26.07.2013 Kerres

Novel (Blend) AEMs and Their Application in DMFC

Jochen Kerres, Anika Katzfuß

AEM for Energy Generation Technologies

Workshop, University of Surrey

Universität Stuttgart, Institut für Chemische Verfahrenstechnik (ICVT), Stuttgart, Germany

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Outline

AEM Based Onto BrPPO

AEM Based Onto MPBIOO, PSUSO2Li, DABCO and DIB

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Outline

AEM Based Onto BrPPO

AEM Based Onto MPBIOO, PSUSO2Li, DABCO and DIB

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Bromination of PPO

* O *

CH2Br

CH2Br

* O *Solvent NBS,

24 h, AIBN

• Green chemistry! • Using NBS insteed of bromine! • Substitution only at the side chain, not on the aromatic ring!

theo. Substitution [%]

exp. Substitution [%]

Yield [%]

100 83 97 50 48 87 30 35 88

Xu Tongwen, Yang Weihua, Journal of Membrane Science 190 (2001) 159–166 A. Katzfuß, V. Gogel, L. Jörissen, J. Kerres, J. Membr. Sci. 425-426 (2013) 131-140.

Prepolymer I for AEM

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Concept of Covalent Crosslinking of AEM

• Leads high crosslinking degree to increasing IEC-values and conductivity?

• FG = functional groups ; • DABCO as diamen to introduce simultaneously a covalent crosslink and a quaternary

ammonium group • CG = conducting groups

[1] B. Bauer, H. Strathmann, F. Effenberger, Desalination 79 (1990) 125-144.

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Embedding into Matrix Polymer

Pure AEM based onto BrPPO, DABCO and DIB (F and G Membranes) are too brittle at large bromination degree

Addition of PVDF as a matrix polymer

Mechanically stable membranes are obtained

*CH2

CF2*

n

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Membran Crosslinking theo. [%]

Crosslinking exp. [%]

IECtotal [meq/g]

F1 0 78.7 1,1

F2 50 79.2 1,0

F3 100 84.4 0,7

G1 0 76.9 1,1

G2 50 82.9 0,9

G3 100 84.7 0,6

Covalent Crosslinking

•High reactivity between BrPPO + DABCO •Higher crosslinking but lower IEC-value

•F-type: BrPPO + DABCO •G-type:. BrPPO + DABCO + DIB

Widening of OH--Conductive Channels

G F

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•Within the first days the IEC value increases slightly • After 10 days IEC value decrease of F-type, stable IEC of G-type

Alkaline Stability

IEC Values of F and G Type Membranes During KOH Treatment

←Before immersion in KOH After immersion in→

KOH

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•Conductivities remain in the same range • Difference in crosslinking degree has influence on the conductivity •DABCO-BrPPO bond is obviously not severely attacked by hydroxide ions •Mechanical stability decreases, because the matrix polymer PVDF degrades (F- detection) •Search for alternative matrix polymers required

Conductivity Values During KOH Treatment

Alkaline Stability

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•Passive DMFC cell, selfbreathing, 4 M MeOH + 1 N KOH as electrolyte, 4 ml/min, 25°C •GDE from gaskatel; Anode: 2.5 mg/cm2 Pt/C; Cathode: Ag/AgO on nickel gauze

Increasing crosslinking degree decreases the UI-curve Only 6% difference in crosslinking degree between F1 and F3 leads to doubling of power density (8% G1 to G3)

DMFC Application

Passive DMFC at RT

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• Active DMFC cell, 2 ml/min, 80°C • Anode: 5 mg/cm2 Pt/Ru/C mit 10% PTFE ; Cathode: 5 mg/cm2 Pt/C mit 10% PTFE • Conditions: a) 1 M MeOH / 1 M KOH; b) 1 M MeOH / 5 M KOH; c) 4 M MeOH / 5 M KOH

a) 1 M MeOH / 1 M KOH; b) 1 M MeOH / 5 M KOH; c) 4 M MeOH / 5 M KOH

• Results for the different DMFC conditions: •a) UI-curve is low •b) strong increase •c) no influence at F1 membrane •c) A006: decrease of UI-curve because of MeOH crossover

F1 A006

DMFC Application

Active DMFC at 80C(at ZSW Ulm)

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UI curve of F1 and A006 using 4 M MeOH / 5 M KOH electrolyte

- 2 ml/min; 80°C; -Anode: 5 mg/cm2 Pt/Ru/C with 10% PTFE ; -Cathode: 5 mg/cm2 Pt/C with 10% PTFE

F1 is better than commercial A006 membrane

DMFC Application

Active DMFC at 80C(at ZSW Ulm)

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Outline

AEM Based Onto BrPPO

AEM Based Onto MPBIOO, PSUSO2Li, DABCO and DIB

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•Shieh et al performed methylation of benzimidazoles without methyl iodide[2-4]

