Hierarchical CaIn2S4/NiTiO3 heterojunction enhanced removal of hexavalent chromium powered by visible irradiation

Given the significance of the visible-light-driven reduction of heavy metal chromium (Cr(VI)), it is promising and challenging to investigate photocatalysts that exhibit strong responsiveness to visible light and possess high carrier separation efficiency. In this research, a CaIn 2 S 4 /NiTiO 3 Z-scheme heterojunction has been successfully constructed through the in-situ growth of CaIn 2 S 4 nanosheets on NiTiO 3 nanorods. The energy band alignment between CaIn 2 S 4 and NiTiO 3 in the hierarchical framework facilitated the formation of the heterojunction, which significantly enhanced visible light absorption, promoted the separation of photogenerated carriers, and maintained the high reducing capability of the CaIn 2 S 4 conduction band electrons. These synergies enabled superior Cr(VI) removal efficiency. At an optimized CaIn 2 S 4 to NiTiO 3 ratio of 1:1, about 95 % removal rate of Cr(VI) was achieved within 80 min of visible-light exposure, accompanied by a reaction rate of 0.036 min −1 that is nearly four times faster than that over CaIn 2 S 4 . Furthermore, the charge transfer driving force and reaction mechanisms were comprehensively investigated by optoelectronic measurements, emphasizing the crucial roles of electrons (e − ) in Cr(VI) reduction. This investigation showcases the potential of the CaIn 2 S 4 /NiTiO 3 Z-scheme heterojunction for photocatalytic applications in Cr(VI)-containing wastewater treatment.