Tuning the Chemical State of Silver on Ag-Mn Catalysts to Enhance the Ozone Decomposition Performance

Ag-Mn catalysts with excellent water resistance and ozone decomposition activity were successfully synthesized by simple precipitation and impregnation methods. Under a relative humidity of 65% and space velocity of 840,000 h^-1, the 6%Ag/α-Mn₂O₃-I catalyst showed 99% conversion of 40 ppm O₃ after 6 h, which was far superior to the performance of the 6%AgMnO-C (49%), 6%Ag/MnCO₃-I (32%), and α-Mn₂O₃ (5%) catalysts. Physicochemical characterization indicated that the chemical state of Ag on the Ag-Mn catalysts determined the O₃ decomposition activity of the catalysts. The Ag species on the 6%Ag/α-Mn₂O₃-I catalyst were mainly metallic silver nanoparticles (Ag_n⁰), which exhibited much better ozone decomposition performance than the Ag_1.8Mn₈O₁₆ and oxidized silver clusters (Ag_n^δ+) existing on the 6%Ag/MnCO₃-I and 6%AgMnO-C catalysts. The 6%Ag/α-Mn₂O₃-I catalyst still had above 85% ozone conversion after 60 h under a relative humidity of 65% and space velocity of 840,000 h^-1. The slight deactivation of the catalyst was ascribed to the oxidation of Ag_n⁰, and its activity could be completely recovered by treatment at 350 °C under an N₂ atmosphere, which indicated that it is a promising catalyst for ozone decomposition. This research provides guidance for the subsequent development of Ag-Mn catalysts for ozone decomposition with high activity.