Studies on Direct Methanol Fuel Cell: An electro-chemical
energy conversion device
Jay Pandey
Research Scholar
Department of Chemical Engineering
Indian Institute of Technology Delhi, New Delhi
Outline
Introduction
Objectives
Experimental details
Membrane characterization
DMFC performance
Conclusions
Fuel Cell
Electrochemical device which converts chemical
energy into electrical energy
 Invented by W.R.Groove, 1839
 Introduced the IEMs in FCs (1963, J.W.Niedrach)
Fuel cell type
Op. Temp.
(oC)
Transported
ion
Membrane used
Power density Fuel cell
mW/cm2
efficiency
Polymer electrolyte
50-80
membrane fuel cell (PEMFC)
H+
Polymeric membrane
350
45-60
Alkaline fuel cell (AFC)
60-90
OH-
Aqueous alkaline
solution
100-200
40-60
Phosphoric acid fuel cell
(AFC)
150-200
H+
Molten phosphoric acid 200
Molten carbonate fuel cell
(MCFC)
600-700
CO32-
Molten alkaline
carbonate
100
60-65
Solid oxide fuel cell (SOFC)
800-1000
O2-
Ceramics
240
55-65
55
Int. J. Hydrogen Energy, 35, 2010, 9349-9384
Direct Methanol Fuel Cell (DMFC)
 Sub-category of PEMFC
 Fuel at anode: Methanol ;
Oxidant at cathode: Oxygen
 Membrane used: Proton exchange membrane (PEM)
 Operating temperature: 50-1200C
 Power density: 240 mW/cm2
 Fuel cell efficiency: ~60%
 Power output: 0.1 – 15W
Contd.....
Why methanol is preferred over hydrogen fuel ?
 Energy density: Methanol: 4.8 Wh/cm3
Hydrogen: 2.7 Wh/cm3
 Easy transportation and handling
 Readily available, relatively lesser cost
 Stable at all atmospheric conditions
(Silva et al, 2005)
Electrochemical reactions involved in DMFC
Anodic reaction(Oxidation): 0.03 V
CO2 + 6H + + 6e-
CH3OH + H2O
Cathodic reaction (Reduction): 1.22 V
3/2 O2 + 6H+
+ 6e-
Overall reaction:
CH3OH + 3/2 O2
(Silva at al. 2005)
3H2O
1.19 V
CO2 + 2H2O
Applications of DMFC
All kinds of portable, automotive and mobile applications
like,
• Powering laptop, computers, cellular phones, digital
cameras
• Fuel cell vehicles (FCVs)
• Spacecraft applications
• Any consumables which require long lasting power
compare to Li-ion batteries
(Dyre et al., 2002)
Objectives
 Synthesis of proton conductive PWA membrane for potential application in
DMFC
 Physico-chemical characterization of membrane in order to characterize the
surface morphology, phase identification, intermolecular bonding, thermal
stability of the membrane
 Electrochemical characterization of the membrane to analyze the
electrochemical behavior of membrane such as specific conductivity,
transport number, areal resistance of the membrane
 Study of the DMFC performance using synthesized PWA membrane
Synthesis protocol of PWA membrane
PWA membrane
Physico-chemical characterization
PWA peak
Silica Peak
XRD patterns show the
presence of silica and
phosphotungustic acid in the
membrane even after the
heat treatment up to 150oC
for 2 h.
XRD patterns of PWA membrane
FT-IR spectra confirms the
stable intermolecular interaction
between silica and tungustate
ions.
Silanol ion peak ~1532 cm-1
Tungstate ion peak~1079, 984,
828, 815 cm-1
FT-IR spectra of PWA membrane
SEM analysis of membrane
The SEM images show the surface
uniformity as well as proper dispersion of
active sol (PWA and TEOS) on graphite
support.
