Nitrogen and Phosphorus Co-Doped TiO₂ for Photocatalytic Removal of Gaseous Chlorobenzene under High Humidity Condition: Preparation, Characterization and Performance

Nitrogen and phosphorus co-doped TiO₂ photocatalysts were synthesized by a hydrothermal sol-gel method using tetrabutyl titanate as titanium source, urea as nitrogen source and phosphoric acid as phosphorus source. Response surface methodology (RSM) was employed to obtain the optimum ratio of 0.5:0.5:0.5:1 (N:P:(NH₄)₂CO₃:Ti) for achieving the best chlorobenzene (CB) removal rate. The catalysts were characterized by XRD, TEM, XPS, etc., and the results suggest that the nitrogen and phosphorus co-doped TiO₂ consists of anatase and rutile with larger surface area. The UV-vis absorption spectra are red-shifted to 497 nm. CB removal efficiency is 94.6% under conditions of relative humidity 10%, initial concentration 150 mg·m^-3 and residence time 60 s. The catalyst remains high removal efficiency (over 70%) under relative humidity 90%, and the removal efficiency decreases slowly under high relative humidity. The catalytic activity slightly reduces from 94% to 74% after continuous running for over 24 h, which reveals that the prepared catalyst has good stability.