Tuning the selectivity of NH3 oxidation via cooperative electronic interactions between platinum and copper sites

Abstract

Selective catalytic oxidation (SCO) of NH₃ to N₂ is one of the most effective methods used to eliminate NH₃ emissions. However, achieving high conversion over a wide operating temperature range while avoiding over-oxidation to NO_x remains a significant challenge. Here, we report a bi-metallic surficial catalyst (Pt_SCuO/Al₂O₃) with improved Pt atom efficiency that overcomes the limitations of current catalysts. It achieves full NH₃ conversion at 250 °C with a weight hourly space velocity of 600 ml NH₃·h⁻¹·g⁻¹, which is 50 °C lower than commercial Pt/Al₂O₃, and maintains high N₂ selectivity through a wide temperature window. Operando XAFS studies reveal that the surface Pt atoms in Pt_SCuO/Al₂O₃ enhance the redox properties of the Cu species, thus accelerating the Cu²⁺ reduction rate and improving the rate of the NH₃-SCO reaction. Moreover, a synergistic effect between Pt and Cu sites in Pt_SCuO/Al₂O₃ contributes to the high selectivity by facilitating internal selective catalytic reduction.