Unraveling the Lattice O Assisted Internal Selective Catalytic Reduction Mechanism on High N<sub>2</sub> Selectivity of CuO<sub><i>x</i></sub>/PtCu Catalysts in NH<sub>3</sub>-SCO
Yanfei Liu, Zhang Liu, Chengxiong Wang, Jie Xu, Jianping Ai, Xiao Liu, Aimin Zhang, Yunkun Zhao, Chun Du, Bin Shan
Abstract
Supported Pt catalysts suffer from low reaction selectivity (<65% at 100% conversion) in the selective catalytic oxidation of ammonia (NH 3 -SCO) because of their intrinsic over-oxidation tendencies. Herein, a strategy based on facilitating byproduct NO x reduction to N 2 is demonstrated at CuO x /PtCu catalysts, aiming to tackle the low selectivity challenge. This PtCu alloy sample with a CuO x -rich surface displays an N 2 selectivity of 95%, while its turnover frequencies are the highest among reported supported Pt-based catalysts. The enhanced reaction activities and N 2 selectivities are primarily attributed to the Pt-Cu δ+ dual-site synergies at the CuO x /PtCu interface, in which dual sites exhibit distinct NH 3 adsorption, activation, and dehydrogenation behaviors. The O lat assisted internal selective catalytic reduction mechanism at CuO x /PtCu with N 2 O 2 2– as the central intermediates is proposed. Density functional theory calculation and temperature-programmed surface reaction measurements show that the N–O bond in N 2 O 2 2– tends to break simultaneously with the assistance of O v in CuO x followed by the easy transition from N 2 O 2 2– to N 2, which serve as the origin of the high selectivity.