The flux growth of single-crystalline CoTiO3 polyhedral particles and improved visible-light photocatalytic activity of heterostructured CoTiO3/g-C3N4 composites

Abstract

Highly crystalline and idiomorphic CoTiO₃ single crystals with a well-defined polyhedral morphology were grown successfully for the first time by a facile flux method. Herein, the effects of the molten salt type and cobalt precursor on the phase composition, crystallization habit and morphology of the CoTiO₃ products were also investigated. Importantly, using the flux-grown CoTiO₃ crystal as the visible-light sensitizer due to its narrow band gap to couple with graphitic carbon nitride (g-C₃N₄) by a direct in situ thermal induced polycondensation route, novel CoTiO₃/g-C₃N₄ composite photocatalysts were obtained. The as-synthesized samples were systematically characterized by XRD, EDS, SEM, TEM, SAED, HRTEM, FT-IR, XPS, DRS and PL techniques. The results revealed that CoTiO₃ polyhedral crystals were closely combined with g-C₃N₄ nanosheets leading to the formation of a heterojunction structure at the interface between CoTiO₃ and g-C₃N₄. Photocatalytic evaluation showed that the heterostructured CoTiO₃/g-C₃N₄ composite exhibited much higher photocatalytic activity for the degradation of methyl orange under visible light irradiation than that of individual CoTiO₃ and g-C₃N₄, which could be mainly ascribed to the synergistic effect between CoTiO₃ and g-C₃N₄, including the enhanced visible-light harvesting ability and more efficient separation and longer lifetime of photogenerated charge carriers. Furthermore, the composite photocatalyst showed an excellent stability and reusability during four successive cycles. Finally, a possible mechanism responsible for the charge separation and improved photocatalytic activity was proposed.