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

Abstract

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.