High-Performance Ag-Cu Nanoalloy Catalyst for the Selective Catalytic Oxidation of Ammonia

High-performance Ag-Cu alloy nanoparticles (NPs) were successfully synthesized by a solventless mix-bake-wash method and tested for NH₃-SCO. The prepared Ag₂Cu₁ catalyst with a perfect Ag-Cu alloy structure exhibited better T₁₀₀ (200 °C, the temperature at which 100% NH₃ conversion was obtained), higher reaction rates, and lower E_a compared to that with ordinary bimetallic Ag-Cu (AgCuO). The characterization data revealed much smaller Ag-Cu alloy nanoparticles of the Ag₂Cu₁ catalyst and more Ag/Cu metallic species on the surface, which can increase the amount of chemisorbed surface oxygen (O_β) and enhance NH₃ adsorption and activation in the low-temperature range, therefore leading to a much higher NH₃-SCO activity. Kinetic studies and density functional theory calculations indicated that Cu decoration at Ag by Ag-Cu alloying could enhance the adsorption/activation of NH₃ and O₂. It has been found that O₂ was more easily transformed from the adsorption state to the transition state than NH₃, which enhanced the performance of NH₃ oxidation. In addition, the Ag₂Cu₁ catalyst exhibited excellent durability because of the stabilization of Ag sites by the Ag-Cu alloy structure.