Hydrocarbon electrolytes with nitrile groups for direct methanol fuel cells

(1)

https://doi.org/10.4224/21085172

Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n’arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca.

Questions? Contact the NRC Publications Archive team at

PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information.

https://publications-cnrc.canada.ca/fra/droits

L’accès à ce site Web et l’utilisation de son contenu sont assujettis aux conditions présentées dans le site LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D’UTILISER CE SITE WEB.

READ THESE TERMS AND CONDITIONS CAREFULLY BEFORE USING THIS WEBSITE.

https://nrc-publications.canada.ca/eng/copyright

NRC Publications Archive Record / Notice des Archives des publications du CNRC :

https://nrc-publications.canada.ca/eng/view/object/?id=8a520a42-f9c2-4fab-8a42-5676eb9aa921

https://publications-cnrc.canada.ca/fra/voir/objet/?id=8a520a42-f9c2-4fab-8a42-5676eb9aa921

NRC Publications Archive

Archives des publications du CNRC

For the publisher’s version, please access the DOI link below./ Pour consulter la version de l’éditeur, utilisez le lien DOI ci-dessous.

Access and use of this website and the material on it are subject to the Terms and Conditions set forth at

Hydrocarbon electrolytes with nitrile groups for direct methanol fuel

cells

Hürter, Stefan; Müller, Martin; Guiver, Michael D.; Scoles, Ludmila; Stolten,

Detlef

(2)

Stefan Hürter

Martin Müller, Michael D. Guiver, Ludmilla Scoles, Detlef Stolten

M it glied der H elm holt z -Gem eins c haf t

Hydrocarbon Electrolytes with Nitrile

Groups for Direct Methanol Fuel Cells

(3)

Outline



Characteristics of a DMFC system



New membranes for DMFCs



Structure



Properties



Application of membranes in DMFC applications



Different MEA- preparation procedures



MEA- assembling by hot pressing

(4)

DMFC System: Introduction

Characteristics (DMFC V3.3)

Membrane material: Nafion 115

Stack temperature: 60 - 70

°C

Fuel: pure methanol

Fuel utilization: ~ 65 %

Efficiency FC: ~ 30 %

(5)

DMFC: Function and Characteristics

Target:

Decrease of MeOH- and H

₂

O-Permeation through utilization of sulfonated

Poly(Ether Ether Nitriles)



~ 30% Fuel loss during operation due to

methanol permeation



Reduction of fuel efficiency



Water permeation during operation



Large amount of water which has to

be recycled within system

(6)

Sulfonated Poly(aryl ether ether nitrile)s-sPAEENs

Kim, Kim, Guiver, Pivovar,

J. Membrane Sci. 321 (2008) 199

Alternative Membranematerial: Structure

Target:

Low water uptake

 Low MeOH- and H

₂

O permeation

High proton conductivities

 Low cell resistance

Nafion

Journal of Membrane Science 326

(7)

Testing conditions:

Drying of membrane: 6h at 60

°C

Wetting of sample for 3h at 80

°C, then for 24h at RT in deionized water

Calculation of WU by remeasuring the weight of the sample (dry and wet)

Water Uptake: sPAEEN-membranes

Membrane- Electrode- Assembly

(MEA)

H

+

Crossover

CH

₃

OH / H

₂

O

e

–

e

–

Nafion 115: DuPont product information

0

10

20

30

40

50

60 m-sPAEEN 57

HQ-sPAEEN 53

W

ater Uptake

[(m

w

e

t

-m

d

ry

)/m

d

ry

] [%]

Nafion 115

(8)

20

40

60

80

100

0.00

0.05

0.10

0.15

0.20 Specific Conductivit

y [S/cm]

Temperature [°C]

Nafion 115

HQ-sPAEEN 53

m-sPAEEN 57

Degree of

sulfonation

[n/(n+m)]

IEC calc.

[meq/g]

Thickness

[µm]

Areic membrane

resistance at 70

°C

**[Ohm*cm**

2 _]

Nafion 115

n.a.

