li-al double-cation borohydrides for hydrogen storage · a high hydrogen density (17.2 wt%). our...

Li-Al double-cation borohydrides for hydrogen

storage

Mehmet Şimşek, Gazi University, Faculty of Science, Physics Department,

Teknikokullar/Ankara, TÜRKİYE

1Şakir Erkoç çalıştayı,07Ekim 2013,ODTÜ-

ANKARA

Objectives

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Recently synthesised complex Al-Li-tetrahydroborate, Al3Li4(BH4)13 and

its derivatives have been investigated by DFT method.

Calculated electronic structure of Al3Li4(BH4)13 indicates that it has

insulator properties.

At very low desorption temperature (70 ⁰C), Al3Li4(BH4)13 combine with

a high hydrogen density (17.2 wt%).

Our density functional theory approximation results revealed that

Al3Li4(BH4)13 and AlLi(BH4)4 are very promising multifunctional materials

for a wide range of hydrogen storage technologies and also for solid state

electronics.

Şakir Erkoç çalıştayı,07Ekim 2013,ODTÜ-ANKARA


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Is hydrogen a good energy carrier?

• Highly abundant– Electrolysis of water 1m³(H2O)→

108.7 Kg(H2)

• Clean– Oxidation product is H2O

• Solid State energy carriers

• High energy density

http://www1.eere.energy.gov/hydrogenandfuelcells

Several hydrogen storage technologies and their operating conditions*.

• Liquid hydrogen (100wt% (at ~-250 ⁰C) • Activated carbon(6-8wt% at ~-200 ⁰C)• Intersititial metal hydrides(~2wt% at ~0-30 ⁰C)• Compressed hydrogen (100wt% at ~25 ⁰C)• Metal-Borohydrides (6-18wt% at ~70-350 ⁰C)• Salt like metal hydrides (~8wt% at ~330 ⁰C)• High temperature Water splitting(11wt% more than 500-1000 ⁰C)

• http://www1.eere.energy.gov/hydrogenandfuelcells


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*R.Helmolt, U. Eberle, J. Power Sources, 165,(2007)833

Two different Storage:

Density: >100 kg/m3

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Solid state H2 storage Compressed H2 storage

~35 kg/m3

Requirements of the solid state storage material

1) High H2 density > 6 wt.% H2 (DOE)*

2) Low temperature

3) Reversibility

4) Environmental

5) portable

http://www.hydrogen.energy.gov


http://www.hydrogen.energy.gov/

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Amides–hydridesLiNH2 + 2LiH = Li2NH + LiH + H2 = Li3N + 2H2 10.5, 150–450CaNH+CaH2=Ca2NH+H2 2.1, 350–650 Mg(NH2)2 + 2LiH = Li2Mg(NH)2 + 2H2 5.6, 100–250 3Mg(NH2)2 + 8LiH = 4Li2NH + Mg3N2 + 8H2 6.9, 150–300 Mg(NH2)2 + 4LiH = Li3N + LiMgN + 4H2 9.1, 150–300 2LiNH2 + LiBH4 → “Li3BN2H8” → Li3BN2 + 4H2 11.9, 150–350 Mg(NH2)2 + 2MgH2 → Mg3N2 + 4H2 7.4, 200- 3802LiNH2 + LiAlH4 → LiNH2 + 2LiH + AlN + 2H2 = Li3A +N2 + 4H2 5.0 ,200-500 3Mg(NH2)2 + 3LiAlH4 → Mg3N2 + Li3AlN2 + 2AlN+12H2 8.5, 200-350 2LiNH2 + CaH2 = Li2Ca(NH)2 + 2H2 4.5, 100–330 4LiNH2 + 2Li3AlH6 → Li3AlN2 + Al +2Li2NH + 3LiH + 15/2H2 7.5, 100–500 2Li4BN3H10 + 3MgH2 → 2Li3BN2 + Mg3N2 + 2 LiH + 12H2 9.2, 100–400 Borohydrides2LiBH4 → 2LiH + 2B + 3H2 13.6 , 200–550 2LiBH4 + MgH2 =2LiH + MgB2 + 4H2 11.5, 270–440 Mg(BH4)2 → MgB2 + 4H2 14.8 290–500 3Mg(BH4)2•2(NH3) → Mg3B2N4 + 2BN +2B + 21H2 15.9, 100–400 Ca(BH4)2 → CaH2 + 2B + 3H2 8.6, 300–500 Zn(BH4)2 → Zn + B2H6 + H2 2.1,90–140 Ammonia borane and amidoboranesnNH3BH3 → (NH2BH2)n + nH2 → (NHBH)n + 2nH2 12.9,70–200 LiNH2BH3 → LiNBH + 2H2 10.9, 75–95NaNH2BH3 → NaNBH + 2H2 7.5, 80–90Ca(NH2BH3)2 → Ca(NBH)2 + 4H2 8.0, 90–245

