The role of potassium in K/Co3O4 for soot combustion under loose contact

This work investigated the effect of potassium (K) on the catalytic activity of Co3O4 prepared by sol–gel method for soot combustion under loose contact. The catalysts were characterized by XRD, TPR, Raman, FT-IR, and XPS. The results showed the deposition of 4.4 wt.% K accelerated the activity of Co3O4 for soot combustion under loose contact, the temperature of maximum soot oxidation rate (Tm) decreased from 490 °C over Co3O4 to 417 °C over K(0.1)/Co3O4(600). It was discovered that there is an exact linear relationship between Tm and the value of active Co3+/Co for the first time, where Co represented the total amount Co3+ and Co2+. Our findings strongly suggested that potassium, as a promoter, not only favors CB–catalyst contact, but also produces more active Co3+ with the increase of K content. Doped K entered the crystal lattice and aroused the lattice distortion. The Tm in TPO decreased linearly with the increase of microstrain. The lattice distortion and the interaction of K and Co3O4 promoted the formation of the surface active Co3+ and active O−, and improved the activity of lattice oxygen.

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► The deposition of K accelerated the activity of Co3O4 for soot combustion under loose contact.
► An exact linear relationship between Tm and the value of active Co3+/Co.
► An exact linear relationship between Tm and crystal microstrain of Co3O4
► K aroused lattice expansion and weakened the Co–O bonds.
► K promoted the formation of the surface active Co3+ sites.