Controllable fabrication of a Cs2AgBiBr6 nanocrystal/mesoporous black TiO2 hollow sphere composite for photocatalytic benzyl alcohol oxidation

Abstract

Photocatalytic selective oxidation of benzyl alcohol into benzaldehyde at normal temperature and pressure is one of the important topics in the catalysis field. Here, a lead-free double perovskite Cs₂AgBiBr₆ nanocrystal/mesoporous black TiO₂ composite was prepared by a vacuum-assisted method, and then it was applied for photocatalytic selective oxidation. The photocatalytic oxidation of benzyl alcohol to benzaldehyde was found to occur with 75% conversion and 99% selectivity with the Cs₂AgBiBr₆ nanocrystal/black TiO₂ composite, which were better than those of single Cs₂AgBiBr₆ nanocrystals and black TiO₂, respectively. This was due to the formation of a Z-type heterogeneous structure between Cs₂AgBiBr₆ nanocrystals and black TiO₂, which effectively promoted the separation and transfer of electrons and holes, ultimately leading to excellent photocatalytic activity. During the whole catalytic process, carbon-centered radicals were the key intermediates for the dehydrogenation of benzyl alcohol. This work may provide some practical suggestions for the fabrication of benzyl alcohol selective oxidation photocatalysts.