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

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_BCu/Al₂O₃ and Co_HCu/Al₂O₃) with strikingly different electronic structures. Compared to Co_HCu/Al₂O₃, the CuO nanoparticles in Co_BCu/Al₂O₃ have longer and weaker Cu-O bonds, with a lower 1s → 4p_z antibonding transition and higher 4p → 1s bonding transition (as demonstrated from HERFD-XANES and valence-to-core X-ray emission spectroscopy). The weaker Cu-O bonds in Co_BCu/Al₂O₃ 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_BCu/Al₂O₃ result in a much reduced activation energy of Co_BCu/Al₂O₃ compared to Co_HCu/Al₂O₃ (40.0 vs. 63.5 kJ/mol), thus leading to an enhancement in catalytic performance in the selective catalytic oxidation of NH₃ to N₂.