The increasing worldwide demand for electricity impels to develop clean and renewable energy resources. In the field of portable power devices not only size and weight represent important aspects to take into account, but the fuel and its storage are also critical issues to consider. In this last 

sense, the direct methanol (MeOH) fuel cells (DMFC) play an important role as they can offer high power and energy density, low emissions, ambient operating conditions and fast and convenient refuelling

Leo Mena, Teresa de Jesus

Mora Peña, Eleuterio

Navarro Arevalo, Emilio

Raso García, Miguel Ángel

Sánchez de la Blanca, Emilia

Servicio de Coordinación de Bibliotecas de la Universidad Politécnica de Madrid

III Iberian Symposium on Hydrogen, Fuel Cells and Advanced Batteries. Zaragoza, June 27
th
-30
th
 2011 
Contribution sharing of a fuel mixture components to the fuel cell 
potential of a Direct Alcohol Fuel Cell 
 
T.J. Leo1,*, E. Navarro 2, E. Mora1, E. Sánchez de la Blanca3, M.A. Raso3 
1 
ETSI Navales-Universidad Politécnica de Madrid. Avda. Arco de la Victoria s/n, 28040 – Madrid (Spain) 
2 
ETSI Aeronáuticos-Universidad Politécnica de Madrid. Pza. Cardenal Cisneros 3, 28040 – Madrid (Spain) 
 
3 
Fac. CC. Químicas-Universidad Complutense de Madrid. Avda. Complutense 18, 28040 – Madrid (Spain) 
(*) corresponding author: teresa.leo.mena@upm.es 
 
Keywords: Methanol, Ethanol, Alcohol blends, Direct Alcohol Fuel Cells, Modelling 
 
 
1 Introduction 
The increasing worldwide demand for electricity 
impels to develop clean and renewable energy 
resources. In the field of portable power devices 
not only size and weight represent important as-
pects to take into account, but the fuel and its stor-
age are also critical issues to consider. In this last 
sense, the direct methanol (MeOH) fuel cells 
(DMFC) play an important role as they can offer 
high power and energy density, low emissions, 
ambient operating conditions and fast and conven-
ient refuelling. Recently, other liquid fuel, ethanol 
(EtOH), is attracting interest and direct ethanol fuel 
cells (DEFC) are being developed [1]. But despite 
the evident advantages of EtOH, that can be easily 
produced in great quantity from renewable sources, 
presents much lower toxicity than MeOH and has 
high power density, its electrochemical oxidation 
features makes the performance of DEFC to be 
rather low. The possibility of using MeOH and 
EtOH together in a direct alcohol fuel cell (DAFC) 
would lead to take profit of the advantages of both 
alcohols and the objective of this work is to study 
the behaviour of a DAFC when the fuel is a mixture 
of MeOH and EtOH. 
This possibility has been theoretically investi-
gated by developing a comparative exergy study of 
a DAFC fed with MeOH/EtOH mixtures against the 
same fuel cell fed with either MeOH or EtOH alone 
[2]. A simple model to calculate the polarization 
curves corresponding to binary aqueous alcohol 
mixtures has been proposed and polarization 
curves exhibiting sharp steps, corresponding to the 
current density values at which anode limiting cur-
rent densities are attained, have been predicted. 
This study concluded that a relative maximum of 
power could be obtained by using a fuel mixture of 
MeOH and EtOH with a relatively low proportion of 
MeOH, being this mixture the unique curve with no 
sharp step, showing an aspect similar to that of a 
polarization curve of single MeOH or EtOH. Up to 
the author’s knowledge, no experimental work has 
been performed using alcohol blends as fuel of fuel 
cells. 
In this work, the experimental polarization 
curves of a single DAFC fed by aqueous MeOH, 
aqueous EtOH and a series of aqueous 
MeOH−EtOH blends have been measured. The 
objective is to study the fuel cell performance under 
a variety of fuel compositions and investigate the 
possibility of taking profit of the advantages of both 
alcohols. 
The reactions taking place at the electrodes and 
the overall current-producing reaction of MeOH in 
the fuel cell are as follows: 
Anode: CH3OH + H2O  CO2 + 6H
+
 + 6e
−
 
