SURFACE AREA MICROSTRUCTURE GAS DIFFUSION LAYER AND ITS EFFECTS ON MEA FUEL CELL.

SEMINAR NASIONAL
L TEKNIK KIIMIA SOEBA
ARDJO BROTOHARDJO
ONO IX
Program Stu
udi Teknik Kimia UPN “V
Veteran” Jawaa Timur
Surabayya, 21 Juni 20012

SU
URFACE AREA
A
MIICROSTR
RUCTURE
E GAS DIF
FFUSION
N LAYER
AND ITS EFFECT
TS ON ME
EA FUEL C
CELL

Raamli Sitangg
gang
a. Fuel
F Cell Insttitute, Univeersiti Kebanggsaan Malayysia, 43600 U
UKM, Bangii, Selangor,
M
Malaysia
b.
b Teknik Kimia, FTI, UP
PN ”Veterann”. Jl. SWK 104 Condonngcatur, Yoggyakarta,
Indonnesia, 552833
Abstract
The Meembrane Electtrode Assembly
ly (MEA) micrrostructure is the path in w
which the inputt gases, namely,
hydrogeen and comprressed air, willl follow throuugh in the proocess of obtainning energy frrom the polym
mer
electrod
de membrane fuel cell (PE
EMFC) system

m. The efficien
ncy of the connversion is deependent on the
t
microsttructure model of the mateerials used in making this gas
g diffusion layer (GDE or
o gas diffusion
electrod
de (GDE). Forr every change in microstructture dimensionn, hence the eleectrical output obtained will be
affected
d. Therefore, controlling the MEA microstrructure in its faabrication is ann imperative step in producing
a good MEA. The conntrolling param
meters used arre the surface area of micro pore inside th
he Gas Diffusion
Layer (GDL).
(
The meethods of BET
T are utilized inn the study of surfaces,
s
respeectively; whilee the single staack
fuel celll simulation iss used in obtain

ning the currennt-voltage relaationship. Resuults of the analyyses showed thhat
the currrent MEA Fuel Cell increasinng as well as iincreasing surfface area GDL
L. Whereas, suurface area GD
DL
is one of
o the parameteer control to geet GDL approppriate.
Keyworrds: surface arrea, cell potenttial fuel cell
I.INTR
RODUCTION
c
wayy. It was as connverter hydroggen
PEM Fuel Cell was electricc power generaator was used continuous
into eleectric, whereaas Hydrogen can be gottenn from anotheer natural resources such as
a air by usinng
photovo
oltaic, plants as
a cane plant by
y cracking proocess and reforrming process. At the first tim
me, fuel cell was
w

used for certain casess like electric generator
g
and tto produce watter but for this time have beeen used transpoort
power station
s
and poortable devices needs. Fuel C
Cell, using hyddrogen gas andd oxygen that theory for 1m
mol
Hydrog
gen at atm, tem
mperature 287oK,
K produce pow
wer of 237.200
0 Joule or equual 1.23 Volt ellectric. Although
the air which was ussed Fuel Cell was
w not pure, humidification
n and hydrogeen rate have been
b
arranged so
hich was produuced 1.16 voltt at open circcuit. Thus, Fueel Cell might not

n produce voolt
voltage maximum wh
um of 1 mol Hydrogen
H
(EG,2000). Besidess that, in it appplication was nneeded volt aboout 200-300 voolt
maximu
installinng cell in Fueel Cell stack was
w done in sseries manner. So that the stack was sm
mall enough thhus
fabricattion of Fuel Cell
C stack used
d MEA cell.. Base on mappping which was
w done in MEA
M
fabricatioon,
lowerin
ng of size and cost
c of PEM Fuuel Cell fabricaation was donee by choice meeans process technique of ME
EA
fabricattion from Hot Pressing techn

nique up to usse Plasma technnique. The foccus of the main fabrication for
f
decreassing thick and interest of cattalyst Pt mg/cm
m 2 of MEA. For ‘ink-baseed’ interest cattalyst about 0.15
mgPt/cm
m2-0.3 mgPt/ccm2 (Thomas,1998). This inteerest is the cosst still high soo the researchees of engineerinng
applied
d type of studyy method in micro
m
scale maanner. Then fab
brication in micro
m
scale man
nner have direect
develop
pment until might get thicck of MEA 3000 micron into
o 15 nm (Spaakovsky, 2000)) and interest of
catalystt Pt of MEA frrom 2 mgPt/cm
m2 (Eisman, 19999) to 0.01 mg
gPt/cm2 (Raim

