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Novel Designs of Polymer Electrolyte Membrane (PEM) Fuel Cells
Ranga PitchumaniAdvanced Materials and Technologies Laboratory
Department of Mechanical Engineering
Virginia Tech
Blacksburg, VA 24061-0238
http://www.me.vt.edu/amtl
Presented at the Department of Mechanical, Aerospace and Nuclear EngineeringRensselaer Polytechnic Institute, October 29, 2008
Advanced Materials and Technologies Laboratory
MISSION: Conduct research towards improving the fundamental description and
understanding of complex physical phenomena governing materials processing
and design, and emerging technologies. The fundamental description and
understanding are applied towards practical development, design, optimization
and control.
LAB PERSONNEL:
6-8 Graduate Students, 1-2 Postdocs
2 Undergraduate Students
2-3 High School Students each summer
RESEARCH AREAS: Advanced Materials Processing
Microsystems and Micromanufacturing
Fuel Cells/Energy
Design and Manufacturing
Core Sciences
Research Sponsors ($4M)
Industries7%NASA
11%
DOD44%
NSF38%
$4.7M total funding
Polymer Electrolyte Membrane (PEM) Fuel Cells
Fuel cells convert chemical energy directly to electrical energy. With the
byproducts being only water and heat, they are attractive candidates for
clean power generation.
Fuel Cell Performance and Related Issues
Measured in terms of a Cell voltage – Current density variation, referred to
as a polarization curve.
Ce
ll V
olt
ag
e, V
Average Current Density, I
Local current density could be high and its spatial
variation is a factor influencing membrane reliability; it is
desirable to minimize the spatial variation.
A second issue pertains to the system complexity
associated with balance of plant; it is desirable to
reduce system complexity.
Outline
Uniformity of current density in fuel cells
Tailoring of operating parameters
Materials design
Air-breathing fuel cells for reduced complexity
Micro fuel cells
cells E
0 y
y const.; p
0 y
v ; 0
y
u
ia
0x
mm
0 x
s
s
Mem
bra
ne
An
od
e g
as d
iffusio
n
An
od
e c
ata
lyst
const.y
const.y ;0y
const.v ;0u
OH
OH
2
22
const.y
0y const.;y
const.v ;0u
OH
OH
2
22
0s
xy
0 y
y const.; p
0 y
v ; 0
y
u
ic
Cath
od
e g
as d
iffusio
n
Cath
od
e c
han
nel
An
od
e c
han
nel
Cath
od
e c
ata
lyst
Computational Modeling
(r V ) Sc
(r V
r V ) p (
r V ) Su
(r V y i) ( Di
eff y i) Si
( s
eff
s) Ss 0.0
( m
eff
m ) Sm 0.0
0
anode:
cathode:
0
0
Sc
0 0Membrane
anode:
cathode:Catalystlayers
0 0GDL/screen
0 00Gas channels
Ss , Sm Si SuDescription
OHc
Oc M
F
jM
F
j22 24
22 H
a MF
j22
Ha MF
j
24 O
c MF
j
OHc MF
j22
0
0
am
as
jS
jS
0
0
cm
cs
jS
jS
Vk
mffFcz
k
kV
k
mffFcz
k
kV
k
cells E
0 y
y const.; p
0 y
v ; 0
y
u
ia
0x
mm
0 x
s
s
Mem
bra
ne
An
od
e g
as d
iffusio
n
An
od
e c
ata
lyst
const.y
const.y ;0y
const.v ;0u
OH
OH
2
22
const.y
0y const.;y
const.v ;0u
OH
OH
2
22
0s
xy
0 y
y const.; p
0 y
v ; 0
y
u
ic
Cath
od
e g
as d
iffusio
n
Cath
od
e c
han
nel
An
od
e c
han
nel
Cath
od
e c
ata
lyst
Butler-Volmer equations: ja ja,ref (xh2
xh2,ref
) a (ea F
RTa
ea F
RTa
); jc jc,ref (xo2
xo2,ref
) c (ecF
