Neutrons for Hydrogen Storage: Dynamics - Kinetics - Reactions

A. Borgschulte,1 E. Callini,1 R. Gremaud,1 E. R. Andresen,3 P.Hamm,3 A. J. Ramirez-Cuesta,2 S. I. Orimo,4 A. Züttel1, F. Zamponi,5 M. Woerner,5 T. Elsaesser5

1Empa, Swiss Federal Laboratories for Materials Testing and Research, Hydrogen & Energy, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland

2ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, United Kingdom

3Physikalisch-Chemisches Institut, Universität Zürich, Zürich, Switzerland

4Institute for Materials Research (IMR), Tohoku University, Japan

5Max-Born Institut, Berlin, Germany

2Andreas Züttel, Switzerland, 9/26/20122

Hydrogen – solid interactions

Hydrogen & metal Physisorption Chemisorption

Solid solution (-phase) Hydride (-phase) Complex hydride

3

0 250 500 750 1000 1250 1500-1.2

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0

5

10

15

20

25w

eigh

t cha

nge

(mas

s.%

)

time (min)

pres

sure

(bar

)

0.0 0.5 1.0 1.50.1

1

10

absorption

desorption

LaNi5Hx @ 24.5°C

equi

libriu

m p

ress

ure

(bar

)Hydrogen content x (mass%)

Gravimetric pcT measurements on LaNi5H6

4

Thermostatic properties: hydrogen content, enthalpies and entropy of all involved phases

Empirical kinetics: meta-stable phases (impurities), time dependence of phase changes (hydrogen evolution / uptake)

Important properties in Hydrogen storage in metal hydrides

This is all the industry needs to know to built a hydrogen storage.However,

if we want to know why, or try to design new materials, knowledge of

Crystal structure of all involved phases Morphology, surface structure of all involved phases

Dynamic processes: transient bulk phases Dynamic surface processes Vibrational structure Diffusion

…might be helpful

Empa, , 5

Bragg peak

Phonon side bands

Elastic scattering: E=0Diffraction, SANS

Inelastic scattering: E0Phonons, Magnons,...quantized modes, periodic motions selection rules:Eneutron= Ephononkneutron= kphonon

Quasielastic scattering: E~0stochastic, non-periodicmotions

Elastic, inelastic, quasielastic scattering of neutrons

6

Neutron diffraction … see talks of John Irvine, Bill David…

Empa, , 7

Bragg peak

Phonon side bands

Elastic scattering: E=0Diffraction, SANS

Inelastic scattering: E0Phonons, Magnons,...quantized modes, periodic motions selection rules:Eneutron= Ephononkneutron= kphonon

Quasielastic scattering: E~0stochastic, non-periodicmotions

Elastic, inelastic, quasielastic scattering of neutrons

8

Vibrational Spectroscopy

Raman light scattering

Infrared spectroscopy

Inelastic neutron scattering

LiBD4

LiBH4

HT-LiBH4

S. Gomes, H. Hagemann, K. Yvon, JalCom 346 (2002) 206–210A. Borgschulte, et al., Faraday Discuss. 2011, 151, 213.

Structures of Ca(BH4)2

H = 35 meV/Ca(BH4)2

H = 69 meV/Ca(BH4)2

STHG

Fddd

P42/m

Pbca

F. Buchter et al., J. Phys. Chem. C 113, 17223 (2009).

Total density of phonon states by DFT

kTE

eEgdEkS 1ln

Free energy as a function of temperature

F. Buchter et al., J. Phys. Chem. C 113, 17223 (2009).

Experimental and calculated density of H phonon states

A. Borgschulte, et al., Phys. Rev. B 83, 024102 (2011).

13

BH4-Vacancy

Enjoy the beauty of the theory of diffusion

Li vacancy

= Schottky defect

Ref.: Z. Lodziana, to be published

Empa, , 14

Bragg peak

Phonon side bands

Elastic scattering: E=0Diffraction, SANS

Inelastic scattering: E0Phonons, Magnons,...quantized modes, periodic motions selection rules:Eneutron= Ephononkneutron= kphonon

Quasielastic scattering: E~0stochastic, non-periodicmotions

Elastic, inelastic, quasielastic scattering of neutrons

j

tiQsiQstiinc

k j

tiQsiQsticoh

jjkj eeedteeedt

ddd

)()0()()0(

2

Theory: Scattering of neutrons

j k k+1…j+1…

tisi

FTN

j

tsiQsiQ etQIdtQSeeN

tQI jj

),(

21),(1,

1

)()0(

intermediate scattering function dynamic structure factor

QENS derivative of jump diffusion (I)

N

jj trPtsrP

Nt

trP 1,,1

,

iQretrPdrtQI ,,

G.T.Chudley and R.J. Elliott, Proc. Phys. Soc. 77, 353 (1961)

Lorentzian curve, width /)(Qf

j

j

iQs

N

j

Qs

eN

ttQI

tQIeNt

tQI

1/exp,

,11,1

I(Q,t)

t

22 /)(/)(),(),(

QfQfetQIdtQS ti

FT

S(Q,)

FT

)(Qf

simple case of hydrogen hopping on interstitial sites forming a simple-cubic structure.

