-
3nd
Hydrogen & Energy Symposium Braunwald, Switzerland 2009
PROGRAM 1
3rd INTERNATIONAL SYMPOSIUM
HYDROGEN & ENERGY
Hydrogen Production, Hydrogen Storage, Hydrogen Applications,
Theory and Modelling, Fuel Cells, Metal Hydride Batteries,
Functional Materials
The 3rd
symposium “Hydrogen & Energy” follows the inaugural
symposium on 16. February 2007 at Empa and the 2
nd symposium “Hydrogen & Energy” in Braunwald 21. – 25.
January 2008. It serves as an
information platform of the fundamental science and the
frontiers of research in Sciences and Technology of Hydrogen &
Energy.
The second symposium consists of invited keynote lectures
reviewing the key elements of the hydrogen cycle. The world leading
experts present the current research challenges and newest results
in invited and contributing talks. Early stage and experienced
researchers present there results and the open questions on posters
as well as in a one slide presentation.
The conference takes place in the hotel Alpenblick in the
beautiful small village Braunwald on 1'256 m (Eggstöcke 2'449 m)
above see level in the Swiss mountains. The village is free of
traffic, quiet and offers, beside the scientific program, relaxing
moments as well as plenty of sport activities.
The number of participants is limited to 90.
25. - 30. January 2009
Hotel Alpenblick CH-8784 Braunwald Tel (+41) (55) 643 1544 URL:
http://www.klausen-resort.ch/en/alpenblick.html
-
3nd
Hydrogen & Energy Symposium Braunwald, Switzerland 2009
PROGRAM 2
-
3nd
Hydrogen & Energy Symposium Braunwald, Switzerland 2009
PROGRAM 3
CONTENTS
Timetable
Abstracts
SUNDAY 25. 1. 2009
Prof. Dr. Heinz Berke I01: METAL-INDUCED AND METAL-FREE
REACTIONS OF DIHYDROGEN AS A BASE FOR CHEMICAL HYDROGEN STORAGE
MONDAY 26. 1. 2009
Dr. Gary Sandrock I02: OVERVIEW OF HYDROGEN STORAGE: GAS,
LIQUID, SOLID
Dr. Robert Bowman I03: SOLID STATE NMR STUDIES OF THE
BOROHYDRIDES
Dr. Andreas Borgschulte O01: THE TANK IS EMPTY
Dr. Adem Tekin O02: DIFFUSION PATHWAYS OF NH3 IN Mg(NH3)xCl2
FROM DFT CALCULATIONS
Dr. Robin Gremaud O03: HYDROGEN VIBRATIONS AND DIFFUSION
MECHANISM IN H/D EXCHANGED LiBH4
Prof. Dr. Joachim Schoenes O04: POLARIZATION DEPENDENT RAMAN
SPECTROSCOPY OF LiBH4 SINGLE CRYSTALS
Dr. Zbigniew Lodziana O05: STUCTURE AND STABILITY OF
BOROHYDRIDES
Dr. Oliver Friedrichs O06: SYNTHESIS OF LIBH4 BY BORANE
ABSORPTION OF LIH
Dr. Elisa Gil Bardaji O07: MECHANOCHEMICAL AND DIRECT WET
CHEMICAL SYNTHESIS OF METAL BOROHYDRIDES, BORODEUTERIDES AND
PARTIALLY DEUTERATED BOROHYDRIDES
Dr. Riccarda Caputo O08: FIRST-PRINCIPLES STUDY OF METAL
BORIDES: ARE THEY INTERMEDIATES OR PRECURSOR COMPOUNDS FOR HYDROGEN
STORAGE?
Mr. Claudio Pistidda O09: A DETAILED STUDY ON THE
DEHYDROGENATION OF 2NaBH4+MgH2
Dr. Gemma Garcia O10: COMBINATORIAL APPROCH FOR THE DISCOVERY OF
NEW MATERIALS FOR HYDROGEN STORAGE
Mr. Sebastiano Garroni O11: DEHYDROGENATION MECHANISM OF THE 2
NaBH4 + MgH2 PREPARED BY BALL MILLING
-
3nd
Hydrogen & Energy Symposium Braunwald, Switzerland 2009
PROGRAM 4
TUESDAY 27. 1. 2009
Prof Dr. Ronald Griessen I04: CAPPED METAL-HYDROGEN SYSTEMS
Prof. Dr. Bengt Kasemo I05: LSPR AND QCM-D MEASUREMENTS OF
HYDROGEN STORAGE IN NANO-MATERIALS
Mr. Suleyman Er O12: HIGH CAPACITY MOLECULAR HYDROGEN STORAGE
NANOMATERIALS
Dr. Nicola Naujoks O13: QUARTZ CRYSTAL MICROBALANCE STUDIES OF
HYDROGEN STORAGE IN NANOSTRUCTURED MATERIALS
Prof. Dr. Mathias Getzlaff O14: HYDROGEN-INDUCED PLASTIC
DEFORMATION OF RARE EARTH METAL THIN FILMS AND COMPARISON WITH
CORRESPONDING NANOPARTICLES
Dr. Kevin Sivula O15: NANOSTRUCTURED PHOTOANODES FOR HYDROGEN
PRODUCTION BY SOLAR WATER SPLITTING
Dr. Mauro Palumbo O16: A THERMODYNAMIC DATABASE FOR HYDROGEN
STORAGE SYSTEMS
WEDNESDAY 28. 1. 2009
Dr. Geert Brocks I06: FIRST PRINCIPLES MODELING OF MAGNESIUM
TRANSITION METAL HYDRIDES
Dr. Martin Johansson I07: HYDROGEN SPLITTING STUDIED BY H-D
EXCHANGE
Mr. Florian Buchter O34: EXPERIMENTAL ELECTRONIC CHARGE DENSITY
OF LiBH4 FROM MAXIMUM ENTROPY METHOD
Prof Wieslawa Sikora O18: ANALYSIS OF POSSIBLE MAGNETIC
STRUCTURES IN ERMN2D2 DEUTERIDE
Prof Dr. Asuncion Fernandez O19: A COMPARATIVE STUDY OF THE
ADDITIVE ROLE IN THE MgH2-Nb2O5 SYSTEM vs. THE LiBH4+MgH2-Ti-iso
SYSTEM
Dr. Fabrice Leardini O20: LOW TEMPERATURE HYDROGEN DESORPTION
FROM MgH2/Mg(OH)2 SYSTEM
Mr. Hidayet Argun O21: PHOTOBIOLOGICAL HYDROGEN PRODUCTION FROM
DARK FERMENTATION EFFLUENT
THURSDAY 29. 1. 2009
Prof. Dr. Jens K. Nørskov I08: ATTEMPTS TO UNDERSTAND
ELECTROCHEMICAL, PHOTOCHEMICAL AND BIOLOGICAL WATER SPLITTING
WITHIN THE SAME CONCEPTUAL FRAMEWORK
-
3nd
Hydrogen & Energy Symposium Braunwald, Switzerland 2009
PROGRAM 5
Prof. Dr. Bill David I09: POWDER DIFFRACTION STUDIES OF LIGHT
WEIGHT HYDROGEN STORAGE MATERIALS
Prof Dr. Andreas Züttel O22: MECHANISM OF HYDROGEN SORPTION IN
COMPLEX HYDRIDES
Dr. Valentina Zakaznova O23: HYDROGEN PRODUCTION BY ALKALINE
ELECTROLYSIS: IS THERE A WAY TO INCREASE ITS EFFICIENCY?
Mr. Daniel Marinha O24: La0.6Sr0.4Co0.2Fe0.8O3-x MICROSTRUCTURES
OBTAINED BY ELECTROSTATIC SPRAY DEPOSITION FOR IT-SOFCs
Dr. Ulrich Vogt O25: HIGH TEMPERATURE ELECTROLYSIS BY SOEC
TECHNOLOGY FOR COST EFFICIENT AND ECONOMICAL HYDROGEN
PRODUCTION
Mr. Daniel Wiedenmann O26: FIB/TEM AND EPMA AS COMPLEMENTARY
TECHNIQUES FOR THE INVESTIGATION OF SOEC AND SOFC
Mr. Shunsuke Kato O27: IMPACT OF THE SURFACE OXIDATION OF LiBH4
ON THE H2 DESORTPITION PROCESSES
Mr. Jian-Cheng Chen O28: H2 DISSOCIATION ON Ti/Al(100)
SURFACES
Mrs. Emilie Deprez O29: SURFACE ANALYSIS AND OXIDATION STATE IN
THE REACTIVE HYDRIDE COMPOSITE 2LiBH4+MgH2+Ti-iso
Dr. Jean-Claude Crivello O30: ELECTRONIC PROPERTIES OF SOME
INTERMETALLIC COMPOUNDS AND THEIR HYDRIDES
Dr. Maciej Krystian O31: KINETICS OF HYDROGEN SORPTION AND
DESORPTION IN ECAP-PROCESSED Mg ALLOY ZK60
Dr. Stefan Schlag O32: THE GLOBAL HYDROGEN MARKET
FRIDAY 30. 1. 2009
Prof. Dr. Bjørn C. Hauback I10: DIFFRACTION STUDIES OF COMPLEX
HYDRIDES
Dr. Jens Oluf Jensen I11: PEM FUEL CELLS AT ELEVATED
TEMPERATURE
Dr. Philippe Mauron O33: HIGH-PRESSURE AND -TEMPERATURE DSC
(DIFFERENTIAL SCANNING CALORIMETER) FOR COMBINED PCT (PRESSURE,
CONCENTRATION, TEMPERATURE) MEASUREMENTS OF HYDRIDES
Dr. Emmanuel Wirth O17: NEW TOOLS FOR THE CHARACTERISATION OF
HYDROGEN STORAGE MATERIALS
-
3nd
Hydrogen & Energy Symposium Braunwald, Switzerland 2009
PROGRAM 6
Prof. Dr. Hans Hagemann O35: VIBRATIONAL SPECTROSCOPY AS A PROBE
FOR STRUCTURE AND DYNAMICS OF INORGANIC BOROHYDRIDES
Dr. Anibal Ramirez-Cuesta O36: INELASTIC NEUTRON SCATTERING
SPECTROSCOPY OF MOLECULAR HYDROGEN IN POROUS MATERIALS AND
SURFACES
Dr. Arndt Remhof O37: HYDROGEN DYNAMICS IN LiBH4 STUDIED BY
QUASIELASTIC NEUTRON SCATTERING
POSTER
MONDAY 26. 1. 2009
Mrs. Carine Rongeat P01: SYNTHESIS OF Ca(BH4)2 BY REACTIVE BALL
MILLING
Mr. Christian Bonatto Minella P02: HYDROGEN SORPTION PROPERTIES
OF MODIFIED CALCIUM BOROHYDRIDE
Dr. Daphiny Pottmaier P03: HYDROGENATION PROCESSES AT LOW
PRESSURES IN THE Na-Mg-B SYSTEM PREPARED BY REACTIVE BALL
MILLING
Mr. Flavio Pendolino P04: TRUE ACTIVATION ENERGY OF
DECOMPOSITION OF LITHIUM BOROHYDRIDE LIBH4
Dr. Chiara Milanese P05: IMPROVEMENT IN THE H2 ABSORPTION