RTc
ecF
RTc
)
Anode: msa c s m EcellCathode:
Local Current Density Variation
Iave = 1.09 A/cm2; ΔI = 1.10 A/cm2
0
1
2
3
4
5
6
7
0.105 0.110 0.115 0.120 0.125
Location across the cell in the membrane, x [cm]
I [A/cm2]
1.700
1.500
1.300
1.100
0.900
0.700E
cell = 0.2 V
Locatio
n a
lon
g the
chan
ne
l, y
[cm
]
(a)
0
1
2
3
4
5
6
7
0.105 0.110 0.115 0.120 0.125
Locatio
n a
lon
g the
chan
ne
l, y
[cm
]Location across the cell in the membrane, x [cm]
I [A/cm2]
0.282
0.278
0.274
0.270
(b)E
cell = 0.8 V
Loca
tion a
long t
he c
hannel, y
[cm
] Iave = 0.28 A/cm2; ΔI = 0.02 A/cm2
Mem
bra
ne
An
od
e g
as d
iffusio
n
An
od
e c
ata
lyst
Cath
od
e g
as d
iffusio
n
Cath
od
e c
han
nel
An
od
e c
han
nel
Cath
od
e c
ata
lyst
xy
Bounds on Operating Parameters
330
340
350
360
370
0.2 0.3 0.4 0.5 0.6 0.7 0.8
Cell Voltage, Ecell
[V]
Cell
Tem
pera
ture
, T
[K
] a = 1.3
2.0
5.0
1.5
8.0
12
18
I/Imax
< 20%
3.0
(c)
A
B
C
A design window can be constructed by identifying the bounds of operating parameter inwhich the current density variation is within a specified constraint. The constraint of 0.2(20 percent) is used as an example to illustrate the methodology.
There is an upper bound on the temperature which keeps the non-uniformity of thecurrent density lower than 20%. Decreasing the temperature can help decrease the non-uniformity of the current density.
The maximum power density occurs around Ecell = 0.5 V and T = 353 K (Point A). Fromthat point, power density decreases with either increasing the temperature or decreasingthe temperature.
The stoichiometry can be another criterion to decide the optimum operating conditions.Increasing anode stoichiometry decreases the non-uniformity of the current density.
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Ecell
= 0.20 V
Ecell
= 0.35 V
Ecell
= 0.50 V
Ecell
= 0.65 V
Ecell
= 0.80 V
323 333 343 353 363 373
Curr
en
t D
en
sity V
ari
atio
n,
I/I m
ax
Temperature, T [K]
(a)
Cu
rre
nt D
ensity V
ariatio
n
I/I m
ax
330
340
350
360
370
0.2 0.3 0.4 0.5 0.6 0.7 0.8
Cell Voltage, Ecell
[V]C
ell
Tem
pera
ture
, T
[K
]
0.45
0.40
0.30
0.20
Pd = 0.20
0.30
I/Imax
< 20%
(b)
A
Ce
ll T
em
pe
ratu
re, T
[K
]
Y. Zhang, A. Mawardi, R. Pitchumani, ASME J. Fuel Cell Sci. Tech., 2006
Operational DesignY. Zhang, A. Mawardi, R. Pitchumani, ASME J. Fuel Cell Sci. Tech., 2006
Cell Voltage 0.60 V Cell Voltage 0.70 V
max Pd min a
max Pd min a max Pd min a
Ecell [V] 0.45 0.39 0.60 0.60 0.70 0.70
T [K] 353 353 353 361 369 353
pa [atm] 3 3 3 3 3 3
pc [atm] 3 3 7 3 3 3
RHa 1.0 1.0 1.0 1.0 1.0 1.0
RHc 1.0 1.0 1.0 1.0 1.0 1.0
ma [kg/s] 6.5 x 10-5
6.5 x 10-5
6.5 x 10-5
6.5 x 10-5
6.5 x 10-5
2.0 x 10-5
Op
era
tin
g P
ara
mete
r
mc [kg/s] 5.0 x 10-3
5.0 x 10-3
5.0 x 10-4
5.0 x 10-4
5.0 x 10-4
5.0 x 10-4
Pd [W/cm2] 0.52
0.51 0.47 0.42 0.40 0.34
Ob
jecti
ve
1.6 1.4 2.5 2.0 2.2 2.1
Design Window Fig. 11c Fig. 11d Fig. 11c Fig. 8b Fig. 8a Fig. 11b
Concept:
The reactant species concentrations decrease along the channel due tothe reaction consumption, which leads to non-uniform speciesdistribution and the non-uniform current density distribution.
