Visible-light-driven Ag3VO4-BiVO4/C3N4 with continuous type II heterojunctions for effective removal of Cr(VI)

Heterogeneous photocatalysis have attracted extensive attention in the field of environmental remediation. The low charge separation efficiency and poor light response of single semiconductor can be remarkably improved through forming heterojunction. The construction of ternary heterojunctions can further inhibit the recombination of photogenerated charge carriers by the separated redox active sites. A novel and highly efficient Ag3VO4-BiVO4/C3N4 ternary heterojunction were successfully synthesized and characterized in terms of structure, chemical composition and photocatalytic properties. The photocatalytic activities of as-synthesized photocatalysts were evaluated by the photocatalytic reduction of Cr(VI) in the aqueous solution. The photocatalytic Cr(VI) reduction rate of ternary heterojunction is 19 times higher than that by single BiVO4. The lower pH, higher concentration of coexisted organics and stronger light intensity endowed photocatalysts with better photocatalytic performance. More Cr(VI) ions were remained in the solution with higher initial concentration of Cr(VI) under the same light irradiation. The Cr(VI) ions could also be totally removed by the ternary heterojunction even after five cycling tests showing good cycling stability. The internal electric field between Ag3VO4, BiVO4 and graphitic carbon nitride (C3N4) facilitated the separation of photogenerated electron/hole pairs. The suitable band alignments endow ternary heterojunction with isolated oxidation and reduction reactions due to the separated holes and electrons, meanwhile, suppressing charge carrier recombination. This research provides guidance for the rational design of multi-components heterojunction for photocatalytic environmental remediation.