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Performance during start-up of proton exchange membrane (PEM) fuel cells at subfreezing conditions

Advances in Electrocatalysis, Materials, Diagnostics and Durability

Advanced diagnostics, models and design

Low-temperature fuel cells

  1. E. L. Thompson1,
  2. W. Gu1,
  3. H. A. Gasteiger2

Published Online: 15 DEC 2010

DOI: 10.1002/9780470974001.f500045

Handbook of Fuel Cells

Handbook of Fuel Cells

How to Cite

Thompson, E. L., Gu, W. and Gasteiger, H. A. 2010. Performance during start-up of proton exchange membrane (PEM) fuel cells at subfreezing conditions. Handbook of Fuel Cells. .

Author Information

  1. 1

    General Motors Corporation, Honeoye Falls, NY, USA

  2. 2

    Acta S.p.A., Pisa, Italy

Publication History

  1. Published Online: 15 DEC 2010

Abstract

This article discusses recent performance studies of PEM (proton exchange membrane) fuel cells operating at subfreezing temperatures. The major sources of voltage loss (kinetic, ohmic, and transport) are experimentally isolated to quantify their contribution to the total voltage loss. Thus, the oxygen reduction reaction (ORR) kinetics and membrane proton conduction resistances are quantified at subfreezing temperatures. To provide a mechanistic explanation for the observed temperature and water-content dependency of proton conductivity, phase transitions and state of absorbed water in Nafion® was measured using differential scanning calorimetry.

While it is reasonably well known that a successful PEM fuel cell cold start strongly depends upon the effective use of membrane and electrode to store product water (ice) until the cell temperature reaches 0 °C, the exact water (or charge) storage capacity of the membrane and the cathode electrode as well as the estimated water partitioning into these two locations as a function of operating conditions has not been discussed in detail and is presented here. In addition, cryo-SEM is used to examine ice formation in the electrode and confirm the above estimates. The electron proton conduction resistance was used to predict the ORR current distribution within the cathode electrode, which provides insight into how ice filling proceeds in the electrode, and is supported by cryo-SEM findings. Finally, the measured and estimated voltage losses are summarized to highlight the contribution of the various voltage loss terms on the overall initial voltage loss during operation at −20 °C, for a wide range of membrane water contents and current densities.

Keywords:

  • proton exchange membrane fuel cell;
  • subfreezing temperatures;
  • cold start;
  • oxygen-reduction reaction kinetics;
  • conductivity;
  • ice storage;
  • cryo-SEM