mundo, 2002). In
I this study was
w
using method
m
which was
w well but done
d
increasingg of Fuel Cell performance bby controlling of surface are of
layers MEA
M
structure at MEA Fuel Cell fabricatioon process
2.THEO
ORY
Perform
mance of fuel cell is depenndent of surfa
face area the mass transfer (EG, 2000) so surface arrea
determiined. Accordinng to Ruthven
n (1997) surfface area mateerial 200-15000 m2/g includ
de type material

micropoorous economiic for MEA Fuuel Cell (Sergeei, 2002, Lean, 2002). In this paper, surfacee area material is
determiined base on diameter
d
microp
pore while diaameter pore deetermined by ppolymer compootition. Knowinng

B.6-1

SEMINAR NASIONAL
L TEKNIK KIIMIA SOEBA
ARDJO BROTOHARDJO
ONO IX
Program Stu
udi Teknik Kimia UPN “V
Veteran” Jawaa Timur
Surabayya, 21 Juni 20012
influencce of surface area
a
pore mateerial in perfoormance MEA fuel Cell, ME
EA consists five of layers liike

figur 1. Correlation su
urface area porre material tow
ward performance MEA is exxplained as folllows.

 
 
 
 
 
 
 

Fig 1. Membbrane Electrodde Assembly (M
MEA)

 
In MEA
A application, transport
t
phenomena from gaas H2 and O2 will

w occur in GDE.
G
It will pro
oduce electron in
layer an
nd H2O in layeer (4). If in fabbrication of sizze of GDE thicck is small moore compared of
o high, then gas
g
flow in steady state at
a GDE and GD
DE producing heat perfectly so distributioon modelling current
c
electric is
1997). Parametter determinedd current electrric
dependeent gas diffusiion, chemical reaction, ohmiic loss (Marr,1
value thhat are surface area active, ko
onductivity, gaas diffusivity efffective and reeaction constannta in DGE layeer.
Evaluattion in this is focussed
f
in parrameter of Difffusivity Efectiive of gas fluidda in DGL, whhereas the otheers

parameter did not in
nfluence. If deesign GDL wiith diameter pore
p
size closee to diameter of molecul gas
g
hydrogeen and oksygenn about 3.28 Ao (Xue-Dong , 1998, Ticiannelli, 1988) butt small more of
o 20 Ao Ruthvven
(1997) so each of porre diameter willl be gotten suurface area poree. If value of surface
s
area po
ore GDL and gas
g
diffusivvity into param
meter of perform
mance MEA fuuel Cell then will
w be gotten coorrelation betw
ween surface arrea
with peerformance ME
EA fuel cell
3.EXPE
ERIMENT
In expeeriment, processs fabrication have
h
two stepss there are (1) formulation m
material by usinng design expeert
(2) coatting Carbon In
nk at karbon klloth by sprayerr system. Sprayyer system connsists sprayer Gun
G and drayinng.
The raw
w materials too grow materiaal consists of Polymertetrafflouroethylenee, 60 w % disppersion in watter
(PTFE)) (Aldrich cheemical Co, Incc ), activated carbon (Ajax
x chemicals), ccarbon cloth (E-TEK)
(
and 2Propanool 99.5 % (Alldrich chemicaal Co, Inc). coompound of PT
TFE, Activatedd Carbon and Alcohol callled
carbon Ink and fabriication result compound
c
bettween carbon ink with carboon cloth calledd Gas Diffusion
(
whereaas GDL is em
mbedded c witth carbon inkk catalyst calleed GDE. In th
his paper whiich
Layer (GDL)
evaluateed is GDL wheereas GDE willl be there in thhe latter paper. Then to know
w GDL morphoologi. GDL usinng
SEM method,
m
characcterisation of surface
s
area byy metode BET
T. Knowing ddiffusivity by metode
m
Ruthvven
(Ruthveen ,1997, Do,1998) and to knnow MEA polaarisation voltagge and current by metodologyy of Programm
mer
Fuel Ceell Group (FCU
UKM,2002).
4.RESU
ULT AND DIS
SCUSSION
Surfacee area pore of Gas Diffusion
n Layer in our experiment, th
he fulfilled carrbon to sprayerr has 1650 m2 /g
surface area with 22 Ả pore diametter. After thatt the carbon in
nk with 1.5 cpp viscosities wiill be fulfilled to
on and PTFE ffrom 0 to 10 % concentratioon.
sprayerr that consists of 20 ml alcohol, 2.156 g aactivated carbo
Another material thatt we used is 50 cm 2 wide ccarbon cloth. The sprayer has
h 60 cm/min
n x-axis sprayinng
speed with
w static y-axxis and height in
i z-axis of 122 cm. The dray
ying temperatuure has to be seet to 110ºC forr 4
hours processing
p
timee. From experim
ment, we couldd observe that with
w larger PTF
FE compositioon, the DGL poore
diameteer will decrease. Using DR method
m
Autosoorb-1 we foundd that with 2%
% to 5% PTFE composition has
h
pore diaameter of 4.5 to 9 Ả. In the DGL,
D
the pore diameter is sm
maller than 20 Ả and larger thhan H2 moleculles
3.464 Ao (Michaelidees, 1998). Bassed on Gregg‘s classificationns (1982), thee growth pore diameter is sttill
above classified
c
micro
opore.

