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.