The catalytic activity and selectivity of Fe-Cu-SSZ-13 samples prepared by a two-step method, i.e., one-pot synthesis and impregnation or ion exchange were evaluated for NH3-SCR with or without H2O in the TPSR mode. The catalysts were characterized by XRD, TEM/EDX/EELS, XRF, N2-sorption, UV–Vis, EPR and operando IR techniques. Speciation of copper and iron sites in various pretreatment and reaction (p \({\text{O}}_{2}\) , p \({\text{H}}_{2}\text{O}\) ), and their interaction with NH3 was examined by DFT and first-principles thermodynamic (FPT) modeling. The SCR versus AMO (ammonia oxidation) competition was examined in the steady-state conditions using 14NH3/15NH3 reactants. The NH3-SCR activity, SCR versus AMO trade-off, and N2, NO2/N2O selectivity of the investigated catalysts depend significantly on the method of introducing iron into the zeolite and the dry and wet reaction conditions. The beneficial effect of water was associated with controlling the oxo/hydroxo nature of the dual active sites. The catalysts obtained by impregnation were active in a wider temperature window and exhibited higher selectivity to N2, compared to their counterparts obtained by ion exchange. Additionally, the introduction of iron by impregnation to parent Cu-SSZ-13 prepared by the one-pot method allows for attenuation of the concomitant NH3 oxidation (AMO), and a fivefold reduction in N2O production.