0.89

127

0.085 HQ-sPAEEN

53

1.84

39

0.043 m-sPAEEN

57

1.80

40

0.04 Conductivity sPAEEN-Membranes

Membrane- Electrode- Assembly

(MEA)

H

+

Crossover

CH

₃

OH / H

₂

O

e

–

e

–

Conductivity

S [S/cm] = d / (R*A)

Relative Humidity:

φ= 100%

(9)

Water Management of FC System

Lower amount of liquid water cycled in FC system lower when sPAEEN

membranes are utilised

Testing conditions: j= 0.1 A/cm

2

1 M aq. MeOH / air

Cathodic Flow Rate: 20 ml / (min*cm

2

₎

Anodic Flow Rate: 0.22 ml / (min*cm

2

₎

Ambient Pressure

55

60

65

70

75

80

85

0.0

0.1

0.2

0.3

0.4 Liquid W

at

er

c

y

c

led

in

F

uel

C

ell

Sy

s

tem

[g/

(h*

c

m

2

)]

Cell Temperature [°C]

Nafion 115

HQs-PAEEN 53

m-sPAEEN 57

(10)

Methanol Utilization of HQ- and m-sPAEEN

HQ-sPAEEN MEAs with higher methanol utilization than MEAs with Nafion 115

m-sPAEEN MEAs show comparable or worse methanol utilization than MEAs with

Nafion 115

Testing conditions: j= 0.1 A/cm

2

1 M aq. MeOH / air

Cathodic Flow Rate: 20 ml / (min*cm

2

₎

Anodic Flow Rate: 0.22 ml / (min*cm

2

₎

Ambient Pressure

55

60

65

70

75

80

85

45

50

55

60

65 M

et

hanol U

tiliz

at

ion

[%]

Cell Temperature [°C]

Nafion 115

HQs-PAEEN 53

m-sPAEEN 57

(11)

Influence Hot Pressing Temperature on sPAEEN- MEAs

Decrease of MEA performance with increasing hot pressing temperatures

 Increase of MEA resistance

 Decrease of proton conductivity

Testing conditions: j= 0.1 A/cm

2

1 M aq. MeOH / air

Cathodic Flow Rate: 36.5 ml / (min*cm

2

₎

Anodic Flow Rate: 0.22 ml / (min*cm

2

₎

Ambient Pressure

T= 70

°C

0

50

100

150

200

0.0

0.1

0.2

0.3

0.4

0.5

0.6 V

ol

tag

e [

V

]

Hot Pressing Temperature [°C]

Current Density 0.1 0.2 0.3 [A/cm

2

]

HQ-sPAEEN 53

m-SPAEEN 57

(12)

Sandwich MEA: Characteristic Methanol Permeation

Nafion 115

Temp.

[

°C]

Cat.Flow

[ml/(min*cm

2 _)]

HQ-sPAEEN 56/ Nafion 1135

Temp.

[

°C]

Cat.Flow

[ml/(min*cm

2 _)]

MeOH-Permeation

[A/cm

2

_]

MeOH-Permeation

[A/cm

2

_]

(13)

Methanol Utilization Sandwich MEA

Testing conditions: j= 0.1 A/cm

2 1 M aq. MeOH / air

Cathodic Flow Rate: 15.0 ml / (min*cm

2 ₎

Anodic Flow Rate: 0.22 ml / (min*cm

2 ₎

Ambient Pressure

55

60

65

70

75

80

85

20

30

40

50

60

70

80

90

100 M

eOH

-

U

tiliz

at

ion

[%]

Cell Temperature [°C]

Nafion 115 (pressed)

(14)

Summary sulfonated Poly(Aryl Ether Ether Nitriles)



Lower methanol permeation of MEAs with sPAEEN-membranes leads to a higher

methanol utilization (increase of ~3 %)



Reduced water flux through sPAEEN membranes leads to lower amount of of cycled

water in the DMFC system (reduction of ~25 %)



MEA assembling at high temperatures leads to performance loss (~10 %)



Sandwich MEA with HQ-sPAEEN 56 and Nafion 1135 leads to large decrease of

methanol permeation (~35 %)

(15)

(16)

DMFC: Function and Characteristics

Anode Reaction:

CH

₃

OH + H

₂

O  CO

₂

+ 6H

+

_{+ 6e}

-

Cathode Reaction

3 _/

2 O

2 + 6H

+

+ 6e

-

 3H

2 O

Complete Reaction

CH

₃

OH +

3 _/

2 O

2  CO

2 + 2H

2 O

Membrane- Electrode- Assembly (MEA)

Anode

–

(Pt/Ru)

+

Cathode

(Pt)

O

₂

(Air)

H

₂

O

CO

₂

H

+

CH

₃

OH

H

₂

O

Crossover

CH

₃

OH / H

₂

O

e

–

e

–