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Ceramic electrochemical reactors are expected for their high performance on conversions of energy and substances; for examples, electric power generation (solid oxide fuel cells: SOFCs), synthesis of hydrogen, and decomposition and purification of environmental pollutants.
Development of novel electrochemical modules for deNOx/PM reactor by nanostructure control
Combination with thermoelectric ceramic modulefor harvesting of waste heat energy
Nanostructured electrochemical reactors for NOx/PM decomposition and micro SOFCs
Masanobu AwanoInstitute of Advanced Industrial Science and Technology(AIST)
Nagoya 463-8560, JAPAN
OECD Conference on Potential Environmental Benefits of Nanotechnology: Fostering Safe Innovation-Led Growth, Session 3. Clean Car Technology Paris, July 15-17, 2009
New type MicroSOFC development of high performance APU unit for vehicles by nano-micro structure control as clean energy source
Various applications of electrochemical reactor (O2--conducting ceramics )
e-
e-
O2-
Air
① H2 H2O (SOFC)② CH4 H2O + CO2 (SOFC)
e-
e-
③ NO N2 (de-NOX)④ H2O H2 (H2 generation)
Air
O2- O2-
O2⑤ CH4 CO + H2 (Syngas)⑥ O2 pumping⑦ CH4 CH3OH (GTL)⑧ C CO2
6th Pacific Rim Conference on Ceramic and Glass Technology, September 15th 2005, Hawaii, USA
Nitrogen oxides ( NOx ) in exhaust gas are known - to cause air pollution problems (acid rain, photochemical smog)- to give damage to human nerves and respiratory organs
The reduction of NOX emission has become one of thegreatest challenges in environment protection.
%100
NO2
50
0
A/F
14.3 14.5 14.7
C O
H C
%100
NO2
50
0
A/F
14.3 14.5 14.7
C O
H C
Active at higher PO2 atmosphere
%100
NO2
50
0
A/F
14.3 14.5 14.7
C O
H C
%100
NO2
50
0
A/F
14.3 14.5 14.7
C O
H C
Active at higher PO2 atmosphere
Japanese regulation
near zero-emission
Environment purifying /Saving energy
NOx→N 2+O 2
NANOSTRUCTURED DE-NOx REACTOR
NOx/PM DECOMPOSITION
ELECTROCHEMICAL/THERMOELECTRIC MODULE
Contents
1. Ceramic electrochemical reactor for NOx decomposition
2. Ceramic electrochemical reactor for PM (particulate matter) decomposition
3. Thermoelectric ceramic module for enhanced deNOx property by using waste heat energy
1. Ceramic electrochemical reactor for NOx decomposition
O 2熱電変換による電力供給
NO x
N 2
高温排ガス クリーンガス
ガス分子吸着サイト
多孔質触媒電極層
固体電解質
(酸素イオン 伝導体)
多孔質電極
O 2
O 2-
高温におけるNO x高選択性
e
e
O 2熱電変換による電力供給
NO x
N 2
高温排ガス高温排ガス クリーンガスクリーンガス
ガス分子吸着サイト
多孔質触媒電極層
固体電解質
(酸素イオン 伝導体)
固体電解質
(酸素イオン 伝導体)
多孔質電極
O 2
O 2-
高温におけるNO x高選択性
ee
ee
Oxygen as an inhibitor to
de-NOx reaction
Large amount of electrical current supply is required →difficulty to the application
Porous Cathode
Solid ElectrolyteOxygen ion conductor
Porous Anode
Catalytic Activation Site
Example: scheme of NOx purifying by an electrochemical cell(under excess oxygen coexistence such as diesel engine exhaust gas)
TEM image of an NiO and YSZ interface, and reaction model of selective NO molecule decomposition. The expected mechanism of the absorption and decomposition of N to Ni, and oxygen capturing and pumping in the region of high defects concentration is also displayed
nano redox-reaction zone
nano pores
2nmO-N
nano particles
O-ion →O2
YSZ
Exhaust gas N2
e-
Ni←NiONiOYSZ
nano-spacenano-space
