NOx Storage Performance of Alkaline Earth-Doped Perovskite-Type BaFeO3 Catalysts

A series of Ba1-xMxFeO3 (M= Mg, Ca, Sr; x=0, 0.1, 0.2) perovskites were prepared by the sol-gel method as NOx storage reduction (NSR) catalysts. The effect of doping with alkaline earth metals (Mg, Ca, and Sr) on the NOx storage and oxidation performance of the BaFeO3 perovskites was investigated. Doping with Mg enhanced the NOx storage capacity (NSC) of the BaFeO3 perovskites in the temperature range 250-400 degrees C, the Ba0.8Mg0.2FeO3 perovskite exhibited the best NOx storage performance, which reached its maximum at 350 degrees C, with NSC>1200 mu mol . g(-1) and NO -> NO2 conversion of 53.4%. Compared with BaFeO3, the monodentate nitrate appeared clearly for the Ba0.8Mg0.2FeO3 sample after storing NOx at 250 degrees C. The amount of the monodentate nitrate on Ba0.8Mg0.2FeO3 varied with the NOx storage temperature in a similar manner to that of its NSC. Fourier transform infrared (FTIR) spectra indicated that doping with Mg induced an A-site deficient perovskite structure in BaFeO3, which readily generates oxygen vacancies that act as the active sites for NOx adsorption. Moreover, the residual MgO on the catalyst might also improve the NSC of the sample by forming the monodentate nitrate.