Supported ceria-modified silver catalysts with high activity and stability for toluene removal

Herein we fabricated the supported single-atom silver catalysts using an in situ molten salt method. The Mn₂O₃ nanowires supported single-atom silver catalyst (i.e., 0.06 wt% Ag/Mn₂O₃) exhibited excellent catalytic activity for toluene combustion, with the temperatures required for 50 and 90% of toluene conversions being 170 and 205 °C, respectively, at a space velocity of 40,000 mL/(g h). However, the toluene conversion at 205 °C quickly decreased from 90 to 30% within 2.5 h of on-stream reaction. Based on the various characterization results, we found that there were no aggregation of Ag particles, no change in crystal structure of the Mn₂O₃ nanowire support, and no carbon deposition on the catalyst surface, and the quick deactivation of 0.06 wt% Ag/Mn₂O₃ was mainly associated with the low oxygen activation ability. The proper CeO₂ addition to the 0.06 wt% Ag/Mn₂O₃ catalyst was found to not only improve the catalytic activity but also significantly enhance the stability of the catalyst. Toluene conversion at 195 °C over 0.63 wt% CeO₂-0.06 wt% Ag/Mn₂O₃ decreased by only 10% in 50 h of on-stream reaction. Because Ag and CeO₂ particles were highly dispersed on the Mn₂O₃ nanowire support, the oxygen species formed at the surface oxygen vacancies of CeO₂ could efficiently migrate to the active sites (i.e., the interface of Ag-Mn₂O₃) and replenish the surface reactive lattice oxygen species. Thus, the present single-atom silver catalyst is an alternative for commercial noble metal catalysts for the removal of VOCs.