The purpose of the gas diffusion layers in a fuel cell is to distribute thereactant gases into the catalyst layers and to allow for electronicconduction simultaneously.
The gas diffusion layer with gradually increasing porosity along thechannel will help to distribute the reactant gases into the catalyst layermore evenly, correspondingly achieving a uniform current densitydistribution.
Larger catalyst loading increases the surface area for electrochemicalreactions and more reactant species are involved into the reactions.
Implementing gradually increasing catalyst loading on the membranesurface along the channel can compensate for depletion of reactantspecies and reduce the current density variation.
Variations most effective on the cathode side.
Innovative Material Designs
tGDL tmesh
eff
tGDL
GDL
tmesh
mesh
The graded gas diffusion layer consists two parallel layers along the channel—a regular carbon paper gas diffusion layer and a layer of metal mesh with graded porosity along the channel.
The effective local GDL porosity is calculated as the thickness-weighted harmonic mean of the porosities of the two layers, expressed as:
1
Graded GDL
Gasket
+ =
Graded metal meshCarbon paper
2
3
C-paper
GDL
Graded
metal mesh
tGDL tmesh
GDL mesh
Fabrication of a Graded Porosity GDL
The catalyst loading is decided by the porosity of the screens; largerporosity of the screen or multiple printing leads to more catalystparticles being deposited on the membrane surface and increases thecatalyst loading.
The mixture ink of the carbon particles, catalyst particles, liquidmembrane solution and related solvent was screen printed on Teflonfilms using a Systematic Automation Model 81 Series Screen Printer.
Multiple screen printings are used to obtain the graded catalystloading: the first printing covers the entire area and the followingprintings gradually decrease the printing area to obtain aprogressively increasing catalyst loading along the length.
screen
screen printer
The MEA with graded cathode catalyst loading was fabricated through screen printing.
first printing second printing third printing final graded catalyst loading
dry dry dry
The decals are placed on the two sides of the Nafion 112 membrane from Du Pont. After dryingand hot pressing at 403 K and 70 kg/cm2 for 3 minutes with Nafion 112, the Teflon support filmswere peeled off from the anode and cathode sides of the MEA.
Fabrication of Graded Catalyst MEA
Teflon
Teflon
uniform catalyst loading
graded catalyst loadingmembrane
copper wire
1, 5. Anode and Cathode flow channel plates – glass-fiber epoxy composite
2. Anode current collector – metal mesh (Nickel, Dexmet)
3. GDL (SIGRACETR® GDL 10BB, SGL Technologies) and MEA (NRE-211, DuPont)
4. Cathode segmented current collector – metal mesh (Nickel, Dexmet)
6. Teflon Gasket
1 2 3 4 5
6
Local Current Density Measurement
data
data
Gas flow
resistors
Fuel
cell
PC
R6
R5
R4
R3
R2
R1
Data
acquisition
V1
V2
V3
V4
V5
V6
Test load
i
ilocal
R
Vi
2
3
4
1. Fuel cell test station
2. Test load
3. Data acquisition
4. Fuel cell
1
0.0
0.1
0.2
0.3
0.4
0.5
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07
Iave
= 0.5 A Iave
= 0.5 A
Iave
= 1.0 A Iave
= 1.0 A
Iave
= 1.5 A Iave
= 1.5 A
Location in the y direction, y [m]
Lo
ca
l C
urr
en
t, I [A
]
The local current distributions with the constant porosity and catalyst loadinggenerally decrease with location along the channel. The variation of the localcurrent along the entire channel increases in magnitude with increase of averagecurrent.
