Photocatalytic characterization of TiO₂ nanotubes with PD particles synthesized by photoreduction process

To decompose dye in aqueous solution, Pd nanoparticle-decorated TiO₂ nanotube photocatalysts were fabricated through electrochemical anodization and photoreduction processes. Morphological and surface characterization of the TiO₂/Pd heterojunction photocatalyst, as well as photoelectrochemical behaviors, were investigated by X-ray diffraction, UV/Vis diffuse reflectance and photocurrent response. It was found that the precipitated Pd particle size and distribution on TiO₂ surface were affected by the photoreduction time. As the photoreduction time increased from 10 min to 180 min, the corresponding average diameter of the precipitated Pd particles on TiO₂ photocatalyst increased from 4.35 nm to 9.29 nm. From the Aniline blue degradation results, the Pd decorated TiO₂ catalysts enhanced photocatalytic activity compared to bare TiO₂ catalyst, and the rate constant for dye degradation was dependent on the Pd particle size on the TiO₂ surface. For an average Pd particle size lower than 7.80 nm, the particles were uniformly precipitated on the surface of the TiO₂ nanotubes, and the dye degradation rate constants increased with increasing Pd particle size. However, for an average Pd particle size of more than 7.80 nm, the particles were agglomerated on the TiO₂ surface, and the dye degradation rate constants gradually decreased. With an optimum Pd particle size of 7.80 nm, the TiO₂/Pd photocatalyst showed higher photocatalytic activity and Aniline blue degradation rate, due to high photo absorbance response, and more efficient charge separation through electron transfer from the conduction band of the TiO₂ to the Pd particles.