Fabrication of MOF-derived tubular In2O3@SnIn4S8 hybrid: Heterojunction formation and promoted photocatalytic reduction of Cr(VI) under visible light

Tubular In2O3@SnIn4S8 hierarchical hybrid photocatalyst was firstly fabricated by a two-step method. The morphology and composition were characterized by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The XRD results show that the obtained In2O3 microtubes were highly crystallized, while the SnIn4S8 flakes prepared at low temperature were poorly crystallized. The SEM image of the hybrid shows that numerous SnIn4S8 nanoflakes were assembled over the surface of In2O3 microtubes. In2O3 served as dispersing-templates have reduced the agglomeration of SnIn4S8 flakes. Meanwhile, the heterojunctions formed at the interfaces between In2O3 and SnIn4S8 could facilitate the interfacial charge transfer, as well as promote the photocatalytic activity of the hybrid. In the treatment of Cr(VI)-containing wastewater, the In2O3@SnIn4S8 hybrid not only exhibited strong adsorption ability, but also showed remarkably enhanced photocatalytic activity compared with pure SnIn4S8. The photocatalytic reaction constant k for In2O3@SnIn4S8 was approximately 2.54 times higher than that of SnIn4S8. The efficient activity of this hybrid photocatalyst should be ascribed to the promoted separation efficiency of electron/hole pairs, which was proved by the following three-dimensional excitation-emission matrix fluorescence spectra (3D EEMs), photocurrent responds, and EIS characterizations.