Effects of A-site replacement (Sm, Y, and Pr) on catalytic performances of mullite catalysts for NO oxidation

Mullite was one of the most promising catalysts that used in the selective catalytic oxidation of NO (NO-SCO), and deciphering its intrinsic properties that affect the catalytic performance was a great challenge but critical to the development of mullite catalysts. Herein, a series of Mn-based mullite nanofibers with different A-site cations were synthesized by electrospinning method and used for catalytic NO oxidation. Activity tests showed that SmMn2O5 exhibited a better NO conversion rate (77.8 %) than those of PrMn2O5 (63.3 %) and YMn2O5 (57.5 %) under typical experimental conditions (GHSV = 120 000 h-1, T = 325 degrees C). To investigate the factors influencing the catalytic activity, various techniques including XRD, N2 adsorption, SEM, TEM, EDX, XPS, H2-TPR, and O2-TPD were employed, and the results showed that abundant surface adsorbed oxygen species and good reducibility contributed greatly to the catalytic performance of SmMn2O5. DFT calculations revealed that A-site cation played the decisive role in the Fermi level relative to the Mn 3d-band centre, thus affecting the adsorption and dissociation of O2 molecule. The present synthetic strategy offered a new viable route for the large-scale preparation of metal oxide catalysts with remarkable NO oxidation performance for practical application.