Cet ouvrage fait partie de la bibliothèque YouScribe
Obtenez un accès à la bibliothèque pour le lire en ligne
En savoir plus

Etude de GdBaCo2-xMxO5+δ (M = Ni, Fe ; x = 0, 0.1,0.2,…) comme nouveaux matériaux de cathode pour l’application de IT-SOFC, Study of GdBaCo2-xMxO5+δ (M=Ni, Fe; x = 0, 0.1, 0.2,…) as new cathode materials for IT-SOFC application

De
146 pages
Sous la direction de Guilhem Dezanneau
Thèse soutenue le 25 mars 2011: Ecole centrale Paris
GdBaCo2O5+δ a été présenté récemment comme un matériau de cathode potentiel pour pile à combustible à oxyde solide. Cependant, sa réactivité chimique avec la zircone yttriée et son fort coefficient de dilatation constituent une limite importante à son utilisation. L’objet de ce travail est l’étude des composés GdBaCo2 xMxO5+δ (M = Ni, Fe, x = 0, 0.1, 0.2…) i.e. substitués au fer et au nickel pour objectif d'améliorer les propriétés du composé original pour l'application pile à combustible. Tout d'abord, différentes méthodes de synthèse ont été essayées et comparées, les méthodes par voie chimique montrant un net avantage pour l'obtention de taux de substitution élevés. Les propriétés physico-chimiques des matériaux synthétisés ont été caractérisées. Si la structure des composés évolue avec la nature et le taux du substituant, les propriétés de ces composés en termes de conduction électronique ou d'évolution du contenu en oxygène sont relativement constantes. Finalement, les performances électrochimiques de plusieurs compositions sous forme d'électrodes poreuses ont été testées avec différents types d'électrolytes. Les résultats montrent que la substitution n'apporte rien pour ce qui concerne la dilatation des composés et par ailleurs ne semble pas améliorer significativement les performances électrochimiques.
-SOFC
-GdBaCo2O5+δ
-Électrochimique
GdBaCo2O5+δ has been recently introduced as a potential cathode material for solid oxide fuel cell. However, its utilization has been strongly limited by its chemical reactivity with yttrium-stabilized zirconia and its significant thermal expansion coefficient. This work focus on the study of compounds GdBaCo2 xMxO5+δ (M = Ni, Fe, x = 0, 0.1, 0.2…) i.e. substituted by Ni or Fe in order to ameliorate the properties of original composition for fuel cell application. Firstly, different synthesis methods have been attempted and compared, and the chemical routes showed a clear advantage for obtaining high substitution proportion. The physico-chemical properties of synthesized materials have been characterized. The structure of these compounds evolves with the substitution nature and proportion, while their properties such as electrical conductivity or changes in the oxygen content are relatively constant. Finally, the electrochemical performances of several compositions serving as porous electrodes were tested with different types of electrolytes. The results exhibit that the substitution neither shows evident influence with respect to the thermal expansion of these compounds, nor significantly improves their electrochemical performance.
-SOFC
-GdBaCo2O5+δ
-Electrochimical
Source: http://www.theses.fr/2011ECAP0017/document
Voir plus Voir moins

ÉCOLE CENTRALE DES ARTS
ET MANUFACTURES
« ÉCOLE CENTRALE PARIS »

THÈSE
présentée par

HU Yang

pour l’obtention du

GRADE DE DOCTEUR

Spécialité : Science des Matériaux

Laboratoire d’accueil : Structures Propriétés et Modélisation des Solides
UMR 8580 CNRS / Ecole Centrale Paris

SUJET :

Study of GdBaCo M O (M=Ni, Fe ; x = 0, 0.1, 0.2, …) as new 2-x x 5+ δ
cathode materials for IT-SOFC application

Soutenue le : 25 mars 2011

Devant un jury composé de :

M. Gilles CABOCHE Professeur à l’Université de Bourgogne Président
M. Alain THOREL Maître de Recherche à Mine Paris Rapporteur
Mme. Rose No ëlle VANNIER Professeur à L’ENSCL
M. Guilhem DEZANNEAU Chargé de recherche à ECP Directeur de thèse





