TiO@Pt@CeO nanocomposite as a bifunctional catalyst for enhancing photo-reduction of Cr (VI) and photo-oxidation of benzyl alcohol.

An solar-light-driven and bifunctional photocatalyst was designed for photo-reduction of Cr(VI) and selective photo-oxidation of benzyl alcohol into benzaldehyde in the presence of water under ambient conditions. Double-shelled and sandwiched TiO@Pt@CeO hollow spheres were prepared by using functionalized polystyrene spheres, sol-gel, hydrothermal reaction, and calcination. The Pt nanoparticles (NPs) were controllably loaded between the TiO shell and CeO shell. Under solar-light irradiation, the photo-reduction rate of Cr(VI) (μmol h) was in the order of TiO@Pt@CeO (1.901) > TiO@CeO (1.424) > TiO (1.040) > CeO (0.992). Among the above-mentioned photocatalysts, the conversion rate of benzyl alcohol for TiO@Pt@CeO was also the best. These results were attributed to the combination of TiO and CeO as photocatalyst and oxygen buffer, the double-shelled and sandwiched nanostructure, and the addition of Pt NPs as cocatalyst and electron trap site, which could store and shuttle photo-generated electrons, reduce the recombination of the electron-hole, and then enhance photo-generation of active radicals. This conclusion was verified by the electron paramagnetic resonance (EPR) spectroscopy. Considering the versatile combination of photocatalyst, oxygen buffer and cocatalyst, this work could provide new insights into the design of high-performance bifunctional photocatalysts for heavy metal removal and selective synthesis.