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Materials Science & Technology, MST-11Fuel Cell ResearchOAAT
Program Review, May 2002
Annual OAAT Fuel Cells Program ReviewNational Renewable Energy
Laboratory, Golden, CO, May 2002
DIRECT METHANOL FUEL CELLS
Piotr Zelenay
Materials Science & Technology DivisionLos Alamos National
Laboratory
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Materials Science & Technology, MST-11Fuel Cell ResearchOAAT
Program Review, May 2002
Major Contributors to DMFC Effort in FY 2002
Eric Brosha (TSM) - Ultrasonic spray/freeze dryJohn Davey (Tech)
- MEA research; technical supportChristian Eickes (PD) -
ElectrocatalysisRobert Fields (TSM) - Controls &
softwareMichael Hickner (GRA) - Membrane & MEA researchFrançois
Le Scornet (GRA) - Single cell & stack testingDon McMurry
(Tech) - Controls & softwareBryan Pivovar (TSM) - Membrane
& MEA researchGerie Purdy (Tech) - Testing & general
supportJohn Ramsey (GRA) - Flow & hardware modelingJohn Rowley
(Tech) - Technical supportMahlon Wilson (TSM) - Cell/stack design
& engineeringChristine Zawodzinski (TSM) - Cell/stack design
& engineeringTom Zawodzinski (TSM) - Membrane & MEA
researchPiotr Zelenay (TSM) - Project management &
electrocatalysisYimin Zhu (PD) - Electrocatalysis
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Materials Science & Technology, MST-11Fuel Cell ResearchOAAT
Program Review, May 2002
Status by the End of FY 2001
• Composition of anodes with reduced catalyst loading
optimized
• 5 gPt/kW successfully demonstrated in a 45-cm2 five-cell stack
with a total Pt loading of 0.53 mg cm-2
• Several membranes with higher selectivity and lower
electro-osmotic drag of water identified; improved overall
efficiency demonstrated with several alternative membranes
• Fourth-generation 30-cell 80-W DMFC stack delivered and
integrated by Ball Aerospace into a complete demonstration system
for the military
• Design/modeling study of a ~500 W APU stack initiated
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Materials Science & Technology, MST-11Fuel Cell ResearchOAAT
Program Review, May 2002
Response to Selected Reviewers’ Comments
“Need more emphasis on automotive applications.”
Manufacturing capability resulting from the likely market-entry
of DMFCs for portable power applications should reduce the cost
andfacilitate commercialization of PEM fuel cells for higher power
applications, automotive transportation in particular. Portable
power -transportation synergy in fuel cell R&D appears to be
the best commercialization strategy.
“Not sure that LANL should be developing fuel cell stacks.”
Fundamental research has been and will remain the focus of
direct methanol fuel cell program at LANL. Few stack prototypes
have been built to prove practical viability of core DMFC
technology developed at LANL, identify possible scale-up issues and
verify adaptability of the technology to complete systems.
R
R
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Materials Science & Technology, MST-11Fuel Cell ResearchOAAT
Program Review, May 2002
Major Collaborations & Commercial Interactions ( )C
• Collaboration with Motorola on fundamental DMFC technology and
high-temperature RHFC membrane for portable power in final stage of
re-instating via CRADA; common research to begin in mid-May.
• Partnership with Ball Aerospace in FY 2002:
Complete 60 W (net power) DMFC system demonstrated to the
military;
Three-year Palm Power research project started in mid-2001,
focusing on fundamental research as well as stack development;
first 22 W stack delivered to Ball for system integration in March
2002;
Operating conditions for the APU system agreed upon; first stack
will be shipped from LANL in the fall of 2002.
R
-
Materials Science & Technology, MST-11Fuel Cell ResearchOAAT
Program Review, May 2002
Major Collaborations & Commercial Interactions (II)
• Catalyst research:
Johnson Matthey – Effect of atomic composition, morphology and
crystallography of Pt-Ru blacks on DMFC anode activity;
OMG – New carbon-supported cathode catalyst with improved
methanol tolerance;
Superior MicroPowders – Carbon-supported catalysts for PEM and
DMFC cathodes; DMFC MEAs (planned).
