In situ construction of a C3N5 nanosheet/Bi2WO6 nanodot S-scheme heterojunction with enhanced structural defects for the efficient photocatalytic removal of tetracycline and Cr(vi)

Abstract

Building step-scheme (S-scheme) heterojunctions is newly emerging as an efficient means to obtain excellent photocatalysts for water pollution control. Herein, a 2D/0D S-scheme heterojunction of C₃N₅/Bi₂WO₆ was synthesized by in situ growing 0D Bi₂WO₆ nanodots on 2D C₃N₅ nanosheets. Photocatalytic removal of tetracycline (TC) and Cr(VI) from water was employed to evaluate the activity of C₃N₅/Bi₂WO₆ under visible light compared to that of C₃N₅, Bi₂WO₆, and their mechanical mixture. Obviously, C₃N₅/Bi₂WO₆ is much more active in the visible-light-driven removal of TC and Cr(VI), indicating strong interaction between the C₃N₅ nanosheets and Bi₂WO₆ nanodots as a result of in situ growth. Such an interaction can be illustrated as the S-scheme transfer behavior of photogenerated electrons and holes, which boosts the interfacial charge separation, retains the optimum redox ability of photo-induced charge carriers and fosters the generation of more active species. Moreover, C₃N₅/Bi₂WO₆ shows more structural defects than single C₃N₅ and single Bi₂WO₆, which may endow C₃N₅/Bi₂WO₆ with better ability in the activation and photo-oxidation of TC as well as the activation and photo-reduction of Cr(VI). In a nutshell, this work affords a deep understanding of the photocatalytic mechanism based on C₃N₅/Bi₂WO₆ as well as presents a new concept for developing highly efficient S-scheme heterojunction photocatalysts for water decontamination.