2261

0)(lim,1)( sQQfe

NQf

Q

iQs j

22 )6/()( DQQQf

)6/(2 sD

Q is small:

Einstein-Smoucholski equation:

QENS derivative of jump diffusion (II)

QENS-measurements on liquid LiBH4

P. Martelli et al., J. Phys. Chem. A 2010, 114, 10117

/scmK)D(TDQ

25

2

106600

Q-dependence of the width

P. Martelli et al., J. Phys. Chem. A 2010, 114, 10117

-15 -10 -5 0 5 10 15 900 950 1600 1700 1800

Inte

nsity

(arb

. uni

ts)

chemical shift (ppm)

300 K

400 K

3'31

Inte

nsity

(nor

m. u

nits

)

Raman shift (cm-1)

f

300 K

402 K

2

QUENS

NMR Raman

Mobility in LiBH4 by spectroscopy (Rotational diffusion)

principle of “line-shape analysis”signal in frequency space

=Fourier transform of thetime correlation function

(= changes in time)

HT-LiBH4

LT-LiBH4

LT-LiBH4

HT-LiBH4

A. Remhof, et al. Phys. Rev. B 2010, 81, 214304; A. Borgschulte, et al., Faraday Discuss. 2011, 151, 213

energy uncertainty

E

Time and space resolution of spectroscopy

1000 750 500 300 2501E-15

1E-14

1E-13

1E-12

1E-11

1E-10

1E-9

1E-8

1E-7

1E-6

1E-5

1E-4

1E-3250 300 350 400 450 500 550 600 650 700

H in MgH2H in NaH

BH4 in LiBH4

Li in graphite

Li in V2O5

H in LaNi5

H in V

H in Ta

H in Pd

H in Ni

diffu

sion

par

amet

er D

(cm

2 /s)

temperature T (K)

1000/T (10-3 K-1)Comparison:Hydrogen Diffusion

Dtx 4

water in pasta:1 mm in 5 min

H in NiMH batteries~ 10 m in min

Li in Li-ion batteries~ m in min

H in ionic/covalent hydridesm in days

Li in LiBH4

H exchange: 10 orders lower

1 2 3 4

0.1ps

0.1 s

H in complex hydridesm in days

23

BH4-Vacancy

There is more than diffusion taking place

Li vacancy

= Schottky defect

Ref.: Z. Lodziana, to be published

slowdetector

probebeam

pumpbeam

sample

delay

Measurement of the time correlation function directly:Pump – probe experiments

S(Q,)

FT

I(Q,t)

t

IR-pump excites a vibration; IR-probe measures the ensuing changes

|10>

|00>

|20>

(ps time resolution, IR-probe: 100 fs)

Pum

p fre

quen

cy [a

.u.]

Probe frequency [a.u.]

2D-IR pump-probe spectrometer (“femto-chemistry”)

Decay of stretching modes 1.5 ps

Rise of temperature 3 ps (libration + external)

1.5 <> 3.0, so there must be intermediate step (bending)

0 10 20 30

0.00

0.02

0.04

0.06

probe = 2186 cm-1

Exp. fit, = 3.0 ps

A

[mO

D]

Delay [ps]

0 10 20 300.0

0.5

1.0

1.5

2.0 probe = 1668 cm-1

Fit, = 1.6 ps

A

[mO

D]

Delay [ps]

IR-pump, t=0

E.R. Andresen, R. Gremaud, A. Borgschulte, A.J. Ramirez-Cuesta, A. Züttel, and P. Hamm, J. Phys. Chem. A 113, 12838 (2009)

Vibrational relaxation pathway

Polarization experiments probing reorientation

highintensity

lowintensity

pump probe

Polarization-dependent measurements:Reorientational motions

1660 1680 1700 1720 1740 1760 1780-100-80-60-40-20

020406080

100 0

20

40

60

80

100

0.1 1 100.0

0.2

0.4

010203040506070

ESA

A [

OD

]

Probe frequency [cm-1]

1 ps 4 ps 2 ps 8 ps

A [

OD

]

Magic-angle

probe = 1667.6 cm-1

= 1.6 ps

Anis

otro

pyDelay [ps]

Averaged anisotropy

probe = 1653.5 - 1672.3 cm-1

Abso

rban

ce [m

OD

]

2para perp

para perp

I IA

I I

Neither BH4 rotation, northermal motion observedwithin 5 ps

Anisotropy

R. Gremaud,et al., Materials Research Society Symposium Proceedings 1216, pp. 111-116 (2010).

Comparison with QENS

5 ps

R. Gremaud,et al., Materials Research Society Symposium Proceedings 1216, pp. 111-116 (2010).A. Remhof et al. Phys. Rev. B 81, 214304 (2010)

