Mechanistic Insights into Potassium-Assistant Thermal-Catalytic Oxidation of Soot over Single-Crystalline SrTiO3 Nanotubes with Ordered Mesopores

Abstract

Soot catalytic combustion using single-crystalline perovskite-type materials holds great promise as an efficient non-noble metal catalyst, with K⁺-modified SrTiO₃ emerging as one of the most desirable candidates. However, balancing the crystallinity and an optimized pore structure and revealing the mechanism underlying the K⁺ action remain challenges. Herein, by the electrospinning technique, we successfully self-assembled the K-doped single-crystalline SrTi_0.95Al_0.05O₃ nanotubular webs with ordered mesopores. The good crystallinity and mesoporous structures contribute to the enhanced catalytic performance with desirable stability. Based on comprehensive characterizations and density functional theory (DFT) calculations, K⁺ ions effectively accumulate defect charges, facilitating the generation of additional oxygen vacancies and expediting oxygen activation during the reaction. Additionally, the presence of K⁺ ions prefers to preserve O₂ bond integrity during activation, significantly increasing NO adsorption capacity. Utilizing KNO₃ as the medium, K⁺ effectively facilitates the storage and subsequent release of active oxygen species, leading to the promised catalytic performance (T₅₀ = 368 °C, E_a = 64.97 kJ mol^–1, TOF_K = 0.017 h^–1). This study provides mechanistic insights into developing advanced materials for thermal catalytic heterogeneous reactions.