SEM images of graphite support
SEM images of PWA membrane
Electrochemical characterization
Membrane potential and transport number measurements
Experimental specifications
Volume of each
compartment
27 cm3
Concentration of NaCl
0.1 M/0.01 M
Maximum cell voltage
0.118 V
Specific conductivity (S/cm) measurements
EIS specifications
Photographic image of diffusion cell
Nyquist Plot for resistance measurement
Frequency range
1Hz- 1 MHz
AC voltage
5 mV
Area of membrane
12.56 cm2
Concentration of NaCl in
both the compartments
0.5 M
Nyquist plot
0.14
1.2
0.12
1
0.1
Transport number
Membrane potential, V
Membrane potential and transport number
0.08
0.06
0.04
0.8
0.6
0.4
0.2
0.02
0
0
0
0.2
0.4
0.6
0.8
PWA/TEOS molar ratio
*As
1
1.2
0
0.5
1
PWA/TEOS molar ratio
the PWA/TEOS ratio is increased the transport as well as the membrane
potential is increased significantly due to increase in the surface charge
density of the synthesized membrane
1.5
Specific conductivity and water uptake
As the wt% of PWA was increased
specific conductivity was also found
to be increased i.e. more ionic
conduction occurred through the
PWA membrane.
Fig. 1: Variation of specific conductivity with molar ratio of PWA and
TEOS
Maximum value of water uptake
was found around 30% for 1 molar
ratio of PWA and TEOS. It indicates
that membranes has high hydration
content at higher wt% of PWA that
will result into high proton
conduction.
30.2
Water uptake, %
30
29.8
29.6
29.4
29.2
29
28.8
0
0.2
0.4
0.6
0.8
PWA/TEOS molar ratio
1
1.2
Fig. 2: Variation of water uptake with molar ratio of PWA and TEOS
Experimental Setup for DMFC
DMFC performance
Experimental specifications:
Cell temperature= 25oC
MeOH flow rate= 5 ml/min
Oxygen flow rate= 100 ml/min
0.5 PWA/TEOS
Power density= 29 mW/cm2
OCV= 0.65 V
1.5 PWA/TEOS
Power density= 35 mW/cm2
OCV= 0.75 V
*It can be inferred that 1.5 PWA/TEOS has better DMFC performance than 0.5
PWA/TEOS membrane, mainly due to high proton conductivity of membrane for 1.5
PWA/TEOS
Conclusions
•
•
•
•
•
•
•
•
The PWA membrane was synthesized using sol-gel method followed by solution casting
on graphite support
The highest obtained value of transport number was 0.90 for the synthesized PWA
membrane
Higher value of transport number indicates that maximum current is being carried across
the membrane
The maximum value of specific conductivity was found 5 mScm-1 at room temperature
(32oC)
Proton conductivity for inorganic membranes being used in DMFC is in the range of 514 mScm-1
Maximum obtained power density was 35 mW/cm2 for 1.5 PWA/TEOS, and OCV was
0.75 V
Synthesized PWA membrane has the potential for wide applications in DMFC
The membrane properties can be further improved by changing the synthesis protocol or
final treatment methods
References
 S.K., Kamarudin, F., Achmad, W.R.W., Daud. Overview on application of direct methanol fuel
cell (DMFC) for portable electronic devices. Int. J. Hydrogen Energy, 34, 6902-6916. 2009.
 U.S.D., Energy. Fuel cell handbook. Science Applications International Corporation E&G
Services, 5th ed., Parson Inc., 2000.
 R., O’Hayre, S.W., Cha. Fuel cell fundamentals. Wiley, 113, 267-268, 2007.
 S.Q., Song, W.J., Jhou, W.J., Li. Direct methanol fuel cells: Methanol crossover and its
influence on single DMFC performance. Solid State Ionic, 10, 458-462. 2004.
 Z.G., Shao, P., Joghee, I.M., Hsing. Preparation and characterization of hybrid Nafion-silica
membrane doped with phosphotungustic acid for high temperature operation of PEMFC. J.
Membr. Sci. 229, 43–51, 2004.