A cluster density functional theory study of the interaction of the hydrogen storage system NaAIH4 with transition metal catalysts
Marashdeh, A.A.
Citation
Marashdeh, A. A. (2008, March 5). A cluster density functional theory study of the interaction of the hydrogen storage system NaAIH4 with transition metal catalysts.
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A cluster density functional theory study of the interaction of the hydrogen storage system NaAlH
4with transition metal
catalysts
PROEFSCHRIFT
Ter verkrijging van
de graad van Doctor aan de Universiteit Leiden,
op gezag van Rector Magnificus Prof. Mr. P. F. van der Heijden, volgens besluit van het College voor Promoties
te verdedigen op woensdag 5 maart 2008 klokke 13.45 uur
door
Ali Awad Marashdeh
geboren te Ramtha, Jordanië in 1973
Promotiecommissie
Promotor: Prof. Dr. G. J. Kroes
Co-
Promotor: Dr. R. A. OlsenReferent: Prof. Dr. R. Broer
Overige leden: Prof. Dr. E. J. Baerends (Vrije Universiteit Amsterdam) Prof. Dr. G. J. Kramer (Technische Universiteit Eindhoven) Prof. Dr. J. Brouwer
Prof. Dr. M. T. H. Koper Prof. Dr. M. C. van Hemert
The work described in this thesis was performed at the Leiden Institute of Chemistry, Leiden University (Einsteinweg 55, 2300 RA Leiden). It is part of the research program of Advanced Chemical Technologies for Sustainability (ACTS) and was made possible by their financial support. For the computer time, the National Computing Facilities Foundation (NCF) is acknowledged.
To my parents, wife, daughter, brothers and sisters
Contents
1 Introduction 7
1.1 Renewable energy technology ……… 7
1.1.1 The source of energy ……… 7
1.1.2 Energy storage ……… 7
1.2 Hydrogen ………. 8
1.3 Hydrogen storage ……… 8
1.4 NaAlH4 ……… 9
1.5 My research goal ……… 12
1.6 The outline of my thesis ……… 12
1.7 Outlook ……… 13
1.7.1 Ti + NaAlH4 ……… 14
1.7.2 Ti2 + NaAlH4 ……… 14
1.7.3 TiH2 + NaAlH4 ……… 14
1.7.4 (Ti, Zr, Sc, Pd, Pt) + NaAlH4 ……… 15
1.7.5 The hydrogenation process and dehydrogenation of Na3AlH6 …… 16
1.8 References ……… 16
2 Methods and approximations 21 2.1 The Born-Oppenheimer approximation: separating the nuclear and electronic motions ...…...……… 21
2.2 Solving the electronic Schrödinger equation by Density Functional Theory… 23 2.3 Finding (local) minima on the potential energy surface ……… 25
2.4 A cluster approach to modeling NaAlH4 ……… 27
2.5 References ……… 28
3 A density functional theory study of Ti-doped NaAlH4 clusters 31 3.1 Introduction ……… 31
3.2 Method ……… 33
3.3 Results and Discussion ……… 34
3.3.1 Undoped NaAlH4 clusters: Electronic structure and stability …… 34
3.3.2 Ti-doped NaAlH4 clusters ……… 38
3.4 Conclusions ……… 41
3.5 References ...……… 42
4 NaAlH4 clusters with two titanium atoms added 45 4.1 Introduction ……… 45
4.2 Method ……… 48
4.3 Results and Discussion ……… 50
4.3.1 The adsorption of two titanium atoms on the surface of the Z=23 cluster ………. 50
4.3.2 The stability of the two titanium doped NaAlH4 clusters ………… 54
4.3.2.1 Ti exchanging with Na ……… 54
4.3.2.2 Ti exchanging with Na and Al ……… 55
4.3.2.3 Ti exchanging with Al ……… 55
4.3.2.4 Ti in interstitial sites ……… 56
4.3.3 Is Ti found on the surface or inside the cluster? ……… 56
4.3.4 Does Ti prefer to be inside the NaAlH4 cluster or in Ti bulk? …… 57
4.3.5 Density of electronic states of Ti doped clusters ……… 58
4.3.6 A proposed model for the role of Ti ……… 61
4.4 Conclusions ……… 62
4.5 References ……….……… 63
5 A density functional theory study of the TiH2 interaction with a NaAlH4 cluster 67 5.1 Introduction ……… 67
5.2 Method ……… 71
5.3 Results and Discussion ……… 72
5.3.1 The adsorption of TiH2 on the (001) surface of the cluster ……… 72
5.3.2 The stability of TiH2 inside the cluster ……… 74
5.3.3 The interaction of H2 with a Ti, Na or Al atom on the surface of the cluster ……… 75
5.3.4 The local structure around Ti ……… 77
5.3.5 Further support of the zipper model ……… 78
5.4 Conclusion ………. 79
5.5 References ……… 80
6 Why Some Transition Metals are Good Catalysts for Reversible Hydrogen Storage in Sodium Alanate, and Others are not: A Density Functional Theory Study 83 6.1 Introduction ……… 83
6.2 Method ……… 87
6.3 Results and Discussion ……… 90
6.3.1 Adsorption of TM atoms on NaAlH4(001) ……… 90
6.3.2 Absorption of TM atoms in the surface of NaAlH4(001) ………… 93
6.3.3 Interpretation with a zipper model for mass transport ……… 97
6.4 Conclusions ……… 98
6.5 References ……… 99
7 Zero point energy corrected dehydrogenation enthalpies of Ca(AlH4)2, CaAlH5 and CaH2+6LiBH4 103
7.1 Introduction ……… 103
7.2 Method ……… 105
7.3 Results and Discussion ……… 106
7.4 Conclusions ……… 110
7.5 References ……… 110
Summary 113
Samenvatting 119
Curriculum Vitae 125
Publication list 127
Acknowledgment 129
