Structural analysis and photocatalytic activities of bismuth-lanthanide oxide perovskites

A series of pure bismuth-lanthanide oxide perovskites of the formula of BiLnO₃ (Ln = Sm, Eu, Tb, Er and Ho) has been synthesized via simple sol-gel methods. The elemental compositions and valence states of these materials were confirmed by X-ray photoelectron spectroscopy (XPS). Powder X-ray diffraction spectroscopy (PXRD) revealed an isostructural cubic system of BiEuO₃, BiTbO₃ BiErO₃ and BiHoO₃, whereas BiSmO₃ adapted a rhombohedral system. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) were employed to further characterize and analyze the structure of these mixed metal oxides. Band gap measurements obtained using diffuse reflectance spectroscopy (DRS) revealed potential photocatalytic activities of BiLnO₃ in the visible light region (2.14 eV, 2.23 eV, 1.50 eV, 2.10 eV and 2.13 for BiSmO₃, BiEuO₃, BiTbO₃, BiErO₃ and BiHoO₃ respectively). Accordingly, the photocatalytic performances of BiLnO₃ were investigated for the cyclic carbonate formation by CO₂ cycloaddition reaction to multiple epoxides. Reaction yields of the reported photocatalysts varied up to 99.9% depending on the epoxide substrate used. The simple sol-gel route explained in this report offers an easy, low-cost, environmentally friendly synthesis of highly efficient photocatalysts for a potential variety of photochemical reactions.