Visible light active Au:TiO₂ nanocomposite photoanodes for water splitting: Sol-gel vs. sputtering

In this study, pure TiO₂ and Au:TiO₂ nanocomposite thin films are both synthesized using sol-gel and RF reactive co-sputtering methods. Physical and photoelectrochemical properties of the thin films deposited by each method are compared. The optical density spectra and scanning electron microscopy images of the Au:TiO₂ films reveal formation of gold nanoparticles in the all nanocomposite films synthesized by two methods. Moreover, the optical bandgap energy of the thin films decreases with addition of Au nanoparticles. X-ray photoelectron spectroscopy indicates that the presence of gold in metallic state and the formation of TiO₂ is stoichiometric. The photoelectrochemical properties of the TiO₂ and Au:TiO₂ thin films are characterized by using a compartment cell containing KOH solution as electrolyte. It is found that in the pure systems, TiO₂ sputtered films shows a higher photocurrent under visible light illumination while a reverse result is obtained for the Au:TiO₂ systems. In addition, photoirradiation on electrode/electrolyte (EE) and substrate/electrode (SE) interfaces for the sputtered samples reveals the EE illumination enhances the photoresponse of the layers as compared to SE case.