Ni nanoparticles
high conc. oxygen defects layer
NOx m olecules
O2-(→O2) N2
NiOYSZ
nano-spaceTEM image of an NiO and YSZ interface, and reaction model of selective NO molecule decomposition. The expected mechanism of the absorption and decomposition of N to Ni, and oxygen capturing and pumping in the region of high
nano-spacenanonanonanonano -space-spacedecomposition of N to Ni, and oxygen capturing and pumping in the region of high
spacedecomposition of N to Ni, and oxygen capturing and pumping in the region of high
spacedecomposition of N to Ni, and oxygen capturing and pumping in the region of high
spacedecomposition of N to Ni, and oxygen capturing and pumping in the region of high
spacespacespacespacespacenano-space
Ni nanoparticles
high conc. oxygen defects layer
NOx m olecules
O2-(→O2) N2
Proposed Mechanism of Selective DeNOx Reaction
Improvement of de-NOx / current efficiency
0 50 100 150 200 2500
10
20
30
40
50
60
70
80oxygen 2%t=7000C
1000ppm-NOPt-13000CAg-8000CPd-8000C Pd-13000CPd-Pt-13000C
Literature
t=6000Coxygen 2% 1000ppm-NO
EC electrode
NO
xC
onve
rsio
n (%
)
Current (mA)0 50 100 150 200 250
0
10
20
30
40
50
60
70
80
0 50 100 150 200 2500
10
20
30
40
50
60
70
80oxygen 2%t=7000C
1000ppm-NOPt-13000CAg-8000CPd-8000C Pd-13000CPd-Pt-13000C
Literature
t=6000Coxygen 2% 1000ppm-NO
EC electrode
NO
xC
onve
rsio
n (%
)
Current (mA)0 50 100 150 200 250
0
10
20
30
40
50
60
70
80oxygen 2%t=7000C
1000ppm-NOPt-13000CAg-8000CPd-8000C Pd-13000CPd-Pt-13000C
Literature
t=6000Coxygen 2% 1000ppm-NO
EC electrode
NO
xC
onve
rsio
n (%
)
Current (mA)0 50 100 150 200 250
0
10
20
30
40
50
60
70
80
0 50 100 150 200 2500
10
20
30
40
50
60
70
80oxygen 2%t=7000C
1000ppm-NOPt-13000CAg-8000CPd-8000C Pd-13000CPd-Pt-13000C
Literature
t=6000Coxygen 2% 1000ppm-NO
EC electrode
NO
xC
onve
rsio
n (%
)
Current (mA)
Energy efficiency of
ordinary catalyst system
previous results
meso-scale
control
nano-scale
control
C ell current (m A)
NO
xde
com
posi
tion
(%)
@2001
@2003
0 50 100 150 200 2500
10
20
30
40
50
60
70
80oxygen 2%t=7000C
1000ppm-NOPt-13000CAg-8000CPd-8000C Pd-13000CPd-Pt-13000C
Literature
t=6000Coxygen 2% 1000ppm-NO
EC electrode
NO
xC
onve
rsio
n (%
)
Current (mA)0 50 100 150 200 250
0
10
20
30
40
50
60
70
80
0 50 100 150 200 2500
10
20
30
40
50
60
70
80oxygen 2%t=7000C
1000ppm-NOPt-13000CAg-8000CPd-8000C Pd-13000CPd-Pt-13000C
Literature
t=6000Coxygen 2% 1000ppm-NO
EC electrode
NO
xC
onve
rsio
n (%
)
Current (mA)0 50 100 150 200 250
0
10
20
30
40
50
60
70
80oxygen 2%t=7000C
1000ppm-NOPt-13000CAg-8000CPd-8000C Pd-13000CPd-Pt-13000C
Literature
t=6000Coxygen 2% 1000ppm-NO
EC electrode
NO
xC
onve
rsio
n (%
)
Current (mA)0 50 100 150 200 250
0
10
20
30
40
50
60
70
80
0 50 100 150 200 2500
10
20
30
40
50
60
70
80oxygen 2%t=7000C
1000ppm-NOPt-13000CAg-8000CPd-8000C Pd-13000CPd-Pt-13000C
Literature
t=6000Coxygen 2% 1000ppm-NO
EC electrode
NO
xC
onve
rsio
n (%
)
Current (mA)
Energy efficiency of
ordinary catalyst system
previous previous previous resultsresultsresults
previous results
meso-scale
control
nano-scale
control
C ell current (m A)
NO
xde
com
posi
tion
(%)
@2001
@2003
Improved de-NOx efficiency for applied current by nano- and meso-scale structurally controlled electrochemical cells in comparison with previous results.
