solid state electrochemical removal of pollutants - … · solid state electrochemical removal of...

Solid State Electrochemical Removal of Pollutants

K.K. Hansen

Department of Energy Conversion and Storage

Technical University of Denmark, DTU

e-mail: [email protected]

DTU Energy Conversion, Technical University of Denmark

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Outline

• Introduction

• Motivation

• The idea

• History/literature

• Work at DTU

– Reduction of NOx

– Oxidation of C3H6

• Conclusion/Outlook

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3 27-01-14

Sources and main pollutants

• Many sources of flue gas and exhaust gas

• Major pollutants are:

• Particulate matter

• sulphur oxides

• nitrogen oxides

• carbon monoxide

• hydrocarbons



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Motivation

• Why are we pursuing this technology?

– Competitive (no noble metals, low fuel penalty, space requirements, highly effective)

– Expertice in functional ceramics and processing

– Expertice in electrochemistry

Kilde: Hamamoto, K. 2009



Electrochemical removal of pollutants

• Current is used to drive the processes; no extra chemicals!

• Cathode

2NO + 4 e- → N2 + 2 O2-

2NO + 2 e- → N2O + O2-

O2 + 2 e- → 2 O2-

• Anode:

C + 2 O2- → CO2 + 4 e-

CO + O2- → CO2 + 2 e-

C3H6 + 9 O2- → 3CO2 + 3H2O + 18 e-

2 O2- → O2 + 4 e-

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Power consumption of an electrochemical reactor

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P =U*I



Literature

• Low current efficiency on noble metals

– Competing reduction of oxygen at cathode

• Addition of adsorption layer increases activity and current efficiency

– RuO2 on silver; 13% current efficiency (Iwayama et al)

– K/Pt/Al2O3 on NiO/Ni; 12% current efficiency (Hamamoto et al)

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Tubular reactor scheme Zoom on the sample position

Image of the whole test-set up

Test set-up

Electrochemical, Catalytic Activity and Structural Characterization

Catalytic activity; CLD, MS, GC

Electrochemical activity; EIS, CV

Cells: Electrolyte supported or porous cell stacks (self supported)

Temperature range: 300-500 oC

Gas compositions: 1000 ppm NO or 1000 ppm C3H6 + 10% O2

Experimental Setup/Conditions



Ni-electrode (1000 ppm NO, 2% O2, -2.5V)

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J. Shao, K.K. Hansen, J. Solid State Electrochem., 16 3331 (2012)



K/Pt/Al2O3|Ag (0.1% NO, 10% O2, 400 oC)

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-E / V

0.50 0.75 1.00 1.25 1.50 1.75

Convers

ion /

%

0

10

20

30

40

50

Curr

ent

eff

icie

ncy /

%

0

2

4

6

8

10

12

14

16

Conversion

Current effciency

J. Shao, K. Kammer Hansen, J. Electrochem. Soc., 160 H294 (2013)



Power consumption (400 oC)

• P = U*I

–1.4 l diesel engine, 2500 rpm, 52 kW, 500 ppm NOx

–Power consumption: 2 kW

• Further reduction of power consumption needed.

• Area:

–16.3 m2, 400 cells, (20*20 cm2), length: 0.2 m

• Further increase of activity needed

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Different cell structures

12

CGO

LSM|CGO

LSM|CGO

Electrochemical cell

Infiltrated with BaO nano particles

Coated with Ba|Pt|Al2O3

adsorption layer

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Ba/Pt/Al2O3|LSM at 450 oC in 0.1% NO, 10% O2

13

DC Square wave

Significantly improved the NOx removal properties above 350 oC

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J. Shao, K. Kammer Hansen, J. Mater. Chem. A, 1 7137 (2013)



A Porous cell stack

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Gas iii



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SEM of a 5 times Ba-infiltrated cell stack



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The use of a storage compound

LSM15

BaO

Anodic polarization

LSM15

Ba(NO3)2

Cathodic polarization

LSM15

BaO

N2

O2-

NO + O2



Non-impregnated LSM15-CGO10 cell stack

0

200

400

600

800

1000

1200

1400

1600

1800

2000

0 100 200 300 400 500 600 700 800

Co

nc.

