Carbon Dioxide Reduction with Hydrogen
Using Photonanocatalyst
Nor Aishah Saidina Amin
Chemical Reaction Engineering Group (CREG)
N01-Faculty of Chemical Engineering
Universiti Teknologi Malaysia
UTM 81310 Johor Bahru, Johor Malaysia.
noraishah@cheme.utm.my
www.cheme.utm.my
Presentation Outline
•
•
•
•
•
•
Background of Study
Research Scope
Methodology
Results and Discussions
Conclusions
Acknowledgement
Background
Majour
contributors
Global anthropogenic greenhouse gas emissions
[http://en.wikipedia.org/wiki/Greenhouse_gas]
broken
down
into
8
different
sectors.
Background
• Energy consumption has been
increasing with world
population
• Fossil fuels are the main source
of energy supply
• Reserves of fossil fuel is fossil
depleting Combustion of fossil
fuels generates greenhouse
CO2
Fossil fuel
Combustion
Greenhouse
Gas CO2
Energy
Crisis and
Global
Warming
Mitigation of
Greenhouse Gas CO2
How?
(i) How CO2 can be re-utilized easily and efficiently
(ii) How CO2 can be recycled or converted to fuels
Recycling of CO2 to Fuels
Conversion of
Carbon Dioxide
Reforming
(CO, H2)
Plasma
reforming
Thermal
reforming
•
•
•
•
Required higher
temperature and
pressure
Thus, instability of
catalysts and
uneconomical
Electrochemical
Biological
Photocatalysis
(EtOH, HCOOH,
CO)
(EtOH, sugar,
CH3COOH)
(CO, CH4, HC,
MeOH, HCOOH)
Required
electricity for
the process
Required high
voltage and
cause fouling on
electrode
surface
•
•
•
•
Required
biocatalyst
Required very
specific
conditions
Specific
bioreactors
Short life time
of biocatalyst
• Workable under
solar energy
• Economical
process
• Required normal
temp and
pressure
• Sustainable
process
• High stability of
catalysts
6
6
Photocatalysis
System
Reducing
Agent
•
•
•
•
Can easily be oxidized
Can reduced CO2
Can help to produce
desire products
Semiconductor
Material
Photocatalytic
Reactor
• Have good photoactivity
• Higher photonic Efficiency,
• Higher charger production
• higher illumination area
• Lower charges recombination
Efficient
Phototechnology
for CO2 Reduction
What we are Offering??
Hydrogen
Reductant
Plasmonic
PhotoCatalysts
Monolith
Photoreactor
Hydrogen Reducing Agent
hv , catalyst
CO2  H 2 
 CO + H 2O
hv , catalyst
2CO2 + 6 H 2 
 C2 H 4 + 4H 2O
hv , caalyst
2CO2 + 7H 2 
 C2 H 6 + 4H 2O
hv , catalyst
3CO2 +9H 2 
 C3H 6 + 6H 2O
hv , catalyst
3CO2 +10H 2 
 C3H8 + 6H 2O
• Hydrogen is good
reducing agent for CO2
conversion via RWGS
(RWGS reaction)
reaction
• Syngas (CO and H2) can
be used for F-T process
Single step
• CO2 reduction with H2
F-T process
can also be produced
hydrocarbons in single
step.
• H2 for CO2 reduction
can be obtained from
water splitting
9
Monolith Photoreactor
√ It has microchannels of
√
√
√
Monolith
 Honeycomb, foam or fibers structure
 Channels have square, circular, and triangular
 Density varies from 9 to 600 cells per square inch
(CPSI)
 Higher void fraction (65 to 91 %) compared to
packed bed catalyst (36 to 45 %)
√
√
√
√
different shape and sizes
Light
distribution
is
effective over the catalyst
surface.
Larger surface area to
reactor volume.
Catalyst loading is higher
with enhanced stability.
Very suitable for systems
operating in gas- solids.
Larger conversion with
improved selectivity.
