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 MnO 2 porous hollow microspheres (Ag/MnO 2 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/MnO 2 PHMSs can completely degrade 70 ppm CH 3 SH within 600 s, much higher than that of MnO 2 PHMSs (79%). Additionally, the catalyst retains longterm stability and can be regenerated to its initial activity through regeneration with ethanol and HCl. The results of characterization of Ag/MnO 2 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 MnO 2 as well as Ag species as activation sites to collectively favor the catalytic ozonation of CH 3 SH. Ag/MnO 2 PHMSs can efficiently transform CH 3 SH into CH 3 SAg/CH 3 S-SCH 3 and then oxidize them into SO 4 2− and CO 2 as evidenced by in situ diffuse reflectance infrared Fourier transform spectroscopy. Meanwhile, electron paramagnetic resonance and scavenger tests indicate that •OH and 1 O 2 are the primary reactive species rather than surface atomic oxygen species contributing to CH 3 SH removal over Ag/MnO 2 PHMSs. This work presents an efficient catalyst of single atom Ag incorporated MnO 2 PHMSs to control air pollution.

MnO2‐Based Materials for Environmental Applications

“…Plasma noble metals (such as Au, [ 296–298 ] Ag, [ 116,299–301 ] and Pt [ 302 ] ) loaded on the surface of MnO 2 can significantly improve its catalytic activity. These composites combine the excellent photoelectric properties of MnO 2 , the superior surface plasmon resonance (SPR) effect, and prominent conductivity of noble metal metals, [ 303,304 ] resulting in the following advantages: 1) the SPR effect can improve its light absorption capacity by scattering resonance photons; 2) its adequate conductivity can promote the migration and separation of carriers; and 3) plasma nanometals can generate hot electrons owing to their photothermal effect, thus providing a driving force for the catalytic reaction conducive to photocatalysis.…”

“…Among many catalysts, MnO 2 ‐based materials have been extensively studied in the catalyst degradation of VOCs due to their natural abundance, environmentally friendliness, low cost, and specific chemical/physical properties, including different crystal structures and suitable redox activity. Currently, the reported types of VOCs degraded by MnO 2 ‐based materials include benzene series (such as toluene, [ 166,217,226,430–438 ] benzene, [ 171,173,439–441 ] ethylbenzene, [ 442–444 ] and o ‐xylene [ 297,445–448 ] ), formaldehyde, [ 54,86,116,123,137,155,156,296,449–455 ] propane, [ 456 ] aerobic sulfide, [ 172 ] methyl mercaptan, [ 299,457 ] acetone, [ 458,459 ] etc. Among them, formaldehyde and benzene series are the most common VOC pollutants in the air that have been studied the most ( Table 3 ).…”

“…Xia et al. [ 299 ] designed and prepared a kind of porous and hollow MnO 2 with atomic grade silver loading (Ag/MnO 2 PHMs) for the effective removal of CH 3 SH. By in situ DRIFTS, they proposed a possible reaction mechanism and route for the adsorption and catalytic ozonation of CH 3 SH.…”

Catalytic ozonation of ethyl acetate over mesoporous manganese oxides synthesized by a sonochemical method

“…Unlike conventional catalytic oxidation, the catalytic ozonation of VOCs with a low concentration is low‐cost because it is able to operate at room temperature. In recent years, a number of VOCs including arenes, alcohols, esters, aldehydes, and mercaptan were treated by catalytic ozonation 5–9 . However, the catalytic ozonation of ethyl acetate has not been reported except that the catalytic ozonation of ethyl acetate was involved in the plasma‐catalytic oxidation 10,11 …”

Lithium Ion Battery Materials as Tunable, Redox Non-Innocent Catalyst Supports

“…Similar oxidative chemisorption involving redox interactions have previously been reported in the grafting of in situ generated Au(0) and Ag(0) on MnO 2 nano materials, as well as in the chemisorption of molecular Ru(0) phosphine complex by oxidative addition to the O-H bond of a silica surface hydroxyl group. [37][38][39] To evaluate the viability of this approach, a solution of bis(cyclooctadiene)nickel(0) (Ni(COD) 2 ) was added to a suspension of LiMn 2 O 4 , which was mechanically agitated and monitored by 1 H NMR spectroscopy over the course of 48 hours ( Figure 2B). The concentration of Ni(COD) 2 decreased sharply upon exposure to the LMO surface, with concomitant appearance of between one and two equivalents of cyclooctadiene (vide infra).…”