Date of Completion

10-29-2014

Embargo Period

10-26-2014

Keywords

PEM fuel cells; durability; water management; hydrogen impurity; cationic contaminants

Major Advisor

Trent M. Molter

Associate Advisor

Ugur Pasaogullari

Associate Advisor

Prabhakar Singh

Field of Study

Materials Science and Engineering

Degree

Doctor of Philosophy

Open Access

Campus Access

Abstract

The polymer electrolyte membrane (PEM) fuel cell is a promising candidate for helping to solve today’s energy problems. However, many challenging issues still need to be addressed before the PEM fuel cell can be used in large-scale commercial applications. Currently, the structural optimization of fuel cell components and the study of the materials for fuel cell applications are feasible ways to advance the technology. In this research, efforts have been made in these fields.

A cutting-edge new design of bipolar plates, the water transport plate, is studied to understand the possible performance improvement and corresponding mechanisms. The cells with the traditional solid graphite bipolar plates and the water transport bipolar plates are analyzed and compared in four testing phases: 375 hours, 750 hours, 1125 hours, and 1500 hours. It is found that performance improvement is mostly related to the enhanced water management, which can lead to a better working environment for fuel cell components during operation.

Impurities in hydrogen are studied to facilitate the hydrogen production as well as PEM fuel cell applications. In this research, cocktail tests are conducted to determine the contaminant effects of mixed impurities in hydrogen. It was found that five times the specification concentration level of mixed impurities—which consists of 1 ppm carbon monoxide, 20 ppb hydrogen sulphide, 1 ppm formic acid, 10 ppm benzene, and 0.5 ppm ammonia in hydrogen—degrade cell performance very rapidly.

Studies have been also conducted on several cations, which are possible contaminants for the PEM fuel cell cathode. Among them, Ca2+ received special attention because of its wide distribution. The test results from salt spray approve that working at high current densities and high Ca2+ concentrations can lead to significant cell performance loss as well as catalyst and membrane degradation. Plugging was found at 0.2 A/cm2 with 5 ppm Ca2+ in cathode air. It is believed to be caused by the Ca2+ precipitation inside the cells under this test condition.

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