Transcript
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-

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

Page 2: Nanostructured electrochemical reactors for …control nano-scale control Cell current (mA) NOx decomposition (%) @2001 @2003 Improved de-NOx efficiency for applied current by nano-

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

Page 3: Nanostructured electrochemical reactors for …control nano-scale control Cell current (mA) NOx decomposition (%) @2001 @2003 Improved de-NOx efficiency for applied current by nano-

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

Page 4: Nanostructured electrochemical reactors for …control nano-scale control Cell current (mA) NOx decomposition (%) @2001 @2003 Improved de-NOx efficiency for applied current by nano-

Environment purifying /Saving energy

NOx→N 2+O 2

NANOSTRUCTURED DE-NOx REACTOR

NOx/PM DECOMPOSITION

ELECTROCHEMICAL/THERMOELECTRIC MODULE

Page 5: Nanostructured electrochemical reactors for …control nano-scale control Cell current (mA) NOx decomposition (%) @2001 @2003 Improved de-NOx efficiency for applied current by nano-

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

Page 6: Nanostructured electrochemical reactors for …control nano-scale control Cell current (mA) NOx decomposition (%) @2001 @2003 Improved de-NOx efficiency for applied current by nano-

1. Ceramic electrochemical reactor for NOx decomposition

Page 7: Nanostructured electrochemical reactors for …control nano-scale control Cell current (mA) NOx decomposition (%) @2001 @2003 Improved de-NOx efficiency for applied current by nano-

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)

Page 8: Nanostructured electrochemical reactors for …control nano-scale control Cell current (mA) NOx decomposition (%) @2001 @2003 Improved de-NOx efficiency for applied current by nano-

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

Page 9: Nanostructured electrochemical reactors for …control nano-scale control Cell current (mA) NOx decomposition (%) @2001 @2003 Improved de-NOx efficiency for applied current by nano-

Improvement of de-NOx / current efficiency

0 50 100 150 200 2500

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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

20

30

40

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80

0 50 100 150 200 2500

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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

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.

Page 10: Nanostructured electrochemical reactors for …control nano-scale control Cell current (mA) NOx decomposition (%) @2001 @2003 Improved de-NOx efficiency for applied current by nano-

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)

Page 11: Nanostructured electrochemical reactors for …control nano-scale control Cell current (mA) NOx decomposition (%) @2001 @2003 Improved de-NOx efficiency for applied current by nano-

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.

Page 12: Nanostructured electrochemical reactors for …control nano-scale control Cell current (mA) NOx decomposition (%) @2001 @2003 Improved de-NOx efficiency for applied current by nano-

GasGas

DCDC

Large size cell (10cm square)

Cell stack (20sheets) Image of a deNOx module of

diesel engine exhaust gas

0

20

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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

Page 13: Nanostructured electrochemical reactors for …control nano-scale control Cell current (mA) NOx decomposition (%) @2001 @2003 Improved de-NOx efficiency for applied current by nano-

Stack using 20 cells

Measurement of deNOx performance of a stack by large cells

Page 14: Nanostructured electrochemical reactors for …control nano-scale control Cell current (mA) NOx decomposition (%) @2001 @2003 Improved de-NOx efficiency for applied current by nano-

0

10

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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)

Page 15: Nanostructured electrochemical reactors for …control nano-scale control Cell current (mA) NOx decomposition (%) @2001 @2003 Improved de-NOx efficiency for applied current by nano-

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

Page 16: Nanostructured electrochemical reactors for …control nano-scale control Cell current (mA) NOx decomposition (%) @2001 @2003 Improved de-NOx efficiency for applied current by nano-

Selective reduction of NOx using our electrochemical cell

Exhaust gas Cleaned gas

N2

-

-

O2

NO

N2

DC

NOx-selective layer

O2- conductor

Page 17: Nanostructured electrochemical reactors for …control nano-scale control Cell current (mA) NOx decomposition (%) @2001 @2003 Improved de-NOx efficiency for applied current by nano-

2. Ceramic electrochemical reactor for PM (particulate matter) decomposition

Page 18: Nanostructured electrochemical reactors for …control nano-scale control Cell current (mA) NOx decomposition (%) @2001 @2003 Improved de-NOx efficiency for applied current by nano-

Cathode : 2NO + 4e- → N2 + 2O2-

Anode : C + 2O2- → CO2 + 4e-

Oxidation of graphite on Ca12Al14O33 / Ag composite anode

Page 19: Nanostructured electrochemical reactors for …control nano-scale control Cell current (mA) NOx decomposition (%) @2001 @2003 Improved de-NOx efficiency for applied current by nano-

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

Page 20: Nanostructured electrochemical reactors for …control nano-scale control Cell current (mA) NOx decomposition (%) @2001 @2003 Improved de-NOx efficiency for applied current by nano-

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-

Page 21: Nanostructured electrochemical reactors for …control nano-scale control Cell current (mA) NOx decomposition (%) @2001 @2003 Improved de-NOx efficiency for applied current by nano-

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

Page 22: Nanostructured electrochemical reactors for …control nano-scale control Cell current (mA) NOx decomposition (%) @2001 @2003 Improved de-NOx efficiency for applied current by nano-

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

Page 23: Nanostructured electrochemical reactors for …control nano-scale control Cell current (mA) NOx decomposition (%) @2001 @2003 Improved de-NOx efficiency for applied current by nano-

3. Thermoelectric ceramic module for enhanced deNOx property by using waste heat energy

Page 24: Nanostructured electrochemical reactors for …control nano-scale control Cell current (mA) NOx decomposition (%) @2001 @2003 Improved de-NOx efficiency for applied current by nano-

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


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