Search

In searching for a suitable semiconductor material for hydrogen production via photoelectrochemical water splitting, α-Fe2O3 received significant attention as a promising photoanode due to its band gap (~2.1 eV), good stability, low cost, and natural occurrence. α-Fe2O3 thin films were prepared by economic and facile dip coating method and subsequently subjected to an anodic potential of 700 mV versus Ag/AgCl in 1M KOH for different anodization times (1, 10, and 900 min) under illumination. X-ray diffractometry revealed increase in crystallites size from ~31 nm for nanoparticles in pristine state to ~38 and 44 nm after anodization for 1 and 900 min, respectively. A clear positive correlation between anodization time and grain (particle) size was observed from field emission gun scanning electron microscopy and atomic force microscopy (AFM); longer exposure time to anodizing conditions resulted in larger grains. Grain size increased from ~57.9 nm in pristine state to ~153.5 nm after anodization for 900 min. A significant smoothening of the surface with increase in anodization time was evident from AFM analysis. [ABSTRACT FROM AUTHOR]

Laser pyrolysis was chosen to synthesize tungsten trioxide starting with tungsten ethoxide precursor. The film was found to have a thickness that varied from 205 nm to 1 µm. X-ray diffraction and Raman spectroscopy confirmed the presence of a mixture of hexagonal and tetragonal phase WO3 in the synthesized film, as well as tungsten bronzes. It was evident that annealing greatly influenced the phases and types of structures formed, and EDXS was carried out in an attempt to quantify the tungstate bronzes to tungsten oxide. I-V curves of the films showed n-type semiconducting behaviour, but the mixed phase appeared to cause a similar behaviour of dopants in a semiconductor. The refractive index decreased with increasing wavelength and gave values of up to 21 at low wavelengths. The average optical band gap was found to be 3.6 eV from UV/Vis spectroscopy. Scanning Electron Microscopy (SEM) showed a mixture of nano- and microstructures after annealing. Nanorod structures were isolated and Pt-contacted using FIB for possible applications such as an active sensing medium in gas sensors. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]