Interfaces and Related Losses in PEM Fuel Cells: Theoretical and Experimental Studies

Drexel University, Philadelphia PA

Investigators

Abstract

1066623 PI Kumbur The objective of this work is to define a scientific framework that enables detailed assessment of the interfacial morphology and interfacial transport mechanisms on the of the polymer electrolyte fuel cell (PEFCs). The PIs hypothesize that a major reason for many shortcomings of current model is the treatment of the interface as an infinitely thin layer, having perfect contact and homogenous properties. Preliminary work by PIs demonstrates that the micro-porous layer (MPL) and catalyst layer (CL) surfaces are not smooth; instead they exhibit surface irregularities, such as elongated surface cracks, holes, and dents. These surface features result in imperfect interfaces, which promote performance loss an. Compelling evidence suggests that interfacial regions are of importance in fuel-cell performance, but a fundamental understanding of the role of these critical regions is still lacking. The PIs will address this issue and perform a verification of the impact of the interface on the performance and durability of PEFCs. To achieve this, the PIs will carry out a combined experimental and computational plan, including: 1) ex-situ and in-situ measurements of a broad range of interfacial transport properties and water retention characteristics using advanced diagnostic tools and neutron imaging, 2) digital characterization of the bonded interface structure through a combined optical profilometry and dual-beam focused ion-beam scanning electron microscope study, 3) development of a validated interfacial contact model ( adapting well-established frameworks from tribology) to create a set of cloned virtual MPL/CL interface structures under compression, and 4) using these virtual interfaces, develop multi-scale transport and performance models to describe the impact of these interface regions on the mass, thermal and electrical transport characteristics of PEFCs. Intellectual Merit: This approach will enable higher fidelity modeling capability with realistic interfacial morphology and interfacial transport. This project will not only have a substantial impact on the engineering of novel materials for high performance, but also will provide significant guidance for durability studies. The proposed methodology also has a strong transformative nature as it will bring a new perspective to approach the interface related performance and durability issues in PEFCs and other types of fuel cells. The proposed methodology for characterizing the interface will be transformable to other fields, as it can be further extended into other electrochemical systems (e.g., Li-ion and other batteries) to help us address similar fundamental gaps. Broader Impact: Specific activities will include: i) training of graduate and undergraduate students in multidisciplinary engineering fields, ii) formation of a yearly graduate student exchange between labs at Drexel and Carnegie Mellon (CMU), iii) development of new instructional materials for fuel cell courses taught at Drexel and CMU, iv) active recruitment and training of women and underrepresented minority engineers by leveraging the established programs (REU, IGERT, GAANN, LSAMP) at Drexel and CMU, v) training of local high school students through Drexel Mentorship Program, vi) hosting local high school teachers through Drexel-Penn NanoRET program to develop educational modules related to alternative energy, vii) semi-annual workshops for high school teachers as a part of the ?What is Engineering? program at CMU, and viii) presentation of results in publications and PIs? websites for broader dissemination.