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Complex Hydrides forHydrogen Storage
George Thomas, ConsultantSandia National Laboratories
G. J. Thomas
Efficient onboard hydrogen storage is a critical enabling technology for the use of
hydrogen in vehicles
• The low volumetric density of gaseous fuels requires a storage method which densifies the fuel.– This is particularly true for hydrogen because of its
lower energy density relative to hydrocarbon fuels.• Storage methods result in additional weight and
volume above that of the fuel.
How do we achieve adequate stored energy in an efficient, safe and cost-effective system?
G. J. Thomas
However, the storage media must meet certain requirements:
– reversible hydrogen uptake/release– lightweight– low cost– cyclic stability– rapid kinetic properties– equilibrium properties (P,T) consistent
with near ambient conditions.
One storage option is to chemically bond hydrogen in a solid material
• This storage approach should have the highest hydrogen packing density.
G. J. Thomas
Where do we start? G r o u p
P e r i o dI A V I I I A
11
H1 . 0 0 8 I I A I I I A I V A V A V I A V I I A
2
H e4 . 0 0 3
23
L i6 . 9 4 1
4
B e9 . 0 1 2
5
B1 0 . 8 1
6
C1 2 . 0 1
7
N1 4 . 0 1
8
O1 6 . 0 0
9
F1 9 . 0 0
1 0
N e2 0 . 1 8
31 1
N a2 2 . 9 9
1 2
M g2 4 . 3 1 I I I B I V B V B V I B V I I B - - - - - - - V I I I - - - - - I B I I B
1 3
A l2 6 . 9 8
1 4
S i2 8 . 0 9
1 5
P3 0 . 9 7
1 6
S3 2 . 0 7
1 7
C l3 5 . 4 5
1 8
A r3 9 . 9 5
41 9
K3 9 . 1 0
2 0
C a4 0 . 0 8
2 1
S c4 4 . 9 6
2 2
T i4 7 . 8 8
2 3
V5 0 . 9 4
2 4
C r5 2 . 0 0
2 5
M n5 4 . 9 4
2 6
F e5 5 . 8 5
2 7
C o5 8 . 4 7
2 8
N i5 8 . 6 9
2 9
C u6 3 . 5 5
3 0
Z n6 5 . 3 9
3 1
G a6 9 . 7 2
3 2
G e7 2 . 5 9
3 3
A s7 4 . 9 2
3 4
S e7 8 . 9 6
3 5
B r7 9 . 9 0
3 6
K r8 3 . 8 0
53 7
R b8 5 . 4 7
3 8
S r8 7 . 6 2
3 9
Y8 8 . 9 1
4 0
Z r9 1 . 2 2
4 1
N b9 2 . 9 1
4 2
M o9 5 . 9 4
4 3
T c( 9 8 )
4 4
R u1 0 1 . 1
4 5
R h1 0 2 . 9
4 6
P d1 0 6 . 4
4 7
A g1 0 7 . 9
4 8
C d1 1 2 . 4
4 9
I n1 1 4 . 8
5 0
S n1 1 8 . 7
5 1
S b1 2 1 . 8
5 2
T e1 2 7 . 6
5 3
I1 2 6 . 9
5 4
X e1 3 1 . 3
65 5
C s1 3 2 . 9
5 6
B a1 3 7 . 3
5 7
