• Neyerlin, Kenneth Charles
• More, Karren L.
• Mauger, Scott A.
• Kumaraguru, Swami
• Kocha, Shyam S.
• Kongkanand, Anusorn
• Pivovar, Bryan S.
• Gu, Wenbin
• Bender, Guido
• Ahluwalia, Rajesh
• Chuang, Abel

Abstract

<jats:p>Significant advances in the development of electrocatalysts that exceed the DOE target of 440 mA/mg<jats:sub>Pt</jats:sub> (H<jats:sub>2</jats:sub>/O<jats:sub>2</jats:sub>, 0.90V, 80<jats:sup>o</jats:sup>C, 100% RH, p<jats:sub>total</jats:sub>=150 kPa) for ORR activity have placed proton exchange membrane fuel cells on a promising path towards achieving the DOE target of a 0.1 mg<jats:sub>Pt</jats:sub>/cm<jats:sup>2</jats:sup><jats:sub>elec</jats:sub> cathode loading by 2020. However, unanticipated voltage losses that manifest at high current density and low Pt loading have prevented the attainment of the 0.125 g<jats:sub>PGM</jats:sub>/kW<jats:sub>rated</jats:sub> 2020 target.<jats:sup>1</jats:sup> While some of the observed voltage losses for low-loaded Pt electrodes (&lt; 0.1 mg<jats:sub>Pt</jats:sub>/cm<jats:sup>2</jats:sup><jats:sub>elec</jats:sub>) has been attributed to oxide dependent kinetics that manifest at the lower iR-free potentials (&lt; 0.75V),<jats:sup>2</jats:sup> it is believed that a significant portion of this unanticipated loss stems from an oxygen transport resistance local to or associated with electrochemically accessible Pt surface area.<jats:sup>2-4</jats:sup> While the exact cause of this phenomenon remains unknown, studies have demonstrated that this loss both: 1) scales with total Pt surface area<jats:sup>4</jats:sup> and 2) can be associated with the incorporation of ionomer into the cathode electrode.<jats:sup>3</jats:sup> As such, this loss has been termed the local Pt resistance (R<jats:sub>O2</jats:sub><jats:sup>Pt</jats:sup>). </jats:p><jats:p>In this work we have applied a variety of in-situ electrochemical diagnostics across a range of material sets (e.g. electrocatalysts, carbon supports, ionomers, and membranes) in order to understand their impact on high current density operation in low-Pt loaded electrodes. Values derived for R<jats:sub>O2</jats:sub><jats:sup>Pt</jats:sup> will be compared to those determined from ex-situ measurements in an effort to elucidate the fundamental reasons for the observed performance loss. </jats:p><jats:p>Additionally, parallel approaches involving novel and state-of-the-art, electrocatalysts, electrodes and MEA designs aimed at mitigating performance loss at high current density and low Pt loading will be presented. </jats:p><jats:p><jats:bold>Acknowledgements</jats:bold></jats:p><jats:p>This work was funded through the DOE FC-PAD Consortium and by the U.S. Department of Energy under CRADA #CRD-14-539. </jats:p><jats:p><jats:bold>References</jats:bold></jats:p><jats:p>1. https://energy.gov/eere/fuelcells /doe-technical-targets polymer-electrolyte-membrane-fuel-cell-components </jats:p><jats:p>2. T. A. Greszler, D. Caulk, and P. Sinha, <jats:italic>Journal of the Electrochemical Society,</jats:italic><jats:bold>159</jats:bold> (12), F831-F840 (2012). </jats:p><jats:p>3. H. Iden, S. Takaichi, Y. Furuya, T. Mashio, Y. Ono, and A. Ohma, <jats:italic>Journal of Electroanalytical Chemistry,</jats:italic><jats:bold>694</jats:bold> 37-44 (2013). </jats:p><jats:p>4. A. Kongkanand and M. F. Mathias, <jats:italic>Journal of Physical Chemistry Letters,</jats:italic><jats:bold>7</jats:bold> (7), 1127-1137 (2016).</jats:p>

Topics

• density
• impedance spectroscopy
• surface
• polymer
• Carbon
• Oxygen
• current density