TiO2 nanorods were prepared with alkaline hydrothermal digestion of high surface area TiO2 nanopowder. The as-synthesized TiO2 nanorods (a-TNR) consisted of a ~8 nm thick amorphous TiO2 layer covering the crystalline anatase TiO2 core. With further calcination of a-TNR in air for 2 h at 500oC we obtained TiO2 nanorods where only anatase TiO2 was present (TNR). The TiO2 NRs were further used to synthesize TiO2+GO composites: the loading of GO in both series of solids was varied from 4 to 20 wt. %. Structural, morphological and surface properties of the obtained TiO2+GO composites were analyzed and correlated to their performance in photocatalytic oxidation of aqueous bisphenol A (BPA) solution. Important difference was observed in the distribution of GO in the composites: aggregates of GO were present in TiO2+GO composites prepared with a-TNR, whereas GO was uniformly dispersed in TiO2+GO composites prepared with TNR. Cyclic voltammetry (CV) experiments show that the peak-to-peak separations (ΔEp) are lower and the oxidation current densities are higher for the TiO2+GO composites in comparison to pure TiO2 NRs. As a result, the electron-hole recombination in composites was slower, resulting in more electrons and holes being able to participate in the photocatalytic reaction. In particular, it was revealed by XPS and UV-Vis diffuse reflectance analyses that charge separation is improved by valence band hole transfer from TiO2 to GO. In very good agreement with these findings, photocatalytic oxidation tests have shown that in both series of composites the highest BPA degradation activity and TOC removal (about 99 % in 2 h reaction time) were achieved with the 10 wt. % GO composite. Excessive amount of GO (20 wt. %) in the TiO2+GO composites decreased the photocatalytic activity, which is attributed to shielding of TiO2 surface from absorbing UV light.

Improved electron-hole separation/migration in anatase TiO2 nanotube/reduced graphene oxide composites for efficient photocatalytic degradation of bisphenol A

253rd National Meeting (2017)

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