Well known Complex hydrides(reaction ,wt. and temperature)

P.Chen and M.Zhu, Materialstoday, 11,DECEMBER ,36,(2008)


Predicted heat of formation some borohydrides


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LiBH4 = - 161 kJ /mol: BH4CuBH4 = 76NaBH4 = - 155Hf(BH4)4 = - 61Mg(BH4)2 = - 71KBH4 = - 198Zn(BH4)2 = 15Sc(BH4)3 = - 72

J.S.Hummelshøj et al, J. Chem. Phys. 131, (2009) 014101

Metal-borohydridesLiBH4 and other monovalent borohydrides generaly could not be suitable for hydrogen storage technology because of requirements of very high extraction energy of hydrogen and also high temperature.

• The desorption of LiBH4: LiBH4↔LiBH2 + H2 ↔ LiH + B + 3/2H2. ∆H ≈ 74 kJ /mol: H2; T≈375 ⁰C.

• The composite LiBH4–Al has been found to

release hydrogen in two steps at T<500 ⁰C :

• 2LiBH4+ Al(s) →AlB2(s)+2LiH (s) + 3H2 (g); ∆H ≈ -59.3 kJ /mol: H2

• 2LiH (s)+2Al(s) → 2LiAl(s)+H2(g): ρ=18.3 wt. % H2

D.B.Ravnsbæk and T.R.Jensen, J.Appl.Phys., 111, (2012) 112621

(BH4)-

M+

8Şakir Erkoç çalıştayı,07Ekim 2013,ODTÜ-ANKARA

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* Y. Nakamori et al., Phys. Rev. B, 74, (2006) 045126** Y. Filinchuk, et al., Phys. Rev.B, 79, (2009) 214111.

The borohydrides decompose to hydrides in the first desorption reaction as

M(BH4)n→MHm + nB +{(4n − m)/2 }H2


For metal borohydrides desorptiontemperature decreases while the Pauling electronegativity of metal increases*

Among them, insteead of light-weight boron compounds, such as lithium-sodium- magnesium(metal) tetrahydroborates, zinc and ziconium tetrahydroboratescould be potential candidate to hold the high hydrogen storage technology**.

Two objections:

a) The dehydrogenation of the magnesium borohydride systems tended to be stable ~ 380 ⁰C. These inflexion points of temperature, there was about 3.2wt.% H2. When the temperature was further increased to 600 C, there was only about 1.5 wt.% more H2 desorbed for the systems*.

b) LiBH4 is so stable that an considerable H-release proceeds at over 375-650 0K and the other is Al(BH4)3 too unstable at room temperature and it has very low decomposition temperature at about 70 0C, so, it easily release hydrogen at room temperature and upon heating**.


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*Y.Yang et al.,I J Hydrogen Energy,37,(2012)10733**Y. Guo et al. ,Angew. Chem. 123(2011) 1119


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Ternary alkali-transition metal borohydrides

Over 700 investigated structures*, about 20 were predicted to form potentially stable alloys with promising decomposition energies. The M1(Al/Mn/Fe)(BH4)4, (Li/Na)Zn(BH4)3, and

(Na/K)(Ni/Co)(BH4)3 alloys were found to be the most promise*

*J.S.Hummelshøj et al, J. Chem. Phys. 131, (2009) 014101

Structure of Al3Li4(BH4)13In this study, structural and electronic properties of a complex Al-Li-tetrahydroborate*, Al3Li4(BH4)13 have been reported by using first-principles plane-wave pseudopotential method. Our density functional theory approximation results revealed that Al3Li4(BH4)13 is very promising multifunctional material for a wide range of hydrogen storage technologies and also for solid state electronics.