The local current variation along the entire channel with graded parametersdecreases compared with the distribution with the constant parameters at thesame average current.
The design task is to determine the optimum variations of the porosity and thecatalyst loading.
Constant = 0.53 (solid lines)
Graded = 0.25, 0.53, 0.79
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07
Iave
= 0.5 A
Iave
= 1.0 A
Iave
= 1.5 A
Iave
= 2.0 A
Iave
= 0.5 A
Iave
= 1.0 A
Iave
= 1.5 A
Iave
= 2.0 A
Lo
ca
l C
urr
en
t, I [A
]
Location in the y direction, y [m]
Constant Lc = 0.3 mg/cm2 (solid lines)
Graded Lc = 0.21, 0.32, 0.43 mg/cm2
Measured Local Current Distributions
Lo
ca
l C
urr
en
t [A
]
Lo
ca
l C
urr
en
t [A
]
Parametrization of the gradations: The porosity and the catalyst loadingdistributions are parameterized using
f f0 a(y
L)b;
f for graded porosity GDL
f Lc for graded catalyst loading
f
f1 (0 y y1)
f2 (y1 y y2)
f3 (y2 y L)
Design of the variations is posed as an optimization problem
Optimum GDL and Catalyst Gradations
power law functional form
piecewise constant form
y = 0 y = L
y1 y2
f1
f2
f3
Optimum
f0, a, b
or
f1, f2, f3
Yes
Fuel Cell Simulation
(Fluent)
Nelder–Mead
Simplex Optimization
(MATLAB)
Initial guess of
parameters
f0, a, b or f1, f2, f3
∆I/Imin and
Pd
Optimality
Conditions
Satisfied?
No
new
f0, a, b
or
f1, f2, f3
Maximizef0 ,a,b or f1 , f2 , f3
Pd
I
Imin
Imax Imin
Imin
%
0 f0 (1 a) 0 < f1 1
a 0 or 0 < f2 1
b 0 0 < f3 1
0.0
0.2
0.4
0.6
0.8
1.0
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08
= 0.482
= 0.20+0.797(y/L)1.84Poro
sity o
f C
ath
ode
GD
L,
Location in the y direction, y [m]
Ecell
= 0.5 V, I/Imin
= 5%
(a)
9000
9500
10000
10500
11000
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08
= 0.482
= 0.20+0.797(y/L)1.84
Lo
ca
l C
urr
ent D
en
sity
, I [A
/m2]
Location in the y direction, y [m]
Ecell
= 0.5 V, I/Imin
= 5%
(b)
Optimum Parameters and Current Density Distributions
GD
L P
oro
sity
Lo
ca
l C
urr
en
t D
en
sity [A
/m2]
4500
4700
4900
5100
5300
5500
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08
Lc = 0.31
Lc = 0.23+0.16(y/L)1.18
Lo
ca
l C
urr
en
t D
en
sity, I [A
/m2]
Location in the y direction, y [m]
Ecell
= 0.50 V, I/Imin
= 5%
(b)
0.0
0.1
0.2
0.3
0.4
0.5
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08
Lc = 0.31
Lc = 0.23+0.16(y/L)1.18
Ca
tho
de
Ca
taly
st L
oa
din
g, L
c [m
g/c
m2]
Location in the y direction, y [m]
Ecell
= 0.50 V, I/Imin
= 5%
(a)
Lo
ca
l C
urr
en
t D
en
sity,
[A
/m2]
Cata
lyst L
oa
din
g [m
g/c
m2]
9000
10000
11000
12000
13000
14000
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08
= 0.175+0.824(y/L)2.92
= 0.184, 0.307, 0.985Lo
ca
l C
urr
ent D
en
sity
, I [A
/m2]
Location in the y direction, y [m]
Ecell
= 0.35 V, I/Imin
= 20%(b)
0.0
0.1
0.2
0.3
0.4
0.5
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08
Lc = 0.18+0.26(y/L)1.74
Location in the y direction, y [m]
Ca
tho
de C
ata
lyst L
oad
ing, L
c [
mg
