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 ABO(3) oxides, as one of the most potential nonnoble 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 La2-xKxNiCoO6 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 La2-xKxNiCoO6 catalysts boosts the increasing surface density of coordinatively unsaturated active B-sites (Co and Ni) and active oxygen. 3DOM La2-xNiCoO6 catalysts exhibited superior performance during the purification of soot particles, and the 3DOM La1.80K0.20NiCoO6 catalyst exhibited the highest activity, that is, the values of T-50, S-CO2, and turnover frequency are 346 degrees C, 99.3%, and 0.204 h(-1) (at 300 degrees 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.

Automated summary

This study demonstrated that the substitution of A-site with potassium ions in double perovskite-type oxides can enhance the surface density of active sites and improve the catalytic performance for soot purification. The 3D ordered macroporous structure of the catalysts significantly promoted the contact efficiency between the catalyst and soot particles, leading to superior purification performance. The proposed mechanism suggests that the increase in surface oxygen density induced by potassium ion doping plays a crucial role in promoting the oxidation of NO to NO2 during the catalytic process.