Facile fabrication of stable r-GO/Pd–TiO2/r-GO thin film and its photoactivity under visible light

In this work, reduced graphene oxide (r-GO) sandwiched Pd–TiO2 thin films were fabricated in the form of moon pie on silica glass slices using a low-cost sol–gel facile coating method and their photocatalytic activity was studied using the degradation of methylene blue dye. The thin film was characterized using various techniques such as x-ray diffraction, x-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy, which revealed an average film thickness of 170 nm and an average crystallite size of 15 nm for Pd–TiO2 wrapped in r-GO layers. The stability and strength of the thin films was enhanced using graphene, preventing the breakage of the thin film during calcination and also the oxidation of the Pd–TiO2 thin film during chemical reactions. The r-GO sandwiched Pd–TiO2 thin film showed excellent activity in the photochemical degradation of methylene blue dye, and retained its activity and stability for ten cycles of recycling. The activity of the r-GO/Pd–TiO2/r-GO was greater than 1.4 × 10−5 g (min × m2)−1 in all of the experiments compared to the bare Pd–TiO2 which dropped markedly to less than 0.60 × 10−5 g (min × m2)−1 after the second run. This study can be considered as simple, environmentally friendly and cost effective methods for the treatment of wastewater.