Cold Start of a Polymer-Electrolyte Fuel Cell III. Optimization of Operational and Configurational Parameters

The two-dimensional cold-start model developed in Part I of this study and verified in Part II is deployed to determine a cold-start protocol and cathode catalyst-layer properties that enable cell performance to meet the Department of Energy's start-time target of 30 s to 50% power from -20 degrees C. Constraints include eliminating the cathode catalyst layer's (cCL's) exposure to high ice pressures, reducing fuel consumption, and increasing the power available from the cell during the cold-start process. It is shown that neither a galvanostatic nor a potentiostatic protocol holds a significant advantage with respect to meeting the start-time target. On the other hand, in either case, operating at a higher current density (corresponding to a lower cell potential) results in high ice pressures within the cCL, primarily near the membrane/cCL interface. Finally, for a given initial start-up temperature, increasing the porosity and the ionomer content of the cCL reduces both start time and the amount of the cCL that experiences high ice pressure. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3592485] All rights reserved.