L a *1 3 8 . 9
7 2
H f1 7 8 . 5
7 3
T a1 8 0 . 9
7 4
W1 8 3 . 9
7 5
R e1 8 6 . 2
7 6
O s1 9 0 . 2
7 7
I r1 9 0 . 2
7 8
P t1 9 5 . 1
7 9
A u1 9 7 . 0
8 0
H g2 0 0 . 5
8 1
T l2 0 4 . 4
8 2
P b2 0 7 . 2
8 3
B i2 0 9 . 0
8 4
P o( 2 1 0 )
8 5
A t( 2 1 0 )
8 6
R n( 2 2 2 )
78 7
F r( 2 2 3 )
8 8
R a( 2 2 6 )
8 9
A c ~( 2 2 7 )
1 0 4
R f( 2 5 7 )
1 0 5
D b( 2 6 0 )
1 0 6
S g( 2 6 3 )
1 0 7
B h( 2 6 2 )
1 0 8
H s( 2 6 5 )
1 0 9
M t( 2 6 6 )
1 1 0
- - -( )
1 1 1
- - -( )
1 1 2
- - -( )
1 1 4
- - -( )
1 1 6
- - -( )
1 1 8
- - -( )
L a n t h a n i d eS e r i e s *
5 8
C e1 4 0 . 1
5 9
P r1 4 0 . 9
6 0
N d1 4 4 . 2
6 1
P m( 1 4 7 )
6 2
S m1 5 0 . 4
6 3
E u1 5 2 . 0
6 4
G d1 5 7 . 3
6 5
T b1 5 8 . 9
6 6
D y1 6 2 . 5
6 7
H o1 6 4 . 9
6 8
E r1 6 7 . 3
6 9
T m1 6 8 . 9
7 0
Y b1 7 3 . 0
7 1
L u1 7 5 . 0
A c t i n i d e S e r i e s ~9 0
T h2 3 2 . 0
9 1
P a( 2 3 1 )
9 2
U( 2 3 8 )
9 3
N p( 2 3 7 )
9 4
P u( 2 4 2 )
9 5
A m( 2 4 3 )
9 6
C m( 2 4 7 )
9 7
B k( 2 4 7 )
9 8
C f( 2 4 9 )
9 9
E s( 2 5 4 )
1 0 0
F m( 2 5 3 )
1 0 1
M d( 2 5 6 )
1 0 2
N o( 2 5 4 )
1 0 3
L r( 2 5 7 )
The online data basehydpark.ca.sandia.gov
lists over 2000 elements, compounds and alloys that form hydrides.
G. J. Thomas
Where do we start? G r o u p
P e r i o dI A V I I I A
11
H1 . 0 0 8 I I A I I I A I V A V A V I A V I I A
2
H e4 . 0 0 3
23
L i6 . 9 4 1
4
B e9 . 0 1 2
5
B1 0 . 8 1
6
C1 2 . 0 1
7
N1 4 . 0 1
8
O1 6 . 0 0
9
F1 9 . 0 0
1 0
N e2 0 . 1 8
31 1
N a2 2 . 9 9
1 2
M g2 4 . 3 1 I I I B I V B V B V I B V I I B - - - - - - - V I I I - - - - - I B I I B
1 3
A l2 6 . 9 8
1 4
S i2 8 . 0 9
1 5
P3 0 . 9 7
1 6
S3 2 . 0 7
1 7
C l3 5 . 4 5
1 8
A r3 9 . 9 5
41 9
K3 9 . 1 0
2 0
C a4 0 . 0 8
2 1
S c4 4 . 9 6
2 2
T i4 7 . 8 8
2 3
V5 0 . 9 4
2 4
C r5 2 . 0 0
2 5
M n5 4 . 9 4
2 6
F e5 5 . 8 5
2 7
C o5 8 . 4 7
2 8
N i5 8 . 6 9
2 9
C u6 3 . 5 5
3 0
Z n6 5 . 3 9
3 1
G a6 9 . 7 2
3 2
G e7 2 . 5 9
3 3
A s7 4 . 9 2
3 4
S e7 8 . 9 6
3 5
B r7 9 . 9 0
3 6
K r8 3 . 8 0
53 7
R b8 5 . 4 7
3 8
S r8 7 . 6 2
3 9
Y8 8 . 9 1
4 0
Z r9 1 . 2 2
4 1
N b9 2 . 9 1
4 2
M o9 5 . 9 4
4 3
T c( 9 8 )
4 4
R u1 0 1 . 1
4 5
R h1 0 2 . 9
4 6
P d1 0 6 . 4
4 7
A g1 0 7 . 9
4 8
C d1 1 2 . 4