/cm
2]
(a)
Ecell
= 0.35 V, I/Imin
= 10%
0.190.22
0.37
0.0
0.2
0.4
0.6
0.8
1.0
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08
= 0.174+0.829(y/L)3.08
Po
rosity
of C
ath
od
e G
DL,
Location in the y direction, y [m]
(a)E
cell = 0.35 V, I/I
min = 20%
0.184
0.307
0.985
6500
7000
7500
8000
8500
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08
Lc = 0.18+0.26(y/L)1.74
Lc = 0.19, 0.22, 0.37Lo
ca
l C
urr
en
t D
en
sity, I [A
/m2]
Location in the y direction, y [m]
Ecell
= 0.35 V, I/Imin
= 10%(b)
Comparison Between Discrete and Continuous Profiles
GD
L P
oro
sity
Lo
ca
l C
urr
en
t D
en
sity [A
/m2]
Lo
ca
l C
urr
en
t D
en
sity,
[A
/m2]
Cata
lyst L
oa
din
g [m
g/c
m2]
Air-breathing Fuel Cells
If the cathode gas channel is eliminated, and the cathode surface is
directly exposed to the ambient air, the fuel cell draws air by natural
convection
The design eliminates the need for a pumping system and flow channels
at the cathode (partially-passive design)
FC System Cost Breakdown (Carlson, et al., 2005):
– 63% stack (77% bipolar plate); 34% BOP
An air-breathing fuel cell cartridge consists of two fuel cells sharing a
common hydrogen flow chamber at the anode
An array of several cartridges can be used to construct a fuel stack to
meet application requirements
Air Breathing PEMFC Cartridge and Stack
Fuel cell cartridges
Power Converter
Active Natural Convection
Area
2b
H
h
Ls
2 15 4 3
yx
H
1. Frame2. Metal mesh3. GDL4. Catalyst5. Membrane6. H2 chamber
Na
tura
l Co
nv
ectio
n
AirH2
Na
tura
l Co
nv
ectio
n
Air
6
Computational Modeling
solidgas
eff
m
51eff
m
s
eff
s
refi
51eff
i
mm
eff
m
ss
eff
s
T
eff
p
ii
eff
ii
V
c
k1kk
1
DD
Where
00S
00S
STkTVc
SyDyV
SgVpVV
SV
)(
)(
.)(
.)(
)()(
)()(
)()(
)(
.
,
.
Symmetric
(stack)
Heated Bottom
Wall (stack)
ST
ja ai2
meff
(anode)
jc ci2
meff
(cathode)
i2
meff
(membrane)
Validation and Results
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Experiment (ma = 0.1 lpm)
Simulation (ma = 0.1 lpm)
0 1,000 2,000 3,000 4,000 5,000
Cell
Voltage, E
cell [
V]
Current Density, I [A/m 2]
T = 298 K, RHa = 0, H = 1.68 cm
0.0
2.0
4.0
6.0
8.0
10.0
Simulation
Experiment
0 1,000 2,000 3,000 4,000
Current Density, I [A/m2]
Sta
ck V
oltage, E
sta
ck [V
]
H = 5.0 cm, Number of Cartridges: 5
0.0
0.2
0.4
0.6
0.8
1.0
h = 0.0 mm
h = 0.5 mm
h = 2.0 mm
h = 10.0 mm
0 2,000 4,000 6,000 8,000
Current Density, I [A/m2]
Cell
Voltage, E
ce
ll [V
]
H = 5.0 cm
0.0
0.2
0.4
0.6
0.8
1.0
b = 2.0 mm
b = 4.0 mm
b = 6.0 mm
0 2,000 4,000 6,000 8,000
Current Density, I [A/m2]
Cell
Voltage, E
ce
ll [V
]
H = 5.0 cm
Fuel cell cartridges
Power Converter
Active Natural Convection
Area
2b
H
h
Ls
Y. Zhang, A. Mawardi, R. Pitchumani, J. Power Sources, 2007
Y. Zhang and R. Pitchumani, Int. J. Heat and Mass Transfer, 2007
Stack Design Example
From the polarization curves for various cartridge spacing, the relation between current densityand power density and cartridge spacing can be derived.
