Inorganic/Polymer Composite Materials for High Temperature PEM ...

Project status: Ongoing
P R O J E C T F A C T S H E E T
Inorganic/Polymer Composite Materials for
High Temperature PEM Fuel Cells
Goal
The goal of this program is to develop a polymer
electrolyte membrane fuel cell (PEMFC) capable of
operating at high temperatures of 120-150 o C and
low relative humidity (RH), below 50%. The impetus
for developing the higher temperature fuel cells is:
(1) faster reaction rates and decrease of the need for
noble metal catalysts; (2) greater anode tolerance to
CO poisoning; (3) mitigation the cathode “flooding”
problem; and (4) creation of a greater driving force
for more efficient cooling, particularly in automotive
applications.
Team
This research program is an interdisciplinary effort of
a team experienced in the fields of high temperature
electrochemistry and PEMFCs (the EMS Energy
Institute’s Electrochemical Laboratory), and a
research group experienced in the synthesis of
inorganic proton conducting materials (Materials
Research Laboratory). The U.S. Department of
Energy and Oak Ridge National Laboratory support
the implementation of this project at Penn State.
Goal
Project Discussion
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A PEMFC consists of a proton-conducting polymer
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membrane, sandwiched between two electrodes. The
blue column. (About 100 words for this section.) Font
electrodes are in contact with current collectors, which
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deliver electrons to the external load. Electricity is
generated by oxidation of fuel at the anode, which
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produces electrons, and the reduction of oxygen at the
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cathode, which consumes electrons.
blue column. (About 100 words for this section). Font
Current PEMFC technology based on Nafion
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membranes operating at a typical temperature of 80 o C
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is limited by the inability of these membranes to operate
should explain what the research
at elevated temperatures due to severe dehydration.
Operating a PEMFC at a higher temperature is highly
desirable, Team particularly for automotive applications. But if
a fuel cell is operated at temperatures above 120 o C
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and under high RH, any efficiency gains reached at
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these temperatures can be outweighed by the fuel cell
pressurization. List team members. A possible Font solution should for be this Arial problem 10 point can
be plain, found in in white. the development List team members. of membranes Font should capable be of
operating Arial 10 at point elevated plain, temperatures in white. List team and low members. RH. To
achieve Font should this goal, be Arial we pursued 10 point extensively plain, in white. the
incorporation of proton conductive hydrophilic oxides or
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plain, in white.
PEM Fuel EMS Cells Energy Institute • www.energy.psu.edu
College of Earth & Mineral Sciences • Penn State University
Background
Creation of new energy conversion devices is a major
challenge for sustainable development in our society. The
use of fuel cells is a fundamentally different way of
generating electrical power from a variety of fuels. The
key feature of a fuel cell is its high-energy conversion
efficiency. Fuel cells are being developed to potentially
replace the internal combustion engines because they
are clean, quiet, energy efficient, and fuel-flexible.
According to the President's Hydrogen Fuel Initiative, the
USA are spending now about $1.2 billion on hydrogen
fuel research to reverse America's growing dependence
on foreign oil by developing the technology needed for
commercially viable hydrogen-powered fuel cells. DOE
established High Temperature Membrane Working Group
consisting of government, industry, and university
researchers. The goal is to develop high temperature, low
RH membrane materials suitable for use in a PEMFC
with performance at 120 °C and 25-50% RH exceeding
that of Nafion® at 80°C and 100%RH.
fuel outlet
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Support
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BASIC COMPONENTS OF PEMFC
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framework above the photo. hydrates (About into Nafion. 1000 characters They are with characterized spaces
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of 10 the point inorganic plain, in particles black. This can text provide can take the hydrogenbonding
sites for water molecules, and thus prevent
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water from fast evaporation. As a result, the membrane
hydration can be maintained internally without
pressurization of the whole PEMFC system.
.
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Results
Powders of inorganic additives were synthesized,
cleaned, and characterized. A comprehensive
experimental and theoretical study of solid
nanomaterials for use in composite proton exchange
membranes for high temperature PEMFC was
conducted. A number of prospective hydrophilic
inorganic compounds, including ZrO 2 , TiO 2 , Al 2 O 3 ,
SiO 2, α-Zr(HPO 4 ) 2 , and H 3 OZr 2 (PO 4 ) 3 were analyzed
with respect to their acid-base properties.
