Adsorption and enhanced photocatalytic activity of the {0 0 0 1} faceted Sm-doped ZnIn₂S₄ microspheres

Graphical abstract: - Highlights: • Sm-doped ZnIn₂S₄ microspheres were synthesized by hydrothermal method. • Sm-doped ZnIn₂S₄ microspheres are composed of nanoplates with {0 0 0 1} facets exposure. • The negatively charged {0 0 0 1} facets are beneficial for the adsorption of RhB. • ZnIn₂S₄ microspheres doped with 2% Sm shows the best visible-light photocatalytic activity. - Abstract: In this study, the doping effect of samarium on the structure, morphology, adsorption and photocatalytic performance of hexagonal ZnIn₂S₄ microspheres was studied. The photocatalytic activity of Sm-doped ZnIn₂S₄ microspheres was evaluated for the photodegradation of Rhodamine B (RhB) and methyl orange (MO) under visible light irradiation. The samples were characterized by XRD, SEM, XPS, UV–vis, TEM, and N₂ adsorption–desorption analysis. The results show that the hexagonal ZnIn₂S₄ microspheres are composed of nanoplates growing along c-axis with the predominant negative-charged S plane. Compared with the photodegadation of MO dye, the negative-charged {0 0 0 1} facets not only are beneficial for the adsorption of RhB by –N(Et)₂ groups but also can accumulate the separation of photogenerated electrons and holes, enhancing photodegradation efficiency by direct-hole photocatalysis. Moreover, Sm is partially substituted for In in the crystal lattice for forming the doping energy level which promotes the separation of photoinduced electron–hole pairs and enhances absorption of visible light. Hexagonal 2% Sm-doped ZnIn₂S₄ microspheres with exposed {0 0 0 1} facets resulted in higher photodegradation efficiency of RhB under visible light irradiation