Characteristics and performance of rutile/anatase/brookite TiO2 and TiO2–Ti2O3(H2O)2(C2O4)·H2O multiphase mixed crystal for the catalytic degradation of emerging contaminants

Rutile TiO2 or binary/ternary/quaternary TiO2-Ti2O3(H2O)2(C2O4)·H2O mixed crystal, possessing self-assembly morphology and serving as a catalyst for photocatalysis degradation of organic pollutants or photoanode for photoelectrochemical (PEC) water splitting, are prepared by in-site growth through changing the concentration of potassium titanyl oxalate. The rutile/anatase TiO2 with mesoporous structure has a specific surface area of 27.896 m2 g-1 and an average pore size of 3.411 nm. The sample has a relatively more regular self-assembly morphology after heat-treated at different temperatures, however its photocatalytic activity is reduced. Excellent catalytic oxidation of methyl orange (MO) and hydroxylbenzoic acid (HBA) is observed on the as-synthesized samples, wherein rutile/anatase TiO2 and rutile/anatase/brookite TiO2-Ti2O3(H2O)2(C2O4)·H2O show excellent photocatalytic activity under UV-light. With the novel TiO2-Ti2O3(H2O)2(C2O4)·H2O mixed crystal catalyst, this study illustrates the photocatalysis mechanism of multiphase mixed crystal for removal of emerging contaminants in water. Based on the Mott-Schottky, XPS and energy band structure, we consider that an indirect Z-scheme transmission mode is generated between rutile/anatase TiO2 or TiO2-Ti2O3(H2O)2(C2O4)·H2O mixed crystal, wherein the photo-induced electrons in rutile TiO2 combined with the holes in anatase TiO2 or Ti2O3(H2O)2(C2O4)·H2O, leading to enhanced charge carrier extraction and utilization upon photoexcitation.