Controlling lattice oxygen reactivity in redox-active oxides is key for NH3 oxidation to N2O. Still, the long-standing focus on CeO2 has narrowed the chemical space for elucidating transferable structure-performance relationships for rare earth oxide-based (REO) catalysts. Here, we employ flame spray pyrolysis to introduce gold (1 wt % Au) as nanoparticles (ca. 10 nm) across eight REOs, including La, Ce, Pr, Nd, Sm, Eu, Gd, and Tb. In the Au-REO catalysts, N2O productivity follows support redox activity, rising from trivalent to tetravalent and peaking on mixed-valent oxides. The best-in-class catalyst is nonstoichiometric Au-PrOx, combining 87% N2O selectivity at full conversion and long-term stability. 18O2 isotope exchange establishes the activation temperature of oxygen-exchange sites and their homogeneity as the governing selectivity descriptors. Combining operando near-ambient-pressure X-ray photoelectron and absorption spectroscopies, we identify cationic Au3+ as Lewis-acid sites that withdraw electron density from NH3, facilitating N–H cleavage by lattice oxygen. The Au–O–Pr ensembles promote redox cooperation between cationic Au species and PrOx lattice, mediating oxygen transfer to surface NH* species forming short-lived nitroxyl (HNO*) intermediates, the rate-determining step preceding rapid HNO* coupling to N2O. These findings introduce a benchmark for N2O synthesis and provide general design principles to tune Mars-van Krevelen chemistry across selective oxidations.
Beshara et al. (Fri,) studied this question.