Microstructure and transport in corroded proton exchange membrane fuel cells

Abstract

Impressive development of proton exchange membrane fuel cells (PEMFC) has been accomplished over the past several decades. Unfortunately, adoption of PEMFC technology has been slow despite global belief that electrified transportation is necessary in response to increasing pollution in cities and impending destabilizing effects of climate change. Cost and durability are the most pressing issues preventing commercialization and the cathode, the subject of this thesis, is the most expensive and least durable component. Further improvement will be required to realize widespread adoption of PEMFCs. PEMFC degradation and transport were investigated, with emphasis on the microstructure of catalyst coated membrane cathode layers of platinum-catalyzed, H2-fueled cells. A central contribution of this thesis was to advocate for and bring to bear new information and new techniques to better quantify the connection between cathode transport and degradation. The principal experimental accomplishment was development and use of focused ion beam and scanning electron microscope tomography that enabled direct three-dimensional imaging of degraded cathode catalyst layers. Much of the subsequent analysis relied upon information obtained by this method.