4 9
I n1 1 4 . 8
5 0
S n1 1 8 . 7
5 1
S b1 2 1 . 8
5 2
T e1 2 7 . 6
5 3
I1 2 6 . 9
5 4
X e1 3 1 . 3
65 5
C s1 3 2 . 9
5 6
B a1 3 7 . 3
5 7
L a *1 3 8 . 9
7 2
H f1 7 8 . 5
7 3
T a1 8 0 . 9
7 4
W1 8 3 . 9
7 5
R e1 8 6 . 2
7 6
O s1 9 0 . 2
7 7
I r1 9 0 . 2
7 8
P t1 9 5 . 1
7 9
A u1 9 7 . 0
8 0
H g2 0 0 . 5
8 1
T l2 0 4 . 4
8 2
P b2 0 7 . 2
8 3
B i2 0 9 . 0
8 4
P o( 2 1 0 )
8 5
A t( 2 1 0 )
8 6
R n( 2 2 2 )
78 7
F r( 2 2 3 )
8 8
R a( 2 2 6 )
8 9
A c ~( 2 2 7 )
1 0 4
R f( 2 5 7 )
1 0 5
D b( 2 6 0 )
1 0 6
S g( 2 6 3 )
1 0 7
B h( 2 6 2 )
1 0 8
H s( 2 6 5 )
1 0 9
M t( 2 6 6 )
1 1 0
- - -( )
1 1 1
- - -( )
1 1 2
- - -( )
1 1 4
- - -( )
1 1 6
- - -( )
1 1 8
- - -( )
L a n t h a n i d eS e r i e s *
5 8
C e1 4 0 . 1
5 9
P r1 4 0 . 9
6 0
N d1 4 4 . 2
6 1
P m( 1 4 7 )
6 2
S m1 5 0 . 4
6 3
E u1 5 2 . 0
6 4
G d1 5 7 . 3
6 5
T b1 5 8 . 9
6 6
D y1 6 2 . 5
6 7
H o1 6 4 . 9
6 8
E r1 6 7 . 3
6 9
T m1 6 8 . 9
7 0
Y b1 7 3 . 0
7 1
L u1 7 5 . 0
A c t i n i d e S e r i e s ~9 0
T h2 3 2 . 0
9 1
P a( 2 3 1 )
9 2
U( 2 3 8 )
9 3
N p( 2 3 7 )
9 4
P u( 2 4 2 )
9 5
A m( 2 4 3 )
9 6
C m( 2 4 7 )
9 7
B k( 2 4 7 )
9 8
C f( 2 4 9 )
9 9
E s( 2 5 4 )
1 0 0
F m( 2 5 3 )
1 0 1
M d( 2 5 6 )
1 0 2
N o( 2 5 4 )
1 0 3
L r( 2 5 7 )
Transition metals (IIIB, IVB, VB) form metallic bond hydrides
• moderate P,T properties• equilibrium properties can be
adjusted over a wide range by alloying.
• Interstitial H: good kinetics• low capacity (heavy metals,
modest H/M)
G. J. Thomas
Where do we start? G r o u p
P e r i o dI A V I I I A
11
H1 . 0 0 8 I I A I I I A I V A V A V I A V I I A
2
H e4 . 0 0 3
23
L i6 . 9 4 1
4
B e9 . 0 1 2
5
B1 0 . 8 1
6
C1 2 . 0 1
7
N1 4 . 0 1
8
O1 6 . 0 0
9
F1 9 . 0 0
1 0
N e2 0 . 1 8
31 1
N a2 2 . 9 9
1 2
M g2 4 . 3 1 I I I B I V B V B V I B V I I B - - - - - - - V I I I - - - - - I B I I B
1 3
A l2 6 . 9 8
1 4
S i2 8 . 0 9
1 5
P3 0 . 9 7
1 6
S3 2 . 0 7
1 7
C l3 5 . 4 5
1 8
A r3 9 . 9 5
41 9
K3 9 . 1 0
2 0
C a4 0 . 0 8
2 1
S c4 4 . 9 6
2 2
T i4 7 . 8 8
2 3
V5 0 . 9 4
2 4
C r5 2 . 0 0
2 5
M n5 4 . 9 4
2 6
F e5 5 . 8 5
2 7
C o5 8 . 4 7
2 8
N i5 8 . 6 9
2 9
C u6 3 . 5 5
3 0
Z n6 5 . 3 9
3 1
G a6 9 . 7 2
3 2
G e7 2 . 5 9