B.6-2

SEMINAR NASIONAL
L TEKNIK KIIMIA SOEBA
ARDJO BROTOHARDJO
ONO IX
Program Stu
udi Teknik Kimia UPN “V
Veteran” Jawaa Timur
Surabayya, 21 Juni 20012

 
 
 
 
 
 
Fig.2. Effectt pore on Surface Area
Table:1
1 Experimenta
al data of Gas Diffusion Laayer (GDL)
PRO
OPERTY ON MEA
M
FUEL CE
ELL
Operatiing pressure
Operatiing temperaturee
Cell voltage
ved hydrogen con.
c At a refereence
Dissolv
Dissolv
ved oxygen con
n. at a referencee
Potentiaal in the electroode phase

G
GDL5
1 barr
80 oC
0.65 V
5.19 mol m-3
3.16 mol m-3

GDL4
1 bar
80 oC
0.65
0
V
5.19 mol m-3
3.16 mol m-3

GDL3
1 bar
80 oC
0.65 V
5.19 mol
m-3

GDE
Commerce.
1 bar
80 oC
0.65 V
5.19 mol
m-3
mol m-3
1.0 V

1.0

V

Potentiaal in the memb
brane phase

0.0

Potentiaal different bettween electrodee and

0.0

Membrrane at equilibrrium

466 µm

4 µm
466

466 µm

480 µm

0.1
0.4

0.1
0
0.4
0

0.1
0.4

01
0.4

Diffusioon coefficient of
o the dissolveed
hydrogeen gas inside thhe micro porouus

964887 A.s
mol-1
8.25xx 10 –6
m2s-11

96487
9
A.s
mol
m -1
7.61x
7
10–6
m2s-1

96487 A.s
mol-1
6.08x10-6
m2s-1

96487
A.s mol-1
8.76 x 106 2 -1
ms

Micro porous
p
radius

6.5 110-10 m

5.99x10-10 m

6.9x 10-10 m

Anode exchange curreent density
Cathodee exchange currrent density

1x1003
A.m--2
1.0 A
A.m-2

1x103
A.m
A -2
1.0 A.m-2

4.79x10-10
m
1x103
A.m-2
1.0 A.m-2

1x103
A.m-2
1.0 A.m-2

Specificc surface area

1.59 10 3 m2m-

2.65
2 x103
m2m-3

2.66 x103
m2m-3

1.71 x 103
m2m-3

Active layer thicknesss of the electro
ode

Dry porrosity of the annode electrode
Dry porrosity of the caathode electrodde
Faradayy’s constant

3.16 mol
m-3

1.0

V

V

0.0
0

V

1.0
0.0

V
V

0.0

V

V

0.0
0

V

0.0

V

0.0

V

3

B.6-3

SEMINAR NASIONAL
L TEKNIK KIIMIA SOEBA
ARDJO BROTOHARDJO
ONO IX
Program Stu
udi Teknik Kimia UPN “V
Veteran” Jawaa Timur
Surabayya, 21 Juni 20012
Width of
o gas channel

