VIS-active TiO2 – graphene oxide composite thin films for photocatalytic applications

Abstract

This paper reports on a novel path to deposit VIS-active composite photocatalytic thin films based on titanium dioxide (TiO2) and graphene oxide (GO) by coupling two up-scalable techniques: spray pyrolysis deposition (SPD) and sol–gel spraying (SG). The first step involves the SPD deposition of aTiO2layer on the FTO substrate, followed by the deposition of a TiO2-GO composite layer from adispersion and the influence of the GO content on the stability, morphology and crystallinity of the two-layered thin film was outlined. The thin films were tested in standard photo-degradation processes, using the methylene blue (MB) dye andimidacloprid (IMD) to outline the effect of a possible dye-sensitization, under simulated solar radiation, UV (~5%) + VIS (~95%), at low irradiance values. Comparative experiments using only UV radiation proved the extension of the activation domain towards VIS as result of the GO insertion in the composite thin films. The thin films proprieties were investigated correlated with the MB and IMD photo-degradation;the results show that the photocatalytic efficiencies were mainly influenced by the composites roughness (specific surface) and crystallinity. The stability of the thin films in the aqueous pollutant environment was good as the experimental results showed no wash-out effect.