Cathode: 3/2 O2 + 6H
+
 + 6e
−
  3H2O 
Overall: CH3OH + 3/2 O2  CO2 + 2H2O (1) 
and the corresponding to EtOH: 
Anode: C2H5OH + 3H2O  2CO2 + 12H
+
 + 12e
−
 
Cathode: 3O2 + 12H
+
 + 12e
−
  6H2O 
Overall: C2H5OH + 3O2  2CO2 + 3H2O (2) 
2 Experimental 
2.1 Experimental setup 
The experimental setup and the single fuel cell 
used have been described in a previous work [3], 
as well as the equipment used to perform electro-
chemical measurements. Bipolar plates have been 
fabricated on 316SS. 
 
2.2 Electrodes 
The electrodes, with an active area of 5 cm
2
, 
have been prepared by QuinTech e.K. The anode, 
GDE Freudenberg H2315 I3C1, contains a total 
PtRu loading of 3 mg cm
−2
 onto GDL Freudenberg 
H2315 I3C1. The cathode, GDE Freudenberg 
H2315 T10A, contains a total Pt loading of 3 mg 
cm
−2
 onto GDL Freudenberg H2315 T10A. 
2.3 Polarization curves 
One series of polarization curves has been reg-
istered in a single direct alcohol fuel cell. The fuel 
consists of liquid MeOH/EtOH mixtures in water at 
1 mol L
−1
 constant total alcohol concentration. To 
register the series, the alcohol mixture composition 
has been varied gradually from MeOH 1 mol L
−1
 to 
III Iberian Symposium on Hydrogen, Fuel Cells and Advanced Batteries. Zaragoza, June 27
th
-30
th
 2011 
 
EtOH 1 mol L
−1
. Intermediate MeOH/EtOH molar 
compositions investigated have been 0.90/0.10; 
0.70/0.30; 0.50/0.50; 0.30/0.70; 0.10/0.90. The 
oxidant has been always pure oxygen. The tem-
perature of the fuel cell has been kept constant at 
80 ºC in every case. Before any test, the cell has 
been preconditioned (it is always run under con-
stant load, 0,150mV, and operation conditions over 
15 minutes) for three times. The polarization curve 
corresponding to each different fuel composition 
has been also registered for three times. 
The experimental conditions used are shown in 
Table 1. 
Table 1. Experimental conditions of measurements. 
Parameter Units Value 
Alcohol (MeOH−EtOH) 
concentration 
mol L
−1
 1.0 
Alcohol flow rate mL min
−1 
3.0 
Oxygen flow rate mL min
−1
 250 
Oxygen pressure bar 1.0 
Temperature ºC 80 
 
3 Polarization curves model 
3.1 The polarization curve when the fuel is a single 
alcohol 
The model used to describe the polarization 
curve of a single aqueous alcoholic solution is de-
scribed in [2] and references therein, and is based 
on several studies involving DAFC [4]. 
The main equations used to model the polariza-
tion curve when the fuel cell is fed by a single 
aqueous alcoholic solution are summarized in the 
following paragraphs. 
The general expression of a fuel cell polariza-
tion curve can be written as: 
ohmiccconcaconccactaactEV   ,,,,  (3) 
where E stands for the Nernst potential in the op-
erating conditions: 
CO2
2
O2
2
CO0
O
ln
a alc
cRT
E E
z F c c


 
  
 
 
 (4) 
When the alcohol is MeOH CO2 = 1, O2 = 3/2 
and za = 6, but if the fuel is EtOH CO2 = 2, O2 = 3 
and za = 12, , as derived from equations (1) and (2), 
respectively. alcc is the fuel concentration in the 
catalytic layer, calculated with the solution to the 
diffusion equations proposed in [5]. 
The crossover rate rc is calculated as: 
  
 
lim
lim
a
d w
c c
d w
a a
am b
w ba a
b m b
j j n j j
r
j j n j j
D l w
j FD
D l l



