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Ag/MnO x catalysts have great potential for practical application in ozone (O 3 ) decomposition due to their superior activity under humid conditions. Metallic Ag nanoparticles (Ag n 0 ) have been identified as the critical active site for O 3 decomposition over Ag/MnO x catalysts. However, the role of Ag n 0 over Ag/MnO x catalysts during the O 3 decomposition remains unclear. In this study, Ag n 0 and oxidized Ag nanoparticles (AgO x ) are constructed on the MnO 2 supports. Under a relative humidity of 65% and a high space velocity of 2800 L·g –1 ·h –1, the conversion of 40 ppm of O 3 over the 4%Ag/γ-MnO 2 catalyst (91%) within 6 h is far superior to that over the 4%Ag/α-MnO 2 (22%) catalyst, which is attributed to the formation of Ag n 0 on the 4%Ag/γ-MnO 2 catalyst and AgO x on the 4%Ag/α-MnO 2 catalyst. Then, the role of Ag n 0 and AgO x during O 3 decomposition was determined by in situ Raman spectroscopy and DFT calculations. Compared with AgO x, the competitive adsorption of H 2 O and O 3 molecules on Ag n 0 is weaker, and O 3 molecules can be activated more rapidly on Ag n 0; most importantly, peroxide species are more easily desorbed on Ag n 0 . These advantages of Ag n 0 are the key to the superior O 3 decomposition activity of the 4%Ag/γ-MnO 2 catalyst under humid gas. This study provides guidance for understanding the Ag active sites for the decomposition of O 3 and the design of highly efficient Ag/MnO x catalysts.
Li et al. (Thu,) studied this question.