Regulating the redox sites of MMoOx (M = Mn, Fe, Cr) catalysts for highly efficient selective catalytic oxidation of NH3

Redox sites and acidic sites are the main active sites of bimetallic oxide catalysts used for selective catalytic oxidation of NH 3 (NH 3 -SCO). In this work, three MMoO x (M = Cr, Fe, and Mn) bimetallic oxides catalysts were prepared by simple grinding and calcination to investigate the effect of redox sites (M sites) on the NH 3 -SCO performance. The NH 3 -SCO test results showed that the activity of MMoO x is in the order of CrMoO x  > MnMoO x  > FeMoO x . The characterization results of H 2 -TPR, O 2 -TPD, NH 3 -TPD, and in situ DRIFTS proposed that the NH 3 -SCO reaction on MMoO x catalysts is proceed via i-SCR mechanism, and the formation of the intermediates of NH 3 -SCR reaction is the decisive reaction step. Owing to the excellent ability in promoting the formation of nitrate/nitrite species, CrMoO x and MnMoO x samples show much higher NH 3 -SCO activity than FeMoO x sample . CrMoO x can facilitate the formation of a large amount of –NH 2 species, which together with nitrate/nitrite species enhance the NH 3 -SCO reaction via i-SCR reaction route. Therefore, CrMoO x shows the highest NH 3 -SCO activity among the MMoO x catalysts. Through this work, the redox sites of bimetallic oxide catalysts are demonstrated as a vital role in inducing the formation of reaction-active intermediates, which highlight the importance of choosing the redox sites in designing NH 3 -SCO catalyst.