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Table of contents
CHAPTER I: BACKGROUND AND OBJECTIVES
1. The Hydrogen Economy
1.1. Hydrogen production
1.2. Hydrogen storage
1.3. Hydrogen use
2. Fuel cells: working principle
2.1. High temperature fuel cells
2.2. An example of low temperature fuel cell: the proton exchange membrane fuel cell (PEMFC) Working principle and applications
Reducing catalyst poisoning
Increasing the catalyst activity
Increasing operative temperature
A PEMFC subcategory: DMFC
2.3. Other low temperature fuel cells
AFC
PAFC
3. The key component of PEMFCs: the Proton Exchange Membrane
3.1. Mechanisms of proton transport in PEMs
3.2. Other desired properties of the membrane
3.3. The PEM state of the art: Nafion
Limitations
3.4. Alternatives PEMs for high temperature PEMFCs
3.5. Azoles and azole-based polymers as proton conductors
Azoles as liquid solvents
Azole-based polymers as anhydrous proton conductors
4. Objectives
5. References
CHAPTER II: THEORETICAL BACKGROUND
1. Quantum Mechanics (QM)
1.3. Molecular orbital (MO) approximation and basis functions
1.4. The Hartree-Fock Theory
The Hartree-Fock Equations
1.5. The correlation energy
1.7. The Coupled-Cluster (CC) theory
1.8. The Density Functional Theory
The Hohenberg-Kohn theorems
The Kohn-Sham method
Exchange-correlation Functionals
1.9. Statistical thermodynamics and partition function
Electronic partition function
Translational partition function
Rotational partition function
Vibrational partition function
2. Molecular Mechanics (MM)
2.1. Force Field
Basic principle
The Verlet integration algorithm
Choosing the time step
The thermodynamic ensembles
Molecular Dynamics at constant temperature
2.3. Free energy calculations: the umbrella sampling technique
3. References
CHAPTER III: DFT STUDY OF PROTON TRANSFER REACTIONS .
1. Modeling proton transfer in imidazole-like dimers
1.1. Introduction
1.2. Methodological details
1.3. Identification of the PT reaction mechanisms
1.4. Basis Set selection
1.5. The reference energy values
1.6. PT in imidazolium-imidazole complex
1.7. PT in 1,2,3-triazolium-1,2,3-triazole complex
1.8. PT in tetrazolium-tetrazole complex
1.9. Comments
1.10. The BMK/B3LYP model
2. PT reactions: a benchmark study
2.1. Introduction
2.2. Methodological details
2.3. Results and discussion
Proton transfer barriers at given structure
Standard energy barrier evaluations on the DBH24/08 database
Optimized structures: PT barriers & H-bond structural parameters
Comments
3. Conclusions
4. References
CHAPTER IV: STUDY OF PROTON TRANSPORT IN P4VI
1. Introduction
1.1. Poly-(4-vinyl-imidazole)
1.2. The Brédas mechanism
2. Methodological details
3. Results and discussion
3.1. Conduction mechanism in small models: DFT investigation
Protonated dimers
Protonated trimer
3.2. Conduction mechanism in large models: molecular dynamics simulations
Force field parametrization
Analysis of the trajectory
3.3. A new charge-transport mechanism
3.4. Support from experimental evidences
3.5. Charges and electrostatic potential: support to the MD simulation quality
4. Conclusions
5. References
CHAPTER V: PROTON CONDUCTION OF H3PO4-DOPED P4VI
1. Introduction
2. Results and discussion
2.1. Identification of a Gotthuss chain in the starting complex
2.2. Proton transfer reactions in the protonated model
2.3. Investigation of the rate-limiting step
2.4. Comments
3. Conclusions
4. References
CHAPTER VI: PROTON TRANSPORT IN 2-TETHERED SYSTEMS .
1. Introduction
2. Methodological details
3. Results and discussion
3.1. Conduction mechanism in small models: DFT investigation
PT in protonated dimers
Cooperative reorientation in a trimeric model
3.2. Conduction mechanism in large models: Molecular Dynamics simulations
Force Field calibration
Analysis of trajectory
4. Comments and experimental evidences
5. Conclusions
6. References
GENERAL CONCLUSIONS
References
ANNEXES
ANNEX I: Supplementary information for chapter III
ANNEX II: Supplementary information for chapter IV
ANNEX III: Supplementary information for chapter VI
Synthèse générale
1. Contexte et objectifs
1.1. Les piles à combustible
La membrane d’échange de protons (PEM)
1.2. Les azoles et les polymères à base d’azoles comme conducteurs de protons
1.3. Objectifs de la thèse
2. Étude DFT des réactions de transfert de proton dans les azoles
2.1. Le modèle BMK/B3LYP
3. Une étude de référence de réactions PT
4. Étude du transport de protons dans P4VI
4.1. Étude DFT du mécanisme de conduction dans les petits modèles
4.2. Étude MD du mécanisme de conduction dans les grands modèles
4.3. Un nouveau mécanisme de transport de charge
5. Conduction protonique des P4VI dopés avec du H3PO4
6. Transport des protons dans les systèmes avec attache en position 2
6.1. Étude DFT du mécanisme de conduction dans les petits modèles
6.2. Étude MD du mécanisme de conduction dans les grands modèles
7. Conclusion générale
8. Références
Abstract
Résumé