Numéro d'ordre : 2011ECAP0017
tel-00619609, version 1 - 6 Sep 2011
Acknowledgements
This work has been done in Laboratoire Structures Propriétés et Modélisation des Solides
(SPMS) of the Ecole Centrale Paris (ECP) and Centre National de la Recherche Scientifique
(CNRS, UMR 8580), with financial support from China Scholarship Council (CSC).
I would like to express my gratitude to my thesis supervisor, Professor Guilhem
DEZANNEAU, whose guidance, encouragement, and instructing have extremly helped and
inspirited me.
I would also like to sincerely thank M. G. CABOCHE, Professor of the University of
Bourgogne, for accepting to be the referees of my thesis. I would also like to sincerely thank
Mme. R.N. VANNIER, Professor of the University of Lille, and M. A. THOREL, Maître de
recherche of University of Paris Mines for accepting as the examiners of my thesis.
I am also very grateful to the fellow students of our group: Emile Bévillon, Marc-david
Braida and Yanzhong Wang, for their valuable helps and advices, as well as all the joyful time
we have spent together. I would also like to thank Jean-Michel KIAT, the director of Labo SPMS,
and professors Brahim DKHIL and Maud GIOT, for their encouragement, help and kind attention.
I would also like to thank the laboratory engineers and technicians: Christine BOGICEVIC
and Fabienne KAROLAK for their help in chemistry related experiments, Gilles BOEMARE for
the very time-costing TGA/TG measurements, Jacques CHEVREUL and Nicolas GUIBLIN for
XRD, Françoise GARNIER for SEM, and other people like Thierry MARTIN, Agnès BÉNARD,
Fabien DEBRAY, Obadias MIVUMBI, Claire ROUSSEL. Thanks to their great help I could
accomplish all the experiments of thesis.
I am thankful to M. Jean-Hubert SCHMIT, the director the research department of ECP,
who has helped me to find financial support of the postponing period, as well as Geraldine
I
tel-00619609, version 1 - 6 Sep 2011
CARBONEL and Catherine LHOPITAL from the secretariat de l' Ecole doctorale for their help,
encouragement and kind attention.
I am eternally grateful to my family. My parents have contributed me with their confidence
and forever support. Thanks to you, I could passed the most difficult time and come to this
accomplishment.
II
tel-00619609, version 1 - 6 Sep 2011
Résumé
Etude de GdBaCo M O (M = Ni, Fe ; x = 0, 0.1, 2-x x 5+ δ
0.2,…) comme nouveaux matériaux de cathode pour
l’application de IT-SOFC

GdBaCo O a été présenté récemment comme un matériau de cathode potentiel pour pile à 2 5+ δ
combustible à oxyde solide. Cependant, sa réactivité chimique avec la zircone yttriée et son fort
coefficient de dilatation constituent une limite importante à son utilisation. L’objet de ce travail est
l’étude des composés GdBaCo M O (M = Ni, Fe, x = 0, 0.1, 0.2 …) i.e. substitués au fer et au 2 x x 5+ δ
nickel pour objectif d'améliorer les propriétés du composé original pour l'application pile à
combustible. Tout d'abord, différentes méthodes de synthèse ont été essayées et comparées, les
méthodes par voie chimique montrant un net avantage pour l'obtention de taux de substitution élevés.
Les propriétés physico-chimiques des matériaux synthétisés ont été caractérisées. Si la structure des
composés évolue avec la nature et le taux du substituant, les propriétés de ces composés en termes de
conduction électronique ou d'évolution du contenu en oxygène sont relativement constantes.
Finalement, les performances électrochimiques de plusieurs compositions sous forme d'électrodes
poreuses ont été testées avec différents types d'électrolytes. Les résultats montrent que la substitution
n'apporte rien pour ce qui concerne la dilatation des composés et par ailleurs ne semble pas améliorer
significativement les performances électrochimiques.