KINETICS OF THE Mg – Ni SYSTEM BY C (GRAPHITE) ADDITION
Mr. Filippo Agresti P06: EVIDENCE OF FORMATION OF LiBH4 BY HIGH
ENERGY BALL MILLING OF LiH AND B IN HYDROGEN ATMOSPHERE
Dr. Ashley Stowe P07: CATALYTIC ROLE OF NANOSTRUCTURED CARBON ON
NaAlH4 HYDROGEN SORPTION
Dr. Mitsuru Matsumoto P08: LIQUID PHASE SYNTHESIS OF MAGNESIUM
AMIDE AND AMIDE BASED HYDROGEN STORAGE MATERIALS
Mr. Pascal Martelli P09: IDENTIFICATION OF STRUCTURAL PHASES OF
Ca[BH4]2 BY NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY
Dr. Francesco Dolci P10: INTERMETIATES IN THE MIXED 2LiNH2/MgH2
HYDROGEN STORAGE SYSTEM
Mr. Deniz Cakir P11: STRUCTURE AND STABILITY OF
Li2xMgy(NH)x+y
Mr. Florian Gebert P12: LOW TEMPERATURE RAMAN SPECTROSCOPY OF
Mg(BH_4)_2 AND Mg(BD_4)_2
-
3nd
Hydrogen & Energy Symposium Braunwald, Switzerland 2009
PROGRAM 7
Dr. Andreas Borgschulte P13: THE TELLER-REDLICH RULE IN COMPLEX
HYDRIDES
Dr. Piotr Szymak P14: CONTROL OF SUPPLY SUBSYSTEMS OF FUEL CELL
STACK
Dr. Józef Malecki P15: VALIDATION OF A MATHEMATICAL MODEL OF 5kW
PEMFC STACK SUPPLIED BY PURE OXYGEN AND HYDROGEN
Dr. Grzegorz Grzeczka P16: CONCEPTION OF POWER SYSTEM OF AN
UNDERWATER VEHICLE BASED ON FUEL CELL TECHNOLOGY
TUESDAY 27. 1. 2009
Mr. Jérémie Brillet P17: TANDEM CELL FOR HYDROGEN PRODUCTION:
EXAMINING HEMATITE-DSC ARCHITECTURE STRATEGIES
Mr. Michal Gorbar P18: DEVELOPMENT OF NEW MEMBRANES FOR ALKALINE
ELECTROLYSER CELLS BASED ON INORGANIC MATERIAL
Dr. Agnieszka Kuna P19: SYMMERTY ANALYSIS OF HYDROGEN RELATED
STRUCTURAL TRAMSFORMATIONS
Dr. Ali Marashdeh P20: ALLOYING EFFECT ON H OCTAHEDRAL VS
TETRAHEDRAL SITE OCCUPATION IN Pd-Au: FIRST PRINCIPLES CALCULATIONS
AND NEUTRON DIFFRACTION MEASUREMENTS
Mr. Abdel El Kharbachi P21: STRUCTURAL CHARACTERIZATION AND
THERMODYNAMIC PROPERTIES OF THE LIBH4-MGH2 SYSTEM
Dr. Chiara Milanese P22: KINETIC FEATURES IN THE H2 SORPTION BY
NaBH4 + MgH2 COMPOSITES UNDER MECHANICAL ACTIVATION CONDITIONS
Dr. Jonathan Morrell P23: ALKALINE SALT MATERIALS PROPERTY AND
AGING STUDY
Dr. Irina Konstanchuk P24: PECULIARITIES OF HYDROGEN INTERACTION
WITH NANOCRYSTALLINE MAGNESIUM
Dr. Marco Vittori Antisari P25: METALLOGRAPHIC STUDY ON THE ROLE
OF CATALYST PARTICLES IN THE KINETICS OF REACTION BETWEEN MAGNESIUM
AND HYDROGEN
Dr. Ashish Khandelwal P26: INVESTIGATION OF MECHANICAL AND
KINETIC STABILITY IN COMPACTED MgH2 BASED SAMPLES
Mr. Siarhei Kalinichenka P27: STRUCTURAL AND HYDROGEN SORPTION
PROPERTIES OF Mg–Ni–Y ALLOYS PREPARED BY MELT SPINNING
-
3nd
Hydrogen & Energy Symposium Braunwald, Switzerland 2009
PROGRAM 8
Mrs. Elsa Callini P28: MAGNESIUM BY GAS PHASE
CONDENSATION:MORPHOLOGY MICROSTRUCTURE AND HYDROGEN SORPTION
Mr. Katarzyna Morawa P29: HYDROGEN STORAGE IN LIQUID ORGANIC
HYDRIDES
Mr. Jon Bergmann Maronsson P30: COMPUTATIONAL METHODS FOR
DESCRIBING REACTION RATES AT INTERFACES OF ENERGY MATERIALS
Mr. Thomas Kollin P31: To be announced
Mr. Ryoji Sahara P32: STRUCTURAL OPTIMIZATION BY TOMBO: CASE
STUDY OF HYDRIDES AND MOLECULES
SCIENCE OF HYDROGEN & ENERGY AWARD
List of Participants
Information
Notes
-
3nd
Hydrogen & Energy Symposium Braunwald, Switzerland 2009
PROGRAM 9
Timetable
-
3nd
Hydrogen & Energy Symposium Braunwald, Switzerland 2009
PROGRAM 10
Su
nd
ay
Mo
nd
ay
Tu
esd
ay
Wed
nesd
ay
Th
urs
day
Fri
day
25
.01
.200
92
6.0
1.2
009
27
.01
.20
09
28
.01
.20
09
29
.01
.200
93
0.0
1.2
009
Cha
irA
. Z
ütt
el
G.
Sa
ndro
kR
. B
ow
ma
nR
. G
rie
ssen
G.
Bro
cks
09
:00
I02:
Gary
Sa
nd
rock
I04
: R
on
ald
Grie
ssen
I06
: G
ee
rt
Bro
cks
I08:
Je
ns K
. N
ors
ko
vI1
0:
Bjø
rn C
. H
au
back
09
:35
I03:
Ro
be
rt B
ow
ma
nI0
5:
Be
ngt
Ka
se
mo
I07
: M
art
in J
oh
ansso
nI0
9:
Bill
Da
vid
I11
: Je
ns O
luf
Jen
se
n
10
:10
Co
ffe
eC
off
ee
Coff
ee
Co
ffe
eC
off
ee
10
:35
O0
1:
And
rea
s B
org
sch
ulte
O1
2:
Su
leym
an
Er
O1
7:
Em
man
ue
l W
irth
O2
2:
An
dre
as Z
ütt
el
O33
: P
hili
pp
e M
au
ron
11
:00
O0
2:
Ade
m T
ekin
O1
3:
Nic
ola
Na
ujo
ks
O1
8:
Wie
sla
wa S
iko
raO
23
: V
ale
ntin
a Z
akazno
va
O34
: F
lori
an B
uchte
r
11
:25
O0
3:
Ro
bin
Gre
ma
ud
O1
4:
Ma
thia
s G
etz
laff
O1
9:
Asu
ncio
n
Fe
rna
nde
z
O2
4:
Da
nie
l M
ari
nha
O35
: H
an
s H
ag
em
an
n
11
:50
O0
4:
Joa
ch
im S
cho
en
es
O1
5:
Ke
vin
Siv
ula
O2
0:
Fa
bri
ce
Le
ard
ini
O2
5:
Ulr
ich
Vo
gt
O36
: A
nib
al R
am
ire
z-C
ue
sta
12
:15
O0
5:
Zb
ign
iew
Lo
dzia
na
O1
6:
Ma
uro
Pa
lum
bo
O2
1:
Hid
aye
t A
rgu
nO
26
: D
anie
l W
ied
enm
ann
O37
: A
rnd
t R
em
ho
f
12
:40
Lun
ch
Lu
nch
Lu
nch
Lu
nch
Lun
ch
Se
ssio
n
Cha
irB
. H
au
back
B.
Ka
se
mo
14
:00
O0
6:
Oliv
er
Fri
edri
ch
sO
27
: S
hu
nsu
ke
Ka
to
14
:25
O0
7:
Elis
a G
il B
ard
aji
O2
8:
Jia
n-C
he
ng
Ch
en
14
:50
O0
8:
Ric
card
a C
ap
uto
O2
9:
Em
ilie
De
pre
z
15
:20
Co
ffe
eS
ocia
l e
ven
tF
ree
Co
ffe
e
15
:45
O0
9:
Cla
ud
io P
istid
da
O3
0:
Jea
n-C
laud
e C
rive
llo
16
:10
O1
0:
Ge
mm
a G
arc
iaO
31
: M
acie
j K
rystia
n
16
:35
O1
1:
Seb
astia
no G
arr
on
iO
32
: S
tefa
n S
chla
g
17
:00
I01
: H
ein
z B
erk
e
18
:00
Din
ne
rD
inne
rD
inn
er
Din
ne
rD
inn
er
Cha
irA
. B
org
schu
lte
A.
Rem
ho
f
19
:30
P1
- P
14 P
oste
rP
15
- P
28 P
oste
r
21
:00
-
3nd Hydrogen & Energy Symposium Braunwald, Switzerland
2009
11
Abstracts
-
3rd Hydrogen & Energy Symposium Braunwald, Switzerland
2009
12
Metal-Induced and Metal-Free Reactions of Dihydrogen as a Base
for Chemical Hydrogen Storage
H. Berke*, Z. Chen, F. Zou, N. Avramovic, C. Jiang, X. Yang, A.
Dybov, X.-Y. Liu, Y. Zhao, O. Blacque, T. Fox, H.W. Schmalle, K.
Venkatesan Institute of Inorganic Chemistry, University of Zurich,
Winterthurer Str. 190, CH-8057 Zurich
Introduction Chemical reactions of dihydrogen comprise the
classes of hydrogenation/dehydrogen-ation and
hydrodecoupling/dehydrocoupling and the related process of transfer
hydrogenation. These transformations may get involved in chemical
hydrogen storage as “fuelling” and “refuelling” processes of the
storage compounds. Most of these reactions types require splitting
of the H2 molecule as the “activating” step, which can be achieved
in two formally distinct ways: Homolytic splitting: H2→ 2H•,
Heterolytic splitting: H2 → H- + H+. Over decades the homolytic
splitting pathways proceeding with oxidative addition of H2 to
transition metal centers were elaborated to a quite high level of
performance. Respective catalyses became routine type
applications.
As a generic descriptor the term “Ionic Hydrogenation” (related
are “Hydridic-Protonic Reactions” or “Bifunctional Catalysis”)
describes the class of stoichiometric and catalytic hydrogenations
/dehydrogenations proceeding with heterolytic splitting of H2 and
with subsequent hydride and proton transfers from Lewis acidic
centers (normally transition metal centers [1] or since recently
also main group element based [2]) and from (Lewis) basic centers
to unsaturated mostly organic XY substrates.
X = CH2, Y = CH2, O, NR; E = LnM = transition metal fragment or
main group element; B = base As it appears now there are three
distinct routes for “Ionic Hydrogenations”, which are
mechanistically distinguished by the sequence of H transfers:
(a) hydride before proton transfer, (b) simultaneous hydride and
proton transfer, (c) proton before hydride transfer.
