Durability of Carbon Nanofiber & Carbon Nanotube as Catalyst Support for Proton Exchange Membrane...
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Durability of Carbon Nanofiber & Carbon Nanotube as Catalyst Support for Proton Exchange Membrane Fuel Cells Shuang Ma Andersen 1 , Peter Lund 2 , Yli-Rantala Elina 3 , Antti Pasanen 3 Pertti Kauranen 3 and Eivind M. Skou 1 1 Institute of Chemical Engineering, Biotechnology and Environmental Technology, University of Southern Denmark 2 IRD Fuel Cells A/S, Svedberg, Denmark, 3 VTT Technical Research Centre of Finland, Tampere, Finland Corresponding author: [email protected] Introduction Carbon Nanotube (CNT) and Carbon Nanofiber (CNF) demonstrate huge potentials in fuel cell developments [1, 2]. In this work, thermal and electrochemical durabilities of CNT and CNF as PEMFC catalyst support were studied and compared to conventional commercial catalyst supports based on both ex-situ and in–situ experiments. Experiment & Results Carbon thermal corrosion properties were tested at 200 o C. Samples were packed individually in aluminum foil, whose weight was proven to be stable during the treatment. The weights of the small packages were examined via a digital balance. The samples were pre-heated at 80 o C to eliminate adsorption water. The weight loss corresponds to carbon thermal corrosion, as shown in fig. 1. [1] M. Okada et al, J. Power Sources 185 (2008), 711–716. [2] G.W. Yang et al, Carbon 45 (2007), 3036–304. [3] S. Ma, et al., Solid State Ionics 178 (2007), 1568-1575. [4] S. M. Andersen et al., Solid State Ionics, in Press, 2010. 0 50 100 150 200 10 20 30 40 50 60 70 80 90 100 110 Tim e /h N om a lized to carbon w eightloss /% C N F (show a denko) C N T-A(G M W C N T) V ulcan K etjenblack M P 059 20% P tG M W C N T BASF 20% P tV ulcan H ispec 9000 H ispec 9100 H ispec 10000 H ispec 10100 Aalto PtV G F TEC 10EA B lank 0 200 400 600 800 1000 -1 20 -1 00 -80 -60 -40 -20 0 20 Fro m to p to bo ttom V ulcan C N T + N a fio n io n om er C N F + N afio n ion o m er N afio n ion o m er 9000 + N afio n ion om er 9100 + N afio n ion om er N om alized to d e structib le m a te rials % Tem p./C o 0.6 0.8 1.0 1.2 1.4 1.6 0 200 400 600 800 1000 [P t]pp b V o ltag e /V KTT BASF 0.0 0.2 0.4 0.6 0.8 1.0 1.2 -0.2 5 -0.2 0 -0.1 5 -0.1 0 -0.0 5 0.00 0.05 0.10 0.15 C urrent/A V olta ge /V BASF F re sh A fter 5 k cycle s A fter 1 0 k cycle s 0.0 0.2 0.4 0.6 0.8 1.0 1.2 -0.1 5 -0.1 0 -0.0 5 0.0 0 0.0 5 0.1 0 C urrent/A V o ltag e /V A alto F resh A fte r 5 k cycle s A fte r 1 0k cycle s Loading Area ESA ESA Change Max power density Max power density Change mg/cm 2 cm 2 cm 2 /mg % w/cm 2 % BASF 2 MEA1430-8 Fresh 0.518 2.25 779 100 0.393 100 After 5k 0.518 2.25 463 59 0.315 80 After 10k 0.518 2.25 392 50 0.306 78 Aalto MEA1431-1 Fresh 0.529 2.25 331 100 0.195 100 After 5k 0.529 2.25 426 129 0.276 142 After 10k 0.529 2.25 330 100 0.218 112 MWCNT MEA1415-2 Fresh 0.530 2.25 310 100 0.147 100 After 5k 0.530 2.25 328 106 0.176 120 After 10k 0.530 2.25 248 80 0.156 106 Carbon thermal decomposition was studied by thermalgravimetry TGA 92-12. Mixing of carbon or catalyst powder and Nafion ionomer solution can be found in our earlier work [3]. About 3-4 mg pretreated powder was transported into Al 2 O 3 crucible for TG analysis. The experiment was performed under argon and oxygen of ratio 3 to 1, total pressure of one atmosphere. Data are summarized in fig.2. Electrochemical stability under high voltage cyclic treatment was performed with a single cell of dimension 1.5*1.5cm 2 , MEA was cycled between 0.04 and 1.6 V v.s. RHE. Single cell performance was carried out with pure hydrogen and lab air were used as fuel and oxidant. The gas was humidified with 1kw humidifier (FumaTech). The system was steered with electrochemical workstation IM6 (ZAHNER). Electrochemical active surface area of the MEA before and after the treatment are shown in fig. 4. Other data are summarized in tab. 1. Fig. 1 Carbon thermal corrosion Fig. 2 TG pattern of catalyst and Nafion ionomer mixture Tab. 1 Summary for electrode electrochemical stability under high potential cycling Fig. 3 Platinum (of different carbon support) dissolution in acidic media Fig. 4 Examples of ESA determined by hydrogen adsorption Conclusions Based on above studies, both carbon nanofiber and carbon nanotube demonstrate outstanding better stability comparing to traditional carbon black (Vulcan). Carbon nanofiber showed better performance than carbon nanotube materials Optimization and activation of membrane electrode assembly – electrode structure is the key point to gain better cell performance for carbon nanofiber based materials. The detailed experiment condition of platinum dissolution in acidic media can be found in our early work [4]. The electrodes were prepared by IRD Fuel Cells. Comparison of carbon nanofiber and carbon black is shown in fig. 3.
