Enhanced photocatalytic activity of CaTiO3-graphene nanocomposites for dye degradation

Calcium titanate (CaTiO3) nanoparticles with an average size of 36 nm were synthesized by a polyacrylamide route. CaTiO3-graphene composites were fabricated by mixing CaTiO3 particles and graphene into absolute ethanol, followed by thermal drying. The prepared samples were characterized by x-ray powder diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and UV-visible diffuse reflectance spectroscopy. Methyl orange (MO) was chosen as the target pollutant to evaluate the photocatalytic activity of the samples under UV irradiation. Our results show that CaTiO3-graphene composites exhibit enhanced photocatalytic activity compared to bare CaTiO3 particles. This can be explained by the effective suppression of electron-hole pair recombination due to the transfer of photogenerated electrons from the conduction band of CaTiO3 to graphene sheets. Hydroxyl (center dot OH) radicals were detected by fluorimetry using terephthalic acid as a probe molecule, revealing an enhanced yield on the irradiated CaTiO3-graphene composites. Ethanol was used as a center dot OH scavenger to investigate its effect on photocatalytic efficiency as well as on center dot OH radical yields. Based on the experimental results, we suggest that center dot OH radicals are the dominant active species responsible for the dye degradation.