Experimental and Results Within the reaction type (a) we
investigated stoichiometric reactions using hydridic hydrides, such
as WH(CO)n(PMe3)4-n(NO) (n = 0,1) and MoH(dippe)2(NO) complexes
(dippe = bis(diisopropylphosphino)ethane), in combination with
alcohols as proton sources to hydrogenate organic carbonyl
compounds. We recently also studied a catalytic CO2 “Ionic
Hydrogenation” using a WH(CPh)(dippe)2 complex to afford a mixture
of formic acid and formates in the presence of a base.
Noyori's and Shvo/Casey hydrogenations or transfer
hydrogenations are good examples for metal mediated double H
transfers of category (b) [3]. In their essential parts these polar
processes follow the principal course of the simultaneous double H
transfer described in eq 2.
X
Y
H
H
X'
Y'+
X
Y
H
H
X'
Y'+ (2)
X,Y and X',Y' = atoms or molecular fragments including main
group and transition elements
Sat. I Unsat. II Unsat. I Sat. II
Unpolar concerted double H transfers, like the degenerate
reaction of ethane with ethylene, have high kinetic barriers and
are therefore rarely observed [4], despite the fact that they are
symmetry allowed and thermally accessible [4 + 2] processes. It
became apparent from our work that the transferred H’s need to be
sufficiently different in
X Y
H- H+
X Y
H2
HX YH
Cat
(1)
BE
-
3rd Hydrogen & Energy Symposium Braunwald, Switzerland
2009
13
polarities to enable still concerted and low energy transition
states. Route (c) occurring with primary H+ transfer was
demonstrated to be operative in olefin, imine and ketone
hydrogenations [5], where less hydridic transition metal hydrides
are combined with relatively strong proton donors as H− and H+
sources. Mechanistically related rhenium and molybdenum catalyzed
“Ionic Hydrogenations” of imines, where H2 complexes act as proton
source, were studied by us [6]. Related in their reaction
mechanisms are metal-free “Frustrated Lewis Pair” catalyzed
hydrogenations of imines [2], for which a primary proton transfer
was established.
References [1] H. Jacobsen, H. Berke, in Recent Advances
in Hydride Chemistry, p. 89, Eds. M.
Perruzzini, R. Poli, Elsevier, Amsterdam, Netherlands, 2001.
[2] P.A. Chase, G.C. Welch, T. Jurca, D.W. Stephan, Angew. Chem.
Int. Ed. 42, 2007, 8050.
[3] R. Noyori, S. Hashiguchi, Acc. Chem. Res. 30, 1997, 97; S.
E. Clapman, A. Hazdovic, R. H. Morris, Coord. Chem. Rev. 248, 2004,
2201; Y. Shvo, D. Szarkie, Y. Rahamim, D. F. Chodosh, J. Am. Chem.
Soc. 108, 1986, 7400; C. P. Casey, N. A Strotman, S. E. Beetner, J.
B. Johnson, D. C. Priebe, T. E. Vos, B. Khodavandi, I. A. Guzei,
Organometallics 25, 2006, 1230.
[4] I. Fernandez, M. A. Sierra, F. P. Cossio, J. Org. Chem. 72,
2007, 1488.
[5] R.M. Bullock, Chem. Eur. J. 10, 2004, 2366. [6] X.Y. Liu, K.
Venkatesan, H. W. Schmalle, H.
Berke, Organometallics, 23, 2004, 3153; Y. Zhao, H. W. Schmalle,
T. Fox, O. Blacque, H. Berke, Dalton Trans. 2006, 73.
Corresponding author: Heinz Berke, email: [email protected],
Tel. (+41) (44) 635 4681
-
3rd Hydrogen & Energy Symposium Braunwald, Switzerland
2009
14
Monday
-
3rd Hydrogen & Energy Symposium Braunwald, Switzerland
2009
15
Overview of Hydrogen Storage: Gas, Liquid, Solid Gary Sandrock
Metal Hydride Technology, 810 Hacienda Ave., Davis, CA 95616,
USA
A hydrogen-based energy system will require stationary, portable
and vehicular H-storage systems. The most technically difficult
application is vehicular storage because there are important
weight, volume, charge/discharge rate, safety and cost
requirements, among others. This presentation will give a broad
review of the three basic approaches being considered today (gas,
liquid and solid), along with the many subsets of those main
categories. Advantages and disadvantages of each technique will be
listed, along with the present systems status of each and
suggestions for future R&D. This talk is aimed at setting the
basic stage for more detailed and focused presentations expected to
follow. Gaseous Hydrogen Compressed H2 gas is typically stored in
advanced carbon-fiber-wrapped epoxy vessels at 35-70 MPa. This
well-established approach suffers from volume and cost problems,
among others. The volume problem can be significantly reduced by
the cryogas (cold storage) approach.
Liquid Hydrogen There are at least four liquid hydrogen
approaches: cryogenic elemental H2, NaBH4 solutions, rechargeable
organic liquids and liquid anhydrous NH3. Each approach has
advantages and disadvantages. For all four of these sub-approaches,
the efficiencies and costs of production and/or regeneration are of
concern, along with possible safety considerations.
Solid Hydrogen Solid hydrogen can be classified into three
categories. High surface area adsorbents rely on physisorption,
with relatively weak binding enthalpies (4-10 kJ/mol H2). Examples
include various carbons, MOFs, zeolites, clathrate hydrates and
certain polymers. Because of their generally low values of ΔHads,
adsorbants generally require low temperatures for effective
H-storage. Metal
incorporation offers some hope for increasing ΔHads.
Non-reversible metal hydrides fall into two categories: (a) those
decomposed by hydrolysis in H2O, and (b) those decomposed
thermally. Although they often have attractive volumetric and
gravimetric H-capacities, as well as controllable decomposition
kinetics, both categories must be chemically regenerated with
significant energy penalties. Reversible metal hydrides offer the
best opportunities for in situ recharging. This family of solid
storage media consists mainly of metallic and complex (mixed
ionic-covalent) hydrides. Although all have good volumetric
H-capacities, those that also have good gravimetric capacities
usually require excessive decomposition temperatures and
“catalysis” for acceptable reversibility. It is this particular
category of materials where most solid-state storage R&D is
presently being performed. There is a focus on metal borohydrides,
nanostructure and phase mixtures.
Systems Status A number of prototype vehicular storage systems
have been built and/or analyzed for most of the storage categories
outlined above. Each has one or more practical shortcoming. More
innovative materials and engineering R&D are clearly
needed.
Corresponding author: Gary Sandrock, email:
[email protected], tel. (+1) (530) 753 0451
-
3rd Hydrogen & Energy Symposium Braunwald, Switzerland
2009
16
Solid State NMR Studies of the Borohydrides R. C. Bowman, Jr.1,
S.-J. Hwang2, C. Kim2, J. Ku2, M. S. Conradi3, D. T. Shane3, R. L.
Corey3,4, J. W. Reiter1, and J. A. Zan1 1Jet Propulsion Laboratory,
California Institute of Technology, Pasadena, CA 91109 USA;
2Division of Chemistry and Chemical Engineering, California
Institute of Technology, Pasadena CA 91125 USA; 3Washington
University, Dept. of Physics, Saint Louis MO 63130 USA; 4South
Dakota School of Mines and Technology, Rapid City SD 57701 USA
High-resolution solid state 11B spectra from LiBH4, Mg(BH4)2,
Ca(BH4)2, and LiSc(BH4)4 confirmed there is similar bonding for
BH4- ions in these hydrides. Following hydrogen desorption at
temperatures ≥ 400 oC, all of these borohydrides formed variable
amounts of the B12H12-2 species as well as the elemental amorphous
boron (B) or boride (e.g., MgB2, CaB6, etc.) phases. Partial
reversibility was noted in LiBH4 + MgH2 mixture and Ca(BH4)2. 1H
and 11B relaxation times were also used to assess motions in the
low (LT)- and high-temperature (HT) phases of LiBH4, Mg(BH4)2, and
Ca(BH4)2,
Introduction Multinuclear nuclear magnetic resonance (NMR)
spectroscopy provides novel insights on the compositions, chemical
bonding, structures, as well as rotational and translational
motions of complex metal hydrides. Because short-range interactions
dominate NMR, highly disordered as well as amorphous materials can
often be more thoroughly evaluated than is possible with X-ray or
neutron diffraction studies that usually require good
crystallinity. Taking examples from our recent investigations of
several borohydrides, we illustrate how these NMR techniques
resolve diverse issues on phase formation and decomposition
processes.
Experimental The solid-state NMR techniques Magic Angle Spinning
(MAS), cross-polarization (CP) MAS, and multi-quantum (MQ) MAS that
were used to assess these borohydrides and their decomposition
products were described previously1,2. The nuclear relaxation times
were measured from 300 K to over 525 K using the methods reported
by Corey, et al.3
Results The presence of the B12H12-2 species following hydrogen
desorption from all the borohydrides was established from the 11B
CPMAS and MQMAS spectra. While the borides MgB2, CaB6, and ScB2
were formed at sufficiently high temperatures, partial
reversibility with H2 gas was only observed for the Ca system and
the mixture of LiH and MgB2. Formation of B12H12-2 anions inhibits
reformation of the borohydrides. Rotation of the BH4- ions controls
the relaxation times of LT-LiBH4, Mg(BH4)2, and Ca(BH4)2 while Li
ion diffusion dominates spin relaxation in HT-LiBH4 with an
activation energy = 0.7 eV3.
Acknowledgments These studies were partially supported by DOE
grants DE-FG02-05ER46256 and DE-AI-01-06EE11105 and were partially
performed at the JPL, Caltech, under a contract with NASA.
References [1] S.-J. Hwang, et al., J. Phys. Chem. C 112
(2008) 3164 [2] J. Purewal et al; J. Phys. Chem. C 112
(2008)
8481 [3] R. L. Corey, et al., J. Phys. Chem. C 112
(2008) On-line.
Corresponding author: Robert Bowman, email: [email protected]
Tel. (001) 818-354-7941
-
3rd Hydrogen & Energy Symposium Braunwald, Switzerland
2009
17
The Tank is empty A. Borgschulte, C. Rongeat, S. Kato, M.
Bielmann, R. Gremaud, A. Züttel Empa Materials Science and
Technology, Dept. Energy, Environment & Mobility, Sec. Hydrogen
& Energy, CH-8600 Dübendorf, Switzerland
What might become a problem when using hydrogen as an energy
carrier in car, is a scientific challenge in current research. A
future hydrogen fuel gauge is just an indicator of the amount of
hydrogen remaining in the used metal hydride. In materials
research, the determination of pressure-composition isotherms (pcT)
is mandatory to obtain the thermodynamic properties of metal
hydrides. Various experimental techniques to measure the plateau
pressures of metal hydrides are reviewed, that is gravimetric and
volumetric pcT measurements, scanning differential calorimetry, and
hydrogenography and resistance measurements on thin films. The
agreement of the data for the archetypical example MgH2 is very
good. Differences are explained by kinetic effects of the sorption
process. The impact of kinetics on the accuracy of the
determination of the equilibrium pressure is demonstrated by a
comparison of dynamic (flux method) with static pcT measurements of
LaNi5Hx. The use of optical probes as hydrogen fuel gauge is
demonstrated. Measurement of equilibrium states The thermodynamic
parameters of hydride formation can be extracted from the
temperature dependence of the equilibrium pressure, by means of the
Van ‘t Hoff relation. The technically challenging problem is the
measurement of such equilibrium isotherms. In static experiments,
the pressure is stepwise enhanced and the system equilibrates. Most
frequently used techniques are scanning methods, in which one
thermodynamic parameter (either pressure or temperature) is varied
and the response of the sample is recorded. As these measurements
are by definition dynamic measurements, the equilibrium values have
to be extrapolated. The quality of the extrapolation relies on the
modelling of the kinetics. We will give an insight in the
underlying elementary steps of H-sorption and apply a quantitative
model [1] on various experimental examples measured by different
systems. Indirect Methods Indirect methods such as hydrogenography
[2] and scanning differential calorimetry [3] make use of the
impact of the change of the
hydrogen content on other physical properties of the
material.
