The
respective action mode between surface-adsorbed oxygen and
bulk lattice oxygen during catalytic soot oxidation is still not fully
recognized. Herein, a series of Ag-loaded Co3O4 catalysts with different Ag loading amounts were prepared by the
impregnation method, and 5% Ag/Co3O4 presented
competitive catalytic activity toward soot combustion with a T
50 below 290 °C in 10% O2/N2. This remarkable improvement in catalytic performance could
be primarily attributed to the enhanced Ag–Co3O4 metal–support interaction induced by the formation
of uniform, dispersive, and suitable size metallic Ag nanoparticles.
The activation, activity, consumption–regeneration, identification,
and reaction of surface-adsorbed oxygen along with the activity of
bulk lattice oxygen were characterized by various designed and in situ techniques. The results demonstrated that the chemisorbed
superoxide species (O2
–) play the potentially
responsible role for boosting soot combustion, while the bulk lattice
oxygen is much less active within the tested temperatures, inducing
a negligible activity contribution. Moreover, soot-temperature programmed
reduction, isothermal kinetic study, and density functional theory
calculation provided supplementary support for the enhancement effect
of Ag–Co3O4 combination in the activation
and utilization of surface-adsorbed oxygen. The overall objective
of this work is to identify the role of surface-adsorbed oxygen and
bulk lattice oxygen for soot oxidation over Ag/Co3O4 catalysts.
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