 

 
 
 (5) 
being wa the water molar concentration and 
lim
aj , 
lim
cj  stand for the anode and cathode limiting cur-
rent densities, respectively: 
lim lim, 4
a a c c
a cb h b h
a a c
b b
D c D c
j z F j F
l l
   (6) 
where 
a
hc  stands for the inlet alcohol concentration, 
a
bl , 
c
bl  are the thicknesses of the anode and the 
cathode backing layers, respectively, and a
bD ,
c
bD  
represent the diffusion coefficient of alcohol and 
oxygen in their respective backing layers. 
The anodic and cathodic activation overvoltages 
as a function of the exchange current density j0 and 
the parameter α have the following expressions: 
, ,
0, 0,
ln ; lnact a act c
a a a c c c
RT j RT j
z F j z F j
 
 
   (7) 
Table 2. Assumed parameter values for MeOH and 
EtOH. 
Parameter MeOH EtOH 
E
0 
1.214 1.146 
za 6 12 
lm (cm) [6]
 
0.0178 0.0178 
lb (cm) [6]
 
0.0300 0.0300 
lc (cm) [8]
 
0.0020 0.0020 
Cathode transfer 
coeff. αc [7, 8] 
1 1 
nd [8] 3.16 3.16 
 2 1cm ·scbD

[9]
 
0.338 0.338 
c [7,8]
 
1[6]
 
1 
0
ref
vA j  
[7]
 
[8] 
 20, A·cmcj

[10]
 
1.87·10
-8
 1.87·10
-8
 
 2 1cm  sabD

[11]
 
2.984·10
−5 
2.984·10
-5 
 2 1cm  smD
  
2.148·10
−5 
[12] 2.97·10
−5 
[9] 
The concentration overvoltage is calculated follow-
ing the expressions: 
lim
,
lim cross
lim
,
lim cross
ln
ln
a
conc a a
a
c
conc c c
c
jRT
z F j j j
jRT
z F j j j


 
  
  
 
  
  
 (8) 
where jlim and the flux of alcohol through the mem-
brane, expressed in current density units, jcross, are 
calculated as in [4]. The ohmic overpotential is ex-
III Iberian Symposium on Hydrogen, Fuel Cells and Advanced Batteries. Zaragoza, June 27
th
-30
th
 2011 
 
pressed as ohmic = Rj, where R stands for the sum 
of membrane and contact resistance times area. 
The anode exchange current density j0,a can be 
estimated as a function of the anode reaction order 
a and the alcohol concentration in the catalytic 
layer calc. 
The fixed parameters assumed in the model, for 
MeOH and EtOH, are shown in Table 2. 
 