Fig. 1. Equilibrium pressures and kinetics of LaNi5Hx measured
gravimetrically.
Optical methods have several advantages, which make them
potential candidates as methods to be used in hydrogen fuel
gauges.
References [1] Borgschulte et al; Phys. Rev. B 78, 094106
(2008). [2] Gremaud et al; Adv. Mater. 19, 2813-2817
(2007) [3] Rongeat et al., J. Phys. Chem. B 2007, 111,
13301
Corresponding author: Andreas Borgschulte, email:
[email protected], Tel. (+41) (44) 823 4639
-
3rd Hydrogen & Energy Symposium Braunwald, Switzerland
2009
18
Diffusion Pathways of NH3 in Mg[NH3]xCl2 from DFT calculations
Adem Tekina,b, Tejs Veggeb, Jens K. Nørskova a) Center for
Atomic-scale Materials Design (CAMD), Department of Physics,
Technical University of Denmark, DK-2800 Lyngby, Denmark b)
National Laboratory for Sustainable Energy, Technical University of
Denmark, DK-4000 Roskilde, Denmark
Ammonia containing metal salts is one of the promising materials
to store hydrogen indirectly. They show a fast and reversible
ammonia ab- and desorption kinetics. Mg(NH3)xCl2 with x=6,2,1 is
selected as a prototype system to enlighten this phenomenon. Bulk
diffusion pathways of ammonia in Mg(NH3)xCl2 is investigated by
employing a planewave density functional theory approach. Results
indicated that diffusion is much faster in the hexa(x=6) ammine
phase. Introduction Indirect storage of hydrogen in the form of
ammonia stored in metal salts, so-called metal ammines, has many
interesting properties as an energy storage medium. Whereas many
metal hydrides suffer from low density of hydrogen, slow release or
a poor reversibility of ab- and desorption of hydrogen, metal
ammines have recently been shown to display superior properties
[1]. In contrast to metal hydrides, metal ammines decompose
thermally by releasing ammonia which can later be cracked into
hydrogen with an ammonia decomposition catalyst. One of the most
promising metal ammines for hydrogen storage is Mg(NH3)6Cl2 (9.1 %
wt of hydrogen), which has been investigated both theoretically and
experimentally [2,3,4]. It has been found that this metal ammine
develops a system of nano-sized pores during ammonia decomposition
enabling a fast ab- and desorption of ammonia.
Results We employed a planewave density functional theory
approach using the RPBE generalized gradient approximation to
account for exchange and correlation effects to determine diffusion
mechanisms and
decomposition pathways for Mg(NH3)xCl2. Results are presented
for diffusion and rotation rates in x=6,2,1, using a combination of
nudged elastic band calculations and transition state theory,
showing that diffusion is much faster in the hexa (x=6) ammine
phase.
Fig. 1. Ammonia diffusion in Mg(NH3)6Cl2.
References [1] Christensen et al; J. Mater. Chem. 15 (2005)
4106 [2] Jacobsen et al; Chem. Phys. Lett. 441 (2007)
255 [3] Hummelshøj et al; J. Am. Chem. Soc. 128
(2006) 16
[4] Vegge et al; Indirect hydrogen storage in metal ammines, ed.
G. Walker, Woodhead Publishing, 2008.
Corresponding author: Adem Tekin, email: [email protected],
Tel. (+45) 4525 3184
-
3rd Hydrogen & Energy Symposium Braunwald, Switzerland
2009
19
Hydrogen vibrations and diffusion mechanism in H/D exchanged
LiBH4 Robin Gremaud1*, Andreas Borgschulte1*, Z. Łodziana1*, Timmy
Ramirez-Cuesta2, Joachim Schoenes3, Paul Hug1°, Andreas Züttel1*
1Empa Materials Science and Technology, Dept. Energy, Environment
& Mobility, *Sec. Hydrogen & Energy, °Sec. Solid State
Chemistry, CH-8600 Dübendorf, Switzerland 2ISIS facility,
Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 OQX,
United Kingdom 3Institute of Condensed Matter Physics, Technical
University Braunschweig, Mendelsohnstrasse 3, D-38106 Braunschweig,
Germany
The effects of H/D isotope exchange on bulk LiBH4 are studied
with Raman, infrared spectroscopy and inelastic neutron scattering.
We show that deuterium is exchanged in the BH4- pseudo-molecule at
temperature below melting. We are able to detect each individual
B(H4-nDn)- unit (n = 1,..,4) and establish that their relative
fraction as a function of deuterium fraction exchanged follows a
statistical distribution. This shows that in molecular solids like
the complex hydride LiBH4, exchange of single hydrogen atoms and
its diffusion through the crystal is possible without breaking the
molecular unit. Introduction LiBH4 is an example of molecular
solid, in which the pseudo-molecule, BH4-, is ionically bound to
the counter ion Li+. As a consequence, phonons in LiBH4 can be well
approximated by so-called “internal” and “external” vibrations,
where internal refers to the motions within the molecular BH4-
unit, and external refers to crystalline vibration of BH4- and
Li+[1]. Raman and infrared spectroscopy are ideally suited
techniques to follow the effects of H/D exchange, especially in the
internal vibrations, as the mass change shifts considerably normal
vibrations. Results We report on the effect of hydrogen isotope
exchange on bulk LiBD4 with Raman spectroscopy at a temperature of
83 K. The experimental results are compared to density functional
calculations of the vibrational spectra of B(H4-nDn)- (n=1…4) both
isolated and under the influence of the surrounding lattice.
We focus on the B-D stretching modes, as they enable us to
detect the presence and to determine the relative fractions of the
B(H4-nDn)- subunits.
Fig. 1. B-D stretching region in the Raman spectra for LiBD4 and
LiB(H0.55D0.45)4. The peaks labelled as ν1(Dn) (n=1…4) refer to
symmetric stretching modes of each B(H4-nDn)- unit.
Reference [1] A. –M. Racu et al.,: J. Phys. Chem. 112, 9716
(2008)
Corresponding author: Robin Gremaud, email:
[email protected], Tel. (+41) (44) 823 4933
-
3rd Hydrogen & Energy Symposium Braunwald, Switzerland
2009
20
Polarization dependent Raman spectroscopy of LiBH4 single
crystals J. Schoenes, B. Willenberg and F. Gebert Institut für
Physik der Kondensierten Materie, Technische Universität
Braunschweig, D-38106 Braunschweig, Germany
A Raman scattering study of the phonon modes is reported for
LiBH4 single crystals. Using the polarization dependence of the
lines the symmetry of the modes is determined, allowing a better
comparison and a more reliable assignment to computed phonon
frequencies. This leads to the revision of a few former assignments
made from Raman measurements on polycrystalline samples.
Introduction Vibrational spectroscopy, like IR absorption and Raman
scattering are particularly suited to study hydrogen bonds, since
the light mass of hydrogen generates high vibrational frequencies
and the isotope effect on substitution of deuterium for hydrogen is
the largest of any element [1,2]. In a previous paper [3] we have
reported an extensive low temperature Raman scattering study on
LiBH4 and LiBD4 powders. The 27 observed lines have been assigned
to phonon modes within the orthorhombic Pnma structure by comparing
the experimental values to density functional theory (DFT) values
[3].
Experimental In the present contribution we present for the
first time Raman scattering measurements on small LiBH4 single
crystals. These have been identified among the grains of the
powders (Alpha Aesar) by searching for large polarization
dependencies of the Raman lines.
Results For optimum orientation Ag modes will appear in a
configuration in which the incoming and scattered light have the
same polarization but not in a configuration in which the scattered
light has a polarization
perpendicular to the incoming light. In contrast, Bg modes will
appear for parallel as well as for perpendicular polarization, the
relative intensity giving indications whether one deals with B1g,
B2g or B3g modes. On the basis of these new results a few of the
former assignments have to be revised. Among the external modes
this concerns the mode near 307 cm-1 which is definitely of Ag
symmetry and not of B2g symmetry as had been concluded on purely
energy arguments.
A second issue is the phase transition to a hexagonal structure
at about 380 K. Several grains of our powder samples did not show
the anticipated changes of the Raman spectra. We have now succeeded
in finding a few grains which, indeed, display the characteristic
simplification of the Raman spectra when the phase transition to
the hexagonal phase occurs.
References [1] H. Kierey, M. Rode, A. Jacob, A. Borgschulte, and
J. Schoenes, Phys. Rev. B 63, 134109 (2001)
[2] J. Schoenes, A.-M. Racu, M. Rode, and S. Weber, J. Alloys
Compd. 446-447, 562 (2007)
[3] A.-M. Racu, J. Schoenes, Z. Lodziana, A. Borgschulte, and A.
Züttel, J. Phys. Chem. A 112, 9716 (2008)
Corresponding author: Joachim Schoenes, email:
[email protected], Tel. (+49) (531) 391 5130
-
3rd Hydrogen & Energy Symposium Braunwald, Switzerland
2009
21
Structure and stability of borohydrides Zbigniew Łodziana and
Andreas Züttel Empa Materials Science and Technology, Dept. Energy,
Environment & Mobility, Sec. Hydrogen & Energy, CH-8600
Dübendorf, Switzerland
Borohydrides of elements of Group 1 and Group 2 of the Periodic
Table form ionic structures (eg. LiBH4, Mg(BH4)2), while transition
metals usually form covalent borohydride molecules that are weakly
bounded in Van der Waals crystals. The structural properties of
these materials result from type of bonding between BH4 molecular
units and metal atoms. We will discuss the stability various
borohydrides with respect to electronic bonding and structural
properties of compounds. Introduction Metal borohydrides form
variety of crystalline structures. They have much better hydrogen
storage capacity than alanates due to low mass of boron.
Unfortunately, at present borohydrides are considered as
irreversible hydrogen storage media that either posses to high
decomposition temperature or are unstable at ambient
conditions.
Method
We report calculations of the stability of selected borohydrides
based on a periodic density functional (DFT) approach. The
Kohn–Sham wavefunctions were expanded in plane-wave basis sets with
energy cut-off of up to 900 eV. Brillouin zone sampling was
performed on meshes with a k-point spacing of ~0.03 Å−1. The
analysis of the valence charge of atoms was performed within Bader
formalism.
Results The binary alkali borohydrides, with monovalent or
divalent cations form crystalline structures with significant
charge transfer between metal cation and BH4 molecular unit. The
charge on BH4 group ranges between –0.88e for NaBH4 and –0.80e for
Ca(BH4)2. During decomposition of
these compounds neutral species with covalent bonds are formed.
Borohydrides of tri- or tetravalent metal atoms form closed
molecules where significant overlap of the electronic density
between metal and BH4 group is observed. The charge transfer
between species is smaller (charge on BH4 group is –0.70e for
Y(BH4)3 and –0.46e for Ti(BH4)4) and occupied Metal-BH4 bonding
orbitals can be distinguished, as can be seen in the Figure 1.
