high-temperature polymer electrolyte membranes
TRANSCRIPT
A U.S. Department of Energy LaboratoryOperated by The University of Chicago
Argonne National Laboratory
High-Temperature Polymer Electrolyte Membranes
Suhas Niyogi, Romesh Kumar, and Deborah MyersChemical Engineering Division
This presentation does not contain any proprietary or confidential information
Project ID: FC-7
Overview
2
Pioneering Science andTechnology
Hydrogen, Fuel Cells, and Infrastructure Technologies Program
• Start date: October 2001• Project end date: Open• Percent complete: 25%
Timeline Barriers• This project addresses DOE’s
Technical Barriers for Fuel Cell Components:
- E: Distributed Generation Durability- O: Stack Material and Manufacturing Cost- P: Component Durability- Q: Electrode Performance- R: Thermal and Water ManagementBudget
• Total FY ’02 – FY ’05: $1285 K • FY ’04: $250 K• FY ’05: $335 K • Provided samples to GM/Giner
Interactions
3
Pioneering Science andTechnology
Hydrogen, Fuel Cells, and Infrastructure Technologies Program
Project objectives• To develop a proton-conducting membrane electrolyte for
operation at 120-150°C and low humidities to meet DOE’s technical targets- High, sustained proton conductivity (0.1 S/cm) at <120ºC and
25 kPa water vapor pressure (dew point 65°C)
- Low oxygen and hydrogen cross-over (5 mA/cm²)- Low cost, $200/m²- Durability of 2,000 hours- Able to withstand temperatures as low as -30°C
• Investigate use of dendritic macromolecules attached to polymer backbones, cross-linked dendrimers, and inorganic-organic hybrids
4
Pioneering Science andTechnology
Hydrogen, Fuel Cells, and Infrastructure Technologies Program
Approach: Dendritic macromolecules and Inorganic/organic hybrids
• Dendritic MacromoleculesHighly branched macromoleculesHigh surface charge densities– May facilitate high proton transfer with
reduced water mediation– May improve water retention at high
temperatures
• Inorganic/Organic HybridsInorganic component improves water retention at high temperatures (e.g., colloidal silica)Organic component chosen to have high density of functional groups and high thermal and dimensional stability
O
O
OO
O
O
O
O
O
O
O
O
O
O
O
HO3S
HO3S
HO3S
HO3S
HO3S
HO3S
HO3S
HO3S
Cl
Cl
O
OO
O
O
O
O
O
O
O O
O O OO
SO3H
SO3H
SO3H
SO3H
HO3SHO3SSO3HHO3S
O
O
OO
O
O
O
OO
OO
OOO
OHO3S
HO3S
HO3S
HO3SSO3H
SO3HSO3H
SO3H
O
O
OO
O
O
O
O
O
O
O
O
O
O
O
SO3H
SO3H
SO3H
SO3H
SO3H
SO3H
SO3H
SO3H
5
Pioneering Science andTechnology
Hydrogen, Fuel Cells, and Infrastructure Technologies Program
Dendrimers have been attached to polyepichlorohydrin to form water-insoluble films
O
O
O
O O
O
O
SO3HHO3S
HO3S
HO3S
O
O
O
O
O
OO
SO3H
SO3H
SO3HHO3S
Cl
Cl
O
OO
OOO
O
SO3H
HO3SHO3S
HO3S
O
O
OO
O
O
O
SO3H
SO3H
SO3H
SO3H
O
O
O
O
O
OO
HO3S
HO3S
HO3S
SO3H
OO
n
O
O
O
Cl
n[G-m]-CH2OH ClSO3H
DCE or CHCl3 at 10oC
degased DMF, dry PyridineDTBMP, at 80oC
PECH-[G-m]
HO3S
HO3S
PECH-[G-m]-SO3H O
O
n
O O
OO
OO
HO3S
SO3H SO3H
SO3H
O
O
n
O
O
O
O
OO
O
O
O
O
OO
O
O
SO3H
SO3H
SO3H
SO3H
HO3SHO3SHO3S
HO3S
O
O n
O
OO
O
O
O
O
O
O O
O O OO
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
SO3H
SO3H
SO3H
SO3H
HO3SHO3SHO3S
HO3S
HO3S
HO3S
HO3S
HO3S
HO3S
HO3S
HO3S
SO3H
m=1 m=2
m=3m=4
PECH-[G-1]-SO3H
PECH-[G-2]-SO3H
PECH-[G-3]-SO3HPECH-[G-4]-SO3H
M.W=100,000 n = 1069.14
PECH-G2-SO3HM.W of Polyepichlohydrin = 100K or 700K
OO
OO
O
O
O
O
OO
OO
O
O
O
HO3SHO3SHO3S
HO3S
HO3S
HO3S
HO3S
HO3S
ClCl
O
OO
O
O
OO
O
O
OO
O OO
O
SO3H
SO3H
SO3H
SO3H
HO3S
HO3SSO
3H
HO3S
O
OO
O
O
O
O
O
O
OO
OOOO
HO3S
HO3S
HO3S
HO3S
SO3H SO
3H SO3H SO
3H
O O
O OO
O
O
O
O O
O O
O
O
O
SO3HSO
3HSO
3HSO
3H
SO3H
SO3H
SO3H
SO3H
PECH-G3-SO3HM.W of Polyepichlohydrin = 100K
6
Pioneering Science andTechnology