3 3
A s7 4 . 9 2
3 4
S e7 8 . 9 6
3 5
B r7 9 . 9 0
3 6
K r8 3 . 8 0
53 7
R b8 5 . 4 7
3 8
S r8 7 . 6 2
3 9
Y8 8 . 9 1
4 0
Z r9 1 . 2 2
4 1
N b9 2 . 9 1
4 2
M o9 5 . 9 4
4 3
T c( 9 8 )
4 4
R u1 0 1 . 1
4 5
R h1 0 2 . 9
4 6
P d1 0 6 . 4
4 7
A g1 0 7 . 9
4 8
C d1 1 2 . 4
4 9
I n1 1 4 . 8
5 0
S n1 1 8 . 7
5 1
S b1 2 1 . 8
5 2
T e1 2 7 . 6
5 3
I1 2 6 . 9
5 4
X e1 3 1 . 3
65 5
C s1 3 2 . 9
5 6
B a1 3 7 . 3
5 7
L a *1 3 8 . 9
7 2
H f1 7 8 . 5
7 3
T a1 8 0 . 9
7 4
W1 8 3 . 9
7 5
R e1 8 6 . 2
7 6
O s1 9 0 . 2
7 7
I r1 9 0 . 2
7 8
P t1 9 5 . 1
7 9
A u1 9 7 . 0
8 0
H g2 0 0 . 5
8 1
T l2 0 4 . 4
8 2
P b2 0 7 . 2
8 3
B i2 0 9 . 0
8 4
P o( 2 1 0 )
8 5
A t( 2 1 0 )
8 6
R n( 2 2 2 )
78 7
F r( 2 2 3 )
8 8
R a( 2 2 6 )
8 9
A c ~( 2 2 7 )
1 0 4
R f( 2 5 7 )
1 0 5
D b( 2 6 0 )
1 0 6
S g( 2 6 3 )
1 0 7
B h( 2 6 2 )
1 0 8
H s( 2 6 5 )
1 0 9
M t( 2 6 6 )
1 1 0
- - -( )
1 1 1
- - -( )
1 1 2
- - -( )
1 1 4
- - -( )
1 1 6
- - -( )
1 1 8
- - -( )
L a n t h a n i d eS e r i e s *
5 8
C e1 4 0 . 1
5 9
P r1 4 0 . 9
6 0
N d1 4 4 . 2
6 1
P m( 1 4 7 )
6 2
S m1 5 0 . 4
6 3
E u1 5 2 . 0
6 4
G d1 5 7 . 3
6 5
T b1 5 8 . 9
6 6
D y1 6 2 . 5
6 7
H o1 6 4 . 9
6 8
E r1 6 7 . 3
6 9
T m1 6 8 . 9
7 0
Y b1 7 3 . 0
7 1
L u1 7 5 . 0
A c t i n i d e S e r i e s ~9 0
T h2 3 2 . 0
9 1
P a( 2 3 1 )
9 2
U( 2 3 8 )
9 3
N p( 2 3 7 )
9 4
P u( 2 4 2 )
9 5
A m( 2 4 3 )
9 6
C m( 2 4 7 )
9 7
B k( 2 4 7 )
9 8
C f( 2 4 9 )
9 9
E s( 2 5 4 )
1 0 0
F m( 2 5 3 )
1 0 1
M d( 2 5 6 )
1 0 2
N o( 2 5 4 )
1 0 3
L r( 2 5 7 )
Group IA, IIA elements form ionic or covalent bond hydrides
•high energy bond: high T, low P•high capacity (lightweight materials)
G. J. Thomas
Where do we start? G r o u p
P e r i o dI A V I I I A
11
H1 . 0 0 8 I I A I I I A I V A V A V I A V I I A
2
H e4 . 0 0 3
23
L i6 . 9 4 1
4
B e9 . 0 1 2
5
B1 0 . 8 1
6
C1 2 . 0 1
7
N1 4 . 0 1
8
O1 6 . 0 0
9
F1 9 . 0 0
1 0
N e2 0 . 1 8
31 1
N a2 2 . 9 9
1 2
M g2 4 . 3 1 I I I B I V B V B V I B V I I B - - - - - - - V I I I - - - - - I B I I B
1 3
A l2 6 . 9 8
1 4
S i2 8 . 0 9
1 5
P3 0 . 9 7
1 6
S3 2 . 0 7
1 7
C l3 5 . 4 5
1 8
A r3 9 . 9 5
41 9
K3 9 . 1 0
2 0
C a4 0 . 0 8
2 1
S c4 4 . 9 6
2 2
T i4 7 . 8 8
