Hydrogen Technology
Surveillance Brief
CENTER FOR FUEL CELL
RESEARCH AND APPLICATIONS
TBH-004
Formic Acid Fuel Cells for Portable Power
Applications
Problem
Direct Methanol Fuel Cells
(DMFC) do not yet meet the
performance targets needed by
developers of portable fuel
cells. Low catalyst activity at
the anode for room temperature
methanol
oxidation
and
methanol cross-over from
anode to cathode are the main
performance detractors. Low
concentrations of methanol
(~30%) are required to reduce
methanol
crossover
to
acceptable levels, the net effect
of which is to reduce the
exceptionally high energy
density of pure methanol (4.7
kWh/liters), thereby negating a
key advantage of methanol.
Solution
Three approaches have been
proposed by portable fuel cell
manufacturers and researchers
to address these problems.
1. The development of catalysts
and membrane materials with
enhanced properties
2. the use of an integrated chipsize methanol reformer to
allow cell operation on pure
hydrogen
3. The use of formic acid as a
replacement
fuel
for
methanol.
The use of formic acid in socalled Direct Formic Acid Fuel
Cells (DFAFC) lowers fuel
cross-over and results in higher
theoretical open circuit voltage
[1]. Reduced fuel cross-over
allows concentrated solutions
of formic acid to be used. By
using up to 80% formic acid
solutions, acceptable gravimetric power density can be
achieved, even though formic
acid’s energy density of 2.1
kWh/liters is less than half that
of methanol.
The formic acid technology
was originally developed in
2002 by Professor Richard
Masel at University of Illinois
under the DARPA grant [2],
and later licensed in 2003 to
Renew
Power,
a
U.S.
subsidiary of Canada based
Tekion. Renew Power holds
the IP surrounding DFAFC
technology and nano-particle
electrocatalysts for formic acid
oxidation,
which
is
a
significant aspect of the
company’s overall technology.
Renew Power demonstrated
prototype devices with a
relatively high current density
of 500 mA/cm2 (at 0.5 V) using
a proprietary anode catalyst.
The Korea Institute of Science
and Technology (KIST) and the
Gwangju Institute of Science
and Technology (GIST) are
also working on formic acid
technology, although, their
work examines the mechanisms
of fuel cross-over [3].
Confidential through May 2007
In Our Opinion . . .
Formic acid fuel cell
technology for portable
power could offer:
¾ Higher performance
than DMFC; similar to
PEMFC
¾ Simplified balance of
plant design
¾ But, further
miniaturization is
required for low power
applications and devices
Discussion
The work being undertaken by
at University of Illinois and
Renew
Power
produced
prototype formic acid cells with
performance competitive with
DMFC. In a 2004 paper
delivered at Fuel Cell Seminar
[4], Renew Power reported the
development of DFAFC for
cell phone applications. The
company claimed that their fuel
cells have same the size as cell
phone battery and that they
have successfully powered the
cell phone without any
supplemental battery.
The key benefit with DFAFC is
the substantially reduced fuel
cross-over, which allows the
use of conventional Nafion
membranes. Depending on the
concentration and membrane
type, cross-over was measured
to be one to two orders of
magnitude better than DMFC
Page 1 of 2 Hydrogen Technology
Surveillance Brief
CENTER FOR FUEL CELL
RESEARCH AND APPLICATIONS
[1]. The lower cross-over
values with formic acid result
from high repulsive forces
between formate anions and
sulphonic acid ions (in Nafion)
[5]. The low tendency for
cross-over allows use of formic
acid concentrations in the range
of ~70-80%, which makes fuel
cell energy density to compare
well with DMFC, even with
lower energy densities values
for formic acid compared to
methanol. Furthermore, the
high theoretical open circuit
voltage (1.45 V) and the use of
concentrated fuel results in
reasonable cell power density.
While the Direct Formic Acid
Fuel Cell technology looks
promising, it will still require
improved catalyst materials to
further enhance the anode
reaction. Conventional Pt or
Pt/Ru catalysts used for low
temperature PEM fuel cells do
not appear to be effective
enough
for
anode
fuel
oxidation. Masel’s group at the
University of Illinois reports
developing proprietary anode
catalysts [6]. The group claims
that their catalyst substantially
enhances the anode oxidation
kinetics, and that their fuel cells
have reached performance
levels similar to that of PEM
fuel cells.
In addition, the use of
concentrated
formic
acid
solutions
may
require
additional safety measures to
avoid acid burns. Furthermore,
with a freezing point of only
TBH-004
5.6 oC, pure formic acid might
have difficulty operating in
cold climates, although this
problem is alleviated somewhat
by using less concentrated
formic acid solutions (70-80%)
which decreases the freezing
point.
Conclusion
Direct Formic Acid Fuel Cell
technology
is
a
viable
alternative to DMFC for
portable applications. The
technology offers the potential
for improved cell performance
relative to DMFC by reducing
fuel
cross-over
through
standard Nafion membranes,
even at concentrations up to
70-80%. Successful development of DFA fuel cell systems
could enable direct use of this
liquid fuel without a reformer,
thereby
achieving
the
simplified balance of plant
designs sought by DMFC
developers.
1. Y-W. Rhee et al., J. Power
Sources 117 (2003) 35.
2. S. Ha et al., U.S. patent
application,
US20040115518 (2003).
3. J. Han et al., 2004 Fuel Cell
Seminar, San Antonio, TX.
4. B. Adams, et al., 2004 Fuel
Cell Seminar, San Antonio,
TX.
5. C. Rice et al., J. Power
Sources 111 (2002) 83.
6. R. Masel et al., U.S. Patent
application, 20040115518.
Additional References
7. R. Masel et al., U.S. Patent
application, 20030198852
8. C. Rice et al., J. Power
Sources 115 (2003) 229
9. Y. Zhu et al., J. Power
Sources 130 (2004) 8
10. S. Ha et al., J. Power
Sources 128 (2004) 119
The results to date are
encouraging, with low power
cells appearing to be quite
competitive
with
DMFC.
Renew Power has shown that
the technology works well in
the milliwatts to watts range.
According to the company’s
website, they are now focusing
on shrinking their system,
reducing costs, designing the
fuel capsule, and engineering
water,
heat
and
CO2
management systems. The
company plans to field test
their system under different
environmental conditions.
Confidential through May 2007
Bibliography
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