Solid State Electrochemical Removal of Pollutants - … · Solid State Electrochemical Removal of Pollutants K.K. Hansen Department of Energy Conversion and Storage Technical University

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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Solid State Electrochemical Removal of Pollutants - … · Solid State Electrochemical Removal of Pollutants K.K. Hansen Department of Energy Conversion and Storage Technical University