Enhanced Photocatalytic Performance and Mechanism of Au@CaTiO(3) Composites with Au Nanoparticles Assembled on CaTiO(3) Nanocuboids

Using P25 as the titanium source and based on a hydrothermal route, we have synthesized CaTiO(3) nanocuboids (NCs) with the width of 0.3–0.5 μm and length of 0.8–1.1 μm, and systematically investigated their growth process. Au nanoparticles (NPs) of 3–7 nm in size were assembled on the surface of CaTiO(3) NCs via a photocatalytic reduction method to achieve excellent Au@CaTiO(3) composite photocatalysts. Various techniques were used to characterize the as-prepared samples, including X-ray powder diffraction (XRD), scanning/transmission electron microscopy (SEM/TEM), diffuse reflectance spectroscopy (UV-vis DRS), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Rhodamine B (RhB) in aqueous solution was chosen as the model pollutant to assess the photocatalytic performance of the samples separately under simulated-sunlight, ultraviolet (UV) and visible-light irradiation. Under irradiation of all kinds of light sources, the Au@CaTiO(3) composites, particularly the 4.3%Au@CaTiO(3) composite, exhibit greatly enhanced photocatalytic performance when compared with bare CaTiO(3) NCs. The main roles of Au NPs in the enhanced photocatalytic mechanism of the Au@CaTiO(3) composites manifest in the following aspects: (1) Au NPs act as excellent electron sinks to capture the photoexcited electrons in CaTiO(3), thus leading to an efficient separation of photoexcited electron/hole pairs in CaTiO(3); (2) the electromagnetic field caused by localized surface plasmon resonance (LSPR) of Au NPs could facilitate the generation and separation of electron/hole pairs in CaTiO(3); and (3) the LSPR-induced electrons in Au NPs could take part in the photocatalytic reactions.