Unraveling the Lattice O Assisted Internal Selective Catalytic Reduction Mechanism on High N2 Selectivity of CuOx/PtCu Catalysts in NH3-SCO

Abstract

Supported Pt catalysts suffer from low reaction selectivity (<65% at 100% conversion) in the selective catalytic oxidation of ammonia (NH3-SCO) because of their intrinsic over-oxidation tendencies. Herein, a strategy based on facilitating byproduct NOx reduction to N2 is demonstrated at CuOx/PtCu catalysts, aiming to tackle the low selectivity challenge. This PtCu alloy sample with a CuOx-rich surface displays an N2 selectivity of 95%, while its turnover frequencies are the highest among reported supported Pt-based catalysts. The enhanced reaction activities and N2 selectivities are primarily attributed to the Pt-Cuδ+ dual-site synergies at the CuOx/PtCu interface, in which dual sites exhibit distinct NH3 adsorption, activation, and dehydrogenation behaviors. The Olat assisted internal selective catalytic reduction mechanism at CuOx/PtCu with N2O22– as the central intermediates is proposed. Density functional theory calculation and temperature-programmed surface reaction measurements show that the N–O bond in N2O22– tends to break simultaneously with the assistance of Ov in CuOx followed by the easy transition from N2O22– to N2, which serve as the origin of the high selectivity.