Visible light photocatalysis employing TiO2/SrTiO3-BiOI composites: Surface properties and photoexcitation mechanism

A series of binary TiO2/SrTiO3 and ternary TiO2/SrTiO3_BiOI composites have been synthesized using multistep preparation method. Characterization of the obtained photocatalysts covered complex analysis including morphology + y (SEM), BET specific surface area, porosity, optical properties (DRS), chemical composition of surface (XPS), crystal structure and crystal size (XRD). UV–vis and Vis ligh induced photocatalytic activity was investigated in the model reaction of phenol degradation in the aqueous phase. The powder TiO2/SrTiO3_BiOI ternary composites exhibited a new photocatalytic properties and could be used in the heterogeneous photocatalysis processes. The photocatalytic activity observed in the phenol degradation reaction significantly increased under the visible light range irradiation. The best photocatalytic activity was observed for the TiO2/SrTiO3_BiOI_4 sample, about 30.2 % of phenol was decomposed after 1 h of visible light irradiation. The utilization of the nanolayered materials facilitates the separation of photocatalysts from the aqueous phase. Moreover, the composite was easily reused without the significant decrease of the photocatalytic activity in three subsequent cycles. After 5 h of Vis irradiation of the isotopically labeled (1-13C) phenol solution in the presence of the TiO2/SrTiO3_BiOI_4 composite, the salicylic, maleic, fumaric and malonic acids were detected using GC–MS equipment. The identification of degradation by-products led to clarification of phenol decomposition pathway. The role of active species during the decomposition process of organic compound was investigated using different types of active species scavengers.