The peak current density and power density decreases as cell voltage density increases
A design case where the fuel cell is specified to operate at Estack = 8 V, Pstack = 40 W, and themaximum stack length, Ls= 8 cm, is considered. The cartridge thickness is t = 6.5 mm.
The required cell voltage density is E’ = Estack/Ls = 0.1 V/mm, which has a peak power density of1700 W/m2 at an inter-cartridge spacing of 2b = 3.5 mm (Point A).
The number of cartridges required is: N = Ls/(2b+t) = 8. The cell voltage Ecell = Estack/2N = 0.5 V.
Since, for the value of E’ = 0.1 V/mm and 2b = 3.5 mm, the current density is I = 3450 A/m2, andthe current required is I stack= Pstack / Estack= 5 A, the active area of each side of the cartridge is A= Istack / I= 14.5 cm2. The cartridge width is W = A/H=2.9 cm.
Y. Zhang, A. Mawardi, R. Pitchumani,
J. Power Sources, 2007
0
500
1,000
1,500
2,000
2,500
3,000
E' = 0.050 V/mm
E' = 0.075 V/mm
E' = 0.100 V/mm
E' = 0.150 V/mm
0 2 4 6 8 10 12
Cartridge Spacing, 2b [mm]
H = 5.0 cm
Po
we
r D
en
sity, P
d [W
/m2]
A
(b)
Pow
er
Density [
W/m
2]
0
3,000
6,000
9,000
E' = 0.050 V/mm
E' = 0.075 V/mm
E' = 0.100 V/mm
E' = 0.150 V/mm
0 2 4 6 8 10 12
Cartridge Spacing, 2b [mm]
H = 5.0 cm
Ave
rag
e C
urr
en
t D
en
sity, I a
ve [A
/m2]
(a)
A
Ave C
urr
ent D
ensity [
A/m
2]
0.0
0.2
0.4
0.6
0.8
1.0
b = 2.0 mm
b = 4.0 mm
b = 6.0 mm
0 2,000 4,000 6,000 8,000
Current Density, I [A/m2]
Cell
Voltage, E
ce
ll [V
]
H = 5.0 cm
Fuel cell cartridges
Power Converter
Active Natural Convection
Area
2b
H
h
Ls
Hybrid Fuel Cell/Battery System
Design specifications:
25 W avg. power, 40 W peak power (9:1 nominal/peak power duration ratio)
Power delivery at 12 VDC (regulated)
Hydrogen fuel, and air-cooled
Provide at least 1800 Wh of energy over 72 hrs
Fuel Cell
DC/DC
Converter12 VDC
01
16
Fu
el C
ell
Sta
ck
Wide Input Range
DC-DC Converter
Up to 16 Channels
12V Output
Computer
RS-232 Serial
Communication
Power Management
MicrocontrollerADC
Memory
(EEPROM)
Real-time Clock
Multiplexer
Backup Battery
CSR
CSR
CSR
CSR: Current Sensing Resistor
ADC: Analog to Digital Converter
Monitor/
ControlControl
On-board
Temperature
Sensor
MultiplexerVoltage/Current
LCD
Prototype System
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5.0
10.0
15.0
0
5
10
15
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25
30
35
0 1 2 3 4
Voltage (V)
Power (W)
Current, I [A]
Sta
ck V
olta
ge
, E
Sta
ck [
V]
Po
we
r, P [W
]
T = 25 oC, RHa = 0 %, H
2 Pressure=5 psi
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2.00
4.00
6.00
8.00
10.00
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5.0
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30
0 10 20 30 40 50
Voltage (V)
Power (W)
Po
wer
(W)
Vo
ltag
e (
V)
Time (Hrs)
Long Term TestFive units (10 fuel cells), room temperature, flow rate = 0.75lpm