[pp

m]

Time [min]

NOx concentration

-3V -5V -7V -9V

Polarisation at 400 oC in 1000 ppm NO +10% O2

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BaO impregnated LSM15-CGO10 cell stack

0

500

1000

1500

2000

0 200 400 600 800 1000

Co

nc.

[pp

m]

Time [min]

NOx concentration

0

100

200

300

400

500

600

700

0 200 400 600 800 1000

Co

nc.

[pp

m]

Time [min]

N2 concentration

-3V

-3V -3V

-3V -5V -5V

-5V -5V

-7V -7V -9V

-7V -7V

-9V Polarisation NOx conversion Current efficiency

[%] [%]

-3V (a) 0 0

-5V (a) 15 6

-7V (a) 41 9

-9V (a) 61 8

-7V (b) 49 11

-5V (b) 21 9

-3V (b) 2 2

Polarisation at 400 oC in 1000 ppm NO +10% O2

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Infiltration of O-2 conductor: CGO10

350 400 450 500

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

0.11

0.12

r C3

H6 (m

ol(

s*g

))

Temperature (°C)

CGO10

-Tr

CGO10

-water

backbone

30 h polarization

2.7 % w/w loading (1 step)

1000 ppm C3H6 , 10% O2 , O.C.V

• it is possible to observe an increase of

reaction rate after 30 hrs of test;

• the CGO10 infiltration improve the

reaction rate towards propene oxidation

as measured at OCV;

200 400 600 800 1000

0.98

1.00

1.02

1.04

1.06

1.08

1.10

1.12

1.14

1.16

1.18

1.20

1.22

r/r 0

applied voltage (mV/cell)

backbone

CGO10

-Tr

CGO10

-waterT= 450ºC

200 400 600 800 1000

1.02

1.05

1.08

1.11

1.14

1.17

1.20

1.23

1.26

r/r 0

applied voltage (mV/cell)

backbone

CGO10-Tr

CGO10-water

Rate enhancement ratio (ρ)

26.4 %

T= 350ºC

48.7 %

37.2 %

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Activity of electrodes with Co substitution 3 % Co at the B-site (La0.85Sr0.15)0.99Co0.03Mn0.97O3-δ

Doping with Co on B-site gives much higher electrochemical activity and

reduces the polarisation resistance.

300 oC, 0.1% NO + 10% O

2 in Ar

E [V]

-5 -4 -3 -2 -1 0 1 2 3 4 5

I [A

cm

-2]

-0.003

-0.002

-0.001

0.000

0.001

0.002

0.003

LSM/CGO

LSMCo/CGO

400 oC, 0.1 % NO + 10 % O

2 in Ar

Z' [ cm2]

0 2000 4000 6000 8000 10000 12000 14000 16000 18000 20000

-Z''

[cm

2]

0

2000

4000

6000

8000

LSM/CGO

LSCoM/CGO

Temp Imax(LSCoM)/Imax(LSM)

300 °C 28

400°C 9

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Mg + Fe infiltration

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Catalytic Activity of La0.65Sr0.35MnO3+

0

20

40

60

80

100

150 200 250 300 350 400 450 500

NO to N2

NO to NO2

C3H

6 to CO

2

T / oC

Conver

sion /

%



Formation of NO2

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0

25

50

75

100

100 200 300 400 500 6000

1x10-6

2x10-6

3x10-6+propene

-propene

Calculated

T / oC

Am

ount

NO

2 f

orm

ed /

%

S



NO2 reduction

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73.8%

38.4%

73.8%

38.4%

7.4%

27.4%

7.4%

27.4%



Conclusions

• NOx removal down to 300 oC

• CE at 400 oC: 15 %, with a silver based electrode

• Oxidation of propene shown possible

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The group

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Kent Kammer Hansen Frederik Berg Nygaard

Kjeld Bøhm Andersen Rebecka Werchmeister

Marie Lund Traulsen Anja Zarah Friedberg Jing Shao Davide Ippolito Cristine Grings Schmidt

Janet Bentzen

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