Photocatalytic activity of cation (Mn) and anion (N) substitution in LaCoO₃ nanoperovskite under visible light

LaCoO₃ compound and novel photocatalysts of LaCo_0.8Mn_0.2O₃ and N-doped LaCoO₃ were synthesized by sol-gel method. The structure, morphology, size of particles and optical properties of the obtained powders were characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM) and ultraviolet–visible (UV–Vis) (DRS mode) spectroscopy. The perovskite structure obtained for all the prepared samples and doping Mn and N do not change the perovskite structure. SEM results revealed that the size of particles of all perovskites was less than 100 nm. Compared to that of parent LaCoO₃, the band gap energy of LaCo_0.8Mn_0.2O₃ and N-doped LaCoO₃ considerably reduced due to the formation of impurity level. The photocatalytic activity of all samples was evaluated by the degradation of malachite green as a model dye under visible light irradiation. The discoloration induced by LaCo_0.8Mn_0.2O₃ was twice that induced by pure LaCoO₃ because of Mn ions with variable valance and smaller band gap energy. The nitrogen incorporation also significantly improved the photocatalytic activity of LaCoO₃ due to more oxygen vacancies and the stronger absorption in visible region. In general, doping has been served as one of the most efficient methods for the improvement in band gap of photocatalysts.