Novel PEMFC Stack Using Patterned
Aligned Carbon Nanotubes as Electrodes in MEA
As
promising as fuel cells are, technical barriers—cost, durability, performance,
and water transport and thermal management issues—persist. To surmount these
hurdles, Argonne is working to develop a new class of carbon materials—aligned
carbon nanotubes (ACNT)—to serve as a unique electrocatalyst support for proton
exchange membrane fuel cells (PEMFCs).
The objective of the project is to create ACNT-based fuel cells through a
three-step development process: developing a method to fabricate and catalyze
ACNT as electrode catalysts; developing a method to fabricate membrane electrode
assemblies (MEAs) and PEMFCs with ACNT-based electrodes; and evaluating the
performance of ACNT-based PEMFCs.
The ACNT PEMFC promises enhancements to catalyst utilization, electrical and
thermal conductivity, and mass transport. Such improvements could lead to better
fuel cell efficiency with reduced platinum usage. The successful outcome of the
project would facilitate the development of PEMFCs that meet the U.S. Department
of Energy’s 2010 stack targets (power density, 650 W/L; cost, $45/kWe).
In an ACNT-based MEA, vertically oriented carbon nanotube layers are
synthesized and functionalized with the electrocatalytic active sites before
they are transferred to the surface of the electrolyte membrane. Inside the fuel
cell, the proton and electron transfers occur at the nanotubes’ surface, which
is also exposed to reactant gases. This electrode structure has the potential to
optimally utilize the catalyst material through improved mass transfer. The
direct contact between the electrolyte and the current collector through the
nanotube layers may enhance electronic and thermal conductivities.
Accomplishments to date include the successful preparation of ACNT with
different morphologies and built-in electrocatalytic activity; the successful
development of catalyzing methods through wet chemistry and gas phase
approaches; and the successful demonstration of the MEA fabrication method. The
test of ACNT-based PEMFC is underway.
The project has thus far led to the submission of two patent applications
(“Method of Fabricating Electrode Catalyst Layers with Directionally Oriented
Carbon Support for Proton Exchange Membrane Fuel Cell” and “Aligned Carbon
Nanotube with Electro-catalytic Activity for Oxygen Reduction Reaction”) and
three publications in peer-reviewed journals.
This work is funded by the Hydrogen, Fuel Cells and Infrastructure
Technologies Program of the DOE Office of Energy Efficiency and Renewable
Energy.
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