Rationally designed Ti3C2 MXene/CaIn2S4 Schottky heterojunction for enhanced photocatalytic Cr(VI) reduction: Performance, influence factors and mechanism

As a highly toxic heavy metal, Cr(VI) reduction by developing high-efficiency photocatalysts is of great significance. Herein, we firstly design few-layer Ti3C2 MXene (FTM) by the hand-operated shaking, showing dual advantages of structural stability and more exposed reactive sites. Then, a refluxed process is performed to fabricate FTM/CaIn2S4 (FTC) composites, where 2D CaIn2S4 (CIS) nanoplates are closely connected with 2D FTM to form Schottky junction. The optimal 1-FTC with the FTM/CIS mass ratio of 1 wt.% exhibits the highest activity toward photocatalytic Cr(VI) reduction under visible light. It is well elucidated that the broadened light absorption range and promoted charge carrier separation rate induced by the introduction of FTM are responsible for improving photocatalytic activity of CIS. During Cr(VI) photoreduction, 1-FTC possesses excellent photo-stability and reusability. The effects of catalyst mass, coexisting ions, water sources and pH values on the Cr(VI) photoreduction efficiency are investigated. Photogenerated •O2− and e− are the main radical species accounting for Cr(VI) photoreduction over 1-FTC. The photocatalytic mechanism along with Cr(VI) removal pathway is exploited. This work may provide some insights into constructing FTM-based Schottky junctions for the efficient water purification.