Noble-metal-free ultrathin MXene coupled with In2S3 nanoflakes for ultrafast photocatalytic reduction of hexavalent chromium

The conversion of highly toxic heavy metal hexavalent chromium (Cr(VI)) in the natural environment into low-toxic trivalent chromium (Cr(III)) is one of the research topics of great concern. Herein, a binary noble-metal-free photocatalyst consisting of ultrathin MXene (Ti3C2) and indium sulfide (In2S3) is prepared for ultrafast photocatalytic reduction of Cr(VI) to Cr(III) under visible light. A simple electrostatic assembly and reflow method uniformly coats the In2S3 nanoflakes on the surface of hollow Ti3C2 nanospheres, which effectively boost the separation of charges and thus enhance the photocatalytic performance. Thus, the prepared heterojunction can reduce Cr(VI) to Cr(III) completely within 6 min with an ultrafast rate constant of k = 0.739 min−1. More importantly, the appropriate band structure ensures the stable existence of Cr(III). Therefore, it provides a new insight for economic MXene-based binary photocatalysts for efficient environmental remediation.