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 (Ov) and lattice oxygen (OL) 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 SO42– 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.