• Cubic unit cell:P-43N (nu:218) a=11.698Å, Z=2

• Complex framework

• Anions:[Al(BH4)4]-

• Cations:[Li4(BH4)]3+


*I. Lindemann et al,Chem. Eur. J., 16, (2010) 8707

Calculation method

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*The structural and electronic properties are performed by using the plane-wave pseudopotential density functional theory, as implemented in CASTEP simulation package .

*The ion-electron interaction is modeled using Vanderbilt ultrasoft pseudopotential, and exchange-correlation effects are treated within the generalized gradient approximation (GGA) by the Perdew-Burke-Ernzerhof (RPBE).

*The states Li: 1s2 2s1, B: 2s2 2p1 and Al: 3s2 3p1 are considered as valence states.

*After convergence tests on cut-off energy and k-point set, the plane wave cut-off energy of 600 eV is employed, and to keep precision of simulations, k-point separation is set to 0.02 /Å, it is corresponding to set of 6×6×16 (recommended ultra-fine cut-off energy is 330 eV and k-point separation 3×3×10).

*Throughout the calculations, the ultra-fine convergence quality of software package is chosen. In this setup, there are no constraints on atomic positions and cell parameters.


4x4 supercell of Al3Li4(BH4)13in(001)


Cation-Anion

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[Al(BH4)4]-[Li4(BH4)]

3+


Calculated Structural parameters of Al3Li4(BH4)13


*I. Lindemann et al, I J Hydrogen Energy,38,(2013)2790

LDA GGA-PW91 GGA-RPBE GGA-

RPBE

(DMol)

Forcite Others*

a(Å) 10.908 11.446 11.686 11.747 12.074 11.364(Exp);

11.388(DFT)

V (Å3) 1298.0 1499.6 1596.0 1621.0 1760.3

ρ (gr/Å3) 0.773 0.668 0.628 0.618 0.569

dLi-B (MP) 2.325(-0.17)

2.380(-0.20)

2.500(-0.17);

2.536(-0.14)

2.568(-0.15)2.632(-0.13)

2.574

2.646

2.750 2.46

2.59

dAl-B (MP) 2.194(0.21) 2.242(0.17) 2.252(0.17) 2.272 3.981 2.237

dB-H (MP) 1.209(1.04)

1.240(0.84)

1.205(1.01)

1.242(0.81)

1.205(1.00)

1.243(0.80)

1.211

1.254

1.190 1.134

DOS of Al3Li4(BH4)13


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Total DOS

Energy(eV)

-10 -5 0 5 10

DO

S(s

tate

s/e

V)

0

20

40

60

80

100

p-orbitals

s-orbitals

Total

Calculated electronic structure of Al3Li4(BH4)13 indicates that it has insulator properties, and s-p hybridizations are dominant at the near of Fermi level.


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Energy Loss Function

Frequency(eV)

0 5 10 15 20

Loss F

un

ctio

n(a

rb.u

nits)

0.0

0.5

1.0

1.5

2.0

There are two separate –cation-anion units: (Li4BH4)(+3) and Al(BH4)4(-), the first peak located at ~9.10 eV (~ 136nm) from (Li4BH4) cationSecond at ~ 9.73 eV(~127nm) from Al(BH4)4 anion for two cation phases


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Electron density maps of Al3Li4(BH4)13

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Al3Li4(BH4)13 → 4(LiBH4)+3Al(BH4)3Al3Li4(BH4)13 → 4(LiBH4) + 9/2(B2H6) + 9/2(H2) + 3Al (1)

Decomposition reactions:

at the reaction(1) mass loss 21.6 wt% at~ 70 ⁰C, of nine of the thirteen (BH4) as B2H6 and H2, and capable of DOEstorage targets

J.S.Hummelshøj et al, J. Chem. Phys. 131, (2009) 014101I. Lindemann et al,Chem. Eur. J., 16, (2010) 8707 LM.Arnbjerg et al, TR. Jensen, I J Hydrogen Energy, 37, ( 2 0 1 2 ) 3 4 5

Can we apply the following two step reactions to theLiAl(BH4)4:?LiAl(BH4)4 → Li(BH4)+ Al(BH4)3LiAl(BH4)4 → LiH+ Al+4B+15/2(H2) (2a)LiAl(BH4)4 → Li+ Al+4B+8(H2) (2b) (2)Al(BH4)3 → 3/2 (B2H6)+3/2(H2)+Al?

