Navy researchers develop non-proprietary method for PEM fuel cells with high power, high current densities and low platinum loadings
A team from the US Naval Research Laboratory has developed a non-proprietary method for preparing laboratory-scale proton exchange membrane fuel cells (PEMFCs) that have high power and high current densities despite their low platinum loadings.
The membrane electrode assemblies (MEAs) feature a commercial PtCo catalyst supported on high surface area carbon and a short-side chain, low equivalent weight ionomer binder in the cathode catalyst layer; these are then compressed with dry-laid paper type gas diffusion media.
The PEMFCs with a Pt loading of 0.08 mgPt cm−2 produced comparatively high power to similarly loaded state-of-the-art PEMFCs. This methodology can be used for further research on high performance catalyst layers, the researchers said in a paper published in the Journal of Power Sources.
Proton exchange membrane fuel cells (PEMFCs) capable of performance at high power are being developed worldwide for advanced electric automotive propulsion. The high power hinges largely on the current density that can be drawn from the platinum-catalyzed electrodes for oxygen reduction at the cathode and hydrogen reduction at the anode. The U.S. Department of Energy (DOE) in collaboration with industrial partners has set the goal of reducing the total loading of the Pt electrocatalysts to 0.125 mgPt cm−2 by the year 2020 for PEMFCs to become cost competitive with batteries and combustion engines.
Such low-Pt fuel cell cathode loadings are predicted to limit performance at high current density operation due to oxygen resistance, water management/flooding in thin catalyst layers, accelerated degradation/reduced durability, and higher risks for contamination in the fuel and air. While major fuel cell system manufacturers report that they are able to make high power PEMFCs with low Pt loadings, there is limited publicly available information on how to create these fuel cells in the laboratory for research purposes to understand their true limitations and opportunities.
Other related electrochemical systems, such as Li-air, Zn-air, electrolyzers, and flow batteries are faced with similar research challenges, making it imperative that information is publicly available on how to create high performance platinum catalyzed electrodes.—Garsany et al.
The MEAs in the study feature low loadings of a PtCo/HSAC catalyst with short-side-chain (SSC) Aquivion ionomer binder in the cathode catalyst layer (CL) that are prepared by direct deposition of the CLs onto Nafion HP membranes using an ultrasonic spray deposition technique.
These are assembled into MEAs with dry-laid paper type gas diffusion media (GDM) (i.e. non-woven) under optimized compressive stress.
Ample research remains on numerous challenges related to the use of such low loading Pt fuel cells, including their durability and ability to manage water appropriately over a range of temperatures and relative humidity.
With the non-proprietary laboratory-scale methods presented herein, researchers can make improvements to high performance PEMFCs, by using their new advanced catalysts for higher cathode ORR activity, or try new PEMs, GDMs for improved water management, and use the data for modeling to further advance the field of PEMFC research.—Garsany et al.
Yannick Garsany, Robert W. Atkinson, Benjamin D. Gould, Karen E. Swider-Lyons (2018) “High power, Low-Pt membrane electrode assemblies for proton exchange membrane fuel cells,” Journal of Power Sources, Volume 408, Pages 38-45 doi: 10.1016/j.jpowsour.2018.10.073.