Page 263 - Polymer-based Nanocomposites for Energy and Environmental Applications

Polyaniline-based nanocomposites for hydrogen storage 235

PANI-V 2 O 5 nanocomposite (PANI-VONC). The hydrogen uptake capacities of
PANI and V 2 O 5 obtained independently were 0.15 and 0.16 wt%, respectively, under
7 MPa at 77 K. The hydrogen sorption capacity was enhanced appreciably (1.8 wt%)
for the PANI-VONC, under the same conditions. This improvement in the hydrogen
sorption capacity of the PANI-V 2 O 5 nanocomposite was due to the increase of
interlayer spacing between the PANI layer and V 2 O 5 (VO) layer from 1.1 to
0.72 nm [58].
Significant hydrogen adsorption capacity was observed for the vanadium
pentoxide-PANI (V 2 O 5 -PANI) nanocomposite at 473 K. On the other hand, chemi-
cally modified vanadium pentoxide-PANI-polythiophene composite with nickel
(V 2 O 5 -PANI-PTH-Ni) was subjected to investigate a hydrogen sorption capacity.
The existence of nickel improved the uptake at a lower pressure [17]. Senkal et al.
reported the hydrogen storage applications of PANI modified with boric acid
(PANI-B) and boron trifluoride (PANI-BF 3 ), and their nanocomposites with PANI-
B-SWNT (10%), PANI-BF 3 -SWNT (10%), PANI-B-MWNT (10%), and PANI-
BF 3 -MWNT (10%) were reported at cryogenic temperature under 10 MPa. It was
noticed that the hydrogen adsorption capacity depends on the nature of CNT used
and the presence of organic functional groups in the composite. So, the SWNT com-
posites exhibited higher storage capacity than that of MWNT composites. The
improvement in adsorption capacity was due to existence of organic functional groups
(PANI-B and PANI-BF 3 ) and along with the molecular separating property [59].

8.4 Conclusions

Hence, this chapter reviewed the hydrogen storage capacity of nonporous and
nanoporous PANI nanocomposites and its important characteristics. It is evidenced
that the hydrogen uptake of PANI structures depends on its unique electronic proper-
ties, surface area, and porous structure of PANI. The measured temperature and hydro-
gen pressure also play a prominent role in hydrogen storage, and its mechanisms have
been proposed based on the electronic conducting property and molecular sieving phe-
nomena (doping-dedoping-redoping process). Further, aromatic ring is the main
active site for hydrogen adsorption in nanoporous PANI. An electron-donating group
of the aromatic ring will increase the electron density and results in increasing the
hydrogen storage capacity of PANI. Among the reported PANI structures, PANI
nanofibers exhibited maximum hydrogen uptake of 8 wt%. Hence, the PANI struc-
tures show its potential in hydrogen storage owing to its fast reaction kinetics and
physisorptive mechanism of hydrogen uptake.

Acknowledgments

BS thanks DST-SERB for providing financial support through NPDF scheme (PDF/
2015/000217). One of the authors (AS) would like to thank CSIR-India for providing financial
support through Research Associateship (ACK No: 324494/2 K15/1 dt: 31.03.2017).