Oxidation of phenols by TiO2single bondFe3O4single bondM (M = Ag or Au) hybrid composites under visible light

Abstract

TiO2 and its hybrid TiO2single bondFe3O4 NPs were prepared, and doped with Ag, or Au NPs to yield TiO2single bondFe3O4single bondAg NPs and TiO2single bondFe3O4single bondAu NPs. The photo-catalytic oxidation of phenols by the above materials were analyzed under both solar and UV light. For TiO2single bondFe3O4single bondAg NPs and TiO2single bondFe3O4single bondAu NPs considerable visible light photo-oxidation was observed, while for other nano-materials UV-light energy required. The materials having Fe3O4 were reused after isolation by magnets. The oxidation rate decreases from phenol to 2,4,6-trichlorophenol in agreement with the Hammett plot, and follows first order kinetics in the substrate, for which a possible mechanism is proposed. The effect of pH, and solvents were also analyzed in the oxidation. To further support our kinetics experiments, Density functional theory (DFT) calculation were performed to predict the rate limiting step of phenol oxidation to yield benzoquinone.