This study examines ammonia borane (AB) and its composite with polyvinylpyrrolidone (PVP) for hydrogen storage applications. Differential scanning calorimetry and Fourier transform infrared spectroscopy measurements were performed on the AB, PVP and various AB-PVP composites. The addition of PVP was found to decrease the enthalpy and entropy of the phase transition of AB, indicating an interaction between AB and PVP. PVP also decreased the hydrogen release temperatures of the composites compared to pure AB, demonstrating its ability to enhance the kinetics of AB decomposition for hydrogen release. Further studies on different composite compositions and their kinetic properties are planned.

1. Study of Ammonia Borane – Polyvinylpyrrolidone
Hydrogen Storage Composite Materials
Sahithya Pati and Ozge Gunaydin-Sen
Department of Chemistry and Biochemistry
Lamar University, Beaumont, TX 77710
Ammonia borane (NH3BH3), a potential hydrogen
storage system, reveals a structural phase transition
around ̃223 K. The transition mechanism was
studied by heat capacity measurements, clearly
indicating a first-order transition.
NH3BH3 (Ammonia Borane, AB) crystallizes in
the tetragonal, I4mm, space group at room
temperature and it becomes orthorhombic below the
phase transition temperature.
 Due to poor thermal kinetics practical application
of AB is still hindered to overcome this we are using
polymers to improve thermal properties and
suppress the byproducts formation.
Introduction
Experimental
 AmmoniaBorane (AB) and Polyvinylpyrrolidone
(PVP, 40,000) were purchased from Sigma
Aldrich.
 Composites of different ratios were prepared with
AB, PVP and were studied.
 AB-based composite of 1:1 mas ratio was obtained
mixing 0.10 g of AB and with an addition of 1 mL
of deionized water. Different mass ratios were
prepared as well.
Heat Capacity measurements were made with
Differential Scanning Calorimeter (TA Instrument
DSC Q20) covered the range of 300 K down to 180
K. Decomposition experiments were performed
between 298 K to 573 K.
Transmittance measurements were made with
Nicolet IS-10 FT-IR at room temperature.
Conclusions
Synthesis
Table 1. ΔH, ΔS and Tp values of AB,
PVP and AB-based composites.
References
Figure 2. Cp and Enthalpy of
AB:PVP(1:1) vs. Temperature
with ramp of 1 K/min (Heating).
Figure 5. FT-IR graph of AB, PVP and AB-
based polymer composites.
1-Gunaydin-Sen, O.; Achey, R.; Dalal, N. S.; Stowe, A. and
Autrey T. J. Phys. Chem. 2012, 112, 1544-1549.
2- Klooster, W. T.; Koetzle, T. F.; Sieghbahn, E. M.; Richardson,
T. B.; Crabtree, R. H. J. Am. Chem. Soc. 1999, 121, 6337-6343.
3- Tang, Z.; Li, S.; Yang,Z.; and Yu,X.; J. Mater. Chem., 2011, 21,
14616
Figure 4. Heat Capacity (Cp) vs
Temperature of AB, AB:PVP(1:1), (1:2)
with ramp of 1 K/min (Heating).
Cp and Enthalpy
Due to interaction between the PVP and ammonia
borane a decrease in ΔH and ΔS values is observed when the
composites are studied in DSC.
The interaction could possibly be disturbing the dihydrogen
bonding network.
Decomposition studies revealed that there is a decrease in
the melting and hydrogen release temperatures with the
increase of polymer proportion in the composite which is an
evidence for the kinetic enhancement.
Results and Discussion IR Analysis
 FT-IR spectra of pure AB, PVP
and the polymer composites
showed changes in their
functional groups
Future Studies
Various compositions of AB and PVP will be prepared
and subjected to DSC and TGA to compare with bulk AB.
VT-IR studies will be carried for change in chemical
interactions and effect of PVP on dihydrogen bond present
in AB.
Kinetic analysis will be done, activation energies will be
calculated.
 Electrospun fibers with AB:PVP will be investigated.
Acknowledgement
Lamar University and Welch Foundation
Cp/T and Entropy
Figure 3. CP/T and Entropy of
AB:PVP(1:1) vs. Temperature with
ramp of 1 K/min (Cooling).
Ramp
(1 K/min)
ΔH (J/g) ∆S(J/gK) Tp (K)
AB 31.81 0.1056 222.81 (±0.5)
AB:PVP(1:1)
9.01 0.06538 222.89(±0.5)
AB:PVP(1:2)
9.465 0.0339 222.76(±0.5)
Figure 7. The proposed thermolysis mechanism of AB
in polymeric system [3].
300 350 400 450 500 550
-8
-6
-4
-2
0
2
4
6
8
Heatflow(W/g)
Temperature (K)
AB
AB:PVP(1:1)
PVP
AB:PVP(1:2)
Figure 5. DSC decomposition graphs 298 K-573 K
Kinetic Studies
Figure 6. Kinetic studies of AB
Figure 1. a) Conformation of the closest N-H…H-B
contact from the neutron diffraction structure of
NH3BH3 [1, 2], b) polyvinylpyrrolidone.
a) b)
ΔH = 𝐶𝑝 𝑇
𝑑𝑇
𝑇
ΔS = 𝐶𝑝
𝑑𝑇
𝑇
Ozawa method Kissinger's method
ln β = -Ea /RTd+ C ln (β/Tp
2) = -Ea /RTd+ C
Where, β is the heating rate, Td is the peak
temperature of the thermal decomposition and R is
the Universal gas constant .
50 100 150 200 250
-30
-20
-10
0
10
20
30
HeatFlow
Temperature (
oC)
5
O
C/min
10
O
C/min
20
O
C/min
1900 1850 1800 1750 1700 1650 1600 1550 1500
30
40
50
60
70
80
90
100
Transmittance(%)
Wavenumber (cm
-1
)
Bulk AB
PVP
(1:1) AB:PVP
(1:2) AB:PVP
1650 cm
-1
1597 cm
-1
1600 cm
-1
1645 cm
-1
1647 cm
-1
C=O stretch
N-H deformation
200 220 240 260 280
1
2
3
4
5
6
7
8
Cp(J/gK)
Temperature (K)
AB:PVP (1:1)
AB:PVP (1:2)
AB
4000 3500 3000 2500 2000 1500 1000
Transmittance
Wavenumber (cm-1
)
2206 cm
-1
2273 cm
-1
2313 cm
-1
3186 cm
-1
3239 cm
-1
3305 cm
-1
1280 cm
-1
1417 cm
-11651 cm
-1
AB:PVP(1:2)
AB:PVP(1:1)
H-N Bond
B-H2
Bond
N-H bond
B-H and B-H2 strech
N-H,N-H2 and N-H3 strech
AB
PVP
725 cm
-1
180 200 220 240 260 280 300
2
4
6
8
10
Cp(J/gK)
Temperature (K)
0
40
80
120
160
200
Enthalpy(J/g)
180 200 220 240 260 280 300
0.01
0.02
0.03
0.04
0.05
0.06
Temperature (K)
Cp
/T(J/gK2)
-0.8
-0.7
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0.0
Entropy(J/gK)