Visible light active carbon modified n-TiO2 for efficient hydrogen production by photoelectrochemical splitting of water

Carbon modified n-type titanium oxide (CM-n-TiO2) photoelectrodes were synthesized by flame oxidation of 0.2 mm thick Ti metal sheets for hydrogen production by photoelectrochemical splitting of water. The photocurrent density at optimized CM-n-TiO2 photoelectrodes (synthesized using flame temperature of 825 degrees C and oxidation time of 15 min) was found to be 6.38 mA cm(-2) at a minimal external applied potential of 0.24V under illumination with light intensity of 70 mW cm(-2) from a 150 Watt Xenon Lamp. The same value of photocurrent density was found when the wavelength dependent photocurrent densities at the same applied potential of 0.24V were integrated. This optimized CM-n-TiO2 photoelectrode was found to split water with maximum photoconversion efficiency of 9.02% under white light illumination. Also, a very close value of photoconversion efficiency of 9.01% was obtained from the wavelength dependent photocurrent density, j(p) (lambda) under monochromatic light illumination. Carbon modification lowered the original bandgap energy from 3.0 to 2.65 eV and generated a mid-gap band at 1.6 eV above the valence band of the optimized CM-n-TiO2, Photocurrent measurements, UV-Vis spectra, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to characterize CM-n-TiO2 photoelectrodes. (C) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.