Fig. 1. The electron density at 0.3 e/Å3 of Y(BH4)3 (left) and
Ti(BH4)4 (right). Dark sphere is for metal, light gray for boron
and small for hydrogen.
These compounds are bound via weak interaction and crystalline
structures are unstable even at modest thermodynamic conditions.
Small charge transfer and directional bonds indicate that
decomposition of metal borohydrides with metal valency larger than
two would produce diborane and higher borohydrides.
Corresponding author: Zbigniew Lodziana, email:
[email protected], Tel. (+41) (44) 823 4083
-
3rd Hydrogen & Energy Symposium Braunwald, Switzerland
2009
22
Synthesis of LiBH4 by borane absorption of LiH Oliver
Friedrichs, Andreas Borgschulte, Shunsuke Kato, Florian Buchter,
Robin Gremaud, Arndt Remhof and Andreas Züttel Empa Materials
Science and Technology, Dept. Energy, Environment & Mobility,
Sec. Hydrogen & Energy, CH-8600 Dübendorf, Switzerland
The solvent free synthesis of LiBH4 from LiH in a borane
atmosphere at 120°C and ambient pressures is demonstrated. The
source of borane is a milled LiBH4/ZnCl2 mixture, in which Zn(BH4)2
is generated by metathesis reaction. The great yield of the
reaction of about 74 % LiBH4 shows, that a bulk reaction is taking
place upon borane absorption by LiH. This indicates that the
formation of B-H bonds is the limiting step for the formation of
LiBH4 from the elements. Therefore, the use of diborane as starting
reactant allows to overcome the reaction barrier for the B-B bond
dissociation and explains the rather moderate synthesis conditions.
Introduction In this work the solvent free synthesis of Li[BH4]
from LiH in borane atmosphere is presented [1-2]. The absorption
reaction is analyzed by volumetric Sieverts method, Raman
measurements, X-ray diffraction (XRD) and thermal mass spectrometry
(TDS).
Experimental Commercial LiH is heated in borane atmosphere
generated by thermal decomposition of Zn(BH4)2. The borane
formation is demonstrated by TDS measurements, while the absorption
of diborane is monitored by volumetric Sieverts and Raman
measurements. After borane absorption the product is analyzed by
XRD, in order to determine the newly generated phases in the
material.
Results We have shown for the first time the synthesis of LiBH4
by a solid gas reaction between LiH and borane at 120°C and ambient
pressures. The reaction is clearly taking place not only on the
surface of LiH but in the bulk, which shows that diffusion is not
the main problem in the formation process. It indicates that the
formation of the B-H bond is the rate limiting step in the
LiBH4
formation [3]. With a suitable catalyst supporting the formation
of this bond the formation of borohydrides in general might be
facilitated. The new synthesis method may be applied also for other
promising tetrahydroborate systems [4]. Thereby LiH is replaced by
a different metal hydride as CaH2 or MgH2 for example. This will be
analyzed in future investigations.
Fig. 1. Schematic presentation of the mechanism of Li[BH4]
formation from borane absorption of LiH
References [1] Friedrichs et al.; Angew. Chem. Int. Edit.
(2008) submitted [2] Schlesinger et al.; J. Am. Chem. Soc.
75
(1953) 186. [3] O. Friedrichs et al.; Acta Mater. 56 (2008) 949.
[4] A. Züttel et al.; Scripta Mater. 56 (2007) 823.
Corresponding author: Oliver Friedrichs, email:
[email protected], Tel. (+41) (44) 823 4153
-
3rd Hydrogen & Energy Symposium Braunwald, Switzerland
2009
23
Mechanochemical and direct wet chemical Synthesis of Metal
Borohydrides, Borodeuterides and pertially deuterated Borohydrides
M. E. Gil Bardají and M. Fichtner Forschungszentrum Karlsruhe,
Institut for Nanotechnology, D-76021 Karlsruhe, Germany
Various procedures based on mechanochemical and direct wet
chemical synthesis have been used to prepare the compounds
Ca(11BH4)2, Ca(11BD4)2, Mg(11BH4)2, Mg(11BD4)2 and the partially
deuterated compounds NaBH3D and NaBD3H. Introduction Metal
borohydrides can assume a variety of crystal structures depending
on the synthesis and the temperature.1 Elastic and inelastic
neutron diffraction experiments can be a useful tool to obtain
structural information of these materials. In order to perform
these measurements calcium and magnesium borohydride as well as
borodeuteride (enriched isotop 11B) have been synthesized. In
addition, the vibrational spectra of isotopic analogous of BH4- in
a crystalline environment can be investigated by using anharmonic
DFT calculations. In order to compare these theoretical results,
NaBD3H and NaBH3D have been synthesized as probe molecules.
Results Mg(11BH4)2 and Ca(11BH4)2 were synthesized according to
the metathesis reaction 2,3:
2Na11BH4 + MCl2 M(11BH4)2 + 2NaCl M = Mg, Ca
The synthesis of the corresponding metal borodeuterides
[M(11BD4)2, M = Mg, Ca] was achieved from the starting compound
Na11BD4. A direct wet chemical synthesis4 from Et3N·11BD3 and metal
deuteride led to the formation of the corresponding metal
borodeuterides, too.
MD2 + Et3N·BD3 M(BD4)2 + Et3N M = Mg, Ca
For the synthesis of partially deuterated metal borohydrides,
namely NaBD3H and NaBH3D, the previous reaction has been modified
by using metal hydride or triethylamine borane, respectively.5
Fig.1. IR spectra of NaBH4, NaBD3H and NaBD4.
Reaction conditions of each procedure as well as
characterization of the products will be presented.
References [1] Buchter, et al ; J. Phys. Chem. B 112 (2008) 8042
[2] James, et al; J Prog. Inorg. Chem. 11 (1970) 99. [3] Siegel at
al;Metal Hydrides, ed. W. M. Mueller, J. P. Blackledgee and
Libowitz G. G., Academic Press, New York (1968) [4] Fichtner at al;
Phys. Chem. C 112 (2008)11575 [5] Davis et al; Indiana Academy of
Science, 236
Corresponding author: M. Elisa Gil Bardaji, email:
[email protected], Tel. (+49) 7247-82-8909
-
3rd Hydrogen & Energy Symposium Braunwald, Switzerland
2009
24
First-principles study of Metal Borides: Are they Intermediates
or Precursor Compounds for Hydrogen Storage? Riccarda Caputo and
Andreas Züttel Empa Materials Science and Technology, Dept. Energy,
Environment & Mobility, Sec. Hydrogen & Energy, CH-8600
Dübendorf, Switzerland
The importance of alkali and earth-alkali metal borides either
as intermediates of the formation reaction of the corresponding
borohydrides either as products of their thermal decomposition to
upload hydrogen is discussed via first-principles calculations. The
hydrogenation and de-hydrogenation cycle runs into a certain degree
of irreversibility due to polymorphism of metal borides. Among
lithium borides, LiB and Li2B6 are reported and discussed and
compared with dehydrogenation phases of LiBH4. Introduction The
hydrogenation of lithium borides, in particular of LiB[1] and Li2B6
[2] is modelled and studied from first-principles calculations
using density functional theory based methods with GGA functional
and norm-conserving type pseudopotential, to model the 1s state of
both lithium and boron. Full geometry optimization is employed as
implemented in CASTEP and CPMD codes.
Results The absorption of lithium in the α-phase of boron is
studied at different compositions in the boron-rich region up to
1:1 atomic ratio Li:B [3]. As increasing the lithium content, the
typical icosahedron-based structure of pure boron phase is
destroyed [4]. Among all the possible phases so far investigated,
LiB and Li2B6 has the lowest energy with the corresponding heat of
formation equal to -0.249 eV and -0.448 eV per formula unit
respectively, calculated referring to Li (bcc) and α-boron. The
hydrogenation of LiB at low concentration of hydrogen has a slight
endothermic heat of reaction equal to +0.160 eV per formula unit
LiBH1.5. The hydrogenation of Li2B6, at even lower hydrogen
concentration, results a highly endothermic reaction. In fact the
heat of reaction is equal to +4.994 eV per formula unit Li2B6H0.8.
That high energy of reaction
confirms the inertness to hydrogen of Li2B6 experimentally
observed.
Figure 1. (a) LiB optimized structure, (b) LiBH1.5 , one of the
corresponding hydrogenated phase. (c) Li2B6 optimize structure, (d)
the corresponding hydrogenated phase, Li2B6H0.8. (Li, violet, B,
pink, H white).
References [1] Wörle, M. et al., Z.Anorg. Allg. Chem., 632
(2006) 1737. [2] Mair, G., et al., Z. Anorg. Allg. Chem., 625
(1999) 1207. [3] Caputo, R. and A. Züttel, (to be submitted). [4]
Caputo, R. and A. Züttel, (submitted) to Phys. Chem. Chem.
Phys.
*Corresponding author: Riccarda Caputo, email:
[email protected], Tel. (+41) (44) 823 4422
-
3rd Hydrogen & Energy Symposium Braunwald, Switzerland
2009
A detailed Study on the Hydrogenation of 2NaH + MgB2
Claudio Pistiddaa, Gagik Barkhordarianb, Sebastiano Garronic,
Christian Bonatto Minellab, Torben Jensend, Martin Dornheimb,
Wiebke Lohstroha, Rüdiger Bormannb, Maximiliam. Fichtnera. a
Institut für Nanotechnologie, Forschungszentrum Karlsruhe GmbH,
Postfach 3640, 76021 Karlsruhe, Germany b Institute of Material
Research, GKSS Research Centre Geesthacht GmbH, Max Planck strasse
1, D-21502 Geesthacht, Germany c Departament de Física, Universitat
Autònoma de Barcelona, 08193 Bellaterra, Spain d Interdisciplinary
Nanoscience Centre (iNANO) and Department of Chemistry, University
of Aarhus, Langelandsgabe 140, DK-8000. Denmark The recent
discovery of the unique kinetic property of MgB2 in facilitating
the hydrogenation of light metal complex borohydrides at moderate
conditions has created new prospects to develop high capacity low
enthalpy hydrogen storage materials. These new composite materials
which consist of a binary light metal hydride (like LiH, NaH and
CaH2) and MgB2 can be hydrogenated in much more moderate conditions
compared to the usual route of hydrogenating the mixture of the
corresponding binary hydride and pure Boron. This suggests that
MgB2 is kinetically superior to pure Boron in these reactions;
however the corresponding mechanisms are not yet understood. With
the aim of clarifying the function of MgB2 functions, we
investigated the hydrogenation of NaH+MgB2 by in-situ Synchrotron
X-ray diffraction, high pressure titration, and HP-DSC.
Introduction
In the present work the hydrogen desorption behavior of the RHC
system 2NaH+MgB2 prepared by ball milling was investigated
Experimental NaH (95% purity) and MgB2 (99.99% purity) were
purchased from Sigma Aldrich and Alfa-Aesar, respectively. The NaH
and the MgB2 were charged into a hardened steel vial and milled for
1 hour in a Spex 8000 ball mill, with a ball to powder ratio
10:1.Results An extensive in-situ PXD study during absorption of
the RHC system 2NaH + MgB2 prepared by BM was performed. The
results revealed that the formation of NaMgH3 is
strongly dependent on the hydrogen pressure.
Fig. 1. Series of SR-PXD patterns of the 2NaH+MgB2 system heated
under 50 bar of hydrogen pressure from RT to 400°C.