2 3
V5 0 . 9 4
2 4
C r5 2 . 0 0
2 5
M n5 4 . 9 4
2 6
F e5 5 . 8 5
2 7
C o5 8 . 4 7
2 8
N i5 8 . 6 9
2 9
C u6 3 . 5 5
3 0
Z n6 5 . 3 9
3 1
G a6 9 . 7 2
3 2
G e7 2 . 5 9
3 3
A s7 4 . 9 2
3 4
S e7 8 . 9 6
3 5
B r7 9 . 9 0
3 6
K r8 3 . 8 0
53 7
R b8 5 . 4 7
3 8
S r8 7 . 6 2
3 9
Y8 8 . 9 1
4 0
Z r9 1 . 2 2
4 1
N b9 2 . 9 1
4 2
M o9 5 . 9 4
4 3
T c( 9 8 )
4 4
R u1 0 1 . 1
4 5
R h1 0 2 . 9
4 6
P d1 0 6 . 4
4 7
A g1 0 7 . 9
4 8
C d1 1 2 . 4
4 9
I n1 1 4 . 8
5 0
S n1 1 8 . 7
5 1
S b1 2 1 . 8
5 2
T e1 2 7 . 6
5 3
I1 2 6 . 9
5 4
X e1 3 1 . 3
65 5
C s1 3 2 . 9
5 6
B a1 3 7 . 3
5 7
L a *1 3 8 . 9
7 2
H f1 7 8 . 5
7 3
T a1 8 0 . 9
7 4
W1 8 3 . 9
7 5
R e1 8 6 . 2
7 6
O s1 9 0 . 2
7 7
I r1 9 0 . 2
7 8
P t1 9 5 . 1
7 9
A u1 9 7 . 0
8 0
H g2 0 0 . 5
8 1
T l2 0 4 . 4
8 2
P b2 0 7 . 2
8 3
B i2 0 9 . 0
8 4
P o( 2 1 0 )
8 5
A t( 2 1 0 )
8 6
R n( 2 2 2 )
78 7
F r( 2 2 3 )
8 8
R a( 2 2 6 )
8 9
A c ~( 2 2 7 )
1 0 4
R f( 2 5 7 )
1 0 5
D b( 2 6 0 )
1 0 6
S g( 2 6 3 )
1 0 7
B h( 2 6 2 )
1 0 8
H s( 2 6 5 )
1 0 9
M t( 2 6 6 )
1 1 0
- - -( )
1 1 1
- - -( )
1 1 2
- - -( )
1 1 4
- - -( )
1 1 6
- - -( )
1 1 8
- - -( )
L a n t h a n i d eS e r i e s *
5 8
C e1 4 0 . 1
5 9
P r1 4 0 . 9
6 0
N d1 4 4 . 2
6 1
P m( 1 4 7 )
6 2
S m1 5 0 . 4
6 3
E u1 5 2 . 0
6 4
G d1 5 7 . 3
6 5
T b1 5 8 . 9
6 6
D y1 6 2 . 5
6 7
H o1 6 4 . 9
6 8
E r1 6 7 . 3
6 9
T m1 6 8 . 9
7 0
Y b1 7 3 . 0
7 1
L u1 7 5 . 0
A c t i n i d e S e r i e s ~9 0
T h2 3 2 . 0
9 1
P a( 2 3 1 )
9 2
U( 2 3 8 )
9 3
N p( 2 3 7 )
9 4
P u( 2 4 2 )
9 5
A m( 2 4 3 )
9 6
C m( 2 4 7 )
9 7
B k( 2 4 7 )
9 8
C f( 2 4 9 )
9 9
E s( 2 5 4 )
1 0 0
F m( 2 5 3 )
1 0 1
M d( 2 5 6 )
1 0 2
N o( 2 5 4 )
1 0 3
L r( 2 5 7 )
Hydrogen can also form complexeswith some elements
G. J. Thomas
Complex hydrides give you another “knob to twist”
• Complex hydrides consist of a H=M complex with additional bonding element(s)
• hydrogen complexes include:– (AlH4)– (alanates)– (BH4)–
– with Group VIII elements• features:
– ionic, covalent, metallic bonding– can have lower formation energy– can have high H/M
• 173 complex hydrides listed on hydpark.ca.sandia.gov
G. J. Thomas
0 2 4 6 8 10 12weight percent hydrogen
