The Contact Resistance of a Double-Sided MPL Coated GDL used in PEMFC

Lead Research Organisation: University of Sheffield
Department Name: Mechanical Engineering

Abstract

Fuel cells are electrochemical devices that convert the chemical energy of a reaction directly into electrical energy. Proton exchange membrane fuel cells (PEMFC) are in particular, an area of substantial interest. This is due to the fact that they are very versatile. For example, they can be used in applications such as portable energy, stationary energy production and transportation. Furthermore, they potentially have an important role to play in the future "hydrogen economy". This includes contributing to reduce greenhouse gas emissions and decreasing the dependence on fossil fuel technologies.
The gas diffusion layer (GDL) is a critical component in the PEMFC. The role of the GDL in the operation of a PEMFC is multifaceted. It provides a medium through which the reactant gases can diffuse through, while simultaneously allowing excess liquid water to be removed. The GDL also facilitates heat and electron transfer through the PEMFC. Additionally, it provides mechanical support for the delicate catalyst layer and membrane.
The GDL is an important medium between the catalyst and bipolar plate; this has led to much research into the GDL performance. Despite this, the GDL is still an area of considerable operational losses in a PEMFC, particularly ohmic losses. These loses become more consequential at the interfacial contacts between components within the fuel cell; this is especially significant for the GDL as it sits in between the bipolar plate and catalyst layer. Electrical losses at the contact interfaces, such as, between the GDL and bipolar plate and the GDL and catalyst layer are significantly higher than individual component bulk losses.
To enhance the properties of the GDL at the interfacial contact with the catalyst layer, a microporous layer (MPL) is conventionally applied. Typically, the MPL consists of carbon particles mixed with PTFE and a binder. The MPL has been proven to improve overall performance of the GDL at the catalyst layer interface, including improvements in electrical contact.
The main objective of the research is to improve the performance of PEMFC by reducing the interfacial contact resistance (ICR) by the application of a double-sided MPL coated GDL. This will be achieved by coating the GDL with a double-sided MPL. One MPL will face the catalyst layer and the other will be facing the bipolar plate. Reducing ohmic losses of the PEMFC has been the focus of many research groups. However, the reduction of ohmic losses via the reduction of ICR using a double-sided MPL coated GDL is still not fully understood. Particular attention will be paid to the ex-situ characterisation measurements, as these will aid in holistic understanding of the GDL.
This study aims to provide greater insight into the ICR and the development of alternative GDL coated MPLs to improve interfacial characteristics. In addition, it is intended to explore novel materials for MPL coatings such as carbon nanotubes and graphene. The development of new combinations of materials and different designs for the GDL is aiming at reducing the interfacial contact resistance, increase electrical conductivity, thus improving the overall performance of PEMFC operation.
The objective of this project is divided into 3 main parts:

Accurately quantify the interfacial contact resistance between GDL and the flow field plate and between the GDL and the catalyst layer.
Optimise the double-sided MPL coated GDL by examining characterisation and holistic performance on PEMFC.
Optimise the use of novel materials for use in the double-sided MPL coated GDL by characterisations and overall PEMFC performance.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/S022996/1 30/09/2019 30/03/2028
2448073 Studentship EP/S022996/1 30/09/2020 29/09/2024 Fernando Ruscillo