Corresponding author: Claudio Pistidda, email:
[email protected]
25
-
3rd Hydrogen & Energy Symposium Braunwald, Switzerland
2009
26
Combinatorial Approach for the Discovery of new Materials for
Hydrogen Storage Roger Domènech-Ferrer, Gemma Garcia,
Alfonso Sepulveda and Javier
Rodriguez-Viejo † Nanomaterials and Microsystems Group,
Department of Physics, UAB, Campus UAB, Bellaterra, 08193 Spain
† MATGAS AIE, Campus UAB, Bellaterra, 08193 Spain
We have developed and tested a thin film membrane-based
calorimeter to measure kinetically limited phase transitions such
as the de/hydrogenation of metallic hydrides. Those microsystems
are used as substrates for singular and combinatorial metal
hydrides thin film deposition and tested for hydrogen storage
applications. Introduction The combinatorial approach provides a
mean to quickly investigate a large number of unexplored material
for Hydrogen storage combining high throughput synthesis and
screening methodologies [1-3]. Furthermore, thin film techniques
offer a unique methodology for studying the nanoscale and
interphase effects on the materials properties.
Experimental We have grown thin film libraries of the Mg-based
system using a sequential deposition of pure elements (for instante
Mg and Al) by an electron-beam evaporation technique [6].
Presently, we are also growing compositional graded libraries using
a co-sputtering technique. Besides, we have developed thin film
membrane-based calorimeters that can be used to characterise
(de)hydrogenation reactions of metallic hydrides [5].
Results Those Microsystems are used as substrates for singular
and combinatorial metal hydride thin film deposition, mainly
magnesium-based alloys. After several hydrogenation treatments at
different temperatures to
induce the hydride formation, we observe a significant reduction
in the onset of dehydrogenation for Mg80Ti20 compared with pure Mg
or Mg/Al layers, which confirms the beneficial effect of Ti on
dehydrogenation. By using libraries containing different Mg-Al
ratios we have also found indirect evidence of the formation of the
alanate phase and that aluminum can act as a catalyzer for the
hydrogenation reaction. Actually, to complement the high-throughput
screening we are developing the Thermal Imaging Technique not only
on standard thin films but also coupled with calorimetric in-situ
experiments.
References [1] C.H. Olk, G.G. Tibbetts, D. Simon, J.J. Moleski,
J. Appl Phys 94, 720–5 (2003). [2] R. Gremaud, C.P. Broedresz, D.
Borsa, A. Borgschulte, P. Mauron, H. Schreuders, Adv Mater 19,
2813–7 (2007) [3] S. Guerin, B. E. Hayden, D. C. A. Smith J. Comb.
Chem., 10 (1), 37–43 (2008) [5] A. Sepúlveda, A.F. Lopeandía, R.
Domènech-Ferrer, G. Garcia, F. Pi, J. Rodríguez-Viejo, F.J. Muñoz;
Inter. J. of Hydrogen Energy 33, 2729 – 2737 (2008) [6] G. Garcia,
R. Domènech-Ferrer, F. Pi, J. Santiso, J Rodriguez-Viejo; J
Combinatorial Chem 9, 230–6,(2007)
Corresponding author: Gemma Garcia, email: [email protected],
Tel. (+34) 935811481
-
3rd Hydrogen & Energy Symposium Braunwald, Switzerland
2009
27
Dehydrogenation Mechanism of 2NaBH4 + MgH2 prepared by Ball
Milling S. Garroni1, C. Pistidda2, M. Brunelli3, G. Vaughan3, S.
Suriñach1, M.D. Baró1 1Departament de Física, Universitat Autònoma
de Barcelona, 08193 Bellaterra, Spain 2GKSS Research Centre,
Geesthacht, Germany 3ESRF European Synchrotron Radiation Facility,
BP220, Grenoble, France
Hydrogen storage materials based on a mixture of complex and
light metal hydrides constitute a class of compounds promising in
the field of hydrogen storage for vehicular applications [1].
Particular attention has been paid recently to Reactive Hydride
Composites (RHC), where the combination of an alkaline borohydride
with a reactive hydride induces a thermodynamic destabilization and
a decrease of hydrogen desorption temperature with respect to the
component phases [2,3]. Although numerous studies are reported in
literature for these functional hydrogen compounds, their
dehydrogenation mechanism is not quite clear and their preparation
has to be optimized. Introduction In this work we focus on the
properties of the system NaBH4 - MgH2 prepared by high energy ball
milling. The aim of the work is to study which phases evolve during
the hydrogen desorption in the mixture 2NaBH4 + MgH2 in order to
understand the mechanism that is involved in that process.
Experimental The mixture was milled in a mol ratio 2:1 by means
of Planetary Fritsch P5 mill. The milling was performed under pure
Argon atmosphere with a ball to powder ratio of 1:10 and a rotation
speed of 230 rpm. With the aim of characterizing the samples, the
morphology, thermodynamic and micro-structural properties were
investigated by Scanning Electron Microscopy (SEM), Differential
Scanning Calorimetry (DSC) and Powder X-ray Diffraction (PXD),
respectively. In addition in situ Powder X-ray Diffraction (SR-PXD)
was performed in order to evaluate the phases evolved during the
desorption process.
Results As shown in fig. 1, after 337ºC the desorption of MgH2
starts and consequently the peaks
of Mg appear. The desorption is complete after 388ºC, in
according with the DSC analysis performed previously.
Fig. 1. “in situ” XRD patterns measured at different
temperatures (25-500º) of 2NaBH4 + MgH2 intimate mixture.
Further analysis confirmed that the formation of MgB2 starts
after the complete desorption of MgH2.
References [1] Materials Go/No-Go Decisions Made Within the
Department of Energy Metal Hydride Center of Excellentce
(MHCoE), Sandia National Laboratories, Livermore, CA 94551,
2007.
[2] John J. Vajo and Gregory L. Olson, Scripta Mater, (2007) 56,
829-834.
[3] G. Barkhordarian, T. Klassen, M. Dornheim, R. Bormann, J.
Alloys. Comp., (2007), 440, L18-L21.
Corresponding author: Sebastiano Garroni, email:
[email protected], Tel. (+34) (93) 5811657
-
3rd Hydrogen & Energy Symposium Braunwald, Switzerland
2009
28
Tuesday
-
3rd Hydrogen & Energy Symposium Braunwald, Switzerland
2009
29
Capped Metal-Hydrogen Systems Ronald Griessen, Andrea Baldi,
Yevheniy Pivak, Herman Schreuders and Bernard Dam Physics
Department, VU university, Amsterdam, the Netherlands
In thin films and nanoclusters the surface to volume ratio is
much larger than in polycrystalline bulk materials. We show that
the thermodynamics of a Mg layer sandwiched between transition
metal (TM) layers can be drastically modified by the elastic
constrain imposed by a surface TM layer. The same applies for Mg
nanoclusters with a hard MgO surface layer. Introduction Many
attempts have been done to destabilize Mg-hydride. We show here
that the plateau pressure of Mg-H can be increased by more than one
order of magnitude by restricting the free expansion of Mg during
hydrogen absorption. One effective way to do so is by sandwiching
Mg layers between transition metal layers. Another way is by
coating nanocrystallites of Mg by a thin layer of a hard
material.
Experimental Ti/Mg/Pd multilayers are deposited on glass in a
UHV system (base pressure = 10-8 mbar) by DC/RF magnetron in argon
atmosphere. The thickness of the Ti and Pd layers is 10 and 40 nm,
respectively, while the thickness of the Mg layer is varied from 10
to 40 nm. This set of samples is used to demonstrate the effect of
elastic clamping. The p-c isotherms at 333 K are measured by means
of hydrogenography.
Results The width of the plateaus in Fig.1 is proportional to
the thickness of the Mg layer that becomes transparent in the
hydrogenated state. Most interesting is the large increase in
plateau pressure with decreasing Mg thickness. This is predicted by
a model in which the lattice expansion of the Mg layer during H
uptake is elastically
hampered by the transition metal layers. This model predicts
that
where ps and pf are the plateau pressures of a sandwiched (s)
and a free (f) Mg layer, respectively. EMg and EMg are the Young
moduli and dMg and dMg the thicknesses of the Mg and TM layers. The
parameter a depends on characteristic properties of the Mg-H
system. A similar model predicts that Mg nano-clusters covered by a
thin MgO surface layer have a plateau pressure at 333K that is
approx. 100 times higher than the plateau of a pure Mg film.
Fig. 1. P-c isotherms at 333 K of a Mg layer sandwiched between
Ti and Pd as a function of the Mg layer thickness (10 – 40 nm).
Corresponding author: Ronald Griessen, email:
[email protected], Tel. (+31) (20) 598 7915
-
3rd Hydrogen & Energy Symposium Braunwald, Switzerland
2009
30
LSPR and QCM-D Measurements of Hydrogen Storage in
nano-Materials. C. Langhammera, N. Naujoksa, E. Larssona, L.
Romanszkia, M. Rodahlb, M. Zächa, V. Zhdanova,c, I. Zorica, B.
Kasemoa aDepartment of Applied Physics, Chalmers, SE-412 96
Gothenburg, Sweden, b Q-Sense AB, 426 77 Vaestra Froelunda, Sweden,
cBoreskov Institute of Catalysis, Russian Academy of Sciences,
Novosibirsk 630090, Russia We report (i) QCM measurements of
hydrogen uptake/release in submonolayer arrays of Pd nanoparticles,
(ii) LSPR measurements on the same system, (iii) preparation of new
nanoparticle model systems for QCM and LSPR measurements, (iv) a
new experimental set up for QCM measurements with HSM materials and
(v) theoretical modeling of hydrogen uptake kinetics in
nanoparticles. Introduction Hydrogen storage materials (HSM) in the
form of nanoparticles (NP) and nano-structured materials are
interesting from the viewpoints of basic physics and applications,
and because the thermodynamics and kinetics of the HSM can be
modified. A challenge working with small, well-defined NPs is the
often limited amount of material available, and the associated
reduced sensitivity. We apply QCM, Localized Surface Plasmon
Resonance (LSPR) sensing, associated preparation, and modeling to
study nano-particle HSM.
Experimental QCM: The QCM technique is well established since
long for HSM studies 1. The sample to be studied is deposited on
the surface of a piezoelectric quartz crystal sensor, acting as a
resonator, allowing measurement of very small frequency (mass)
changes, caused by hydrogen uptake or loss. LSPR: LSPR is the
optical response caused by collective oscillations of conduction
band electrons (plasmons) in a confined particle < light
wavelength. Changes in the dielectric environment of the NP, or a
change in the NP’s electron structure, cause a change in the
optical response which is frequently used for biosensing. We have
recently shown that this can be used to sensitively measure
hydrogen uptake and release in Pd nanoparticles2.
Results Combined QCM and LSPR measurements on relatively large
Pd NPs demonstrate (i) that thermodynamic values (enthalpy and
entropy) for the alpha and beta phases of Pd bulk can be obtained
by both methods. The LSPR, calibrated by QCM, has superior
sensitivity and can be used to follow fast kinetics in both phases.
For sufficiently small particles, interesting new thermodynamics
and kinetics are observed, partly addressed also by modeling3. We
further give a progress report on a new measurement system for QCM
measurements of HSM, and the associated sample preparation to
increase the sensitivity of the QCM measurements (see presentation
by Naujocs et al).
