Temperature-driven dynamic evolution process of Ag species on silver-loaded Zr0.2Sn0.8O2 catalyst for selective catalytic oxidation of ammonia.

[Display omitted] • Temperature drives the evolution of Ag species dynamics. • The NH 3 -SCO reaction mechanism varies at different Ag sites. • The products formed depend on the state of the Ag species. Silver-based catalysts are extensively utilized in the selective catalytic oxidation of ammonia (NH 3 -SCO). However, enhancing low-temperature activity often causes a decline in N 2 selectivity, presenting a substantial challenge in balancing activity and N 2 selectivity. In this work, we introduced zirconium into the SnO 2 support, resulting in a significant enhancement of low-temperature activity by 200 °C for the Ag/Zr 0.2 Sn 0.8 O 2 catalyst; yet, this also led to the formation of N 2 O at low temperatures and NO x at high temperatures. Characterizations such as XPS and in situ DRIFTS revealed that the dynamic changes of silver species driven by temperature had a profound impact on the reaction mechanism and guided the formation of different products. Below 200 °C, the predominance of Ag+ directed the imide mechanism, with the –HNO species being the key intermediate leading to the production of N 2 O. Above 300 °C, Ag0 became dominant, favoring the internal selective catalytic reduction (i-SCR) mechanism and the production of NO x. This work provides novel insights into improving N 2 selectivity of Ag-based catalysts and contributes to a deeper understanding of the reaction mechanisms. [ABSTRACT FROM AUTHOR]