@article{26518,
  keywords = {Model, Transport, Temperature, Performance, Water, Wettability, Behavior, Cold-start, PEFC, Gas-diffusion layer},
  author = {Thomas J Dursch and Gregory J Trigub and Roger Lujan and J F Liu and Rangachary Mukundan and Clayton J Radke and Adam Z Weber},
  title = {Ice-Crystallization Kinetics in the Catalyst Layer of a Proton-Exchange-Membrane Fuel Cell},
  abstract = {<p>Nucleation and growth of ice in the catalyst layer of a proton-exchange-membrane fuel cell (PEMFC) are investigated using isothermal differential scanning calorimetry and isothermal galvanostatic cold-starts. Isothermal ice-crystallization rates and ice-nucleation rates are obtained from heat-flow and induction-time measurements at temperatures between 240 and 273 K for four commercial carbon-support materials with varying ionomer fraction and platinum loading. Measured induction times follow expected trends from classical nucleation theory and reveal that the carbon-support material and ionomer fraction strongly impact the onset of ice crystallization. Conversely, dispersed platinum particles play little role in ice crystallization. Following our previous approach, a nonlinear ice-crystallization rate expression is obtained from Johnson-Mehl-Avrami-Kolmogorov (JMAK) theory. A validated rate expression is now available for predicting ice crystallization within water-saturated catalyst layers. Using a simplified PEMFC isothermal cold-start continuum model, we compare cell-failure time predicted using the newly obtained rate expression to that predicted using a traditional thermodynamic-based approach. From this comparison, we identify conditions under which including ice-crystallization kinetics is critical and elucidate the impact of freezing kinetics on low-temperature PEMFC operation. The numerical model illustrates that cell-failure time increases with increasing temperature due to a longer required time for ice nucleation. Hence, ice-crystallization kinetics is critical when induction times are long (i.e., in the “nucleation-limited” regime for <em>T</em> &gt; 263 K). Cell-failure times predicted using ice-freezing kinetics are in good agreement with the isothermal cold-starts, which also exhibit long and distributed cell-failure times for <em>T</em> &gt; 263 K. These findings demonstrate a significant departure from cell-failure times predicted using the thermodynamic-based approach.</p>},
  year = {2014},
  journal = {Journal of the Electrochemical Society},
  volume = {161},
  pages = {F199 - F207},
  month = {01/2014},
  issn = {0013-4651},
  doi = {10.1149/2.004403jes},
}