TiO2−x prepared by radio-frequency thermal plasma: optical switching of hydrophilicity and hydrophobicity used in the efficient recovery of photocatalysts

Abstract

Titanium dioxide (TiO₂) has attracted considerable attention in the photocatalytic degradation field because of its rapid degradation rate, resistance to photo-corrosion, and chemical inertness. Developing an efficient, green, and economical approach for recovering TiO₂ catalyst from spent reaction systems has become a research hotspot recently. Herein, a new TiO₂ catalyst powder with substantial introduced oxygen vacancies (TiO_2−x) was synthesized using radio-frequency (RF) thermal plasma. The oxygen vacancies (V_O) in the TiO_2−x allow switching between hydrophilicity and hydrophobicity by the adsorption and desorption the hydroxyl groups (–OH) under the effect of illumination, thus regulating the dispersion and agglomeration of the TiO_2−x catalyst particles, which achieve uniform dispersion during catalysis but can form floating balls for easy recycling. Thus “salvage” of the ball-shaped catalysts can achieve green, convenient, and efficient recovery with almost no loss. Moreover, the as-prepared TiO_2−x catalyst has a good degradation effect in photocatalytic degradation of methylene blue, with 90% degradation in 25 min under full-spectrum conditions, and 94% and 93% degradation in the second and third cycles. Therefore, our research provides a promising strategy for the design and synthesis of new photocatalysts with high recovery and high catalytic efficiency for the cyclical regeneration of TiO₂ used as a catalyst in photocatalytic degradation.