Nafion/inorganic additive composite membranes were
fabricated using different techniques and tested in a
H 2 /O 2 PEM fuel cell over a range of RH from 13 to
100% at temperatures of 80 and 120 o C. The
incorporation of selected inorganic additives led to
significant improvement of the membrane water
retention properties and the PEMFC performance,
especially, at low RH.
Effects of TiO 2 content and TiO 2 surface properties
such as specific surface area (SSA), morphology, and
electrochemical properties on the performance of
Nafion/TiO 2 composite membranes in PEMFCs were
studied at RHs from 13 to 100% at temperatures of 80
and 120 o C. The Nafion/TiO 2 composite membranes
showed a marked improvement over unmodified Nafion
membranes when operated at 120 °C and reduced RH.
For instance, at 50% RH, the Nafion/20%-TiO 2
membrane demonstrated performance comparable to
that of bare Nafion at 80 o C.The composite membranes
containing TiO 2 with SSA of 15.5 m 2 g -1 showed a
significant advantage over the membranes containing
TiO 2 with SSA of 2.9 m 2 g -1 . Thus, they provided much
higher fuel cell performance at 120 °C and reduced RH
presumably due to an increased number of hydrophilic
sites inside the membrane. The higher zeta potential
at TiO 2 /water interface is believed to be also an
important characteristic responsible for the significant
boost of the fuel cell.
Nafion/zirconium phosphate (ZP) composite
membranes with ZP of different structures were studied
in an H 2 /O 2 PEMFC at the same conditions. The
Cell Potential, V
1
0.8
0.6
0.4
0.2
0
Al2O3
alpha - Zr(HPO4)2
TiO2-II
Recast Nafion 26%RH
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
Current Density, A cm -2
Performance of H 2/O 2 PEMFC based on Nafion composite membranes
with different inorganic additives at 120 o C, 2 bar, and 13% RH.
incorporation of all types of ZP into Nafion led to significant
improvement of the PEMFC performance. The highest
performance at 120 o C and reduced RH was demonstrated
by Nafion/α-Zr(HPO 4 ) 2 with layered structure. Research on
a new type of composite membranes (Nafion/Al 2 O 3
membranes) is in progress. In an initial test, these
membranes demonstrated performance even higher than
that of Nafion/α-Zr(HPO 4 ) 2 membranes.
The observed improvement in the performance of
composite membranes is mainly attributed to two factors:
(1) enhanced water retention of the new membranes due to
hydrophilicity of inorganic particles, which in turn maintains
high Nafion conductivity and (2) enhanced proton
conductivity of the membranes due to the contribution of
the highly protonated surface of inorganic additives.
Key Contacts
Serguei Lvov, lvov@psu.edu, (814) 863-8377
Elena Chalkova, exc147@psu.edu, (814) 865-3280
Mark Fedkin, mvf3@psu.edu, (814) 865-3280
Key Publications
Name, email address, (814) phone
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E. Chalkova, M.V. Fedkin, D.J. Wesolowski, and S.N. Lvov, J. Electrochem. black. Name, email Soc. 2005, address, in press. (814) phone
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E. Chalkova, M.B. Pague, M.V. Fedkin, D.J. Wesolowski, and S.N. Lvov, J. Electrochem. Soc. 152, 6, A1035, 2005.
(About 2500 characters with spaces total). Font should be
M.V. Fedkin, X.Y. Zhou, J.D. Kubicki, A.V. Bandura, S.N. Lvov, M.L. Arial Machesky 10 point D.J. plain, Wesolowski, in black. Langmuir This text 19, can 3797, take 2003. up the 2
columns provided on the back, (About 2500 characters with
M.V. Fedkin, High Temperature Microelectrophoresis Studies of the spaces Solid Oxide/Water total). Interface, PhD Thesis, The Pennsylvania
State University, 2003.
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E. Chalkova, X.Y Zhou, C.M Ambler, M.A Hofmann, J.A Weston, (About H.R Allcock., 2500 characters and S.N. Lvov, with Electrochem. spaces total and Font Solid should State be
Letters, 5, 10, A 221, 2002.
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This publication is available in alternative media on request.
Penn State is committed to affirmative action, equal spaces opportunity, total). and Font the diversity should of its be workforce. Arial 10 (August point 2005) plain, U. Ed. in EMS black. 06-08
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