Type-II band alignment in CNT-modified SrTiO3-Fe2TiO5 heterostructure nanocomposite for photocatalytic degradation of organic dyes

[Display omitted] •SrTiO3/Fe2TiO5/CNT nanocomposite was synthesized as a heterojunction photocatalyst.•Structural, morphological, optical and electrochemical properties were studied.•The mechanism of charge transfer between Fe2TiO5 and SrTiO3 was determined.•Photocatalytic activity for degradation of organic dye was optimized by RSM method. Carbon nanotube (CNT)-modified SrTiO3/Fe2TiO5 nanocomposite was synthesized as a novel heterojunction photocatalyst by a co-precipitation method. The composition of SrTiO3 with Fe2TiO5 and incorporation of CNT in the composite decreased the mean particle size from 70 to 45 nm, reduced the band gap energy from 3.2 to 2.82 eV, and increased the surface area about 3 times greater than the pure SrTiO3. The valence band X-ray photoelectron spectroscopy (VB-XPS) and UV–visible diffuse reflectance spectroscopy (DRS) results demonstrate that SrTiO3 and Fe2TiO5 phases effectively formed a charge transfer mechanism of type-II heterostructure. The lower intensity of photoluminescence (PL) spectroscopy peak, augmented photocurrent density, and less resistance of charge transfer indicated that the ternary SrTiO3/Fe2TiO5/CNT nanocomposite has a more significant charge transfer efficiency in comparison with pure SrTiO3 phase and binary SrTiO3/Fe2TiO5 nanocomposite. The prepared composite exhibited excellent photocatalytic activity and degraded the methylene blue dye completely. Using response surface methodology (RSM) method for experimental design, the optimum amounts of irradiation time, initial dye concentration and catalyst dosage of 71 min, 13.2 mg/L and 1.32 g/L were obtained, respectively. After four cycles, the photocatalyst showed high reusability and stability. The synthesized nanocomposite exhibited lower degradation efficiencies for Rhodamine-B and methyl orange dyes.