3.2 The polarization curve when the fuel is a mix-
ture of alcohols 
To develop this study the total alcohol concen-
tration and the volumetric flow rate at the fuel cell 
inlet are kept constant, thus the molar flow rate of 
alcohol 
in M ,in E ,in
n n n   entering the fuel cell is kept 
constant. Then, the proportion of MeOH, yM, in the 
mixture can be expressed as 
,M M in iny n n  and 
that of EtOH, 
,E E in iny n n . Therefore, 1M Ey y  . 
Three possible models have been proposed to 
study the behaviour of polarization curves corre-
sponding to a DAFC fed with a fuel consisting of 
aqueous MeOH/EtOH blends. 
3.2.1 Model I 
Each alcohol contributes independently to the total 
cell voltage: 
   , , , ,M M M M E E E EV y V P j y c y V P j y c   (9) 
where c is the total alcohol concentration and 
iP  is 
the parameter set of alcohol i (those collected in 
Table 2 and a , a  and R ). 
3.2.2 Model II 
A total cell voltage is calculated with averaged pa-
rameters, that is, the cell voltage is assumed to 
result from an “averaged pure fuel”: 
  , ,M M E EV V y P y P j c     (10) 
3.2.3 Model III 
This model is similar to Model II, but parameters a, 
αa and R are assumed as unique (they are not av-
eraged) for each MeOH/EtOH mixture. Therefore, 
they are fitted in each case. 
4 Results and discussion 
Performance of the DAFC under study fed with 
different MeOH/EtOH aqueous solutions is shown 
in Fig. 1. Experimental polarization and power den-
sity curves of the single fuel cell operating with a 
fuel consisting of 1M aqueous solution of: pure 
MeOH; 90% MeOH/10% EtOH; 70% MeOH/30% 
EtOH; 50% MeOH/50% EtOH; 30% MeOH/70% 
EtOH; 10% MeOH/90% EtOH and pure EtOH are 
depicted in Fig. 1. As observed, the fuel perfor-
mance diminishes gradually from pure MeOH to 
pure EtOH. Even at a low EtOH concentration, 
yEtOH=0.1 and yMeOH =0.9, EtOH affects in a signifi-
cant way the behaviour of the fuel cell. 
Polarization curves corresponding to pure MeOH 
and pure EtOH have been fitted to the model de-
scribed in Subsection 3.1. The results obtained for 
pure alcohols are collected in Table 3. 
Figure 2 shows the results obtained by using 
Model I to describe the performance of the single 
DAFC. 
Table 3. Fitting parameters of the V−j model used for 
MeOH and EtOH. 
Parameter a αa R (Ω cm
2
) 
MeOH 0.8147 0.1439 3.2852 
EtOH 0.6346 0.0478 9.0140 
 
0.00 0.03 0.06 0.09 0.12 0.15
0.0
0.3
0.6
0.9
 
 
c/(mol/L) MeOH EtOH
1.000 0.000
0.900 0.100
0.700 0.300
0.500 0.500
0.300 0.700
0.100 0.900
0.000 1.000
V
 (
V
)
j (Acm
-2
)  
Fig. 1. The performance comparison of a DAFC fed with 
MeOH/EtOH aqueous solutions. Total alcohol concentra-
tion 1 M. Temperature 80 ºC. 
0.00 0.03 0.06 0.09 0.12 0.15
0.0
0.3
0.6
0.9
 
 
c/(mol/L) MeOH EtOH
1.000 0.000
0.900 0.100
0.700 0.300
0.500 0.500
0.300 0.700
0.100 0.900
0.000 1.000
V
 (
V
)
j (Acm
-2
)  
Fig. 2. Experimental and Model I fitted V-j curves of a 
DAFC fed with aqueous MeOH/EtOH mixtures at 80 ºC 
and 1M total alcohol concentration. 
Figure 3 shows the results obtained by using 
Model II to describe the performance of the single 
DAFC.  
Finally, the results from fitting the experimental 
V−j curves to Model III are depicted in Fig. 4 and 
the parameter values of a, αa and R derived for 
each mixture are collected in Table 4. The results 
are quite satisfactory in this case, and it seems that 
the aqueous alcohol mixture behaves as a “pure 
averaged alcohol”. 
 
III Iberian Symposium on Hydrogen, Fuel Cells and Advanced Batteries. Zaragoza, June 27
th
-30
th
 2011 
 
0.00 0.03 0.06 0.09 0.12 0.15
0.0
0.3
0.6
0.9
 
 
c/(mol/L) MeOH EtOH
1.000 0.000
0.900 0.100
0.700 0.300
0.500 0.500
0.300 0.700
0.100 0.900
0.000 1.000
V
 (
V
)
j (Acm
-2
)  
Fig. 3. Experimental and Model II fitted V-j curves of a 
DAFC fed with aqueous MeOH/EtOH mixtures at 80 ºC 
and 1M total alcohol concentration. 
0.00 0.03 0.06 0.09 0.12 0.15
0.0
0.3
0.6
0.9
 
 
c/(mol/L) MeOH EtOH
1.000 0.000
0.900 0.100
0.700 0.300
0.500 0.500
0.300 0.700
0.100 0.900
0.000 1.000
V
 (
V
)
j (Acm
-2
)
 
