Soot particles from the diesel vehicles could lead to the serious environmental and health problems, which is one of the main source of smog. The aftertreatment method by catalysts is one of the most efficient techniques to remove soot particles. Herein, alkali metals (especially K) contianing catalytsts exhibit superior catalytic soot combustion performance, which is hopeful to substitute for commercially used noble metal catalysts. A team from University of Jinan has investigated K-supported oxides (K/Al₂O₃, K/TiO₂) for catalytic soot combustion. The catalytic activity and stability have been studied in detail. A strategy for balancing the activity and stability has been proposed aiming at the trade-off relationship between them. Their research has been published on Catalysis Today in 2016.

K/Al₂O₃ shows two kinds of K species consisting of the dispersed K⁺--O–CO₂ species (free K species) and a K₂Al₂O₄ phase (K⁺ having been incorporated into Al₂O₃). However, all the supported K entered into the lattice of TiO₂ to form K₂Ti₆O₁₃ for K/TiO₂. K/Al₂O₃ shows much higher activity for soot combustion. Comparatively, K/TiO₂ is hardly active. The active species is confirmed to be the free K⁺ species. After water washing, the catalytic activity of K/Al₂O₃ decreased to a large extent due to the loss of free K⁺ species, leading to the poor water-resistant stability. A strategy for making a balance between activity and stability, two sides of the coin for K-containing catalysts, is encapsulating of active K species in the pore structures of the catalyst, as demonstrated by the tunneled cryptomelane. This tunneled configuration secured free K⁺ against leaching in water, which opens an efficient pathway to practical usage of K-containing catalysts for soot removal.

The normalized absorption of K K-edge for K/Al₂O₃, K/TiO₂ and K₂CO₃ were obtained using synchrotron radiation at BSRF. For K/Al₂O₃, peaks were located at the similar energy as that for K₂CO₃, suggesting that the K carbonate species are present in K/Al₂O₃. Besides, a new peak at 3616 eV appeared, indicating that the coordination state of K was influenced by the presence of Al, which is attributed to the formation of K₂Al₂O₄ from XRD results. However, for K/TiO₂, completely different absorption peaks from that of K₂CO₃ were observed, with the peak at 3612 eV shifting to higher energy while that at 3619 eV shifting to lower energy. This confirmed that in K/TiO₂, all supported K₂CO₃ has been transformed into a new phase K₂Ti₆O₁₃ according to XRD results.