• Membrane/MEA research & development; polymer
fabrication:
Virginia Tech – Development of alternative polymers (BPSH) and
MEAs with significantly improved selectivity;
Hydrosize Technologies, Inc. – Fabrication of BPSH initiated;
first two batches of BPSH polymer ordered and synthesized; polymer
to be shipped to LANL within a week.
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Materials Science & Technology, MST-11Fuel Cell ResearchOAAT
Program Review, May 2002
Cathode ResearchCarbon-Supported vs. Unsupported Pt
Catalysts
Cathode Loading (mgPt cm-2)
0 1 2 3 4 5 6
i DM
FC @
0.4
5 V
(A c
m-2
)
0.0
0.1
0.2
0.3
0.4
40% Pt / C Cathode (80°C)
0.46 sLm - 10 psig
0.46 sLm - 30 psig0.05 sLm - 30 psig
0.05 sLm - 10 psig
Cathode Loading (mgPt cm-2)
0 1 2 3 4 5 6
i DM
FC@
0.4
5 V
(A c
m-2
)
0.0
0.1
0.2
0.3
0.4
Pt Black Cathode (80°C)
0.46 sLm - 10 psig
0.46 sLm - 30 psig0.05 sLm - 30 psig
0.05 sLm - 10 psig
Pt < 1.0 mg cm-2 - Pt / C catalyst
Pt > 1.0 mg cm-2 - Pt black catalyst
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Materials Science & Technology, MST-11Fuel Cell ResearchOAAT
Program Review, May 2002
Cathode ResearchNafion Content; Improved Cell Performance with
Low Total Pt Loading
Cell Current Density (A cm-2)
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
Cel
l Vol
tage
(V)
0.0
0.2
0.4
0.6
0.8
Power D
ensity (W cm
-2)
0.00
0.04
0.08
0.12
0.16
80°CTotal Pt: 1.2 mg cm-2
Pt-X / C
Nafion Weight Fraction(Cathode)
0.1 0.2 0.3 0.4 0.5
H2-
Air
Cel
l Vol
tage
@ 0
.2 A
cm
-2 (V
)
0.70
0.75
0.80
0.85
0.90
Pt / C
80°C
Achievements: (1) Nafion content in the cathode optimized at a
low Pt loading (0.6 mg cm-2)
(2) Very good performance demonstrated at 80°C with 1.2 mg cm-2
total Pt loading
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Materials Science & Technology, MST-11Fuel Cell ResearchOAAT
Program Review, May 2002
Cathode ResearchNew Binary Catalyst with Improved O2 Activity
& Methanol Tolerance
Current Density (A cm-2)
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
Cel
l Vol
tage
(V)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Pt-X / C
Pt / C
80°C, 30 psig0.6 mgPt cm-2 (cathode) 80°C
Potential (V vs. DHE)0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
Cur
rent
(mA
)
-60
-40
-20
0
20
40
60
80
Pt / C
Pt-X / C
Achievement: Even at low a Pt loading of ~ 0.6 mg cm-2, the new
binary Pt-X / C catalyst shows significantly better activity in
oxygen reduction and improved methanol-tolerance over commercial Pt
/ C catalyst (E-Tek).
Collaboration with OMG (formerly Degussa-dmc2)C
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Materials Science & Technology, MST-11Fuel Cell ResearchOAAT
Program Review, May 2002
(111)
(311)
(200)
(222)(220)
aPt = 3.910Å
0
500
1000
1500
2000
2500
3000
3500
20 40 60 80 100
Inte
nsity
(c.p
.s)
Two-Theta (degrees)
In-House Catalyst EffortNew Carbon-Supported Pt Catalyst:
80wt%Pt / C
Ultrasonic-spray / free-dry method10-µm droplets quickly frozen
in LN26.1 nm Pt particle size determined by whole-profile fitting
of XRD dataPt very well dispersed Pt (SEM)DMFC performance very
close to that of best cathode catalysts commercially available!
