Thin film nano-photocatalyts with low band gap energy for gas phase degradation of p-xylene: TiO2 doped Cr, UiO66-NH2 and LaBO3 (B = Fe, Mn, and Co)

Cam Loc Luu, Thi Thuy Van Nguyen, Tri Nguyen, Phung Anh Nguyen, Tien Cuong Hoang and Cam Anh Ha

Abstract

By dip-coating technique the thin films of nano-photocatalysts TiO₂, Cr-doped TiO₂, LaBO₃ perovskites (B  =  Fe, Mn, and Co) prepared by sol-gel method, and UiO66-NH₂ prepared by a solvothermal were obtained and employed for gas phase degradation of p-xylene. Physicochemical characteristics of the catalysts were examined by the methods of BET, SEM, TEM, XRD, FT-IR, TGA, Raman and UV–vis spectroscopies. The thickness of film was determined by a Veeco-American Dektek 6M instrument. The activity of catalysts was evaluated in deep photooxidation of p-xylene in a microflow reactor at room temperature with the radiation sources of a UV (λ  =  365 nm) and LED lamps (λ  =  400–510 nm). The obtained results showed that TiO₂ and TiO₂ doped Cr thin films was featured by an anatase phase with nanoparticles of 10–100 nm. Doping TiO₂ with 0.1%mol Cr₂O₃ led to reduce band gap energy from 3.01 down to 1.99 eV and extend the spectrum of photon absorption to the visible region (λ  =  622 nm). LaBO₃ perovkite thin films were also featured by a crystal phase with average particle nanosize of 8–40 nm, a BET surface area of 17.6–32.7 m² g⁻¹ and band gap energy of 1.87–2.20 eV. UiO66-NH₂ was obtained in the ball shape of 100–200 nm, a BET surface area of 576 m² g⁻¹ and a band gap energy of 2.83 eV. The low band gap energy nano-photocatalysts based on Cr-doped TiO₂ and LaBO₃ perovskites exhibited highly stable and active for photo-degradation of p-xylene in the gas phase under radiation of UV–vis light. Perovskite LaFeO₃ and Cr–TiO₂ thin films were the best photocatalysts with a decomposition yield being reached up to 1.70 g_p-xylene/g _cat