References [1] G. A. Frazier, R. Glosser, J. Phys. D : Appl.
Phys., 12, (1979).; J. Rydén et. al., J. Less-Comm. Met., 152,
295-309, (1989).; I. Kulchytskyy et. al., Appl. Phys. Lett., 91,
113507, (2007).
[2] C. Langhammer et. al., Nano Lett., 7, 3122-3127, (2007).
[3] V. P. Zhdanov, B. Kasemo, Chem. Phys. Lett., 460, 158,
(2008), and tentatively new results.
Corresponding author: Bengt Kasemo, email: [email protected]
Tel. (+46) (31) 772 33 70
-
3rd Hydrogen & Energy Symposium Braunwald, Switzerland
2009
31
High Capacity Hydrogen Storage Nanomaterials Süleyman Er1,
Gilles A. de Wijs2 and Geert Brocks1 1 Computational Materials
Science, Faculty of Science and Technology and MESA+ Institute for
Nanotechnology, University of Twente, P.O. Box 217, 7500 AE
Enschede, The Netherlands. 2 Electronic Structure of Materials,
Institute for Molecules and Materials, Faculty of Science, Radboud
University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen, The
Netherlands. In the first part, lithiated carbon and oxygen
molecular structures are considered for hydrogen storage
applications. Using First Principles calculations we predict the
interaction of hydrogen molecules with such materials. Within these
compounds it is found that the Li atoms connected to a central C or
O atom bear partial positive charges. Hydrogen molecules are then
clustered around these Li atoms via electrostatic interactions
(Fig.1). According to our calculations such molecules can attach
hydrogen up to ~40 wt. % with average hydrogen binding energies
between 0.1 and 0.2 eV/H2. However, to maintain a reversible
system, molecular dimerization need to be prevented. Here, we
consider attaching the lithiated molecular structures to graphene.
The immobilized molecules have a similar interaction with hydrogen
molecules as free molecules. However, hydrogen weight percentages
are reduced to 5-8 wt. % due to the additional weight of the
graphitic template.
Fig. 1. CLi4 (left side figure) and OLi2 molecules in their
fully hydrogenated stages.
In the second part, we discuss the hydrogen storage properties
of novel boron sheets[1] and buckyballs[2]. We find that the
interaction of molecular hydrogen with these systems is weak as in
the case of carbon based graphitic and buckyball structures.
However, both of the boron structures bind to lightweight alkali
and some of alkaline earth metals strongly. Deposited metals on the
surface of boron systems bind several hydrogen molecules (Fig.2).
Hydrogen weight percentages and binding energies vary depending on
the choice of the metal. Ca is found to be a promising doping
element for both of the boron sheet (6wt. %H, 0.15 eV/H2) and
buckyball (9 wt %H, 0.11 eV/H2) structures.
Fig. 2. Boron buckyball doped with 12 Ca atoms in its fully
hydrogenated stage.
References [1] H. Tang and S. Ismail-Beigi, Physical Review
Letters 99, 115501 (2007). [2] Szwacki et al. , Physical Review
Letters 98,
166804 (2007).
Corresponding author: Süleyman Er, email: [email protected] , Tel.
(+31) (53) 489 3167
-
3rd Hydrogen & Energy Symposium Braunwald, Switzerland
2009
32
Quartz Crystal Microbalance Studies of Hydrogen Storage in
nanostructured Materials Nicola Naujoks, Loránd Románszki, Michael
Zäch, and Bengt Kasemo
Chalmers University of Technology, Applied Physics, SE-412 96
Göteborg, Sweden
Nano-structured materials (thin films and nanoparticles) are
investigated regarding their (de-) /hydrogenation properties with
the help of Quartz Crystal Microbalance (QCM). Introduction
Reducing the geometrical dimensions of hydrogen storing
materials to the nanoscale is expected (and shown) to result in
advantageous kinetics. One approach to study this effect is to
observe the hydrogenation properties of thin metal films [1] and
nanostructured metal particles [2] with the help of a Quartz
Crystal Microbalance (QCM). By detecting shifts in resonance
frequency the QCM enables the measurement of minute mass changes
that correspond to a fraction of monolayer of hydrogen atoms.
Model experiments / QCM To be studied in a QCM setup, the sample
structures have to be fabricated onto the surface of quartz sensor,
as shown in Fig.1. The feasibility of the QCM technique to
investigate hydrogenation of thin metal films is demonstrated at
the example of a Pd covered Mg film. Fig.2 shows thermodynamic data
of obtained with a QCM setup. Applying this technique to the
investigation of hydrogen storage in nanoparticles (NP) requires a
method of attaching a sufficiently large amount of NPs onto the
crystal (a 2d disperse layer on the sensor surface suffers from a
limited sensitivity of the QCM). First results on embedding
hydrogen storing NPs into porous supports that are coated onto the
crystal will be presented, thereby allowing a larger number of
particles to be accessed by
the H2 gas. We will further present a new QCM gas cell setup
that will enable measurements over a wider range of temperatures
and pressures.
Fig. 1. The samples – thin metal films - are deposited onto
quartz crystal sensors.
Fig. 2. Hydrogenation and dehydrogenation cycle of a sandwich
structured sample (Pd and Mg)
References [1] A. Krozer, and B. Kasemo; J. Less Comm.
Met. 160 (1990). 323. [2] Langhammer C., Zoric I. and Kasemo B;
Nano
Lett. 7 (2007) 3122.
Corresponding author: Nicola Naujoks, email:
[email protected], Tel. (+46) (31) 772 3331
-
3rd Hydrogen & Energy Symposium Braunwald, Switzerland
2009
33
Hydrogen-induced plastic Deformation of Rare Earth Metal Thin
Films and Comparison with corresponding Nanoparticles Mathias
Getzlaff1, Astrid Pundt2 1. Institute of Applied Physics,
University of Düsseldorf, D-40225 Düsseldorf, Germany 2. Institute
of Materials Physics, University of Göttingen, D-37077 Göttingen,
Germany The hydrogen induced plastic deformation processes of Gd
metal thin films are determined on the nanometer scale by means of
the corresponding surface modifications. These results are compared
to high Gd islands representing nanoparticles being clamped to the
substrate at the interface.
Experimental Surface modification of thin Gd films and high
islands representing nanoparticles during hy-drogen adsorption as
well as absorption has been investigated on the nanometer scale by
means of scanning tunnelling microscopy.
Results The adsorption occurs in two steps. It is initiated by
surface imperfections (see left part of Fig. 1). Starting from
these nucleation centers a domain-like spreading is present which
is strongly hindered at surface steps (see right part of Fig.
1).
Fig. 1. Gadolinium islands on a W(110) surface. The bar
corresponds to 100 nm. Left: The system was exposed to 0.2 L
hydrogen. Hydrogen is adsorbed at that areas appearing deeper which
is due to an electronic effect. Right: With increasing amount (1 L)
a domain-like spreading occurs.
The measurements have shown that during further hydrogen loading
two different types of surface pattern develop above a particular
concentration: disc-like islands and slope fields (see Fig. 2).
Fig. 2. Gadolinium thin films on a W(110) surface. The system
was exposed to 70 L hydrogen. Two different patterns occur:
disc-like islands (upper part) and slope fields (middle part).
These surface patterns can be well described by two plastic
deformation processes in the films that lead to glide steps on the
film sur-face. First, the emission of dislocation loops during
hydride precipitation occurs. Second-ly, misfit dislocations near
the film-substrate interface are present. Since plastic
deforma-tion leads to stress release a lot of thin metal films
being clamped to a substrate relax pla-stically after reaching a
certain hydrogen-in-duced stress that corresponds to a critical
hy-drogen concentration. This conclusion is cor-roborated due to
free-standing Gd islands being without structural deformation.
Overall, combining the ability of preparing high-quality epitaxial
thin films with the detailed analysis of the mechanical proper-ties
during hydrogen absorption may lead to a deeper fundamental
understanding of hy-drogen switchable thin films. It may also
improve their industrial applications.
Corresponding author: Mathias Getzlaff, email:
[email protected], Tel. (+49) (211) 81 12291
-
3rd Hydrogen & Energy Symposium Braunwald, Switzerland
2009
34
Nanostructured Photoanodes for Hydrogen Production by Solar
Water Splitting Kevin Sivula, Scott C. Warren, Florian le Formal,
Adriana Paracchino, Jeremie Brillet, and Michael Grätzel
Laboratoire de Photonique et Interfaces, Ecole Polytechnique
Fédérale de Lausanne, CH-1015, Lausanne, Switzerland
Recently we have reported nanostructed, silicon doped Fe2O3
photoanodes prepared by atmosphere pressure CVD which exhibit a
remarkable photocurrent under standard conditions (2.2 mA/cm2 at
1.23 V vs RHE and AM 1.5G 100 mW/cm2 simulated solar illumination).
When these transparent photoanodes are combined with a
bias-supplying photovoltaic cell (a dye sensitized solar cell),
unassisted solar-to-hydrogen conversion efficiencies of 3.3 % can
be obtained. Here we will describe the current research efforts of
PECHouse, the Swiss photoelectrochemical centre of excellence, in
continuing the development of these nanostructured photoanodes for
solar hydrogen production. Introduction
The world’s most abundant renewable energy source, the Sun, has
the potential to meet current and future energy needs. The direct
hydrogen production by water photoelectrolysis from solar
illumination is one promising route to directly convert solar
energy into a storable and transportable medium, but a scalable and
inexpensive photoelectrolysis strategy is essential. Due to its
abundance, environmental stability, and favorable bandgap, iron
(III) oxide (hematite) is a promising photocatalyst for this
application. However, the poor photon absorptivity and charge
carrier transport of hematite have remained obstinate limitations
preventing its full exploitation.
Experimental Nanostructed, silicon doped Fe2O3 photoanodes were
prepared by the atmosphere pressure chemical vapor deposition from
Fe(CO)5 and Si(OC2H5)4. The process temperature, dopant
concentration, and the growth time were varied in order to
determine the major factors which influence performance. High
resolution electron microscopy, impedance spectroscopy and micro
Raman analysis were subsequently used to reveal how the
process conditions affect the nanostructure and
crystalinity.
Results We show film growth during deposition to be linear with
an incubation time. No concern with electron transport for films up
to 600 nm is found, but a higher recombination rate of
photo-generated carriers in the hematite near the interface with
the fluorine doped tin oxide, as compared to the bulk section of
the film is noted. The observed feature sizes of the film are found
to depend strongly on this temperature and the presence of silicon
dopant precursor (TEOS). We also find evidence for an unusually
high donor density which allows the formation of a space-charge
field inside the nano-sized features of the polycrystalline
hematite photoanode—a factor which could play a major role in the
separation of charges and enhancement of performance, even in the
surface features of 5 nm.
References [1] Kay et al; J. Amer. Chem. Soc. 128 (2006)
15714 [2] Cesar, et al; J. Amer. Chem. Soc. 128 (2006)
4582 [3] Gratzel, M., Nature, 414 (2001), 338
Corresponding author: Kevin Sivula, email: [email protected],
Tel. +41 (0) 21 693 3669
-
3rd Hydrogen & Energy Symposium Braunwald, Switzerland
2009
35
A thermodynamic Database for Hydrogen storage Systems M.
