Spray pyrolytically deposited nanoporous Ti4+ doped hematite thin films for efficient photoelectrochemical splitting of water

Nanoporous hematite (alpha-Fe2O3) thin films doped with Ti4+ deposited by spray-pyrolysis were successfully used in photoelectrochemical splitting of water for solar hydrogen production. X-ray diffraction, field emission scanning electron microscopy, UV-visible absorption and photoelectrochemical studies have been performed on the undoped and Ti4+ doped hematite thin films. Morphology of alpha-Fe2O3 a thin films was observed to be nanoporous, with increased porosity (pore size similar to 12 to 20 nm) on increasing doping concentration. A significant decrease in the bandgap energy from 1.95 to 1.27 eV was found due to doping alpha-Fe2O3 a film doped with 0.02 M Ti4+ ions exhibited best solar to hydrogen conversion efficiency (photoconversion efficiency) of 1.38% at 0.5 V/SCE. Highest photo-current densities of 0.34 mA/cm(2) at zero bias and 1.98 mA/cm(2) at 0.5 V/SCE were obtained by incorporating 0.02 M Ti4+ in alpha-Fe2O3, which are significantly larger than earlier reported values. Donor density (30.8 x 10(20) cm(-3)) and flatband potential (-1.01 V/SCE) obtained were also maximum for this sample. Hydrogen collected in 1 hr at Pt electrode with the best photoelectrode was 2.44 mL with 150 mW/cm(2) visible light source. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.