LiBH4-LT

LiBH4-HT

Femtosecond X-ray diffraction

Woerner et al. J. Chem. Phys. 133, 064509 (2010)

Zamponi et al. Opt. Express 18, 947 (2010)

z = 2.14 => Li0.86+

z = 9.86 => BD40.86-

A fs photon pulse runs through a LiBH4 crystal

with/without

electric field

BH4-Li+

Electric field from Laser, E = 1.5 eV << Egap Laser intensity ~4x1011 W/cm2

F. Buchter et al. Phys. Rev. B 83, 064107 (2011).

Femtosecond X-ray diffraction on LiBH4

J. Stingl, F. Zamponi, B. Freyer, M. Woerner, T. Elsaesser, and A. Borgschulte, accepted by PRL (2012)

Is this possible with neutrons?

Time-resolved quasielastic neutron scattering studies of native photosystems

J. Pieper et al. Phys. Rev. Lett. 100, 228103 (2008)

NMR

Neutrons?IR/UV-vis

Raman

XRD

EPR

in

out

XAS

Mössbauerproduct detectionIRMSGC…

Operando approach

Time-resolution by modulated excitation spectroscopy

see, e.g., D. Ferri et al, Phys. Chem. Chem. Phys. 2010, 12, 5634;C. F. J. König et al., JPC ASAP (2012).

Neutron scattering gives an insight into hydrogen storage in hydrides

Neutron diffraction and inelastic neutron scattering are perfect tools for equilibrium properties

Simple (rotational diffusion, jump diffusion) and fast (ps~ns) time dependent processes can be investigated by quasi-elastic neutron scattering

modulation excitation spectroscopy might bridge the gap

optical spectroscopy is the perfect complementary method

Summary and Outlook

37

1. After 1850: Rate constants:(Ludwig Wilhelmy, Poggendorfs Ann. 81 (1850) 413, 499)Quantitative time dependence

2. After ~1900: Reaction mechanisms and Elementary ReactionsIncreasing detail, complexity, sophistication(van’t Hoff, Arrhenius, Amsterdam 1903)

3. After 1950: 1st time resolved experimentsRelaxation techniques, Flash Photolysis, Shock waves, chemical exchange by NMR, molecular beams

4. After ~1960: Laser Pump-Probe Techniques=> ns (1960) => ps (1970) => x fs (1980) => fs (1990) => as (2000)

M. Quack, Chimia 57 (2003) 147–160

Reaction dynamics on simple systems

383

EQUILIBRIUM Phase diagram Hydrogen in Metals

H(

½ (H2)=

H(

½ (H2)=

-Phase: Solid Solution -Phase: Hydride Phase

MinxxxGi

ii

is temperature dependent => Van ‘t Hoff R

SRTH

pp H

0

021 2ln

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

0.01

0.1

1

10

100

p(b

ar)

x (H/M)

0 2 4 6 80.1

1

10

100

LiBH4 @ T = 491°C NaAlH4 @ T = 130°C LiNH2 @ T = 260°C

3 NaH + Al + 3/2 H2 <= Na3AlH6

<= LiNH2 + LiHLi2NH + H2

Na3AlH6 + 2 Al + 3/2 H2 <= 3NaAlH4

LiH + B + 3/2 H2 <= LiBH4

hydr

ogen

pre

ssur

e (b

ar)

m/m (%)

Phase diagram Hydrogen in Complex Hydrides

Ref.: Ce-doped NaAlH4 (Lohstroh2007), LiBH4 (Mauron2007), and LiNH2+LiH (David2007)

3 NaAlH4

=> Na3AlH6 + 2Al + 3 H2

=> 3 NaH + 3Al + 9/2 H2

= 5.6 mass %

50 100 150 200 250 300-6

-5

-4

-3

-2

-1

0

mas

s lo

ss (%

)

temperature (°C)50 100 150 200 250 300

-6

-5

-4

-3

-2

-1

0

mas

s lo

ss (%

)

temperature (°C)

Thermo - Desorption of pure and Ti-doped NaAlH4

Constant p = 1.5bar H2,Heating rate 1 K/min

B. Bogdanovic, M. Schwickardi, J. Alloys Compd. 253–254 (1997) 1.

41

Small-angle neutron scattering

S. Sartori et al. Nanotechnology 20 (2009) 505702

42

Hydrogen supply

Ar-glove box

Balance electronics

sam

ple

balance

Measurement principle to correct for buoyancy contribution to the sample mass.

Gravimetric hydrogen sorption measurements

“Sieverts” Pressure automation

bala

nce

(100

...20

0 m

l)

pressure 0...200 bars

vacuum

hydrogen

E E

p

valve , 1 2

time