Pt 80°C
Current Density (A cm-2)0.0 0.1 0.2 0.3 0.4 0.5 0.6
Cel
l Vol
tage
(V)
0.0
0.2
0.4
0.6
0.8Cathode: ~ 0.6 mgPt cm
-2
_____ In-House 80 wt% Pt / C Cathode Catalyst________ 6
Commercial Pt
/
C Cathode Catalysts
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Materials Science & Technology, MST-11Fuel Cell ResearchOAAT
Program Review, May 2002
Anode ResearchPt-Ru Blacks: Catalytic Activity vs. Atomic
Ratio
XRu,bulk [%]0 20 40 60
j [A
cm
-2]
0.0
0.1
0.2
0.3
0.4
0.580°C 60°C40°C
Achievement: Optimum bulk composition of the anode catalyst
found to be 55 ± 5 at% Ru, regardless of temperature.
Collaboration with Johnson MattheyC
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Materials Science & Technology, MST-11Fuel Cell ResearchOAAT
Program Review, May 2002
Membrane / MEA ResearchEffect of Processing on Membrane
Performance
Membrane MeOH Permeability Conductivity Selectivity Relative
ED10^6 (cm2/s) mS/cm 10 -̂6 mS s/cm3 Selectivity
N117 2.73 84.7 31.0 1.0 ~3.3
BPSH-40 (A) 0.50 38.5 76.3 2.5 ~1.5BPSH-35 (B) 0.81 43 53.1 1.7
1.3BPSH-40 (B) 1.40 38.1 27.2 0.9 2.7
(a) (b)
(c) (d)
A B
BPSH-40
BPSH-35
A B
A – Membrane before processingB – Membrane after processing
Processing greatly affects BPSH polymer properties and
morphology; after processing, BPSH-35 (B) becomes similar to
BPSH-40 (A).
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Materials Science & Technology, MST-11Fuel Cell ResearchOAAT
Program Review, May 2002
Membrane / MEA ResearchDMFC MEAs with Alternative Polymers
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0 50 100 150 200 250
Current Density (mA cm-2)
Volta
ge (V
)
0
20
40
60
80
100
120
140
0 100 200 300 400 500
Current Density (mA cm-2)
Cro
ssov
er C
urre
nt (m
A c
m-2
)
N117
N117
BPSH-35 (B)
BPSH-35 (B)
Achievement: In short-term testing, with ambient air at 80°C and
1.0 M MeOH anode feed, BPSH-35 (B) offers significantly reduced
methanol crossover and comparable performance to Nafion 117.
Collaboration with Virginia Tech C
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Materials Science & Technology, MST-11Fuel Cell ResearchOAAT
Program Review, May 2002
Membrane / MEA ResearchMEA Issues Critical to Further
Progress
Membrane Fuel Cell
Conductivity (mS cm-1)
Membrane Conductivity
(mS cm-1)
Fuel Cell Relative
Selectivity
Membrane Relative
Selectivity
Nafion 117 85 110 1.0 1.3 BPSH-40 (A) 38 80 2.5 4.4 BPSH-50 (A)
40 100 1.3 3.8 BPSH-60 (A) 52 170 1.1 2.5
Ion Clad 26 130Tricoli 1.5 5.7
• Based on membrane properties alone, relative selectivity of
“alternative” MEAsshould be higher than observed in DMFC
testing.
• “Fuel cell conductivity” needs to be improved.• More research
required - with Nafion-free catalyst layers in particular.
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Materials Science & Technology, MST-11Fuel Cell ResearchOAAT
Program Review, May 2002
22 W DMFC Stack for Portable PowerHigh Efficiency, Ambient
Pressure & Low Cathode Air Flow
Current Density (A cm-2)
0.00 0.05 0.10 0.15
Stac
k Po
wer
(W)
0.00
5.00
10.00
15.00
20.00
25.00
30.00
60°C
70°C
80°C
fMeOH = 3.0 mL min-1 cell-1
fAir = 0.1 sLM cell-1
pAir = 0.76 atm (ambient)
Achievement: Very good performance demonstrated at ambient
cathode pressure (0.76 atm), low air flow (λ < 3) and relatively
high stack voltage of ~12V (0.55 V cell-1).
