Enhanced photocatalytic activity of La3+ and Se4+ co-doped bismuth ferrite nanostructures

Photocatalysis is attracting huge interest for addressing current energy and environmental issues by converting solar light into chemical energy. For this purpose, we investigated the effect of La³⁺ and Se⁴⁺ co-doping on the photocatalytic activity of BiFeO₃. BiFeO₃ and Bi_0.92La_0.08FeO₃ nanoparticles containing different Se⁴⁺ doping content (BiFe_(1−x)SexO₃, x = 0.0, 0.02, 0.05, and Bi_0.92La_0.08Fe_(1−x)Se_xO₃, x = 0.0, 0.02, 0.05, 0.075, 0.1) were synthesized by a double solvent sol–gel route. The co-doped nanoparticles were characterized by X-ray diffractometry (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), and UV-vis diffuse reflectance spectroscopy (DRS), and their photocatalytic activity was studied by the photocatalytic degradation of Congo Red (CR) in aqueous solution under different wavelengths of light illumination. The band-gap of the pure BiFeO₃ was significantly decreased from 2.06 eV to 1.94 eV. It was found that La³⁺ and Se⁴⁺ co-doping significantly affected the photocatalytic performance of pure BiFeO₃. Moreover, with the increment of Se⁴⁺ doping into Bi_0.92La_0.08FeO₃ up to an optimal value, the photocatalytic activity was maximized. In order to study the photosensitization process, photo-degradation of a colourless organic compound (acetophenone) was also observed. On the basis of these experimental results, the enhanced photocatalytic activities with La³⁺ and Se⁴⁺ co-doping could be attributed to the increased optical absorption, and efficient separation and migration of photo-generated charge carriers with the decreased recombination of electrons–holes resulting from co-doping effects. The possible photocatalytic mechanism of La³⁺ and Se⁴⁺ co-doped BiFeO₃ was critically discussed.