Design of heterostructured perovskites for enhanced photocatalytic activity: Insight into their charge carrier dynamics

Abstract

The perovskite semiconductors, having intrinsic polarization induced by the non-centrosymmetric metal center, have superior ability for the separation of photogenerated charge carriers. In order to exploit this highly desired distinctive property for photocatalysis, the synthesis of visible light active bismuth ferrite (BiFeO3) and its modification to form BiFeO3-Bi2S3, BiFeO3-NiS2, and BiFeO3-NaNbO3 heterostructured photocatalysts, to further tune the light harvesting and charge-separation is reported. These photocatalysts have been synthesized by facile and low-cost synthesis routes: (i) hydrothermal (namely the Bi2S3 and NiS2 heterostructures), and (ii) sol-gel (namely the NaNbO3 heterostructure) methods. The morphology of the BiFeO3 nanoparticles (300 +/- 50 nm) changes to rod like structures (length and width of 4.0 +/- 0.8 mu m and 250 +/- 70 nm, respectively) when modified with Bi2S3. In addition to their structural and optical properties (band gap), the detailed investigation undertaken on photocatalytic activity (dye degradation) and their kinetics are discussed. The BiFeO3-Bi2S3 heterostructured photocatalyst exhibits reduced band gap (ca. 1.4 eV), lower fluorescence intensity and enhanced dye degradation (k= 0.1839 h(-1)) as compared to that of the bare BiFeO3. This enhancement in photocatalytic activities is attributed to the unified effect of better visible light harvesting, improved charge separation, faster charge transfer kinetics and enhanced reduction potential of the conduction band electrons. (C) 2020 Elsevier Ltd. All rights reserved.