Metal oxide/oxynitride nanotube arrays towards solar light harvesting

by Dr. Subarna Banerjee (CVD Equipment Corporation, USA)

Monday, January 2, 2012 from 16:00 to 17:00 (Asia/Kolkata)
at Colaba Campus ( AG-69 )

TIFR, Colaba Mumbai 400005

Description

Ever increasing cost of fossil fuels and drastic effects of global climate drives us to search for sustainable alternative energy sources. Hydrogen (H₂) is one of the best sources for clean and renewable energy that can be used in vehicular applications and energy systems as it produces water on combustion. H₂ can be generated from many sources. Solar light driven hydrogen generation by water photoelectrolysis is the best way to achieve sustainable and green energy.Titanium dioxide (TiO₂) is one of the most suitable materials due to its abundant availability, inexpensive cost and high corrosion resistance in aqueous solution. However, owing to its relatively large band gap (3.2 eV) TiO₂ absorbs light in the UV region and hence has small energy conversion efficiency of solar energy. To improve the photocatalytic efficiency, several strategies have been adopted, which include doping and coupling with a low band gap semiconductor material such as CdS. Fe₂O₃ (hematite) is theoretically an ideal candidate with low band gap (around 2 eV) for photoelectrochemical applications as it is economical, abundant, chemical and photocorrosion stable. Unfortunately, the photoefficiency is very low due to the high level of electron-hole recombination in the solid and at grain boundaries. Among all the one-dimensional nanostructures, vertically aligned nanotubes attract special attention as they being highly ordered enhance field-effect carrier mobility,together with increased electrical conductivity and reduced activation energy for electrical conduction in comparison with nanoparticles. These qualities make the vertically oriented nanotubesarrays better candidate for photoelectrochemical generation of H₂ and solar cell applications.Challenges to grow metal oxide and metal oxynitride nanotubes and their applications will be discussed.