Subfreezing operation of polymer electrolyte fuel cells: Ice formation and cell performance loss

In this work, we investigate the cold-start operation of polymer electrolyte fuel cells (PEFCs) through high-resolution neutron radiography, experimental testing, theoretical evaluation, and comparison with model prediction. Ice formation location, voltage evolution, and loss of the electro-catalyst surface area (ECSA) are examined. A dimensionless parameter , characterizing the spatial variation of the reaction rate across the cathode catalyst layer, is discussed at subfreezing temperature using newly determined membrane ionic conductivity. The evaluation identifies the operating range that the reaction rate can be treated uniform across the catalyst layer, in which the model is valid. © 2012 Elsevier Ltd. All rights reserved

An experimental study of polymer electrolyte fuel cell operation at sub-freezing temperatures

The ability of polymer electrolyte fuel cells (PEFCs) to startup at subfreezing temperatures is governed by whether it is able to overcome the freezing point (0°C) before product ice prevents the electrochemical reactions. In this work, we experimentally investigated the coulombs of charge Qc transferred in PEFCs under subfreezing operation before the output voltage drops to 0.0V. PEFCs with various membranes and catalyst-layer thicknesses, ionomer-carbon ratios, operating current density, and initial hydration of PEFCs were studied, and their influences on cold-start performance and coulombs of charge were experimentally measured. We find that subfreezing temperature, ionomer-catalyst ratio, and catalyst-layer thickness, significantly affect the amount of charge transferred before operational failure, whereas the membrane thickness and initial hydration level have limited effect for the considered cases. © 2013 The Electrochemical Society

Doctor of Philosophy

dissertationWith the introduction of Superman in Action Comics #1 (published June 1938), Americans became fascinated with superheroes. Following the immediate success of Superman, the comic book industry created hundreds of characters that defied and surpassed all human capabilities. Radio, television, advertising, traditional publishing, and the film industry recognized the monetary potential of superheroes and these characters very quickly began proliferating across American popular culture. The economic success of this genre might be unprecedented, but American interest in strong, charismatic, extraordinary figures prefigures the birth of the superhero. In both the political and social arenas of the 1930s and 1940s, not only in the U.S. but also globally, citizens were curious about the human potential to control and transcend physical limitations. As a response to the fascism that threatened to overtake European countries, the United States produced their own strong leaders in mythic, fantastical, serial narratives. Embodying and evoking the sublime, superheroes astounded and terrified. They interact with a sublime aesthetic and paradoxically represent the appeal and irrevocable danger of absolute power. Through close readings of narratives about Superman, Batman, the Lone Ranger, Captain America, and Wonder Woman, I explore the contradictory nature of the sublime superhero, detailing how each character's origin story creates a figure who both celebrates and challenges the moral and political virtues of American society