Experimental Study On Photocatalytic Oxidation Of NO Over Pt And Pd Doped TiO₂ Catalysts

Photocatalytic oxidation over titanium dioxide has advantages of mild reactive conditions, low energy consumption, no secondary pollutants, etc, which has broad application prospects in NOx control. A systemic research on photocatalytic oxidation of NO over noble metal (Pt or Pd) modified TiO2 catalysts was carried out in this paper. The influence of preparation conditions of Pt/TiO2 and Pd/TiO2 was emphatically investigated, and the optimal processing conditions were then obtained. Based on the characterizations of these catalysts prepared under different conditons by XRD, XPS, TPD, PL, et al, the effecting mechanism on photocatalytic oxidation of NO over Pt or Pd modified TiO2 was investigated. Furthermore, the TiO2 nanotubes (TNTs) with fine surface structure were prepared by alkali hydrothermal method. The photocatalytic oxidation of NO over TNTs and the influences of doping noble metal on the photocatalytic activity are studied.Firstly, a series of Pt-modified TiO2 were prepared by deposition-precipitation method at different pH values. And the influences of pH value on the characteristics and activity of photocatalyst were investigated. It was found that the catalysts had the highest photocatalytic activity for NO conversion as pH value was kept at around 7. Furthermore, the influences of precipitator on the catalysts were studied. The experimental results showed that the NO conversion of catalysts prepared by using ammonia as precipitator is higher than catalysts prepared by NaOH.Secondly, Pd-modified TiO2 prepared by impregnation method was used in this work for photocatalytic oxidation of NO. This study has been undertaken to investigate the influence of palladium source and sintering temperature on the Pd/TiO2. It was found that the doping of Pd could improve the photocatalytic activity, and the activity of catalysts would be affected greatly after calcination treatment. The difference of the calcination temperature would change the crystal phases, oxidation state of Pd and NO dasorption capacity, which further affect the activity of catalysts.Finally, the TiO2 nanotubes (TNTs) and Pd doped TNTs were prepared by alkalihydrothermal method and impregnation method, respectively. The influences of the calcination temperature, modified method, Pd doped content on the the crystal structure, morphology and catalytic activity of Pd/TNTs. The experimental results indicated that the optimum calcination temperature was 400℃, the optimum modified method was the impregnation method, and the optimum Pd doped content was 0.02%.