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Materials Science and Nanotechnology | Volume 2
May 21-22, 2018 | New York, USA
International Conference on
Nanoscience & Technology
H
ydrogen as a fuel from renewable energy resources has
drawn immense attention recently. Among the various
methods of H
2
production, sun light assisted water splitting
using TiO2 catalyst is of high interest. The two major intrinsic
issues with TiO
2
are high electron-hole pair recombination
and absence of visible light absorption. An effective strategy
to inhibit the charge recombination is generation of hetero-
junctions formed by various TiO
2
phases. Among the various
modifications adopted for making TiO
2
visible light active,
nitrogen doping and native defect creation are the widely
recognized ones. Hence smooth charge transfer pathways for
effective charge separation wi th tuned band gap for visible
light absorption, can be achieved by having large number of
three phase heterojunctions modified with nitrogen doping
and or native defects. The main drawback with doping is that
the dopants have the high probability to act as recombination
centres. Hence modification of titania to make it visible light
active without external doping is appreciated. In this regard,
band gap tuning of triphase TiO
2
with native defects is of
interest. Although there are reports on H
2
generation using
biphase TiO
2
, studies on facile methods for the synthesis of
tunable TiO
2
hetrojunctions of pristine, nitrogen doped and
native defects are still under progress. Herein, we report a
novel synthesis method to prepare pristine, N-doped and
oxygen deficient TiO
2
nanotubes having anatase -rutile,
rutile-brookite, anatase-brookite and anatase -rutile-
brookite heterojunctions by simple tuning of applied voltage
in a novel electrochemical anodization technique, as well
as their application in H
2
generation by water photolysis.
The synthesized triphase TiO
2
nanotubes are found to be
1.6 times efficient than that of biphase nanotubes and 2.5
times that of single phase nanotubes. Similarly, the nitrogen
doped anatase-rutile-brookite heterojunctions shows 7.5
times hydrogen generation efficiency than that of triphase
TiO
2
nanotubes. The water splitting efficiency of triphase
heterojunctions with native defects is found to be 16 times
that of pristine triphase TiO
2
hetrojunctions. In addition, the
charge transfer characteristics to determine the underlying
physics behind the high efficiency of such systems will be
presented. A band diagram is proposed for pristine and
modified triphase hetrojunctions with the possible electron
transfer pathway using synchrotron valence band edge
analysis. It is found that the photoexcited charge transfer
takes place from rutile to anatase to brookite in triphase TiO
2
nanotubes.
e:
tom@igcar.gov.inDoped and defective three phase Tio
2
Hetrojunctions for enhanced H2 generation by solar water
splitting
Tom Mathews
Indira Gandhi Centre for Atomic Research, India