Fabrication of perovskite-type macro/mesoporous La_1-xK_xFeO_3-Δ nanotubes as an efficient catalyst for soot combustion

Perovskite-type macro/mesoporous nanotube shows large specific surface area and high utilization of catalytic sites, which gives rise to the enhancement of catalytic activity and broaden their application. In this work, perovskite-type La_1-xK_xFeO_3-δ nanotubes were prepared for efficient soot oxidation by a simple electrospinning technique following calcination. The as-prepared samples were characterized by XRD, FI-IR, FE-SEM, TEM, XPS, N₂ adsorption-desorption, H₂-TPR and O₂-TPD techniques to investigate the physical-chemical properties. A certain amount of K⁺ doped in to LaFeO_3-δ nanotubes sample could inhibit the growth of crystallites during the calcination at a high temperature, which could prevent the destruction of macro/mesoporous tubular structure and contribute to the more contact between soot particles and active sites. Meanwhile, it could also bring about the higher oxygen vacancy density responsible for the enhancement of redox abilities. However, excessive doping of K⁺ could lead to the collapsing of macro/mesoporous tubular structure, ascribable to the formation of low-melting compounds or eutectics with other components of the catalyst, which would have a negative influence on the catalytic performance. The performance for soot catalytic oxidation was evaluated in a temperature programmed oxidation device using O₂ (without or with NO) as oxidant. Among the as-prepared catalysts, the well-structured La_0.8K_0.2FeO_3-δ nanotubes catalyst is the best candidate for soot removal.