Fig. 4. Experimental and Model III fitted V-j curves of a 
DAFC fed with aqueous MeOH/EtOH mixtures at 80 ºC 
and 1mol L
−1
 total alcohol concentration. 
Table 4. Fitted parameters of the V−j model for aqueous 
MeOH/EtOH mixtures. 
MeOH 
/EtOH ratio 
a αa R (Ω cm
2
) 
9:1 0.5173 0.0868 3.2986 
7:3 0.5389 0.0718 4.1787 
5:5 0.5339 0.0615 4.8116 
3:7 0.5630 0.0551 6.8815 
1:9 0.6042 0.0505 9.1881 
5 Conclusions 
To investigate the possibility of using direct al-
cohol fuel cells fed with alcohol mixtures, an exper-
imental study of polarization curves of a direct al-
cohol fuel cell fed with alcohol mixtures has been 
performed. 
As it can be expected, MeOH/water solution 
yields the best performance, since this fuel cell has 
been designed and developed to work with MeOH.  
The fuel cell performance decreases as the 
EtOH content increases. It becomes worse respec 
to the reaction kinetics and to the protonic conduc-
tivity, as it can be deduced from the models fitting 
results. 
Models I and II show that the cell behavior, 
when it is fed with alcohol mixtures, does not re-
spond to concentration differences and the mixture 
does not seem to be an alcohol whose properties 
vary proportionally to the MeOH/EtOH rate. 
The results are quite satisfactory for model III, 
and it seems that the aqueous alcohol mixture be-
haves as a “pure averaged alcohol”. 
6 Acknowledgements  
This work has been financially supported by the 
Spanish Ministerio de Ciencia y Tecnología in the 
frame of the Project Code Nº ENE2007-67584-
C03-03ALT. The authors gratefully acknowledge 
Dr. F. Molleda for his help. 
7 References 
[1] G. Andreadis, V. Stergiopoulos, S. Song, P. 
Tsiakaras. DEFC: The effect of the cell discharge 
current on the products distribution. Applied Cataly-
sis B: Environmental 10, pp 157-164, 2010. 
[2] Teresa J. Leo, Miguel A. Raso, Emilio Navarro, Emilia 
Sánchez-de-la-Blanca. Comparative exergy analysis 
of DAFC using fuel mixtures. J. Power Sources 196, 
pp 1178-1183, 2011. 
[3] TJ Leo, MA Raso, E Navarro, E Sánchez-de-la-
Blanca, M Villanueva, B Moreno. Response of a 
DMFC to fuel change. Int. J. Hydrogen Energy 35, 
pp 11642-11648, 2010. 
[4] Kulikovsky, A.A., Electrochem. Commun. 5, pp 
1030-1036, 2003. 
[5] H Pramanik, S Basu, Modeling and experimental 
validation of overpotentials of a direct ethanol fuel 
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[6] A.A. Kulikovsky, The voltage-current curve of a 
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[7] C. Xu, A. Faghri. Water transport characteristics in a 
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[8] G.M. Andreakis, A.K.M. Podias, P.E. Tsiakaras. A 
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[9] G.M. Andreadis, A.K.M. Podias, P.E. Tsiakaras, The 
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[10] A. Parthasarathy, S. Srinivasan, A.J. Appleby, C.R. 
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Contribution sharing of a fuel mixture components to the fuel cell potencial of a direct alcohol fuel cell

The increasing worldwide demand for electricity impels to develop clean and renewable energy resources. In the field of portable power devices not only size and weight represent important aspects to take into account, but the fuel and its storage are also critical issues to consider. In this last sense, the direct methanol (MeOH) fuel cells (DMFC) play an important role as they can offer high power and energy density, low emissions, ambient operating conditions and fast and convenient refuelling

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Contribution sharing of a fuel mixture components to the fuel cell potencial of a direct alcohol fuel cell

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