Palumboa,b, J. Urgnanib, J. F. Torresb, D. Baldissinb, M. Bariccob
aParticle Simulation and Thermodynamics Group, Computational
Materials Science Center (CMSC), National Institute for Materials
Science (NIMS), 1-2-1 Sengen, Tsukuba, Ibaraki, 305-0047, Japan
bDipartimento di Chimica I.F.M. and NIS/INFM/CNISM, Università di
Torino, via Giuria 7/9, 10125 Torino, Italy
The thermodynamic behaviour of hydrogen related systems has been
investigated by coupling the CALPHAD approach and ab initio
calculations. Several binary and ternary systems have been
considered, including La-Ni-H, Al-Mg-H, Na-B-H. The development of
a thermodynamic database for hydrogen systems is on going. In the
latest years, hydrogen storage in intermetallic compounds has been
proposed as a suitable way to accumulate energy for several
applications [1]. However, the diffusion of this technology,
especially in the automotive industry, has been hindered by some
difficulties and limitations. Many researchers are active nowadays
in this field trying to overcome present drawbacks. To this
purpose, knowledge of thermodynamic stability of these compounds is
much helpful to study the hydrogenation/dehydrogenation process. In
order to be suitable for applications the thermodynamic stability
of a candidate material should not be to high, thus avoiding a
large heat absorbed/released during hydrogenation/dehydrogenation.
Moreover, thermodynamics and phase diagrams are useful to
rationalize synthesis reactions of these compounds and to suggest
possible alternative reaction routes. By mixing some of these
hydrides with other compounds, it is possible to make easier the
hydrogenation/dehydrogenation process. A thermodynamic analysis is
very useful in rationalizing this behaviour and the CALPHAD
approach is the most suited to this goal.
The purpose of this work is to develop a consistent
thermodynamic database for hydrogen storage systems. The La-H and
La-Ni-H phase diagrams have been reviewed and thermodynamically
assessed using the CALPHAD method, while other binary systems (Ni-H
and La-Ni) have been adapted to be incorporated in the present
database. Other Al, Mg, Na, B-based compounds/systems of interest
for hydrogen storage are also included [2-5]. For example, the
Al-Mg-H system has been thermodynamically assessed including the
magnesium alanate Mg(AlH4)2 which has a theoretical hydrogen
content of 9.3 wt% [4]. A critical assessment of available
experimental data has been performed. Key ab initio calculations
have been carried out. Calculated and experimental thermodynamic
properties have then been compared and a satisfactory agreement has
been achieved.
References [1] L. Schlapbach et al; Nature 414 (2001) 353 [2] K.
Zeng et al; IJHE 24 (1999) 989 [3] B.-M. Lee et al; J. Alloys
Compd. 424 (2006) 370 [4] M. Palumbo et al; CALPHAD 31 (2007) 457
[5] J. Urgnani et al; IJHE 33 (2008) 3111
Corresponding author: Mauro Palumbo, email:
[email protected]
-
3rd Hydrogen & Energy Symposium Braunwald, Switzerland
2009
36
Wednesday
-
3rd Hydrogen & Energy Symposium Braunwald, Switzerland
2009
37
First Principles Modeling of Magnesium Transition Metal Hydides
Süleyman Er,1 Michiel J. van Setten,2,3 Dhirendra Tiwari,1 Gilles
A. de Wijs,2 Geert Brocks1 1Computational Materials Science,
Faculty of Science and Technology and MESA+ Institute for
Nanotechnology, University of Twente, P.O. Box 217, 7500 AE
Enschede, the Netherlands. 2Electronic Structure of Materials,
Institute for Molecules and Materials, Faculty of Science, Radboud
University, Heyendaalseweg 135, 6525 AJ Nijmegen, the Netherlands.
3Institut für Nanotechnologie, Forschungszentrum Karlsruhe, P.O.
Box 3640, D-76021 Karlsruhe, Germany.
Lightweight metal hydrides are strong candidates for future
hydrogen storage materials. Alloying Mg with lightweight transition
metals (TM = Sc, Ti, V, Cr) could provide a viable route towards
materials with fast (de)hydrogenation kinetics and suitable
thermodynamic properties. We study the structure and stability of
MgxTM(1-x)H2, x = [0,1] by first-principles calculations. The
stability of these compounds decreases along the series Sc, Ti, V,
Cr. The dehydrogenation enthalpy of .MgxTi(1-x)H2 can be markedly
improved by adding Al or Si, which destabilizes the hydride,
whereas it stabilizes the alloy. MgxTi(1-x)H2 also has remarkable
optical properties, such as a black state. We argue that the black
state is an intrinsic property of these compounds, unlike similar
optical phenomena observed in other metal hydride films.
Introduction MgH2 has been studied intensively since it has a
relatively high hydrogen gravimetric density of 7.7 wt.%.
Bottlenecks in its application are its thermodynamic stability and
slow kinetics. Alloying Mg with early transition metals (TMs) is
found experimentally to increase the hydrogenation kinetics. Here
we study the structure, the thermodynamics and the optical
properties of magnesium transition metal hydrides by
first-principles calculations at the level of density functional
theory.
Results We find that the experimentally observed sharp decrease
in hydrogenation rates of MgxTM(1-x)H2 for x > 0.8 correlates
with a phase transition from a fluorite to a rutile phase. Varying
the transition metal (TM) and the composition x, the formation
enthalpy can be tuned over the substantial range 0-2 eV/f.u.
Assuming however that the alloy does
not decompose upon dehydrogenation, the enthalpy associated with
reversible hydrogenation of compounds with a high magnesium content
(x = 0.75) is close to that of pure Mg [1]. Adding Al and Si to
MgxTi(1-x)H2, however, destabilizes the hydrides, whereas it
stabilizes the MgxTi(1-x) alloy [2]. Thin films of MgxTi(1-x)H2
show an optical black state upon hydrogenation. We calculate the
dielectric function and the optical properties of MgxTi(1-x)H2, x =
0.5, 0.75, 0.875, and argue that the black state is an intrinsic
property of these compounds [3]. In particular, the plasma
frequency drops below 1 eV in disordered structures, which then
show a low reflection and transmission in the range 1-6~eV, i.e. a
black state.
References [1] Er et al; Phys. Rev. B, submitted (2008). [2] Er
et al; in preparation (2009). [3] van Setten et al; Phys. Rev. B,
submitted
(2008).
Corresponding author: Geert Brocks, email:
[email protected], Tel. (+31) 534893155
-
3rd Hydrogen & Energy Symposium Braunwald, Switzerland
2009
38
Hydrogen splitting studied by H-D Exchange M. Johansson Danish
National Research Foundation's Center for Individual Nanoparticle
Functionality (CINF), Department of Physics, Technical University
of Denmark (DTU), 2800 Lyngby, Denmark
It is shown how the H-D exchange reaction can be utilized to
measure the splitting rate of hydrogen at 1 bar. Examples of
results are given for transition metals, metal alloys and supported
metal nano-particles.
Introduction The H-D exchange reaction offers a convenient way
to measure the rate of hydrogen splitting on surfaces at
atmospheric pressure. Such measurements can help understanding the
anode processes of the Proton Exchange Membrane Fuel Cell (PEMFC),
and could potentially be useful when designing systems for storage
of hydrogen in solids.
Experimental The sticking probability for hydrogen, S, is
calculated from the rate of the H-D exchange reaction, which is
measured with laterally resolved mass spectrometry. A simple model
is used in order to extract S from the rate data [1]. It is assumed
that S is the same for H2, HD and D2, and that the desorption rates
are second order in the coverages of H and D. The apparent
activation energy for hydrogen desorption, Eapp, can be obtained
from data for S as a function of temperature.
Results With the anode reaction of the PEMFC in mind, an
investigation was carried out for a number of transition metals,
deposited as 50 Å films on Highly Ordered Pyrolytic Graphite
(HOPG). The values for S and Eapp are in reasonable agreement with
literature values obtained at high hydrogen coverage under vacuum
conditions [2]. Metals which bind hydrogen strongly would be
expected to have a high coverage of H, and thus to give a low value
for S. However, Ru and Rh bind H stronger than Pt, but give larger
values for S.
The fact that Pt works better than Ru and Rh in a PEMFC may be
due to Ru and Rh being oxidized under typical operating conditions.
S was also measured with 10 ppm CO added to the hydrogen. The
influence of CO on S is strongest for Ir and Pt. These metals show
the largest difference between the heats of adsorption for CO and H
[3]. S for Pt is significantly more sensitive to CO than the
current of a PEMFC with Pt as anode catalyst. This indicates that
reactions which consume CO are important for the resistance to CO
poisoning of a real PEMFC. Investigations were also carried out for
Ru and Pt nano-particles produced by metal evaporation onto
sputtered HOPG. There is a maximum in S for a particle diameter, d,
of about 3 nm for Ru, but for Pt, S increases with decreasing d.
Eapp increases with decreasing d for both Pt and Ru, but the effect
is more pronounced for Ru. Presently, metal alloys such as Pt/Bi
and Pt/Ru are investigated in order to study the ligand effect
separately from the bi-functional effect. So far, it seems that a
surface which contains about equal amounts of Pt and Ru gives an
even higher value for S than pure Ru, whereas no improvement in S
was obtained by adding Bi to a Pt surface.
References [1] M. Johansson, O. Lytken, I. Chorkendorff,
Topics in Catalysis 46 (2007) 175. [2] M. Johansson, O. Lytken,
I. Chorkendorff, J.
Chem. Phys. 128 (2008) 034706. [3] M. Johansson, O. Lytken, I.
Chorkendorff,
Surf. Sci. 602 (2008) 1863.
Corresponding author: Martin Johansson, email:
[email protected], Tel. (+45) 45253191
-
3rd Hydrogen & Energy Symposium Braunwald, Switzerland
2009
39
Experimental electronic charge density of LiBD4/LiBH4 from
maximum entropy method F. Buchter1, Z. Lodziana1, A. Remhof1, Ph.
Mauron1, A. Züttel1, Y. Filinchuk2, T. Noritake3, S. Orimo4 1Empa
Materials Science and Technology, Dept. Energy, Environment &
Mobility, Sec. Hydrogen & Energy, CH-8600 Dübendorf,
Switzerland 2Swiss-Norwegian Beamline, ESRF, BP220, Grenoble Cedex,
France. 3Toyota Central R&D Labs., Inc., Nagakute, Aichi
480-1192, Japan. 4Institute for Materials Research, Tohoku
University, 980-8577 Sendai, Japan.
Combining neutron diffraction data and X-ray diffraction data,
the experimental charge density distribution using the maximum
entropy method has been determined for LiBD4/LiBH4. This method
gives a fundamental information about the charge transfer and
bonding nature between the different atoms within the compound and
can be directly compared to ab-initio calculations of the charge
density. Introduction Alkali and alkali-earth complex hydrides are
promising hydrogen storage materials, but desorb hydrogen at a high
temperature and pressure level, due to either their thermodynamical
stability or a kinetic barrier. In order to tailor the
temperature/pressure level to suitable conditions, it is important
to understand their mechanism of formation/decomposition. An
accurate experimental investigation of the electronic charge
density distribution of the complex hydrides give important
information about the charge transfer and bonding nature between
the different atoms within the compounds.
Experimental Combining neutron diffraction data for the
refinement of the structural model, and subsequently X-ray
diffraction data for the structure factor extraction, allows the
calculation of the experimental charge density distribution1 (see
Figure 1). Due to the limited number of extracted structure
factors, the maximum entr