Water-driven boost in the visible light photocatalytic performance of Cs2AgBiBr6 double perovskite nanocrystals

Abstract

In recent years, the focus on lead-free halide perovskite nanocrystals (NCs) has now been shifted to their utilization as photocatalysts due to their strong light absorption and tunable photo-responsive range. Current studies have promised Cs₂AgBiBr₆ NCs to be a born photocatalytic material that will self-passivate to generate BiOBr when it encounters water. In this work, a unique Cs₂AgBiBr₆/BiOBr composite was found in water-soaked Cs₂AgBiBr₆ NCs, which was further diagnosed as a Z-type heterojunction to enhance the photocatalytic process. Meanwhile, variations in the structure and photocatalytic behavior of Cs₂AgBiBr₆ NCs in RhB solution with different water contents were investigated in detail. Results showed that appropriate water content could accelerate the visible-light-driven degradation of RhB by almost 1.5 times, but excessive water (more than 50 vt%) may result in weak or negative enhancement. Accordingly, the bandgap matching, carrier separation and the resultant photocatalytic mechanism of water-soaked Cs₂AgBiBr₆ NCs were discussed and proposed. This research will offer a new idea for the application of halide perovskite in a water-involved photocatalytic system.