Sn(AlH4)4
Ce(AlH4)3
Zr(AlH4)4
In(AlH4)3
Ti(AlH4)4
CsAlH4
Ga(AlH4)3
Ti(AlH4)3
AgAlH4
Fe(AlH4)2
Mn(AlH4)2
Ca(AlH4)2
CuAlH4
Mg(AlH4)2
Na2LiAlH6
Be(AlH4)2
KAlH4
NaAlH4
LiAlH4
incr
easi
ng m
ol. w
eigh
tTotal hydrogen content of some alanates
G. J. Thomas
Issues with complex hydrides
• Reversibility– role of catalyst or dopant
• Thermodynamics– pressure, temperature
• Kinetics– long-range transport of heavy species
• Cyclic stability• Synthesis• Compatibility/safety
only NaAlH4 has been studied in detail to datethis material serves as a model system to better
understand other complex hydrides
G. J. Thomas
Brief history of NaAlH4
• Compound first reported by Finholt & Schlesinger in 1955
• Direct synthesis developed by Ashby (1958) and Clasen (1961)
• Principal use has been as a chemical reducing agent• There have been numerous characterization studies:
(Dymova, Zakharkin, Claudy, Wiberg...)• Reversibility demonstrated by use of Ti catalyst
(Bogdanovic and Schwickardi MH96, JAC 253(1997) 1)this development spurred renewed interest in using
complex hydrides as storage materials
G. J. Thomas
Na Alanate -a reversible complex hydride
• There are five labs within USDOE program during FY02 working on complex-based hydrides, focused mainly on NaAlH4
– Univ. of Hawaii Prof. C. Jensen– Sandia Nat. Lab. Dr. K. Gross– Florida Solar Energy Center Dr. D. Slattery– United Tech. Res. Center Dr. D. Anton– Savannah River Tech. Center Dr. R. Zidan
• These labs have formed a working group tocorrdinate their activities and share information.
G. J. Thomas
Na Alanate -a reversible complex hydride
• There are development projects outside of the US.– B. Bogdanovic, Max Planck Inst., Mulheim, Germany
• GM Opel support– A. Zaluska, L. Zaluski
• recently left McGill Univ. (Canada)• HERA (HydroQuebec, GfE, ShellHydrogen)
– Japan funding development through WENET, AIST
• Ames Laboratory has recently published some work on Li alanate
G. J. Thomas
catalystcatalyst3NaAlH4 Na3AlH6 + 2Al +3H2 3NaH + Al + 3/2H2
0.1
1
10
100
1000
2 2.5 3 3.51000/T
Pres
sure
(atm
)
33o C
110o C
100o C180o C 25o C
Bogdanovic, et alSandia Nat. Lab.