0.0015 m

0.0015
0
m

0.0015 m

0.0015 m

Henry’ss constant for hydrogen
h

3.9.1104Pa
m3m
mol-1
3.2.1104Pa
m3m
mol-1

3.9.104 Pa
m3mol-1
3.2.104Pa m3
mol
m -1

3.9.104 Pa
m3mol-1
3.2.104Pa
m3mol-1

3.9 104 Pa
m3mol-1
3.2.04
Pa m3 mol-

Henry’ss constant for oxygen
o

1

L with 10.000 times
t
enlargem
ment. Each of thhe GDL ball shhape particle consists
c
of poree around 4.5 too 9
If GDL
Ǻ. Witth larger PTFE
E composition using sprayer method will grow
g
larger succh kind of partticle (around 160
to 330 nm).
n
It meanss that with larg
ger PTFE com
mposition, the micro
m
pore willl tend more doominant than the
t
macro pore.
p
From th
he mentioning above, we couuld conclude that
t
GDL is a micro pore ty
ype as shown in
Figure 3, and the largger pore diametter will be reacched with largeer pore surfacee area. The inccreasing of PTF
FE
compossition in GDL will
w decrease th
he surface areaa of active carbbon particle thaat used in the sp
prayer.
From Figure
F
3, we coould also conclu
ude that our G
GDL (GDL3) haas 151 m2/g acctive carbon suurface areas. Our
O
active carbon
c
surfacee area is still above
a
the com
mmercial GDL with around 1110 – 120 m2/g
g but below 200
m2/g thhat based on Ru
utheven meanss still has micrro porous moddel property. A
And finally, wee could concluude
that surrface area of GD
DL3 is suitablee for Gas Diffuusion Electrodee (GDE) anodee of MEA.
Fuel Ceell Voltage /Cuurrent model. Figure
F
4 show
ws the Autosorbb-1 method whhere the adsorpption of nitroggen
on GDL
L was carried out
o at 77 K andd with the presssure ratio P/Po
o varies from 0 to 1.

 
 
 
 
 
 
 
Based on
o nitrogen phy
ysisorption on micro porous model in ml/g
g unit of calculaation using DA
A method will be
acquired 95 cc(STP)/g GDL3 maxim
mum capacity of adsorption or still 24 cc (STP)/g abovee the commercial
GDL orr even 43 cc(S
STP)/g below G300
G
material (Dillen,2001). Compared too commercial- and G300 GD
DL
the GDL3 have betterr performance due to larger m
maximum capaacity of adsorpption and couldd be expanded as
GDE an
node of MEA. Therefore, in the
t implementation of GDL, hydrogen willl diffuse from GDL
G
interface to
surface headed to cataalyst. Using Ruuthven equation (Ruthven 19
997) for the difffusivity of hyd
drogen gas insiide
GDL sttructure at 70ºC
C and 1 Atm pressure
p
has bbeen calculatedd within 8.25 x 10 –6 m2s-1 up
u to 6.08 x 100-6
2 -1
-6
2 -1
m s , meanwhile GDLc
G
about 8.776 x 10 m s . It has been reported that the range of diffusivity
d
is sttill
very im
mpressive for mass
m
and trannsport applicatiion (Lean 200
02). We havee observed thaat the diffusiviity
indicatees the performaance of GDL iss correlates witth Teflon distriibution and porosity of GDL on carbon clotth.
In appliication fuel ceell, the sum of gas for time aaccros from DG
GL to electrodde area is madee as surface arrea
pore GD
DL (cm2) is mu
ultiplyed gas fllux ( gmol cm-22 second-1).
This gaas will be reaktiion at surface area
a pore carboon-platinum to produce electrron and proton
n.
Then ellectron (curren
nt) accros GDL
L before enterr cathode. From
m this, each off surface area micropore GD
DL
will prooduce cell poteential. Base on
n experiment aand design data of simulationn cell potentiaal on table 1 will
w
show prrofil of perform
mance polarizaation fuel cell liike figur 5.

B.6-4

SEMINAR NASIONAL
L TEKNIK KIIMIA SOEBA
ARDJO BROTOHARDJO
ONO IX
Program Stu
udi Teknik Kimia UPN “V
Veteran” Jawaa Timur
Surabayya, 21 Juni 20012
L that are GDL
L5, GDL4, GD
DL3 and GDL C
Commerce havving surface arrea
In figurr 5, each of Surrface area GDL
1.59 1003 m2m-3, 2.65 x103 m2m-3, 2.6
66 x103 m2m-3 and 1.71 x 103 m2m-3.
L3 of 1A/m2 annd GDLc is 0.6
65 A/m2. All off
GDL5, produce electrric 0.63 A/cm2, GDL 4 of 0.886 A/cm2, GDL
mance GDL expperiment havee the same proffil with GDLc and
a current GD
DL3 has more than
t
GDLc.
perform
From fiigur or data, caan be conclude that surface arrea GDL is big
g more will get higher currentt fuel cell. Thiss
means surface
s
area veery influence performance cuurrent fuel cell. GDL have miccroporous propperties model
which have
h
higher currrent than mak
kro homegeneous dan aglomeerate (Sui et al,1999 ) althouggh GDL Voltagge
is lowerr. Used as paraameter in GDL
L fabrication.