•For the first time transfer of this low-molecular reaction to polymers •Methylation of PBI without using toxic methyl iodide! •Using Dimethylcarbonate and DABCO

Methylation of PBIOO

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N

N

O

N

N

O* *

H

H

N

N

O

N

N

O* *

CH3

CH3

DMC, DABCO145°C, 96 h

[2] W. Shieh, S. Dell, O. Repic, Org. Lett. 3(26) (2001) 4279-4281. [3] W. Shieh, M. Lozanov, M. Loo, O. Repic, T.J. Blacklock, Tetrahedron Lett. 44 (2003) 4563-4565. [4] W. Shieh, S. Dell, A. Bach, O. Repic, T.J. Blacklock, J. Org. Chem. 68 (2003) 232-239.

Prepolymer II for AEM

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Membranes from mPBIOO

Add DIB + DABCO O

N

N

O *

CH3

N

N

*

CH3DIB

O

N

N

O *

CH3

N

N

*

CH3

O

N

N

O

CH3

N

N

CH3

* *

(CH2)4

I

I

NN

I

(H2C)4

I

DABCONN

(H2C)4

I

• Strong inhomogeneity

Quaternization of PBIOO with Diiodobutane (DIB) and DABCO

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•Membranes are homogenious and flexible •IEC-values between 2.0 and 2.8 meq/g possible •Membranes called „BAK 39“

O

N

N

O *

CH3

N

N

*

CH3+DABCO + DIB

Adding DIB + DABCO + PSU-SO2Li

Membranes from mPBIOO

Addition of a Second Polymer: Sulfinated PSU

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Variation of the Cross-Linking Degree

Dependence of the insolubles percentage (crosslinking degree) on the temperature

Temperature [°C]

Crosslinking degree*

[%]

IEC [meq/g]

50 0 2.6 80 0 2.6

100 56 2.9 120 60 2.9 140 65 2.4 160 70 2.4

The higher the temperature during solvent evaporation, the higher the %insolubles content (crosslinking degree) of the blend membranes.

Membranes from mPBIOO and PSU-SO2Li

*insolubles content

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Alkaline Stability of Type II AEM

• Immersion of samples in 1 N KOH at 90°C • After different immersion times the IEC values and conductivity were determined •. BAK 39 membranes with various crosslinking degrees

The IEC values and the conductivity are very stable until 7 days. After 10 days the properties slightly decrease The membranes remains flexible in the mechanical stability. BAK 39 membrane has superior alkaline stability.

IEC and Conductivity During KOH Treatment

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Comparison of Type I and Type II Membranes

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The higher the crosslinking degree, the lower the MeOH uptake

Tokuyama A006 membrane has the highest MeOH uptake from all tested samples.

BAK 39 membrane

Very low MeOH uptake of all samples

High hydrophobicity of G because of using additional DIB

Reaching highest uptake at 25°C

F- and G-type membrane

•Immersion of samples in 4 M MeOH at different temperatures for 24 h

Comparison of MeOH Uptake

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• Passive DMFC cell, selfbreathing, 4 M MeOH + 1 N KOH as electrolyte, 4 ml/min, 25°C • GDE from gaskatel; Anode: 2.5 mg/cm2 Pt/C; Cathode: Ag/AgO on nickel gauze

F1 and G1 equal to commercial A006 membrane from Tokuyama BAK 39 membrane worse in the passive DMFC

Comparison of Type I and Type II Membranes

Comparison of DMFC Performance (RT)

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•All samples are equal • maximum power density of 130 mW/cm2 is reached!

Comparison of the developed membranes with A006

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- 2 ml/min 4 M MeOH, 5 M KOH; 80°C -Anode: 6% Pd/CeO2/C ; Cathode: 4% FeCo/C

Comparison of Type I and Type II Membranes

•Usage of non-Pt catalyst

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Development of two different AEM systems

One is based on BrPPO, the other on methylated PBIOO

Both are very stable under alkaline conditions

Influence of different crosslinking degree was shown

The higher the crosslinking degree, the lower the IEC value, conductivity and methanol uptake

Power density of 130 mW/cm2 reached!

Search for other matrix polymers (including other alkylated PBIs)

Use of different diamines and dihalogenes

Longlife stability tests in DMFC

Conclusions and Outlook

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26.07.2013 Kerres

My group: K. Aniol, V. Atanasov, A. Carlsson, A. Chromik, I. Hajdok, A. Katzfuss, I. Kharitonova, G. Schumsky, C. Seyb

Funding:

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Acknowledgement

AiF: Joint Project „Novel stable anion-exchange membranes and MEAs for alkaline fuel cells“

AiF: Joint Project „Alkaline Electrolysis with Novel AEMs“