Thermodynamic data
NaAlH4 to Na3AlH6∆Hf = 37 kJ/mol
Na3AlH6 to NaH∆Hf = 47 kJ/mol
melting point
G. J. Thomas
Current studies on NaAlH4
• Mechanisms– experimental– modelling
• catalysts, doping
• mechanical processing
• synthesis
• engineering properties
G. J. Thomas
Understanding NaAlH4 mechanisms will help in developing higher capacity hydrides
NMR shows Ti doping enhances proton mobility
ESR spectracharacterisitic of Ti+3
Decomposition of undoped NaAlH4
G. J. Thomas
Crystal structure and modeling
Ab initio calculations using VASP
Neutron diffractionRietveld refinement
G. J. Thomas
Catalysts/Doping
• Initially, reversibility believed due to catalytic effects.recent evidence, however, indicates bulk doping.
• 3 factors affect hydride performance:(1) catalyst/dopant
• numerous compounds evaluated.• Ti-based most effective.
(2) method of introduction• mechanical mixing (dry process)• wet chemistry• precursor must react with alanate
(3) amount of catalyst/dopant
G. J. Thomas
Catalyst/Doping level affects kineticsNaAlH4
• Initial kinetics exhibit Arrhenius behavior• different activiation energy in doped
material• activation energy constant for 2 mol%
and greater doping• faster kinetics with higher doping levels
(G. Sandrock, K. J. Gross, G. Thomas, JAC 339 (2002) 299)
• Trade-off between faster kinetics and loss of capacity with increasing doping levels
and capacity
G. J. Thomas
Engineering Properties
• Thermal conductivity– similar to IM hydrides
cycling– stable to ~100 cycles
• material compatibility– no issues with Al, SS
• safety– sensitive to impact,
thermal environment with air exposure.
NaAlH 4 +4 mol% Ti - Temperature Profile During 125ÞC/60 atm Charging2nd Absorption
100
120
140
160
180
200
0 0.1 0.2 0.3 0.4 0.5
Time, hrs
Outer Midplane Midradius Midplane Center Midplane
Simulated Bulk Autoignition Test (SBAT)
-10
-5
0
5
10
15
20
25
30
35
40
100 150 200 250 300 350 400 450 500
Reference Temperature, deg F
<<<E
ndot
herm
, deg
F |
Ex
othe
rm, d
egF>
>>
G. J. Thomas
Volumes of 5 kg H2 Systems
100
150
200
250
300
350
400
0 1 2 3 4Number of Cylindrical Tanks
Volu
me
(lite
rs) 20 cm (8 in.)
25 cm (10 in.)30 cm (12 in.)
Tank Diameter
10 cm (4 in.)15 cm (6 in.)20 cm (8 in.)
cryotank 40 cm diameter
High pressure Tanks5000 psi
5 wt.% Alanate
5 kg H2 system volumes
1200 Wh/liter
560 Wh/liter
Target: 1100 Wh/liter
Reformer2005 target
G. J. Thomas
System weights for 5 kg H2
0
50
100
150
200
0 1 2 3 4
Number of Cylinders
Wei
ght (
kg)
alanate
cryotank
compressed gas
5 kg H2 system weights
1100 Wh/kg
1300 Wh/kg
2500 Wh/kg7.5 wt.% tanks
Target: 2000 Wh/kgReformer
2005 target
G. J. Thomas
A complex hydride based on BH4– forms the
basis for a chemical hydride storage system
• Development efforts largely financed privately.– Millenium Cell
an IP company with no plans to manufacture.– Kogakuin Univ., Japan (Prof. S. Suda)
• Both based on borohydride chemistry.– each use different catalyst.
• System has 4-10 wt.% capacity• reversibility a problem with boron-based systems
NaBH4 + 2H2O → NaBO2 + 4H2 + heat
20 - 35% sol.Stabilized with
1-3% NaOH
Borax in NaOH
Proprietarycatalyst
G. J. Thomas
• What’s beyond NaAlH4?– Capacity appears limited to ~5 wt.%– modifications or new complexes needed.
• Some improvements in weight, volume and cost can be realized by better container engineering.
Intermetallic hydrides were studied for thirty years before doped alanates provided a significant
improvement in capacity.
Where do we go from here?
We need to be a little faster!
