PHD RESEARCH PROJECT

2015-2018 www.lemta.fr

NMR and MRI investigation of water transport through multilayer PEMFC components Institution University of Lorraine / LEMTA Laboratory / CNRS PhD supervisor Prof. Olivier Lottin Co-supervisor Dr. Jean-Christophe Perrin Contact [email protected] e-mail : phone : +33 (0)3.83.59.55.86 activities of the research group : http://lemta.univ-lorraine.fr/pac.html Mailing address 2 avenue de la Forêt de Haye, TSA60604 54518 Vandoeuvre Cedex, France International context The quest for more sustainable energy has become a worldwide priority. During the past decades, the global demand for energy has exploded, raising the need for highly efficient energy conversion devices. Today, hydrogen has gained importance as an energy carrier in future transport applications and fuel cells have reached a state-of-the-art that makes them highly attractive for car propulsion. Groups of researchers around the world are carrying out the environmental and economic assessments of the entire hydrogen supply chain and it is generally believed that, when combined with the right energy sources, fuel cells, and more particularly polymer electrolyte membrane fuel cells (PEMFCs), have the highest efficiencies and lowest emissions of any vehicular power source. Fundamental and technological research in the field of PEMFC systems is intense and, in the past years, more than 35% cost reduction has been achieved in their fabrication. In PEMFCs, hydrogen and oxygen react to form water and, due to the separation of the anodic and cathodic processes, electrical energy. Protons migrate through the membrane (PEM) and recombine with oxygen on the surface of the cathodic catalyst where oxygen is reduced and forms water (Figure 1). The electrolyte of the PEMFC is usually a polymer membrane composed of poly(tetrafluoroethylene) backbones with sulfonate-terminated side chains, like Nafion®. To reach the target for transportation fuel cell of $30/kW to compete with the conventional technology of internal-combustion engines, breakthroughs in material development, acquisition of fundamental knowledge, and development of experimental methods are still needed. More specifically, the development of new methods to investigate water management in PEMFC materials will provide insights into a number of critical phenomena that occurs in running fuel cells. These methods have the potential to provide critical feedback for validating models of water transport phenomena for fuel cell research and development.

MEA

bipolar plate

catalyst coating

PEM

bipolar plate GFC : Gas Flow Channel

O2

H2

PEM : Proton Exchange Membrane GDL : Gas Diffusion Layer

H2 O

MEA : Membrane Electrode Assembly MPL : Micro Porous Layer

GFC sealing gasket GDL+MPL

sealing gasket

Figure 1. Proton Exchange Membrane Fuel Cell (PEMFC) components.

Scientific project This project aims at studying the properties of complex assemblies composed of the ionomer membrane and one or more elements such as the catalyst layer (electrode) and/or the gas diffusion layer. The main experimental technique will be MRI (Magnetic Resonance Imaging) and NMR (Nuclear Magnetic Resonance) spectroscopy. The experimental methodology will be based on the recent advances made in our group in the imaging of water profiles through a PEM membrane with both high spatial and temporal resolutions [Figure 2(a) and (b) and ref(1)]. Figure 2 (a) Experimental setup developed for the MRI of water distribution in the thickness of a PEM. The 2D NMR probe is placed under the cell containing the membrane exposed to air flows with controlled hygrothermal conditions.

t0

T = 24°C (b) Water profiles measured by MRI through a 250 µm thick Nafion membrane. Acquisition time = 70 seconds/profile. Spatial resolution = 6 µm / point.

The study will be focused on the observation of water behavior in the membrane when its interfaces are exposed to different phenomena: - inhomogeneities in gas supply due to the electrode; - mass transfer resistances due to the GDL or the GDE (gas diffusion electrode);

- electrochemical reaction with water formation at the membrane / electrode interface. The measurements will be systematically compared to the reference case (Nafion membrane exposed to controlled hygrothermal conditions) and used to develop a coherent modeling for water transport through the multilayer. The experimental methodology will be also exploited to characterize PEMs after long runs in fuel cell conditions, the final objective being the development of a new versatile diagnostic tool of aged membranes. References 1) M. Klein, J.-C. Perrin, S. Leclerc, L. Guendouz, J. Dillet, O. Lottin. Spatially and temporally resolved measurement of water distribution in Nafion using NMR imaging, ECS Transactions, 58 (1) 283-289 (2013). Related references: 2) J.-C. Perrin, M. Klein, S. Leclerc, L. Guendouz, J. Dillet, O. Lottin. NMR Investigation of Water Diffusion in a Nafion membrane Under Traction, ECS Transactions, 58 (1) 781-788 (2013). 3) M. Klein, J.-C. Perrin, S. Leclerc, L. Guendouz, J. Dillet, O. Lottin. Anisotropy of water selfdiffusion in a Nafion membrane under traction, Macromolecules, 46, 23, 9259-9269 (2013). 4) M. Klein, J.-C. Perrin, S. Leclerc, L. Guendouz, J. Dillet, O. Lottin. NMR Study of the anisotropic transport properties of uniaxially stretched membranes for fuel cells, Diffusion Fundamentals 18-7 (2013) 1-4. PhD thesis (Mathieu Klein, 2014) [non-definitive version] : https://docs.google.com/viewer?a=v&pid=sites&srcid=ZGVmYXVsdGRvbWFpbnxqZWFuY2hyaXN0b3BoZXBlcnJpbnxne DoxMTYyMTRmYmY0YTZjMDdk

Application procedure Informal inquiries can be made to Dr Jean-Christophe Perrin ([email protected]) with a copy of your curriculum vitae and cover letter. Applications should be received and complete by 29 May 2015.