Lowering the Cu-O bond energy in CuO nanocatalysts enhances the efficiency of NH3 oxidation

Abstract

Abstract Tuning the electronic properties of nanocatalysts via doping with monodispersed hetero-metal atoms is an effective method used to enhance catalytic properties. Doping CuO nanoparticles with monodispersed Co atoms using different reductants affords catalysts (Co B Cu/Al 2 O 3 and Co H Cu/Al 2 O 3 ) with strikingly different electronic structures. Compared to Co H Cu/Al 2 O 3 , the CuO nanoparticles in Co B Cu/Al 2 O 3 have longer and weaker Cu-O bonds, with a lower 1 s → 4 p z antibonding transition and higher 4 p → 1 s bonding transition (as demonstrated from HERFD-XANES and valence-to-core X-ray emission spectroscopy). The weaker Cu-O bonds in Co B Cu/Al 2 O 3 lead to superior redox activity of the CuO nanoparticles, evidenced from operando XAFS and in-situ near ambient pressure-near edge X-ray absorption fine structures studies. Such superior redox properties of CuO in Co B Cu/Al 2 O 3 result in a much reduced activation energy of Co B Cu/Al 2 O 3 compared to Co H Cu/Al 2 O 3 (40.0 vs. 63.5 kJ/mol), thus leading to an enhancement in catalytic performance in the selective catalytic oxidation of NH 3 to N 2 .