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Transcript of Durability of Carbon Nanofiber & Carbon Nanotube as Catalyst Support for Proton Exchange Membrane...
Durability of Carbon Nanofiber & Carbon Nanotube as Catalyst Support for Proton Exchange Membrane Fuel CellsShuang Ma Andersen1, Peter Lund2, Yli-Rantala Elina3, Antti Pasanen3 Pertti Kauranen3 and Eivind M. Skou1
1 Institute of Chemical Engineering, Biotechnology and Environmental Technology, University of Southern Denmark2 IRD Fuel Cells A/S, Svedberg, Denmark, 3 VTT Technical Research Centre of Finland, Tampere, Finland
Corresponding author: [email protected]
Introduction
Carbon Nanotube (CNT) and Carbon Nanofiber (CNF) demonstrate huge potentials in fuel cell developments [1, 2]. In this work, thermal and electrochemical durabilities of CNT and CNF as PEMFC catalyst support were studied and compared to conventional commercial catalyst supports based on both ex-situ and in–situ experiments.
Experiment & Results
Carbon thermal corrosion properties were tested at 200oC. Samples were packed individually in aluminum foil, whose weight was proven to be stable during the treatment. The weights of the small packages were examined via a digital balance. The samples were pre-heated at 80oC to eliminate adsorption water. The weight loss corresponds to carbon thermal corrosion, as shown in fig. 1.
[1] M. Okada et al, J. Power Sources 185 (2008), 711–716. [2] G.W. Yang et al, Carbon 45 (2007), 3036–304.[3] S. Ma, et al., Solid State Ionics 178 (2007), 1568-1575. [4] S. M. Andersen et al., Solid State Ionics, in Press, 2010.
0 50 100 150 200
10
20
30
40
50
60
70
80
90
100
110
Time / h
Nom
aliz
ed to
car
bon
wei
ght l
oss
/ %
CNF (showa denko) CNT-A(GMWCNT) Vulcan Ketjenblack MP 059 20% Pt GMWCNT BASF 20% Pt Vulcan Hispec 9000 Hispec 9100 Hispec 10000 Hispec 10100 Aalto Pt VGF TEC 10EA Blank
0 200 400 600 800 1000-120
-100
-80
-60
-40
-20
0
20
From top to bottom Vulcan CNT + Nafion ionomer CNF + Nafion ionomer Nafion ionomer 9000 + Nafion ionomer 9100 + Nafion ionomer
N
omal
ized
to d
estr
uctib
le m
ater
ials
%
Temp. / Co
0.6 0.8 1.0 1.2 1.4 1.6
0
200
400
600
800
1000
[Pt]
pp
b
Voltage / V
KTT BASF
0.0 0.2 0.4 0.6 0.8 1.0 1.2
-0.25
-0.20
-0.15
-0.10
-0.05
0.00
0.05
0.10
0.15
C
urr
en
t / A
Voltage / V
BASF Fresh After 5k cycles After 10k cycles
0.0 0.2 0.4 0.6 0.8 1.0 1.2
-0.15
-0.10
-0.05
0.00
0.05
0.10
C
urre
nt /
A
Voltage / V
Aalto Fresh After 5k cycles After 10k cycles
Loading Area ESA ESA ChangeMax power
densityMax power
density Change
mg/cm2 cm2 cm2/mg % w/cm2 %
BASF 2MEA1430-8
Fresh 0.518 2.25 779 100 0.393 100
After 5k 0.518 2.25 463 59 0.315 80
After 10k 0.518 2.25 392 50 0.306 78
AaltoMEA1431-1
Fresh 0.529 2.25 331 100 0.195 100
After 5k 0.529 2.25 426 129 0.276 142
After 10k 0.529 2.25 330 100 0.218 112
MWCNTMEA1415-2
Fresh 0.530 2.25 310 100 0.147 100
After 5k 0.530 2.25 328 106 0.176 120
After 10k 0.530 2.25 248 80 0.156 106
Carbon thermal decomposition was studied by thermalgravimetry TGA 92-12. Mixing of carbon or catalyst powder and Nafion ionomer solution can be found in our earlier work [3]. About 3-4 mg pretreated powder was transported into Al2O3 crucible for TG analysis. The experiment was performed under argon and oxygen of ratio 3 to 1, total pressure of one atmosphere. Data are summarized in fig.2.
Electrochemical stability under high voltage cyclic treatment was performed with a single cell of dimension 1.5*1.5cm2, MEA was cycled between 0.04 and 1.6 V v.s. RHE. Single cell performance was carried out with pure hydrogen and lab air were used as fuel and oxidant. The gas was humidified with 1kw humidifier (FumaTech). The system was steered with electrochemical workstation IM6 (ZAHNER). Electrochemical active surface area of the MEA before and after the treatment are shown in fig. 4. Other data are summarized in tab. 1.
Fig. 1 Carbon thermal corrosion
Fig. 2 TG pattern of catalyst and Nafion ionomer mixture
Tab. 1 Summary for electrode electrochemical stability under high potential cycling
Fig. 3 Platinum (of different carbon support) dissolution in acidic media
Fig. 4 Examples of ESA determined by hydrogen adsorption
Conclusions
Based on above studies, both carbon nanofiber and carbon nanotube demonstrate outstanding better stability comparing to traditional carbon black (Vulcan). Carbon nanofiber showed better performance than carbon nanotube materials
Optimization and activation of membrane electrode assembly – electrode structure is the key point to gain better cell performance for carbon nanofiber based materials.
The detailed experiment condition of platinum dissolution in acidic media can be found in our early work [4]. The electrodes were prepared by IRD Fuel Cells. Comparison of carbon nanofiber and carbon black is shown in fig. 3.
