Porous core-shell TixSn1-xO2 solid solutions with broad-light response: One-pot synthesis and ultrahigh photooxidation performance

[Display omitted] •Porous core-shell TixSn1-xO2 solid solutions are self-developed via Ostwald ripening process.•The solid solutions possess effective light harvesting capacity and charge separation.•The prepared Ti0.7Sn0.3O2 sample shows ultrahigh photo-activity in MO and As(III) removal.•The holes are detected as the main active species for the photooxidation of MO and As(III). Low light-absorption capacity and separation efficiency of photo-generated charges are two major limit factors to achieve high performance of photocatalysts. Herein, porous core-shell TixSn1-xO2 solid solutions with effective light-absorption capacity and charge separation are fabricated through one-pot mild solvothermal method without any surfactant and template. The self-development mechanism of the porous core-shell microspheres includes prior Ti-alkoxide hydrolysis and the spontaneous nucleation of TixSn1-xO2 combined with Ostwald ripening. Interestingly, although both TiO2 and SnO2 are wide band gap semiconductors, the prepared yellow TixSn1-xO2 solid solutions are of controllable band structure and broad-light response capacity. When Ti:Sn molar ratio is 7:3, the Ti0.7Sn0.3O2 sample shows the highest MO-photodegradation rate constant of 0.62 min−1 under UV irradiation, exceeding that of commercial TiO2 (0.04 min−1) by more than 15 times. Particularly, the sample also exhibits ultrahigh photocatalytic activity in MO-photodegradation (0.038 min−1) and As(III) removal (up to 100%) under visible-light (≥420 nm) irradiation. The mechanism study reveals that due to the proper redox potential of SnIV/SnII and the structural defects (e.g., oxygen vacancies) caused by lattice distortion, the photogenerated electrons would be trapped and the holes act as the main active species for the photooxidation reaction of MO and As(III) over TixSn1-xO2 photocatalysts.