希土類元素を含む酸化物光触媒の可視光応答化

抄録

Perovskite oxides containing lanthanides BaCeO₃ and BaCe_0.95R_0.05O₃ (R = La, Pr, and Gd) were synthesized by pechini method: the calcination of gel precursor consisting of metal ion complexes with citric acid and propylene glycol. Obtained samples were examined by XRD measurement to clarify the crystal structure. BaCeO₃ mainly absorbed ultraviolet light, while all of BaCe_0.95R_0.05O₃ absorbed visible-light. Furthermore, All of BaCe_0.95R_0.05O₃ showed higher photocatalytic activity than BaCeO₃ under visible-light irradiation. It was found that perovskite oxides containing rare earths BaCe_0.95R_0.05O₃ drive as visible-light responsive photocatalysts. This suggests that the band gap of the photocatalyst can be freely controlled by inserting the 4f orbital of the rare earth. Photocatalytic degradation of methylene blue has been investigated in aqueous suspension under artificial sunlight irradiation for the evaluation of these photocatalysts. The relationship between the calcination temperature and remaining impurities in the synthesis of BaCeO₃, a UV-responsive photocatalyst, was clarified by XRD, TG/DTA and IR measurements. However, in the MB dye decomposition test, BaCeO₃ calcined at 1000°C showed the highest photocatalytic activity. This may be the result of the increase in specific surface area due to the control of particle size rather than the presence of impurities, since the presence of impurities, BaCO₃, does not interfere with the photocatalytic activity. In the MB dye decomposition test, all the solid solution samples of BaCe_0.95R_0.05O₃ showed higher MB decomposition efficiency than BaCeO3. The diffuse reflection spectra suggested that all the BaCe_0.95R_0.05O₃ samples have a narrower band gap than BaCeO₃. For example, the MB decomposition efficiency of BaCe_0.95Pr_0.05O₃ was 96% with a band gap of 2.46 eV. The visible-light responsive photocatalyst BaCe_0.95R_0.05O₃ (R = La, Pr, and Gd) was synthesized without loss of photocatalytic activity even with a reduced band gap.