Higher
quantum
efficiency
Higher light distribution
over the catalyst
10
Plasmonic Au/TiO2 Photonanocatalyst
LSPR of Au
(a)
(b)
TiO2
 When the incident light is (in the
range of LSPR) absorbed by Aumetal NPs, electric filed (e-/h+ ) is
produced (Fig. a)
 Plasmonic electrons are transferred
to TiO2 CB band for its activation
(Fig. B)
 Efficient separation of electrons
 Efficient CO2 reduction via SPR
effect
 Higher efficiency for trapping
electrons
 Au can enhance efficiency under
UV and visible light
11
Experimental Setup
Monoliths
Schematic of Monolith Reactor
Experimental Rig
Catalyst Preparation and Coating
Ti (C3H7O)4
+ isopropanol
Aging
Dried at 80 oC
for 24 h
Hydrolysis
Acetic acid
+ isopropanol
Au-loading
Gold chloride
+ isopropanol
Dip-coating
Monolith
Drying and
Calcination
Calcined at 500oC
for 5h @ 5oC/min
SEM and TEM Analysis
TEM (Au/TiO2)
SEM
Front view
TiO2
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•
•
Side View
Au/TiO2
Uniform coating of catalysts over the
monolith surface
TiO2 particles are spherical in shape
and uniform size
Au/TiO2 have mesoporous structure
 TEM images of Au/TiO2 exhibit
uniform particle size and mesoporous
structure of TiO2
 TiO2 d-spacing confirmed anatase
TiO2.
XRD, BET and UV-Vis Analysis
(a)
A
A=anatase
A
10
20
Volume adsorbed (cm3/g at STP)
0.2% Au-TiO2
Intensity (a.u)
XRD
160
30
40
0.3% Au-TiO2
0.5% Au-TiO2
A A
50
60
70
0.3% Au/TiO2
Absorbance (a.u)
0.5% Au/TiO2
Plasmon effect
UV-Vis
400
500
Wavelength (nm)
120
BET
100
80
60
40
20
600
700
0.2
0.4
0.6
0.8
1.0
Relative pressure (P/Po)
TiO2
300
0.5 wt.% Au/TiO2
0.0
(c)
(b)
0.3 wt.% Au/TiO2
140
0
80
2-Theta (degree)
200
TiO2
TiO2
800
(a) Anatase phase in TiO2 and Au/TiO2
samples
(b) N2 adsorption-desoprtion plots show
isothersms of type IV, confirming
mesoporous materials of TiO2 and
Au/TiO2
(c) UV-Visible analysis confirmed
Plasmonic effect in Au/TiO2 catalyst
Summary
of Analysis
Table 1
Catalysts
TiO2
0.3 wt.% AuTiO2
0.5 wt.% AuTiO2
BET
BJH
surface area adsorption
(m2/g)
surface area
(m2/g)
Nanocatalyst
BJH
pore volume
(cm3/g)
Crystallite
size
(nm)
Band gap
energy
(eV)
43
46
52
58
0.134
0.23
19
17
3.12
3.03
47
74
0.24
18
2.93
Table 2
Element
Ti2p
B.E (eV)
459.50
State
Ti4+
Au4f
465.20
83.86
Au
O1s
88.12
530.72
O-O
C1s
532.94
284.60
O-H
C-C
286.05
C-O
 Au has no effect on BET
surface area
 Au has no effect on
Crystallite size
 Band gap energy shifted to
visible region in Au/TiO2
 Gold was present over TiO2
in metal state
Photoactivity Test of Continuous
CO2 Reduction to CO
(a) CO production
TiO2
16000
0.3% Au-TiO2
Yied of CH4 (µmole g-catal.-1)
0.5% Au-TiO2
0.7% Au-TiO2
-1
Yield of CO (µmole g-catal. )
TiO2
22
0.2% Au-TiO2
14000
(a) CH4 production
24
12000
10000
8000
6000
4000
2000
0.2% Au-TiO2
20
0.3% Au-TiO2
18
0.5% Au-TiO2
16
0.7% Au-TiO2
14
12
10
8
6
4
2
0
0
0
2
4
6
8
Irradiation time(h)
10
0
2
4
6
8
10
Irradiation time (h)
Fig. Effects of Au-loading and irradiation time on CO2 reduction with H2 at CO2/H2 ratio 1.0, molar flow rate
20 mL/min, and temperature 100oC; (a) CO production, (b) CH4 production.