Planar PEM Micro Fuel Cell (µPEMFC)
Traditional fuel cell designs are based on a ―sandwich‖ construction of
stacking constituent layers
Micro and miniature fuel cell designs have also focused primarily on the
layered design, while shrinking the size
Proposed concept is that of combining microfabrication techniques with
fuel cell technologies to achieve compact, modular, and scalable designs
for high power density
A unique feature of the PEMFC design is that the cathode and the
anode channels are patterned in a planer configuration. The design also
eliminates gas diffusion layers
Design lends itself to fabrication of fuel cell arrays with associated
circuitry on a single wafer
Planar PEM Micro Fuel Cell (µPEMFC)
H+
Patterned Nafion® micro channels
No gas diffusion layers
H2 and air operation
Concept also applicable to direct methanol fuel cells (DMFC)
H2
O2
Membrane
x
y
(a) y
zCatalystCatalyst
H2 O2
(b)
View A-A’
PDMS
A
A’
500 m Si Substrate
40~50 m Nafion®
Fabrication
Si Substrate
Nafion®
Si Micro Die
1. Solution casting
2. Hot pressing of microchannels
3. Current collector depositionAu Au
mask
Substrate
Substrate
Nafion
Pt/C Catalyst
mask
4. Catalyst deposition
Substrate
PDMS
H+H2 O2
5. Sealing with PDMS Active area ~0.33 mm2
Channel width = 500 um
Channel length = 25 mm
PEMFC Testing
0
0.1
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0.7
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0.9
0.00 42.67 85.33 128.00 218.66 253.33
I (mA/cm2)
V (
V)
0
10
20
30
40
50
60
70
80
P (
mW
/cm
2)
V (V)
P (mW/cm2)
0
20
40
60
80
100
120
140
Po
we
r D
en
sit
y (
mW
/cm
2)
Min
ne
so
ta
Fra
un
ho
fer
UC
ON
N
Be
ll La
bs
Sta
nfo
rd
Illino
is
Ca
se
We
ste
rn
Lo
uis
ian
a T
ech
Research Group
Comparison of Power Densities Obtained by Various Research Groups
PEMFC Arrays and Interdigitated Stacks
Parallel stack of 7 PEMFCs
Series-parallel stack of 21 PEMFCs
Summary
Strategies for achieving uniformity of current density in a PEM fuel cell were discussed. One approach is based on tailoring the operating parameters while the other approach is that of using graded gas diffusion and/or catalyst layers.
A semi-passive air-breathing fuel cell design was presented. A prototype stack was developed to meet target requirements.
A novel planar micro fuel cell design was discussed, which presents opportunities for high density micro power generation and integration with microelectronics.
Acknowledgments
The work was funded by the U.S. Army RDE-COM through Contract No. DAAB07-03-3-K-415.
Students, postdocs and collaborators
Dr. Andryas Mawardi (Chrysler Corporation)
Dr. Yanyan Zhang (GM Fuel Cells)
Dr. Richard Johnson (ASML)
Brian Elolampi (Analog Devices)
Simon Wong (Cornell)
Runhong Deng (Symbol Technologies)
Profs. Lei Zhu (CMBE) and Robert Magnusson (ECE)