329 Kandavel

Optimization of AB2 - type alloy composition with superior

hydrogen storage properties for stationary applications

Kandavel Manickam, David Grant and Gavin Walker

Energy and Sustainability Research Division

Faculty of Engineering

The University of Nottingham

ICAER 2013, IIT Bombay

Outline

1. Introduction

2. Results of AB2 type alloys

• Materials preparation and characterization

• P-C-I measurements

• Thermodynamics

• Hydrogenation kinetics

• HP-DSC studies of alloys

3. Summary of results and conclusions

Year Limited reserves CO2 Global warming

Alternative clean energies

Hydrogen can be a clean energy carrier

• High energy density (three time higher than the fossil fuels)

• Environmental friendliness (H2O)

Introduction

Hydrogen economy

• Production

• Storage

• Utilization

CPV- 15 kWp

120 kWh per day

End

use

r

Electrolyser H store

Bio gas plant (14 m3) Genset

14 kWh 7.5 kWh

Hydrogen

7 kWh

16 kWh

90 kWh

12 kWh

22 kWh

Bio waste

2520 litres

14000 litres

2350 litres

BioCPV

• Indo – UK BURD (Bridging the Urban and Rural Divide) Project

• Integration of different types of energy sources and energy storage technologies

Vill

age e

lectr

ific

ation

Materials selection requirements

Hydrogen storage

• 7.5 kWh(H2) : 225 g H2

• equivalent to 2520 litres (stp)

• Solid State Storage

• 15 kg AB alloy (1.6 wt %)

• 13 kg of AB2 alloy (1.8 wt %)

Requirements

Kinetics

1 g H2/min

Commercial Hydralloy C - AB2 alloy • Plateau Pressure : 13 bar • Capacity : 1.3 wt %

Aim of the present work

• AB2 type Laves phase alloys

• Composition variation to improve

hydrogen storage properties

• Effect of non-stoichiometry on the

hydrogen storage properties

• Identification of suitable composition

for the BioCPV application

30 40 50 60 70

30 40 50 60 70

x = 0

Inte

nsity (

arb

. u

nits)

2

x = 0.1

(112)

(004)

(200)

(201)

(103)

(110)

(202)

(104)

(213)

(302)

(205)

x = 0.05

x = 0.075

• Single phase formation

• Hexagonal structure (C14)

• space group P63/mmc

0.00 0.04 0.08 0.12169.0

169.5

170.0

170.5

171.0

171.5

172.0

A1+x

B2

Un

itce

ll vo

lum

e (Å

3)

x in A1+x

B2

A1+xB2(x = 0, 0.05, 0.075 and 0.1)

Synthesis & Characterization

Composition is similar to initial composition (± 1%)

x = 0 x = 0.05

x = 0.075 x = 0.1

Hydrogen storage

Pressure – Composition Isotherms

0.0 0.4 0.8 1.2 1.6 2.00.01

0.1

1

10

100

Equili

birum

Pre

ssure

(bar)

Hydrogen concentration (wt %)

32 oC

50 oC

60 oC

70 oC

A1.05

B2

Plateau pressure

α

α phase

α+β

α+β phase

β

β phase

2.1 wt %

0.0 0.4 0.8 1.2 1.6 2.00.01

0.1

1

10

100

0.0 0.4 0.8 1.2 1.6 2.00.01

0.1

1

10

100

32 oC

50 oC

60 oC

70 oC

Dehydrogenation

Eq

uili

biru

m P

ressu

re (

ba

r)

Hydrogen concentration (wt %)

32 oC

50 oC

60 oC

70 oC

Hydrogenation

Pressure – Composition Isotherms

1 bar

15 bar

1.55 wt %

Working capacity (1 to 15 bar) at 32 oC ~ 1.55 wt %

A1.05B2

0.0 0.4 0.8 1.2 1.6 2.00.01

0.1

1

10

100

Eq

uili

briu

m P

ressu

re (

ba

r)

Hydrogen Concentration (wt %)

x = 0

x = 0.05

x = 0.075

x = 0.1

A1+x

B2

T = 32 oC

Pressure – Composition Isotherms

0.00 0.05 0.100.4

0.8

1.2

1.6

2.0

2.4

Pla

tea

u p

ressu

re (

ba

r)

Hyd

rog

en

co

nce

nta

rtio

n (

wt

%)

x in A1+x

B2

Storage capacity

Working capacity

0.00 0.05 0.10

0

4

8

12

16

20

Plateau pressure

Increase in storage capacity

• Modification of chemical

environment of interstitial

sites

• Size of the interstitial sites

Rietveld analysis and neutron

diffraction

0.0028 0.0030 0.0032 0.0034

0.8

1.6

2.4

0.0028 0.0030 0.0032 0.00340.0

0.8

1.6

2.4

x = 0.05

x = 0.075

x = 0.1

1/T (1/K)

