Modeling the Effects of Interfaces on Water Management and Performance of Polymer Electrolyte Fuel Cells.

摘要

Polymer electrolyte fuel cells (PEFCs) are of great importance as a clean alternative to conventional heat engines. However, PEFCs need further improvements to be economically utilized in stationary and transport applications. To achieve the highest performance, a delicate water balance in PEFCs must be maintained. The polymer membrane must remain hydrated in order to maximize proton conductivity, while excess liquid water should be removed from the cathode to avoid any flooding issues. This water management issue is hypothesized to be affected by the interfaces of the components. Presently, little is known about the transport through the interfaces and its related effects on the water distribution and performance of the PEFCs.;This Ph.D. work addresses this critical gap by exploring the effects of the interfaces on water management and performance of PEFCs through a computational modeling study. The overall objective of this dissertation study is to introduce a modeling framework which incorporates component interfaces in order to evaluate their effects on water transport and performance of PEFCs. To achieve this goal, a series of computational studies were established. First, a 2-D, steady state, multiphase PEFC model for the cathode side was developed. Then, the computational model was integrated with the key interfaces which dominates the overall water transport in PEFCs: (i) the microporous layer (MPL)| catalyst layer (CL) interface which governs the mass and ohmic transport losses, (ii) morphologically modified MPL which provides pathways for water transport, and (iii) bipolar plate (BP)| gas diffusion layer (GDL) interface where the contact resistance dominates. Using these models, an in-depth understanding of the roles of the interfaces in water transport and performance of PEFCs has been obtained. One of the most important findings is that the interfaces affect the water distribution inside the fuel cell components which leads to a significant drop in the cell performance.