Microstructure development of electro-catalytic electrode by the factors of applied voltage and temperature
YSZ(covering layer)
NiO+YSZ(catalytic electrode)
YSZ+Pt(electrode)
YSZ(electrode)
Optimization of Nano-space reaction zone (applied voltage)
Microstructure development of electrocatalytic electrode at the interface of NiO-YSZ grain boundaries as a function of applied voltage; (a)before applying current, (b)voltage 1V, (c)1.5V,(d)2V,(e)2.25V,(f)2.5V,(g)2.75V,(h)3V.
GasGas
DCDC
Large size cell (10cm square)
Cell stack (20sheets) Image of a deNOx module of
diesel engine exhaust gas
0
20
40
60
80
100
0 10 20 30 40 50
データ 14 7:26:24 2003/09/18
%NFC-4-1 500C
%NFC-7-2 500C
%NFC-7-2 600C
%NFC-4-1 600C(2)
%NFC-10-2 500C
電流密度 (mA/cm2)
NO
x転換
率(%
)
実験セルの電流効率(1.65%)
0
20
40
60
80
100
0 10 20 30 40 50
データ 14 7:26:24 2003/09/18
%NFC-4-1 500C
%NFC-7-2 500C
%NFC-7-2 600C
%NFC-4-1 600C(2)
%NFC-10-2 500C
電流密度 (mA/cm2)
NO
x転換
率(%
)
0
20
40
60
80
100
0 10 20 30 40 50
データ 14 7:26:24 2003/09/18
%NFC-4-1 500C
%NFC-7-2 500C
%NFC-7-2 600C
%NFC-4-1 600C(2)
%NFC-10-2 500C
電流密度 (mA/cm2)
NO
x転換
率(%
)
実験セルの電流効率(1.65%)
deNOx property of large size cells
Current efficiency of typical small cell
Cell current (mA/cm2)
NO
x de
com
posi
tion
(%)
Sequential development of the electrochemical cell from laboratory to a real application and NOx decomposition properties of a large size electrochemical cell (10cm square). Inserted photograph is a stack model of 20 cells assembled for exhaust gas purification of vehicles.
Research for application of de-NOx cell to diesel engine exhaust gas purification
Stack using 20 cells
Measurement of deNOx performance of a stack by large cells
0
10
20
30
40
50
60
70
0 200 400 600 800Power [mW]
NO
Con
vers
ion
[%]
C2H2
: 0 %: 0.2%: 0.3%
: 0 %: 0.2%: 0.3%
0
10
20
30
40
50
60
70
0 200 400 600 800
Power [mW]
NO
Con
vers
ion
[%]
SO2
: 0ppm: 3ppm:30ppm
: 0ppm: 3ppm:30ppm
Durability under operating conditions
No degradation for CO,CH / high conc.SOx causing damage in the electrodeInitial degradation less than 10% ---stable for prolonged operation over 200h
0.0
0.2
0.4
0.6
0.8
1.0
1.2
0 4 8 12 16 20 24
経過時間 (h)
NO 転
化率 (-)
Time(h)
NO
xco
nver
sion
(rat
io)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
0 4 8 12 16 20 24
経過時間 (h)
NO 転
化率 (-)
Time(h)
NO
xco
nver
sion
(rat
io)
Nano-wire electrode
Exhaustgas
Cleanair
Electrochemical reaction
Nano particles
Electric wire to power source
wire
electrolyte
cathode
anode
power
Electrochemical cell operation at low temperature by introduction of a nano-wired structure
DeNOx property at 250゚C under 20%O2coexistence
Network of metallic nano- wires between electrolyte micron particles
Selective reduction of NOx using our electrochemical cell
