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

Carbon modified n-type titanium oxide ( CM - n - TiO 2 ) 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 - TiO 2 photoelectrodes (synthesized using flame temperature of 825 ∘ C and oxidation time of 15 min) was found to be 6.38 mA cm - 2 at a minimal external applied potential of 0.24 V 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 0.24 V were integrated. This optimized CM - n - TiO 2 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 ( λ ) 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 - TiO 2 . Photocurrent measurements, UV–Vis spectra, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to characterize CM - n - TiO 2 photoelectrodes.