→ Al+3B+6(H2)orAl(BH4)3 → AlB2+B+ 6H2 (3)



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4x4 supercell of AlLi(BH4)4in(101)

Aluminum-lithium double cation borohydrides: Cubic structures of Al3Li4(BH4)13 , and tetragonal

and orthorhombic structures of AlLi(BH4)4. Structural parameters, atomic charges, nearest distances with Mulliken populations, total energies of unit cells, phase separation and decomposition energies.


Al3Li4(BH4)13 AlLi(BH4)4

Unit cell Symmetry P-43N (nu:218)

Cubic, Z=2

P-42M (nu:111)

Tetragonal, Z=1

I-4 (nu:82)

Tetragonal Z=2

F222(nu:22)

Orthorhombic Z=4

Lattice parameters(Å) a=11.686 a=b=6.358 c=7.057 a=b= 7.917; c=10.617 a=11.668 b=9.773

c=11.271

Density 0.626 0.543 0.466 0.482

QAl 1.86 1.84 1.91 1.89

QB -0.73--1.12 -0.62 -0.76 -0.74

QLi 1.44 1.39 1.51 1.52

dLi-B (MP) 2.570(-0.15)

2.639(-0.13)

2.999(-0.09) 2.537(-0.18) 2.524(-0.18)

dAl-B (MP) 2.253(0.17) 2.240(0.17) 2.251(0.18) 2.252(0.17)

dB-H (MP) 1.205(1.00)

1.243(0.80)

1.198(0.95)

1.236(0.82)

1.207(0.98)

1.243(0.79)

1.206(0.99)

1.246(0.78)

∆Ealloy(eV/fu) -0.435 +0.516 -0.201 -0.330

∆Edecomp(eV/H2) -0.170(2a); -0.366(2b) -0.060(2a);-0.251 (2b) -0.179(2a) ;-0.347(2b) -0.201(2a) ;-0.364(2b)

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Phase separation into binary components*:

∆Ealloy = ELiAl(BH4)4 - (ELiBH4 + EAl(BH4)3)

phase separation criteri *: ∆Ealloy ≤ 0.0 eV/f.u., ∆Edeco ≈{-0.5,0.0} eV/H2

Al(BH4)3:orthorhombic,PNA21(33) symmetry group: E=-1926.63806eV/(4fu)

http://www1.eere.energy.gov/hydrogenandfuelcells

*J.S.Hummelshøj et al., J. Chem. Phys. 131, (2009) 014101

Li(BH4):orthorhombic,PNMA(62) symmetry group: E=-1335.12535eV/(4fu)


As seen from Table, the lowest lying structure of Al3Li4(BH4)13 in cubic symmetry and three phases of AlLi(BH4)4 in tetragonal and orthorhombic symmetries, which are reexamined within DFT approximation by the level of GGA/RPBE.

Conclusion

*Double cation Aluminum-lithium borohydride Al3Li4(BH4)13

have high hydrogen wt capacity (17.2 wt%) and decomposes at about70 ⁰C, are capable of DOE storage targets. It is consist of [(BH4)Li4]3+ cations and [(BH4)4]- anions. The possible reaction is not reversible at low temperatures. **s-p hybridizations are dominant at the near of the Fermi level. **two phases of AlLi(BH4)4 in thetragonal symmetry group P-

42M (nu:111).

**Three different phases of AlLi(BH4)4 are possible,

**orthorhombic phase is the ground state.

•The possible reaction phats are under consideration for last twostructure .


Teşekkürler

Thanks for your attention


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Şakir Hocama nice mutlu ,

sağlıklı ve başarılı yıllar diler. en içten saygı ve sevgilerimi

sunarımMehmet Şimşek


li-al double-cation borohydrides for hydrogen storage · a high hydrogen density (17.2 wt%). our...

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