Search

Photocatalytic oxidation of toluene to valuable fine chemicals is of great significance, yet faces challenges in the development of advanced catalysts with both high activity and selectivity for the activation of inert C(sp 3 )-H bonds. Halide perovskites with remarkable optoelectronic properties have shown to be prospective photoactive materials, but the bulky structure with a small surface area and severe recombination of photogenerated electron-hole pairs are obstacles to application. Here, we fabricate a hierarchical nanoflower-shaped CsPbBr 3 /TiO 2 heterojunction by assembling CsPbBr 3 nanoparticles on 2D TiO 2 nanoflake subunits. The design significantly downsizes the size of CsPbBr 3 from micrometers to nanometers, and forms a type II heterojunction with intimate interfacial contact between CsPbBr 3 and TiO 2 nanoflakes, thereby accelerating the separation and transfer of photogenerated charges. Moreover, the formed hierarchical heterojunction increaseslight absorption by refraction and scattering, offers a large surface area and enhances the adsorption of toluene molecules. Consequently, the optimized CsPbBr 3 /TiO 2 exhibits a high performance (10 200 μmol g -1 h -1 ) for photocatalytic toluene oxidation with high selectivity (85%) for benzaldehyde generation under visible light. The photoactivity is about 20 times higher than that of blank CsPbBr 3 , and is among the best photocatalytic performances reported for selective oxidation of toluene under visible light irradiation.

Noble metal nanoparticles are often used as cocatalysts to enhance the photocatalytic efficiency. While the effect of cocatalyst nanoparticle size and shape has widely been explored, the effect of the crystal phase is largely overlooked. In this work, we investigate the effect of Ru nanoparticle crystal phase, specifically regular hexagonal close-packed (hcp) and allotropic face-centered cubic (fcc) crystal phases, as cocatalyst decorated onto the surface of TiO 2 photocatalysts. As reference photocatalytic reaction the simultaneous photocatalytic production of benzaldehyde (BAD) and H 2 from benzyl alcohol was chosen. Both the fcc Ru/TiO 2 and hcp Ru/TiO 2 composites exhibit enhanced BAD and H 2 production rates compared to pristine TiO 2 due to the formation of a Schottky barrier promoting the photogenerated charge separation. Moreover, a 1.9-fold photoactivity enhancement of the fcc Ru/TiO 2 composite is achieved as compared to the hcp Ru/TiO 2 composite, which is attributed to the fact that the fcc Ru NPs are more efficient in facilitating the charge transfer as compared to hcp Ru NPs, thus inhibiting the recombination of electron-hole pairs and enhancing the overall photoactivity.