Hydrogen, Fuel Cells, and Infrastructure Technologies Program
Sulfonated dendronized PECH retains more water than Nafion• Water absorption at 25°C and 97% RH, desorption at 25°C and 40% RH
• Polymers of comparable equivalent weights
AbsorptionDesorption
1
1 .05
1 .1
1 .15
1 .2
1 .25
1 .3
0 50 100 150 200
Wei
gh
t
T im e in h o urs
7
Pioneering Science andTechnology
Hydrogen, Fuel Cells, and Infrastructure Technologies Program
Thermal stability has been improved by cross-linking dendronized PECH
Temperature (oC)
99.3
99.4
99.5
99.6
99.7
99.8
99.9
100
40 60 80 100 120 140
X-PECH-G3-SO3HPECH-G3-SO3HX-PECH-G2-SO3HPECH-G2-SO3HW
eigh
t (%
)
Air Flow: 200 ml/min; Heating rate: 5 oC/min
8
Pioneering Science andTechnology
Hydrogen, Fuel Cells, and Infrastructure Technologies Program
PECH-G2-SO3H is stable under oxidizing conditions
• Fenton’s Test Conditions: Wt. Ratio FeSO4:H2O2:Polymer = 25:165:254; pH 3.5, 32°C, 24 hours
• Viscosities of PECH-G2-SO3H in DMF at 24.5°C
0.26
0.28
0.3
0.32
0.34
0.36
0.38
0.4
0 0.2 0.4 0.6 0.8 1 1.2 1.4
BeforeAfter
Red
uced
Vis
cosi
ty (d
L/g)
Concentration (g/dL)
9
Pioneering Science andTechnology
Hydrogen, Fuel Cells, and Infrastructure Technologies Program
Dimensional stability and conductivity have been improved by cross-linking dendronized PECH
PECH-700K-X-L-G2-SO3
0
5
10
15
20
25
30
35
20 40 60 80 100Temp. (°C)
Con
duct
ivity
(mS/
cm)
Cross-linked
Not cross-linked
• PECH-G2-SO3H (MW PECH = 700 K)• 100% RH, except where noted• Reference: Nafion 112, 80°C, 25 kPa steam (53% RH), ~35 mS/cm
53% RH 90% RH
10
Pioneering Science andTechnology
Hydrogen, Fuel Cells, and Infrastructure Technologies Program
Route for further improvements in dimensional stability of dendronized polymers
N
HN
N
HN
*
n
Polybenzimidazole
O O
O O OO
X
(i) DMAC; 90 oC; (ii) LiH
(where X = Br)G2-Br
N
N
N
N
*
G2 G2
n
(SO3H)4 (SO3H)4
Sulfonated dendronized PBI
_______________________
(iii)
(iv) ClSO3H
11
Pioneering Science andTechnology
Hydrogen, Fuel Cells, and Infrastructure Technologies Program
Inorganic/organic hybrids are thermally stable
94
95
96
97
98
99
100
100 150 200 250 300
2132-402132-412132-432132-45
Wei
ght(%
)
Air Flow: 250 ml/min; heating rate: 5 oC/min
Temperature (oC)
Sample 2132-40
90% Binder, 10% sulfonatedcyclic organic component
Sample 2132-41
91.9% Binder, 8.1% sulfonatedcyclic organic component-colloidal silica
Sample 2132-43
84.1% Binder, 15% sulfonatedcyclic organic component, 0.9% alumina fiber
Sample 2132-45
89.2% Binder, 8.8% sulfonatedcyclic organic component, 2% alumina fiber
12
Pioneering Science andTechnology
Hydrogen, Fuel Cells, and Infrastructure Technologies Program
Inorganic-organic hybrids are proton-conducting despite low organic component content• Water vapor partial pressure: 25 kPa (dew point of 65°C)• 8.8% cyclic organic component, 89.2% binder, 2% alumina fibers
2132-45 Hybrid
1.0
2.0
3.0
4.0
5.0
6.0
20 30 40 50 60 70 80Temp. (°C)
Con
duct
ivity
(mS/
cm)
13
Pioneering Science andTechnology
Hydrogen, Fuel Cells, and Infrastructure Technologies Program
FY 2005 milestones and progress• Measure thermal stabilities and conductivities of
dendronized PECH membranes (12/04)- Completed; measured stabilities and conductivities of G2, G3,
and G4-containing materials
• Complete 100 h durability test on dendronized PECH membrane (06/05)- Re-designed cross-linking process for improved high-
temperature properties- Synthesizing materials with PBI as film-forming backbone
• Fabricate and test MEAs using high temperature membranes (08/05)- Will begin once suitable membrane is identified
14
Pioneering Science andTechnology
Hydrogen, Fuel Cells, and Infrastructure Technologies Program