Collaboration with Ball AerospaceC
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Materials Science & Technology, MST-11Fuel Cell ResearchOAAT
Program Review, May 2002
500 W Prototype Stack / System Development for APUOn Track with
Stack Deliverable in Fall 2002
Current Density (A cm-2)
0.0 0.1 0.2 0.3 0.4 0.5 0.6
Cel
l Vol
tage
(V)
0.0
0.2
0.4
0.6
0.8
Cell Pow
er (W)
0
6
12
18
24
100 cm2 MEA, 80°C
Stoich 2.1
APU Stack: High-conductivity 100-cm2 graphite hardware used in
the first-generation APU cell. Performance recorded:
2.1 air stoich, 30 psig cathode back pressure: ~ 21 W1.3 air
stoich, ambient cathode pressure: ~ 11 W
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Materials Science & Technology, MST-11Fuel Cell ResearchOAAT
Program Review, May 2002
APU Hardware & Flow ModelingPressure Drop – Air Flow – Stack
Hardware
0.0
0.4
0.8
1.2
1.6
2.0
0 200 400 600 800 1000
Cathode Feed Rate (sccm)
Cel
l Pre
ssur
e D
rop
(psi
)
Calculated Pressure Drop
Experimental Data
100-cm2 Cell Pressure Drop
Manifold Flow Models
Air flow: 0.6 m/s
Alternative Compression Approach
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Materials Science & Technology, MST-11Fuel Cell ResearchOAAT
Program Review, May 2002
FY 2002: Summary
Reduction in Catalyst Loading:
Composition of cathodes with reduced Pt loading optimized; good
performance with a total precious metal loading of 1.2 mgcm-2
demonstrated at 80°C – task completed
Catalyst Research:Alternative Pt-X cathode catalyst identified
(patent pending)In-house catalyst fabrication capability
established; system used to make - commercially unavailable -
80wt%Pt/C cathode catalystStudy of the effect of Pt-to-Ru atomic
ratio on anode performance at different cell operating temperatures
– task completed
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Materials Science & Technology, MST-11Fuel Cell ResearchOAAT
Program Review, May 2002
FY 2002: Summary (II)
Membrane Research:Well-performing BPSH (sulfonated poly(arylene
ether sulfone))MEAs with significantly reduced methanol crossover
demonstrated – task completedDemonstration of short stack with 3×
better selectivity – pending
Stack R&D:
Components for 22 W DMFC stack for portable power applications
designed, fabricated and optimized in single-cell and short-stack
testing; first 22 W stack built and delivered to Ball Aerospace
Components for 500 W stack for auxiliary power applications
under development; single cell operation of 100-cm2 hardware
demonstrated with good results – task on schedule (stack delivery
planned for the fall of 2002)
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Materials Science & Technology, MST-11Fuel Cell ResearchOAAT
Program Review, May 2002
FY 2003 Plans
• Continue fundamental research and development in
electrocatalysis of methanol oxidation and oxygen reduction;
improve performance by optimizing hydrophilic/hydrophobic
properties of the cathode (Sep 03)
• Study and report on the effect of sulfonation on performance
of BPSH membranes in direct methanol fuel cells; narrow the gap
between bench-top and fuel-cell selectivity of alternative
membranes to no more than 30% (May 03)
• Demonstrate for at least 500 hours durability of Nafion and
alternative MEAs (no more than 15% performance loss) (May 03)
• Demonstrate for at least 100 hours sustained operation of a
“portable power” DMFC stack with air stoich below two (May 03)
• Investigate composition of the DMFC cathode exhaust as a
function of cell operating conditions (Sep 03)