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Plasmonic Au/TiO2 registered significantly
enhanced CO production activity over irradiation
time
Optimum Au-loading of 0.5%Au
was
determined
Maximum yield of CO was 12445 µmole gcatal.-1
Steady sate process achieved after 2h of
(a) Maximum production of CH4 initially
(b) CH4 production decreased due to photooxidation back into CO2 by O2 produced over
catalyst surface
(c) Saturation of catalyst sites with intermediate
species or deactivation of catalyst
(d) photo-reduction of products back to CO2.
Summary of Results
(a)
CO
(b)
TiO2
0.5 wt.% Au/TiO2
0.5% Au/TiO2
4000
80
CO selectivity
92% to 99%
3500
3000
Selectivity (%)
Yield rate (µmole g-catal-1 h-1)
4500
100
CH4
318
fold
2500
2000
60
40
1500
1000
20
500
TiO2
0
0
TiO2
0.2% Au-TiO2
0.3% Au-TiO2
0.5% Au-TiO2
0.7% Au-TiO2
Photocatalysts
Fig. (a ) Yield rates of products over Au/TiO2
catalysts
C2H4
C2H6
CH4
CO
Products
Fig. (b) Selectivity of products over
Au/TiO2 catalysts.
Catalyst Stability Test
a= CO production
14000
12000
8
0.6
Cycle R-1
Cycle R-2
Cycle R-3
7
CH4
Cycle R-1
Cycle R-2
Cycle R-3
C2H6
0.5
8000
6000
Yield of C2H6 (ppm)
6
10000
Yield of CH4 (ppm)
Yield of CO (ppm)
b= hydrocarbons production
Cycle R-1
Cycle R-2
Cycle R-3
5
4
3
0.4
0.3
0.2
4000
2
0.1
2000
1
0.0
0
0
0
0
2
4
6
8
10
2
4
6
Irradiation time (h)
8
10
0
2
4
6
Irradiation time (h)
Irradiation time (h)
(a) In the cyclic runs over prolonged irradiation time, higher stability of
catalysts
(b) In second and third cycles, photoactivity slightly reduced
(c) Decreased in photoactivity of Au/TiO2 catalyst was possibly due to active
sites blockage with intermediate species.
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10
Conclusions
 Enhanced efficiency of monolith photoreactor for CO2






reduction to fuels
Efficient CO2 reduction with H2 to CO and HCs over
Au/TiO2.
Yield of CO production over Au/TiO2 increased to 318
times higher than TiO2
Selectivity of CO production reached above 99% by Au
Enhanced Au/TiO2 activity was due to plasmonic effect
Efficient trapping of electrons and inhibited charges
recombination by Au-metal
Tests revealed prolonged stability of Au/TiO2 in cyclic
runs.
Acknowledgements
 Ministry of Higher Education (MOHE) Malaysia for financial
support under NanoMite LRGS (Long-term Research Grant
Scheme , Vot 4L839),
 Universiti Teknologi Malaysia (UTM) for the RUG (Research
University Grant, Vot 02G14) and
 FRGS (Fundamental Research Grant Scheme, Vot 4F404).
THANK YOU FOR YOUR ATTENTION
Chemical Reaction Engineering Group (CREG)
N01-Faculty of Chemical Engineering
Universiti Teknologi Malaysia
UTM 81310 Johor Bahru, Johor Malaysia.
noraishah@cheme.utm.my
www.cheme.utm.my/staff/noraishah