Elucidation of the Correlation between the Electrochemical Activity of Oxygen Reduction and the Molecular Structure of the Platinum/Ionomer Interface in Proton Exchange Membrane Fuel Cells
This thesis focuses on the Proton Exchange Membrane Fuel Cell (PEMFC), used in the transportation sector to generate electricity and heat from hydrogen and oxygen. Although promising for reducing CO2 emissions through the use of green hydrogen, the PEMFC needs to enhance its performance and durability to compete with combustion engines and batteries. The electrode plays a crucial role, but the molecular complexity of the electrochemical interface between the platinum-based catalyst and the ionomer makes characterization challenging. Currently, the qualitative understanding of this interface is limited, impeding progress and model predictability. The thesis aims to establish a correlation between the molecular structure of the electrochemical interface and the electrochemical kinetics, focusing on platinum oxidation and ionomer adsorption. A unique device developed at CEA allows simultaneous electrochemical and spectroscopic characterizations. The novelty lies in using Atomic Force Microscopy (AFM) coupled with Raman spectroscopy and synchrotron-based micro-infrared spectroscopy as original techniques to obtain crucial information for PEMFC applications.
Glass gaskets sealing characterization and modeling for High-temperature steam electrolysis technologies
Carbon free hydrogen production is a key challenge for the energy mix of the future. One of the technologies identified is based on high-temperature steam electrolysis (HTE). The operating conditions of this process require the development of specific glass gaskets to seal the electrolysis cells. The technical issues with these gaskets are directly related to the loss of seal occurring because of interface adhesion problems or material cracking during HTE thermal cycling.
The objective of this PhD work is to study the sealing performance of the glass gasket. Firstly, leakage tests will be carry out to discriminate the origin of seal loss according to the selected glasses. Then, mechanical characterization of the glass at high temperature will be performed in order to build the constitutive equation of the material. The overall PhD work will establish a link between the physico-chemical properties of glass and its mechanical and sealing properties. The results of the experimental tests and modeling will issue recommendations on the glass gasket to ensure the proper electrolyzer operation at industrial scale.
The thesis is part of the development of HTE technologies in sight of an industrial-scale production. The project is based on a close collaboration between GENVIA (CIFRE thesis), CEA (ISEC) and the Institute of Physics of Rennes.
Applicant must hold a master’s degree or an engineering degree in material sciences. The student will have to acquire extensive knowledge in mechanic, a first experiment in this field will be highly appreciated. Applicant is expected to show good synthesis and communication skills in order to collaborate with the various teams involved in the project.
The expertise developed in glass mechanics and the experience acquired in the HTE field will be an asset for the future PhD. It is a great opportunity for the student to take advantage of his scientific knowledge to support the energy transition.
New sustainable electrode materials for High Temperature Electrolysis
High temperature electrolysis is considered as the high efficiency technology for hydrogen production with low carbon emissions. The electrolysis reaction occurs in a solid oxide cell (SOC) composed of a dense electrolyte of yttria stabilized zirconia (YSZ), sandwiched between two porous electrodes. The most common hydrogen electrode material is a cermet of Ni and YSZ, and the oxygen electrode is a perovskite La0.6Sr0.4Co0.2Fe0.8O3 (LSCF).
To make the high temperature electrolysis more sustainable to better support the European eco-system towards the achievement of the Sustainable Development Goals and the objectives of the Paris Agreement, there is a critical need to reduce reliance on critical raw materials (CRM).
The objective of the thesis is therefore to limit the use of CRM in the oxygen electrode material. Critical elements such as cobalt will be substituted by new cations on the A and/or B site of the crystal lattice, while maintaining equivalent performance and long-term stability. At the same time, in order to limit losses during synthesis, a part of the work will be carried out on the synthesis process efficiency and on the increase in capacity of the synthesis method.
After a bibliographic study on oxygen electrode materials for high temperature electrolysers, the proposed work will initially be focused on the synthesis by chemical routes as well as on fine characterization of the perovskites. The thermal and chemical compatibility with the other materials constituting the cell will be studied, then this work will lead to the shaping of the materials with the most interesting properties in order to test them electrically and electrochemically. The electrochemical behaviour of the electrodes will be analysed in order to understand the influence of substitutions and to determine the electrochemical performance of the different compositions studied.