Proton Exchange Membrane Fuel Cells (PEMFC) are mainly developed for transportation applications. Over the past decade, significant progress has been made, leading to the commercialization of the first generation of fuel cell cars. Recently, R&D efforts have shifted to heavy-duty vehicles, where PEMFCs are more competitive with Li-ion batteries. The use of PEMFCs for trucks will require different operation conditions but also much longer lifetimes (25,000 hours instead of 5,000 hours for cars). To reach these objectives, it is essential to optimize the materials and structure of the electrodes, but also to better understand their degradation mechanisms. To progress on these fields, transmission electron microscopy and the various associated techniques have become indispensable tools.
The electrodes of PEMFCs are a nano-porous material composed of carbon grains (30 nm) supporting platinum nanoparticles (3 nm) - the catalysts of electrochemical reactions - and linked together by ionomer (a protonic conducting polymer). For several years at the CEA in Grenoble, we have been studying these electrodes in detail in order to better understand the components that limit the performance of the fuel cell and those that degrade during operation. Using the most advanced transmission electron microscopes, we use different advanced techniques (high resolution, chemical analysis, 3D imaging...) which have recently made impressive progress.
The objective of the thesis will be to use the different electron microscopy techniques available on the CEA-Grenoble nanocaracterization platform to study the electrode microstructure and their degradation mechanisms during the fuel cell operation. In particular, the electron tomography technique more recently used in the laboratory to characterize the electrodes in 3D will be developed.
This thesis will be carried out in close collaboration with the other teams of the CEA-Grenoble which manufacture and characterize the electrochemical properties of electrodes. It is part of a national project that includes many academic laboratories. An exchange with the Oak Ridge National Laboratory in the United States could also be planed during this thesis.