CHARACTERIZATION AND TAILORING OF THE MICROPOROUS LAYER|CATALYST LAYER INTERFACIAL STRUCTURE IN POLYMER ELECTROLYTE MEMBRANE FUEL CELLS

Open Access
- Author:
- Hizir, Fahri Erinc
- Graduate Program:
- Mechanical Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- April 09, 2010
- Committee Members:
- Clinton Matthew Mench, Thesis Advisor/Co-Advisor
Matthew M Mench, Thesis Advisor/Co-Advisor
Emin C Kumbur, Thesis Advisor/Co-Advisor - Keywords:
- polymer electrolyte fuel cell
water management
catalyst layer
microporous layer
interface
characterization - Abstract:
- The interface between the micro porous layer (MPL) and the catalyst layer (CL) can have an impact on thermal, electrical and two-phase mass transport in a polymer electrolyte fuel cell (PEFC). However, there is scant information available regarding the true morphology of the MPL and CL surfaces. In this work, optical profilometry is used to characterize the MPL and CL surfaces at the sub-micron level scale to gain a better understanding of the surface morphology. Selected MPL and CL surfaces are sputtered with a thin layer of gold to enhance the surface reflectivity for improved data acquisition. The results show that, for the materials tested, the MPL surface has a relatively higher roughness than the CL surface, indicating the potential dominance of the MPL surface morphology on the local transport and interfacial contact across the MPL|CL interface. Another surface characteristic that can have a profound influence on multi-phase transport is the existence of deep cracks along the MPL and CL surfaces. In the second part of this study, the MPL and CL surfaces are tailored via polishing for improved interface mating characteristics. Furthermore, hydrophilic micro-channels are integrated into diffusion media (DM) structure and the MPL surface is artificially cracked via laser ablation. The tailored samples are expected to reduce water accumulation inside the CL, GDL and the interfacial gaps between the MPL and the CL. Finally, behavior of liquid water inside the MPL cracks is investigated using an environmental scanning electron microscope (ESEM). ESEM observations suggest that liquid water removal from the CL could take place through the MPL cracks which are connected to preferential water pathways in the GDL. Canalization of the water condensed in the MPL pores towards the MPL cracks could also be influential on the water transport in the MPL.