Enhancement of photoresponse to ultraviolet region by coupling perovskite LaMnO₃ with TiO₂ nanoparticles

Mixed oxides of rare-earth elements and 3d transition metal perovskite materials were studied for their catalytic application. We have previously reported the catalytic performance of perovskite LaMnO₃ nanoparticles under visible light and ultrasonic irradiation separately and simultaneously. However, LaMnO₃ perovskite's narrow optical gap can absorb only a small portion of the solar spectrum in the ultraviolet region, resulting in low catalytic performance. Coupling LaMnO₃ with other metal oxides with an optical gap in the ultraviolet light range offers an effective solution to this problem by improving catalytic performance. To this end, sol-gel was used to prepare LaMnO₃/TiO₂ nanocomposites with varying LaMnO₃ to TiO₂ molar ratios. The LaMnO₃/TiO₂ nanocomposites were characterized using X-ray diffraction (XRD), a vibrating samples magnetometer (VSM), and UV-visible diffuse reflectance spectroscopy (DRS). The anatase phase of TiO₂ and the orthorhombic structure of LaMnO₃ facilitate the coupling of LaMnO₃ with TiO₂, and the incorporation of TiO₂ nanoparticles tends to increase the optical gap of the nanocomposite. The samples were used to remove organic dyes by means of simultaneous light and ultrasonic irradiation. The results confirm that the photosonocatalytic performance of LaMnO₃/TiO₂ nanocomposites successfully extends to the ultraviolet light region, and the main factors influencing photosonocatalytic activity are studied and discussed. (paper)