Preparation of a layered hexaniobate-titania nanocomposite and its photocatalytic activity on removal of phenol in water

A nanocomposite photocatalyst of two photocatalytically active semiconductor oxides was prepared by flocculation of exfoliated layered hexaniobate K4Nb6O17 with TiO2 fine particles in presence of acid electrolyte, and evaluated as photocatalyst by using photodegradation of phenol as a test reaction. Disappearance of (0k0) peaks which correspond to the basal spacing in the X-ray diffraction (XRD) patterns of the nanocomposite suggested that the exfoliated niobate nanosheets were randomly hybridized with TiO2 particles without restacking to the layered structure. Scanning electron microscopy revealed that the nanocomposite was an agglomerate of closely packed niobate nanosheets and TiO2 particles. The nanocomposite is mesoporous and has a specific surface area larger than those of the original K4Nb6O17 and TiO2 as indicated by N-2 adsorption-desorption isotherms. The increase in surface area is ascribed to the porous structure constructed by the exfoliated niobate nanosheets and TiO2 particles. The photocatalytic activity of the porous nanocomposite was superior to those of K4Nb6O17 and TiO2 in terms of degradation of phenol.