Boosting Catalytic Purification of Soot Particles over Double Perovskite-Type La2–xKxNiCoO6 Catalysts with an Ordered Macroporous Structure

The catalytic performances for soot purification over the perovskite-type ABO₃ oxides, as one of the most potential non-noble metal catalysts, are closely correlated with the substitution of A-site and B-site ions. Herein, three-dimensional ordered macroporous (3DOM) structural catalysts of double perovskite-type La_2-xK_xNiCoO₆ were prepared by a method of colloidal crystal template. The contact efficiency between the catalyst and soot particles is significantly promoted by the 3DOM structure, and the partial substitution of A-site (La) with low-valence potassium (K) ions in La_2-xK_xNiCoO₆ catalysts boosts the increasing surface density of coordinatively unsaturated active B-sites (Co and Ni) and active oxygen. 3DOM La_2-xK_xNiCoO₆ catalysts exhibited superior performance during the purification of soot particles, and the 3DOM La_1.80K_0.20NiCoO₆ catalyst exhibited the highest activity, that is, the values of T₅₀, S_CO2, and turnover frequency are 346 °C, 99.3%, and 0.204 h^-1 (at 300 °C), respectively. According to the results of multiple experimental characterizations and density functional theory calculations, the mechanism of the samples during soot removal is proposed: the increase in surface oxygen density induced by the doping of K ions significantly promotes the critical step of the oxidation from NO to NO₂ in catalyzing soot purification. It is one new strategy to develop the high-efficient non-noble metal catalysts for soot purification in practical application.