Fig 4. Fuel Cell volttage and Curreent model
5.CON
NCLUSION
The inccreasing of PTFE compositioon in GDL willl decrease the surface area oof active carboon particle whiich
used in the sprayer. We
W could concllude that surface area of GDL
L3 include miccro porous mo
odel property annd
i suitable for Gas Diffusion
n Electrode (G
GDE) anode off MEA. Compaared to commeercial, the GDL
L3
GDL3 is
have beetter performannce due to largeer maximum caapacity of adsoorption and couuld be expandeed as GDE anode
of MEA
A because of thhe range of difffusivity is still very impressivve for mass andd transport appplication. Surfaace
area GD
DL is bigger thhen MEA Fuel Cell will prodduce higher currrent. Then, suurface area GDL can be took as
of the any
a parameter control
c
to get performance
p
M
MEA suitable too Fuel Cell.
ACKNOWLEDGEM
MENTS
The autthors would likke to express their
t
gratitude to the UKM University
U
andd Environmentt of Malaysia for
f
the finaancial support through
t
IRPA grant: IRPA 022-02-02-0003-PR0023 11-088
REFER
RENCES
Gregg ,S.J.
,
and Sing,, K.S.W. 19822. Adsorption, Surface Area and Porosity. Academic Preess london. Neew
York Nijkam
mp, M.G, Raaym
makers, J.E.M.J., Van
Ruthvenn D. 1997. Enccyclopedia of Seperation
S
Tecchnology. Vol.,, John Wley, New
N York
Do and K. Wang.19988. Dual Diffusiion and Finite Mass Excangee Model for Addsorption Kineetics in Activatted
Carbon. AIC
ChE Journal, 41, 68
micchaelides, E.1998.Tanspo
ort Processes Of
O Water and Protons
P
Through
Xue-Doong Din and Effstathioosh , Em
Micropores. AIChE Journaal, 44, No1
Marr, C.
C & Li, X. 19999. Composittion and perfoormance modelling of catalyyst layer in a proton
p
exchannge
membrane fu
uel cell. Journaal of Power Sources 77: 17 – 27
Sergei, G. 2002. Recent progress inn performancee improvementt of the protonn exchange membrane fuel cell
(PEMFC). Jo
ournal of Poweer Sources 1077: 5 – 12.

B.6-5

SEMINAR NASIONAL
L TEKNIK KIIMIA SOEBA
ARDJO BROTOHARDJO
ONO IX
Program Stu
udi Teknik Kimia UPN “V
Veteran” Jawaa Timur
Surabayya, 21 Juni 20012
Ticianeelli, E.A. Derouuin, C.R. Redoondo, A. & Srinnivasan, S. 19888. Methods too advance technnology of proton
exchange meembrane fuel cells. J. Electroochem. Soc. 1355: 2209 – 22144

Marr, C. & Li, X. 19999. Composittion and perforrmance modellling of catalystt layer in a pro
oton exchange
membrane fuel
f cell. Journnal of Power SSources 77: 17 – 27
Raimun
ndo, R.P. & Tiicianelli, E.A. 2002. Effect oof the operationn conditions oon the membranne and electrode
properties off a polymer electrolyte fuel ceell. J. Braz. Chhem. Soc Vol. 12,
1 No. 4: 483 - 489.
Lean,G
G., Djilali,N., Whale,M.,
W
Niett, T. 2000. Application of Micro-Scale Tecchniques to Fuuel Cell System
ms
Design. Instiitut for Integratted Energy Sysstems, Universsity of Victoriaa , B.C., Canadaa, VBW3P6
Mar.X.L
Li. 1998. An Enginering
E
moddel of Proton E
Exhange memb
brane Fuel Celll Performance. Ari 50:190-2000,
Springer-Verrlag
Sui andd L.D Chen. 19
999. Modeling and Optimizattion of PEMFC
C Catalyst Layyer. Honda RUD
D Cd. Ltd Jepuun
EG & G Service. 2000. Fuel Cell
C
Hanbook .Science Ap
plications Inteernational Corrporation . U..S.
N
Energgy Technology
y Laboratory, Morgantown,, West Virginnia
Departementt of Enegy National
26507-0880
P
Inc. 2000. Fuel Cell Hanbook. U.S Departemennt of Energy offices
o
of Fosssil
AG & G Services Person
Energy, Morrgantown, West Virginia 265007- 0880
Sharon Thomas and Zalbowitze.1998. Fuel Cellls-Green Pow
wer. Los Alam
mos National Laboratory, Los
L
Alamos, Neew Mexico
 
 

B.6-6