Nanostructured electrochemical reactors for …control nano-scale control Cell current (mA) NOx...
Transcript of Nanostructured electrochemical reactors for …control nano-scale control Cell current (mA) NOx...
![Page 1: Nanostructured electrochemical reactors for …control nano-scale control Cell current (mA) NOx decomposition (%) @2001 @2003 Improved de-NOx efficiency for applied current by nano-](https://reader030.fdocuments.us/reader030/viewer/2022041110/5f0f5fc07e708231d443d791/html5/thumbnails/1.jpg)
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
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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
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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
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Environment purifying /Saving energy
NOx→N 2+O 2
NANOSTRUCTURED DE-NOx REACTOR
NOx/PM DECOMPOSITION
ELECTROCHEMICAL/THERMOELECTRIC MODULE
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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
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1. Ceramic electrochemical reactor for NOx decomposition
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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)
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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
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Improvement of de-NOx / current efficiency
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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
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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
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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
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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
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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
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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
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30
40
50
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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
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30
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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.
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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)
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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.
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GasGas
DCDC
Large size cell (10cm square)
Cell stack (20sheets) Image of a deNOx module of
diesel engine exhaust gas
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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%)
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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(%
)
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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
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Stack using 20 cells
Measurement of deNOx performance of a stack by large cells
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0
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0 200 400 600 800Power [mW]
NO
Con
vers
ion
[%]
C2H2
: 0 %: 0.2%: 0.3%
: 0 %: 0.2%: 0.3%
0
10
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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
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経過時間 (h)
NO 転
化率 (-)
Time(h)
NO
xco
nver
sion
(rat
io)
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1.0
1.2
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経過時間 (h)
NO 転
化率 (-)
Time(h)
NO
xco
nver
sion
(rat
io)
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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
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Selective reduction of NOx using our electrochemical cell
Exhaust gas Cleaned gas
N2
-
-
O2
NO
N2
DC
NOx-selective layer
O2- conductor
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2. Ceramic electrochemical reactor for PM (particulate matter) decomposition
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Cathode : 2NO + 4e- → N2 + 2O2-
Anode : C + 2O2- → CO2 + 4e-
Oxidation of graphite on Ca12Al14O33 / Ag composite anode
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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
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0
20
40
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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-
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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
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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
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3. Thermoelectric ceramic module for enhanced deNOx property by using waste heat energy
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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