Synthesis of BiOI nanosheet/coarsened TiO2 nanobelt heterostructures for enhancing visible light photocatalytic activity

Abstract

For high photocatalytic activity, BiOI nanosheets were deposited on acid-corroded TiO₂ nanobelts, where a large number of BiOI nanosheet/TiO₂ nanobelt heterojunctions could be built. The structure, morphology and optical properties of the BiOI nanosheet/coarsened TiO₂ nanobelt heterostructure composites (BiOI/TiO₂ CNHs) were characterized by XRD, XPS, SEM, HRTEM, DRS, PL, TOC and nitrogen sorption. The XRD results show that only two phases of TiO₂ and BiOI were found in the composites. The HRTEM image shows clear lattice fringes, which prove the formation of heterojunctions at the interface between BiOI and coarsened TiO₂. The photocatalytic activity of the BiOI/TiO₂ CNHs for the degradation of methyl orange under visible-light irradiation was evaluated. The results reveal that the BiOI/TiO₂ CNHs exhibited much higher photocatalytic activity compared with coarsened TiO₂ nanobelts and pure BiOI nanosheets due to the introduction of BiOI onto the surface of the coarsened TiO₂ nanobelts and the formation of heterojunctions. BiOI acts as a visible light photosensitizer in the BiOI/TiO₂ CNHs. In addition, the large surface area and matched energy bands of the BiOI/TiO₂ CNHs both contribute to enhancing the photocatalytic activity. In addition, the possible mechanism of promotion of the photocatalytic performance of the new heterostructure system is explained.