ABSTRACT Iron‐exchanged zeolites are promising materials for mitigating N 2 O emissions and selectively transforming CH 4 into CH 3 OH. The complex iron speciation in these materials, ranging from isolated centers to nanoparticles, still prevents thorough assessments of the active site structures. Here, we present a site‐specific kinetic analysis of N 2 O activation over Fe‐SSZ‐13 in inert conditions and in the presence of reducing agents, including CH 4 , NH 3 , and H 2 . Operando electron paramagnetic resonance measurements with phase‐sensitive detection proved essential for distinguishing active sites from spectator species. To capture fast kinetics, a novel step‐scan methodology is introduced that improves the temporal resolution of EPR by an order of magnitude. We found that isolated Fe 2+ species in axial coordination contribute solely to N 2 O decomposition in an Ar atmosphere, while Fe x O y clusters and Fe 2+ centers in distorted geometries exhibit redox activity in the presence of reducing agents. Quantitative kinetic analysis reveals that, in Ar or in the presence of CH 4 or H 2 , the reduction half‐cycle is rate‐limiting, whereas with NH 3 , the oxidation half‐cycle becomes rate‐limiting.
Fischer et al. (2026) studied this question.