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

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.