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.