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)

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.