Photocatalytic discoloration of an azo-dye using LaMn0.5Ti0.5O3 double perovskite under visible light irradiation and enhancement of photocatalytic activity by using graphene

Abstract

In this study, rare-earth perovskite-type oxides LaTiO3±δ, LaMnO3 and LaMn0.5Ti0.5O3 were prepared by the sol–gel method and tested for the photocatalytic decomposition of an azo dye, basic red 46, under visible light. The experimental results showed that the photocatalytic activity of LaMn0.5Ti0.5O3 was much higher than that of LaMnO3 and LaTiO3±δ. Then, the discoloration efficiency of basic red 46 was studied over LaMn0.5Ti0.5O3 prepared by several methods. The structure, morphology and light absorption of prepared samples were characterized by XRD, SEM and UV–vis (DRS mode) spectroscopy. The best photocatalytic performance exhibited by the LaMn0.5Ti0.5O3 prepared using the Pechini sol–gel method and its excellent activity results from narrower band-gap energy, smaller particles size and porosity structure which is capable of supporting the enhanced loading of organic contaminants on surface. In the following, graphene/LaMn0.5Ti0.5O3 nanocomposite photocatalysts were synthesized for the first time. The photocatalytic efficiency of the graphene/LaMn0.5Ti0.5O3 nanocomposites was higher than that of pristine LaMn0.5Ti0.5O3 and graphene(50%wt)/LaMn0.5Ti0.5O3 had the greatest photocatalytic activity (degradation 90% after 5 h). The excellent photocatalytic activity can be attributed to the high separation efficiency of photoinduced electron–hole pairs resulting from the excellent conductivity of in graphene/LaMn0.5Ti0.5O3.