Mots-clés: SOFC, GdBaCo O , substitution, synthèse, conduction, électrochimique, transport2 5+ δ
III
tel-00619609, version 1 - 6 Sep 2011
Abstract
Study of GdBaCo M O (M=Ni, Fe; x = 0, 0.1, 0.2, …) 2-x x 5+ δ
as new cathode materials for IT-SOFC application

GdBaCo O has been recently introduced as a potential cathode material for solid oxide fuel cell. 2 5+ δ
However, its utilization has been strongly limited by its chemical reactivity with yttrium-stabilized
zirconia and its significant thermal expansion coefficient. This work focus on the study of compounds
GdBaCo M O (M = Ni, Fe, x = 0, 0.1, 0.2 …) i.e. substituted by Ni or Fe in order to ameliorate the 2 x x 5+ δ
properties of original composition for fuel cell application. Firstly, different synthesis methods have
been attempted and compared, and the chemical routes showed a clear advantage for obtaining high
substitution proportion. The physico-chemical properties of synthesized materials have been
characterized. The structure of these compounds evolves with the substitution nature and proportion,
while their properties such as electrical conductivity or changes in the oxygen content are relatively
constant. Finally, the electrochemical performances of several compositions serving as porous
electrodes were tested with different types of electrolytes. The results exhibit that the substitution
neither shows evident influence with respect to the thermal expansion of these compounds, nor
significantly improves their electrochemical performance.


Keywords: SOFC, GdBaCo O , substitution, synthesis, conduction, electrochimical, transport2 5+ δ
IV
tel-00619609, version 1 - 6 Sep 2011
Table of contents
Acknowledgements....................................................................................................................I
Résumé ............................................................................................................................... III
Abstract IV
Table of contents...................................................................................................................... V
Chapter 1 Introduction.............................................................................................................. 1
1.1 Fuel cells .................................................................................................................. 1
1.1.1 Principles........................................................................................................................................... 1
1.1.2 Thermodynamics and efficiences...................................................................................................... 2
1.1.3 Various types of fuel cells................................................................................................................. 5
1.2 Solid oxide fuel cells (SOFCs) ................................................................................ 6
1.2.1 Principle and components ................................................................................................................. 6
1.2.2 Advantages and challenges ............................................................................................................. 10
1.3 Cathode materials for IT-SOFCs ........................................................................... 11
1.3.1 ABO perovskite oxides.................................................................................................................. 14 3
1.3.2 Ruddlesden-Popper structure .......................................................................................................... 16
1.3.3 Ordered double layer perovskites.................................................................................................... 18
1.4 Scope of the thesis ................................................................................................. 21
REFERENCES......................................................................................................................... 23
Chapter 2 Synthesis, Processing and Physical-Chemical Characterisation............................ 29
2.1 Introduction............................................................................................................ 29
V
tel-00619609, version 1 - 6 Sep 2011
2.2 Synthesis of Ceramic Materials ............................................................................. 29
2.2.1 Solid state reaction (SSR) ............................................................................................................... 29
2.2.2 Gel Combustion Process ................................................................................................................. 30
2.2.3 Microwave-assisted combustion synthesis...................................................................................... 32
2.3 Structural and Microstructural properties .............................................................. 33
2.3.1 XRD characterization of synthesized compositions........................................................................ 33
2.3.2 Powder morphology........................................................................................................................ 36
2.4 Oxygen nonstoichiometry...................................................................................... 37
2.4.1 Introduction..................................................................................................................................... 37
2.4.2 Experimental................ 38
Iodometry .......................................................................................................................................... 39
Thermogravimetric reduction (TG/H reduction).............................................................................. 39 2
2.4.3 Results and discussion..................................................................................................................... 40
2.5 Structural analysis.................................................................................................. 43
2.5.1 GdBaCo O ................................................................................................................................... 43 2 5+ δ
2.5.2 Structural analysis by Rietveld refinement......................................................................................44
2.6 High temperature phase transition ......................................................................... 53
2.6.1 Differential Scanning Calorimetry (DSC)....................................................................................... 54
2.6.2 High-temperature X-ray diffraction ................................................................................................ 55
2.7 Conclusion ............................................................................................................. 64
REFERENCES......................................................................................................................... 65
Chapter 3 Electrochemical Characterization .......................................................................... 67
3.1 Characterization of cathodes.................................................................................. 67
VI
tel-00619609, version 1 - 6 Sep 2011
