Tuning the selectivity of NH3 oxidation via cooperative electronic interactions between platinum and copper sites
Lu Chen, Xuze Guan, Zhaofu Fei, Hiroyuki Asakura, Lun Zhang, Zhipeng Wang, Xinlian Su, Zhangyi Yao, Luke L. Keenan, Shusaku Hayama, M. A. Van Spronsen, Burcu Karagoz, Georg Held, Christopher S. Allen, David G. Hopkinson, Donato Decarolis, June Callison, Paul J. Dyson, Feng Ryan Wang
Abstract
Abstract Selective catalytic oxidation (SCO) of NH 3 to N 2 is one of the most effective methods used to eliminate NH 3 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 S CuO/Al 2 O 3 ) with improved Pt atom efficiency that overcomes the limitations of current catalysts. It achieves full NH 3 conversion at 250 °C with a weight hourly space velocity of 600 ml NH 3 ·h −1 ·g −1 , which is 50 °C lower than commercial Pt/Al 2 O 3 , and maintains high N 2 selectivity through a wide temperature window. Operando XAFS studies reveal that the surface Pt atoms in Pt S CuO/Al 2 O 3 enhance the redox properties of the Cu species, thus accelerating the Cu 2+ reduction rate and improving the rate of the NH 3 -SCO reaction. Moreover, a synergistic effect between Pt and Cu sites in Pt S CuO/Al 2 O 3 contributes to the high selectivity by facilitating internal selective catalytic reduction.