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Table of contents
Chapter I – State of the art of proton-exchange membrane fuel cell (PEMFC) systems
1. Overview of PEMFC
1.1. Operating principle of PEMFC
1.2. Fuel cell components
2. Generalities on PFSA membranes
2.1. Chemical structure and morphology
2.2. Sorption and transport of water and protons
2.3. Mechanical properties
3. Degradation mechanisms of membrane-electrode assemblies (MEA)
3.1. Gas diffusion media
3.2. Catalyst layers
3.3. PFSA membranes
Conjoint chemical and mechanical degradations
4. Objectives of the thesis work
Chapter II – Experimental techniques
1. Chemical and electrochemical characterizations
1.1. Fluoride emissions measurement via ion-selective electrode (ISE)
1.2. ATR-FTIR spectroscopy
1.3. NMR spectroscopy
2. Characterization of membrane functional properties
2.1. Liquid-state 1H-NMR
2.2. Water uptake measurements
Chapter III – Accelerated chemical degradation of PFSA membranes: Fenton’s reaction protocol
1. State of the art: chemical degradation of PFSA membranes induced by Fenton’s reaction
2. Description of the aging and cleaning protocols
2.1. Sample pretreatment
2.2. Aging protocol based on Fenton’s reaction and operating conditions
2.3. Cleaning of aged samples
3. Effect of Fenton’s reagent concentrations on the chemical degradation of PFSA membranes
3.1. Macroscopic morphology evolution of aged membranes
3.2. Fenton solutions analysis: quantification of the chemical degradation
4. Conclusions
Chapter IV – Time-resolved monitoring of PFSA membranes degradation induced by Fenton’s reaction
1. Introduction
2. Establishment of the time-resolved monitoring of ex-situ chemical degradation
3. Chemical structure evolution after exposure to Fenton’s reagents
3.1. ATR-FTIR spectroscopy
3.2. Solid-state 19F-NMR spectroscopy
4. Quantification of the chemical degradation
4.1. Weight loss and fluoride emissions
4.2. Liquid-state 19F NMR spectroscopy
4.3. Correlation between weight loss and emissions of degradation products
5. Impact of the degradation on PFSA membranes functional properties
5.1. Water sorption capacity in aged membranes
5.2. Water self-diffusion after chemical degradation
6. Discussions
6.1. Comparison of PFSA membrane degradation with literature
6.2. Contribution of reinforcement layer and radical scavengers against chemical degradation
7. Conclusions
Chapter V – Effects of conjoint chemical and mechanical stress on PFSA membranes
1. Introduction
2. Experimental device and protocols
2.1. Description of the aging device
2.2. Ex-situ coupled mechanical and chemical stress tests
2.3. Electrochemical tests in single cell
3. Characterization of membrane degradation
3.1. Preliminary tests
3.2. Cyclic compression stress
3.3. Influence of the mechanical strength
3.4. Impact of aging test duration
3.5. Impact of the presence of GDL
4. Impact of conjoint chemical and mechanical stress on the membrane structure and functional properties
4.1. Chemical structure evolution of membranes after conjoint chemical and mechanical stress
4.2. Evolution of water sorption and transport properties in aged membranes
4.3. Cell performances after conjoint mechanical and chemical stresses
5. Contribution of the mechanical stress on membrane properties: comparison with pure ex-situ chemical stress tests
6. Conclusions
Conclusions and Perspectives
Appendix A – Optimization of the experimental protocols
Appendix B – Impact of a static compressive stress on the functional properties of PFSA membranes
