Mechanistic Insights into Ammonia Oxidation over Electron Transfer-Induced Pt–O–Cu Dual Sites

Abstract

The low selectivity for N₂ in the oxidation of NH₃ over commercial Pt/Al₂O₃ catalysts is primarily due to the overoxidation of NH₃ facilitated by Pt sites, leading to the formation of unwanted byproducts such as N₂O and NO. In this study, we present a novel strategy to enhance N₂ selectivity while maintaining NH₃ conversion by constructing Pt–O–Cu dual sites. These dual sites exhibit synergistic acid-redox characteristics through surface electron transfer mediated by bridged lattice oxygen. Additionally, the ability of surface-adsorbed oxygen to exchange with lattice oxygen is significantly improved. The electron-deficient Cu sites enhance NH₃ adsorption by providing empty 3d orbitals, while the electron-rich Pt sites promote NH₃ dehydrogenation. Subsequently, the formation of –NH or –N intermediates at the Pt sites can react with adsorbed NH₃ on the Cu sites to produce N₂, predominantly following the integrated selective catalytic reduction mechanism. The optimized dual-site catalyst achieves over 95% NH₃ conversion and N₂ selectivity at 180 °C.