Exhaust gas Cleaned gas
N2
-
-
O2
NO
N2
DC
NOx-selective layer
O2- conductor
2. Ceramic electrochemical reactor for PM (particulate matter) decomposition
Cathode : 2NO + 4e- → N2 + 2O2-
Anode : C + 2O2- → CO2 + 4e-
Oxidation of graphite on Ca12Al14O33 / Ag composite anode
Mechanism of Oxidation using Active oxygen on Anode of Electrochemical Reactor
YSZ,CGO
O2-
Porous Anode
C12A7(O*)
O*
e-
NO
e-Cathode
Graphite (PM)
CO2
Supplying
O Ion to Catalysts
Reaction
Between C and O*
at Anode
+
-
Pump O ion into YSZ
from NO
High Partial Voltage
1µm
Microstructure of Ag/Ca12Al14O33/8YSZ
Porous Anode
1µm
Microstructure of Ag/Ca12Al14O33/8YSZ
Porous Anode
Nanostructure
controlled
electrode
0
20
40
60
80
100
-10
0
10
20
30
40
50
0 0.5 1 1.5 2 2.5Voltage /V
Deg
ree
of C
O2
form
atio
nB
y gr
aphi
te o
xida
tion(
ppm
)475℃NOx 100ppm(50ml/min)Graphite 0.8mg
NO
x de
com
posi
tion
(%)
Anode
Cathode
Electrolyte
CGO + AgAg
CGO
CGO + NiOAg
graphite
Simultaneous clean up of solid carbon (PM) and nitrogen oxide (NOx)
cell surface through electrochemical reaction
Reducing electrode : 2NO + 4e- → N2 + 2O2-
Oxidizing electrode : C + 2O2- → CO2 + 4e-
Amount of Applied Charge (c)
0 100
0 50 100 150 200
Pt + YSZ
Re
move
d G
ra
ph
ite
(m
ol)
Pt+YSZ+Ca12Al14O33(14%)
2x10-5
1x10-5
Theoretical Value
( C + O2-
= CO2
+2e-)
Effect of C12A7 addition on Reaction Rate
1.6 g/hElectrochemical Reactor(ca 1 m2)
Estimated Amount of PM
from Exhaust Gas
1.9 g/h 1.199nm
12CaO 7Al2O32 3
Cubic2000cc Diesel Engine
Table 1. Amount of electrochemical decomposition of graphiteon the surface of anode at 2.5V and 475 q C.
Anode material Decomposed graphite(mol/cm2-h)
Pt+8YSZ
Ag+8YSZ
Ca12Al14O33+8YSZ
0.3x10-5
0.7x10-5
1.3x10-5
3. Thermoelectric ceramic module for enhanced deNOx property by using waste heat energy
Thermoelectric conversion
High-T
Low-T
N-type
Current
Heat
ΔTP-type
electron holeHigh-T
Low-T
N-type
Current
Heat
ΔTP-type
electron hole
Thermoelectric conversion
High-T
Low-T
N-type
Current
Heat
ΔTP-type
electron holeHigh-T
Low-T
N-type
Current
Heat
ΔTP-type
electron hole
NOx
O2
N2
T
e-
Thermo-electric Ceramic module
ElectrochemicalCeramic Reactor
Power generation for Electrochemical Reaction
Exhausted Gas
heating
Application of thermoelectric energy conversion for supplying electric power from waste heat
30% torque15%operation
40% radiator Total energy 100%
5% Pressure / Friction loss
Electric components & system
Battery
5-10% Alternator (efficiency<50%)
30% Exhaust gas
FUEL
30% torque15%operation
40% radiator Total energy 100%
5% Pressure / Friction loss
Electric components & system
Battery
5-10% Alternator (efficiency<50%)
30% Exhaust gas
FUEL
Waste heat energyWaste heat energyWaste heat energyWaste heat energy