Hydrogenation

ln P

H2

ln P

H2

x = 0.05

x = 0.075

x = 0.1

Dehydrogenation

van’t Hoff relation : 𝑙𝑛𝑃𝐻2 =

∆𝐻

𝑅𝑇 −

∆𝑆

𝑅

Thermodynamics

Hydrogenation

ΔH = - 25 to -28 kJ/mol H2

ΔS = - 92 to -100 J/K/mol H2

Dehydrogenation

ΔH = 28 to 32 kJ/mol H2

ΔS = 94 to 112 J/K/mol H2

0 20 40 60 80 100

1.0

1.5

2.0

32 oC

50 oC

60 oC

70 oC

Hydro

gen C

oncentr

ation (

wt

%)

Time (min)

A1.05

B2

Hydrogenation Kinetics

0 20 40 60 80 1000

1

2

3

4

5

6

32 oC

50 oC

60 oC

70 oC

- ln

(1

-F)

Time (min)

A1.05

B2

Avrami-Erofeev rate eq: F = 1- exp(-ktn); n = 0.54 to 3

First order rate equation : - ln(1-F) = kt

α+β

β

0.0028 0.0030 0.0032 0.0034

-1.4

-0.7

0.0

lnk vs 1/T

ln k

1/T (1/K)

α+β phase Arrhenius relation

k = k0 exp(-Ea/kbT)

Ea : 24 ± 1 kJ/mol

0.0028 0.0030 0.0032 0.0034

-30.6

-30.0

-29.4

ln D vs 1/T

ln D

1/T (1/K)

β phase

kd=π2𝐷

𝑟2

r = 5 μm

Arrhenius relation

D = D0 exp(-Ea/kbT)

Ea : 29 ± 1 kJ/mol

Working Capacity

50 100 150 200 250

-0.1

0.0

0.1

0.2

DS

C H

ea

t flo

w (

mW

/mg

)

Temperature (oC)

20 bar

16 bar

12 bar

8 bar

A1.05

B2

Dehydrogenation

Hydrogenation

Hydrogen gas

Heating rate = 5 oC/min

Flow rate = 100 ml/min

High Pressure DSC

A2B2 Interstitial sites: 24l, 12k, 6h1, 6h2

Low temperature peak : 24l and 6h1

High temperature peak : 12k and 6h2

Hydrogenation

ΔH = - 29 ± 2 kJ/mol H2

ΔS = - 100 ± 4 J/K/mol H2

Dehydrogenation

ΔH = 32 ± 4 kJ/mol H2

ΔS = 117 ± 9 J/K/mol H2

0.0026 0.0028 0.0030

1.4

2.1

2.8

A1.05

B2

Hydrogenation

Dehydrogenationln

PH

2

1/T (1/K)

𝑙𝑛𝑃𝐻2 =

∆𝐻

𝑅𝑇 −

∆𝑆

𝑅 van’t Hoff relation :

Validation of PCI measurements

Alloy Plateau slope factor

ln(P2/P1)

ΔH

(kJ/mol H2)

ΔS

(J/K/mol H2)

ΔH

(kJ/mol H2)

ΔS

(J/K/mol H2)

Alloy 1 (x = 0) 2.7 - - - 29 ± 2

- 100 ± 5

Alloy 2 (x = 0.05) 2.4 - 26 ± 2 - 98 ± 5 - 29 ± 2 - 100 ± 4

Alloy 3 (x = 0.075)

2.2 - 25 ± 1 - 92 ± 3 -26 ± 3 - 96 ± 8

Alloy 4 (x = 0.1)

1.9 - 28 ± 1 - 100 ± 2 - 28 ± 1 - 99 ± 1

PCI measurements DSC measurements

Summary of results

Alloy Plateau pressure

(bar)

32 oC 50 oC

Max. Storage capacity (wt%)

@ ~ 35 bar

Storage capacity at 15 bar

Residual storage capacity (1 bar)

Working capacity (15 to 1

bar)

Charge time : 95

% (min)

Alloy 1 (x = 0) 6.0 3.2

1.7 1.6 0.3 1.3 6

Alloy 2 (x = 0.05) 5.3 8.2 2.8 5.6

2.1 1.85 0.3 1.55 5

Alloy 3 (x = 0.075) 3.0 5.4 1.7 3.5

2.1 2.0 0.55 1.45 5

Alloy 4 (x = 0.1) 2.2 4.1 1.4 2.4

2.2 2.1 0.7 1.4 5

Summary of results

Conclusions

Single phase non-stoichiometric AB2 Laves phase alloys have

synthesized successfully

Alloy 2 (x = 0.05) is most promising for the BioCPV application

Working capacity reached within 5 min at 32 °C

16 % increase in

storage capacity

than Hydralloy C

Interstitial sites can be

modified by preparing

non stoichiometric

alloys

Thank you

Acknowledgement

- Research group members

[email protected]

[email protected]

[email protected]