3.1.1 Electrochemical Impedance Spectroscopy (EIS): Technique tool .................................................. 67
3.1.2 Oxygen reduction mechanisms and kinetics: Theoretical ............................................................... 70
3.1.3 Concerning for characterization by EIS: practical .......................................................................... 74
3.2 Experimental.......................................................................................................... 75
3.2.1 GBCM electrodes based on ceria electrolyte .................................................................................. 75
3.2.1.1 Symmetric cells.................................................................................................................. 75
3.2.1.2 Fuel cells tests .................................................................................................................... 77
3.2.2 Electrodes in proton conducting fuel cells ......................................................................................78
3.3 Results and Discussion .......................................................................................... 78
3.3.1 Symmetric cell ................................................................................................................................ 78
3.3.1.1 Morphology and Microstructure Characterization ............................................................. 78
3.3.1.2 Electrochemical performance with CGO electrolytes........................................................ 81
3.3.2 Fuel cell test with Ni-YSZ/Ce Gd O /GBCM configuration ...................................................... 91 0.8 0.2 2
3.3.3 Electrochemical performance in proton conducting fuel cell.......................................................... 94
3.3.3.1 Morphology and Microstructure Characterization ............................................................. 94
3.3.3.2 Electrochemical performance with La Ca NbO electrolytes ................................... 95 0.995 0.005 4
3.4 Conclusion ............................................................................................................. 98
REFERENCES....................................................................................................................... 100
Chapter 4 Oxygen nonstoichiometry and the transport properties ....................................... 102
4.1 Electrical conductivity relaxation (ECR)............................................................. 102
4.1.1 General equation and solutions ..................................................................................................... 103
4.1.2 Flush-time correction .................................................................................................................... 105
4.1.3 Equation for rectangular sample.................................................................................................... 106
4.2 Experimental........................................................................................................ 106
VII
tel-00619609, version 1 - 6 Sep 2011
4.2.1 Thermogravimetry (TGA) for oxygen nonstoichiometry determination....................................... 106
4.2.2 Set-up for Electrical conductivity relaxation (ECR) ..................................................................... 107
4.3 Results and discussion ......................................................................................... 108
4.3.1 Oxygen nonstoichiometry ............................................................................................................. 108
4.3.1.1 Oxygen nonstoichiometry at high temperature for GBCM.............................................. 108
4.3.1.2 B site substitution on oxygen nonstoichiometry for other perovskites............................. 112
4.3.2 Electrical conductivity................................................................................................................... 113
4.3.2.1 Total conductivity as a function of temperature............................................................... 113
4.3.2.2 Conductivity under decreasing P ................................................................................. 116 O2
4.3.3 Electrical conductivity relaxation (ECR) ...................................................................................... 117
4.3.3.1 Flush time......................................................................................................................... 117
4.3.3.2 Determination and evaluation of oxygen transport properties ......................................... 121
4.3.3.3 Oxygen transport kinetics ................................................................................................ 122
4.3.3.3 Experimental limitations and propositions....................................................................... 129
4.4 Conclusion ........................................................................................................... 130
REFERENCE......................................................................................................................... 132
Chapter 5 Conclusion 134
Summary ..................................................................................................................................................... 134
Perspectives................................................................................................................................................. 137
VIII
tel-00619609, version 1 - 6 Sep 2011Chapter 1 Introduction
Chapter 1 Introduction
1.1 Fuel cells
1.1.1 Principles
The chemical energy stored in hydrogen and several hydrocarbon fuels is significantly higher
than that found in common battery materials. This fact provides the impetus to develop fuel cells for a
variety of applications, as well as the concerning of environmental consequences of fossil fuel utilized
in modern industry. Fuel cells are an ideal primary energy conversion device for remote site locations
and find application where an assured electrical supply is required for power generation, distributed
[1]power, remote, and uninterruptible power .


Figure 1.1 Summary of the reactions and processes that occur in the various fuel
[2]cell systems .
The basic physical structure of a fuel cell consists of an electrolyte layer in contact with a porous
anode and cathode on either side. The fuel or oxidant flows through the anode or cathode, and
generates electrical energy by the electrochemical oxidation of the fuel and the electrochemical
reduction of the oxidant. Figure 1.1 depicts a schematic representation of various functional fuel cells
with the reactant/product gases and ion-conduction trough the cells. Apart from batteries, the fuel and
oxidant are not contained within the fuel cell component but supplied continuously from an external
source. As long as the fuel and oxidant are fed in the system, the energy conversion process should
theoretically remain persistent.
Fuel cells are quiet in operation and can be located close to the application. They produce much
less green house emissions and can be more efficient in conversion of chemical energies in a fuel into
1
tel-00619609, version 1 - 6 Sep 2011