Abstract
In search of better materials for visible light photocatalytic performance, perovskite Sr-0.3(Ba/Mn)(0.7)ZrO3 nanopowders anchored on graphene oxide were synthesized for the evaluation of their photocatalytic activity against methylene blue (MB). The chemical coprecipitation method was used to synthesize SrZrO3 (SZO) and a series of doped derivatives having a nominal composition of Sr1-x(Ba,Mn)(x)ZrO3 (x = 0.1-0.9) at an annealing temperature of 700 degrees C for 12 h. However, Sr-0.3(Ba,Mn)(0.7)ZrO3 with a bandgap value of 3.50 eV was further processed for the formation of composite with graphene oxide (GO) owing to its lowest bandgap value in the synthesized series. The inclusion of larger Ba2+ cations in the lattice resulted in the redistribution of cations creating antisite defects which were evident from the shrinkage of the lattice. The incorporation of Mn2+ resulted in the hybridization of Mn2+ (3d) orbitals with the split Zr4+ (4d) orbitals. This reduced the bandgap and composite formation with GO further enhancing the delocalization of excited electrons to GO hence, reducing electron-hole recombination. Adsorption assisted photocatalysis under a 100 W tungsten lamp was performed using the designed catalysts for the removal/degradation of MB. The pi-pi conjugation and the ionic interactions were found responsible for the adsorption of MB at the GO surface. High surface coverage, initial dye concentrations, heterogeneous catalyst surface, weak van der Waals interactions, pH and availability of center dot OH radicals were found to be the decisive factors for the removal/degradation process. Improved charge separation enhances the generation of center dot OH and better performance of the GO composites as opposed to the pristine strontium zirconate perovskites.