A Cu–Pd single-atom alloy catalyst for highly efficient NO reduction

Abstract

A series of Cu-Pd alloy nanoparticles supported on Al₂O₃ were prepared and tested as catalysts for deNO _<i>x</i> reactions. XRD, HAADF-STEM, XAFS, and FT-IR analyses revealed that a single-atom alloy structure was formed when the Cu/Pd ratio was 5, where Pd atoms were well isolated by Cu atoms. Compared with Pd/Al₂O₃, Cu₅Pd/Al₂O₃ exhibited outstanding catalytic activity and N₂ selectivity in the reduction of NO by CO: for the first time, the complete conversion of NO to N₂ was achieved even at 175 °C, with long-term stability for at least 30 h. High catalytic performance was also obtained in the presence of O₂ and C₃H₆ (model exhaust gas), where a 90% decrease in Pd use was achieved with minimum evolution of N₂O. Kinetic and DFT studies demonstrated that N-O bond breaking of the (NO)₂ dimer was the rate-determining step and was kinetically promoted by the isolated Pd.