Enhanced Performance and Conversion Pathway for Catalytic Ozonation of Methyl Mercaptan on Single-Atom Ag Deposited Three-Dimensional Ordered Mesoporous MnO₂

Abstract

In this study, Ag deposited three-dimensional MnO₂ porous hollow microspheres (Ag/MnO₂ PHMSs) with high dispersion of the atom level Ag species are first prepared by a novel method of redox precipitation. Due to the highly efficient utilization of downsized Ag nanoparticles, the optimal 0.3% Ag/MnO₂ PHMSs can completely degrade 70 ppm CH₃SH within 600 s, much higher than that of MnO₂ PHMSs (79%). Additionally, the catalyst retains long-term stability and can be regenerated to its initial activity through regeneration with ethanol and HCl. The results of characterization of Ag/MnO₂ PHMSs and catalytic performance tests clearly demonstrate that the proper amount of Ag incorporation not only facilitates the chemi-adsorption but also induces more formation of vacancy oxygen (O_v) and lattice oxygen (O_L) in MnO₂ as well as Ag species as activation sites to collectively favor the catalytic ozonation of CH₃SH. Ag/MnO₂ PHMSs can efficiently transform CH₃SH into CH₃SAg/CH₃S-SCH₃ and then oxidize them into SO₄^2- and CO₂ as evidenced by in situ diffuse reflectance infrared Fourier transform spectroscopy. Meanwhile, electron paramagnetic resonance and scavenger tests indicate that •OH and ¹O₂ are the primary reactive species rather than surface atomic oxygen species contributing to CH₃SH removal over Ag/MnO₂ PHMSs. This work presents an efficient catalyst of single atom Ag incorporated MnO₂ PHMSs to control air pollution.