐coated’
along
en're
length.
• Bulb
modifica'on
tubes
concentrate
nanopar'cles
in
gas
expansion
zone.
• Nanopar'cles
applied
dry
to
glass
wool.
• Bulb
and
glass
wool
packing
promote
gas
turbulence,
mixing,
and
contact
with
nanopar'cle
sample.
50. HV
Chamber
Upgrades
50
Corrugated Steel Flex Line
(Swagelok Tube Fittings)
Corrugated Steel Flex Line
( VCR Female Fittings)
Male - Male
VCR Union
VCR to
Swagelok
Union
VCR-FVCR-F
SS-4BK-VS1
VCR-FVCR-F
SS-4BK-VS1
VCR to
Swagelok
Union
VCR to
Swagelok
Union
Swagelok
Tee Fitting
Swagelok
Tee Fitting
SS-4H
Glass-to-Metal
Simulant Bulb
SS-4H
Glass-to-Metal
Simulant Bulb
SS-4H
Swagelok
Tee Fitting
SS-4H
Swagelok
to VCR-F
Weldment
PBaratron Sensor
SS-4H
Glass-to-Metal
Simulant Bulb
VCR to
Swagelok
Union
VCR-FVCR-F
SS-4BK-VS1
Swagelok
SS-4CS
Mini Cylinder
SS-4H
Swagelok
1/4 - 1/8
Reduncing
Union
1/8" Line from Gas
Mixing Manifold
To Vacuum Pump
Vacuum
Chamber
Manifold
Plate
Gas
Dosing
Manifold
and
Pressure
Monitoring
Vacuum
Gate
Valves
Pneuma/cs
Pneumatic
Gate Valve
Manual
Gate Valve
Chamber
Pump
Pump
Pressure
Sensor
Pressure
Sensor
( Side View )
51. HV
Chamber
Upgrades
51
Detector
Op'cs
FTIR
Source
Op'cs
IR
Op/cs
IR
Beam
Flag
52. HV
Chamber
Upgrades
52
Sample
Temperature
Control
Soiware-‐Controlled
Resis've
Hea'ng
LN2
Chamber/
Sample
Cooling
53. Au/TiO2
Methanol
Treatment
53
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
∆Absorbance
4000 3500 3000 2500 2000 1500 1000
Wavenumber / cm
-1
20
min.
40
min.
50
min.
75
min.
170
min.
200
min.
220
min.
1300
to
1150
cm-‐1:
adsorbed
carbonates
3900
cm-‐1:
free
-‐OH
loss
55. Gas-‐Phase
Propene
in
Vacuum
Chamber
55
0.01
0.00
∆Absorbance
4000 3500 3000 2500 2000 1500 1000
Wavenumber / cm
-1
Gaseous
CO
Gaseous
Propene
Features
0.9
Torr
1.4
Torr
No
Propylene
(Baseline
W-‐Mesh
Spectrum)
T
=
293
K
56. TiO2
Methanol
Treatment
56
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
∆Absorbance
4000 3500 3000 2500 2000 1500 1000
Wavenumber / cm
-1
8
min.
20
min.
30
min.
50
min.
70
min.
170
min.
200
min.
220
min.
57. Propene
and
H2
at
Au/TiO2
(293
K)
57
0.25
0.20
0.15
0.10
0.05
0.00
∆Absorbance
4000 3500 3000 2500 2000 1500 1000
Wavenumber / cm
-1
10
min.
20
min.
30
min.
40
min.
50
min.
60
min.
70
min.
80
min.
90
min.
1170
cm-‐1:
adsorbed
bicarbonate
1590
cm-‐1:
adsorbed
molecular
H2O
loss
of
-‐CH3
stretches
CO
on
Au
?
