A Microstructural Model for a Proton Exchange Membrane Fuel Cell Catalyst Layer
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Authors
Baker, Craig
Date
2012-09-08
Type
thesis
Language
eng
Keyword
Catalyst Layer , Diffusivity , Percolation , Fuel Cell
Alternative Title
Abstract
This thesis presents a framework for a microstructural model of a catalyst layer in a proton exchange membrane (PEM) fuel cell. In this study, a stochastic model that uses individual carbon, platinum and ionomer particles as building blocks to construct a catalyst layer geometry, resulting in optimal porosity and material mass ratios has been employed. The construction rule set in this design is easily variable, enabling a wide range of catalyst layer geometries to be made. The generated catalyst layers were found to exhibit many of the features found in currently poduced catalyst layers. The resulting geometries were subsequently examined on the basis of electronic percolation, mean chord length and effective diffusivity of the pore phase. Catalyst layer percolation was found to be most effected by the number of carbon see particles used and the specified porosity. The mean chord lengths of all of the catalyst layer geometries produced Knudsen numbers ranging in order of magnitude between 0.1 and 10, thus indicating that gas diffusion within the catalyst layers lies in the transition regime between bulk and Knudsen diffusion. Calculated effective diffusivities within the pore space of the model were shown to be relatively insensitive to changes in the catalyst layer composition and construction rule set other then porosity, indicating that the pore size distribution does not significantly vary when the catalyst layer mass ratios vary.
Description
Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2012-08-31 08:52:55.747
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This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.