Response to FY ’04 Reviewers’ Comments• “Only membrane work, not integrated with other MEA
components”- Will include determination of oxygen reduction kinetics and MEA
fabrication after obtaining a membrane with properties approaching targets
• “Initial samples being characterized for conductivity at temperatures <100°C even though target is >120°C”- Conductivity cell has been re-designed to allow operation up to
120°C, dimensional stability of membranes at high temperatures is being improved
• “It is not apparent that the epichlorohydrin polymers will have sufficient stability for the fuel cell operation”- Fenton’s test results showed polymer to be stable under
oxidizing conditions
15
Pioneering Science andTechnology
Hydrogen, Fuel Cells, and Infrastructure Technologies Program
Future work• Improve dimensional stability and conductivity of dendronized
polymers at high temperatures- Improve film processing to ensure complete removal of
plasticizing/conductivity masking solvent- Optimize dendrimeric network with better cross-linker for
dendronized materials - Evaluate PBI and other film-forming polymers as backbones- Incorporate ionic liquids into membrane to improve
conductivity and reduce dependence on water
• Improve dimensional stability and conductivity of inorganic/organic hybrid films- Increase content of sulfonated organic component- Improve homogeneity of dispersed, proton-conducting phase
• Fabricate and test MEAs using the most promising materials
16
Pioneering Science andTechnology
Hydrogen, Fuel Cells, and Infrastructure Technologies Program
Acknowledgments
• Funding from the U.S. Department of Energy, Energy Efficiency, Renewable Energy: Hydrogen, Fuel Cells, & Infrastructure Technologies Program is gratefully acknowledged
• Nancy Garland, DOE Technology Development Manager
17
Pioneering Science andTechnology
Hydrogen, Fuel Cells, and Infrastructure Technologies Program
Publications and presentations
• “High-Temperature Polymer Electrolyte Fuel Cell Electrolytes Based on Dendronized Polymers”, Seong-Woo Choi, Suhas Niyogi, Romesh Kumar, and Deborah Myers, presentation and extended abstract, 206th Fall Meeting of the Electrochemical Society, Honolulu, Hawaii, Oct. 3-8, 2004
• “High-Temperature Polymer Electrolyte Membranes Based on DendriticMacromolecules and Organic/Inorganic Hybrids”, Seong-Woo Choi, SuhasNiyogi, Deborah J. Myers, and Romesh Kumar, poster and extended abstract, 2004 Fuel Cell Seminar, San Antonio, Texas, Nov. 1-5, 2004
• “High-temperature polymer electrolyte development at ANL”, International Energy Agency-Polymer Electrolyte Fuel Cell Annex, Fall, 2004 Workshop, Rome, Italy, Nov. 18-19, 2004
18
Pioneering Science andTechnology
Hydrogen, Fuel Cells, and Infrastructure Technologies Program
Hydrogen safety
• Hydrogen is not used during the processing and fabrication of the polymer membranes
• “Safe” hydrogen (<4% H2 in He) is used as a purge gas in the membrane conductivity apparatus to stay below the flammability limit of hydrogen in air
The submitted manuscript has been created by the University of Chicago as Operator of Argonne National Laboratory (“Argonne”) under Contract No. W-31-109-ENG-38 with the U.S. Department of Energy. The U.S. Government retains for itself, and others acting on its behalf, a paid-up, nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.
The submitted manuscript has been created by the University of Chicago as Operator of Argonne National Laboratory (“Argonne”) under Contract No. W-31-109-ENG-38 with the U.S. Department of Energy. The U.S. Government retains for itself, and others acting on its behalf, a paid-up, nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.