Surface engineering on porous perovskite-type La_0.6Sr_0.4CoO_3-δ nanotubes for an enhanced performance in diesel soot elimination

The porous perovskite-type La_0.6Sr_0.4CoO_3-δ nanotubes are synthesized by sol-gel method combined with electrospinning technique following the calcination, while the porous nanotubular structure can increase the utilization of active sites related to the catalytic activity in soot oxidation. In order to further improve the catalytic activity, porous La_0.6Sr_0.4CoO_3-δ nanotubes are further treated with nitric acid to obtain a larger specific surface area in this work. The as-prepared catalysts are characterized by different techniques to study their physical and chemical properties. The soot catalytic activity is evaluated by the temperature programmed oxidation tests and the values of activation energy. Based on the characterizations and catalytic activity evaluation, the correlation between the specific surface area and catalytic activity is well revealed by the isothermal kinetic measurements. The higher specific surface area (more than 150.0 m² g⁻¹) contributes to a larger amount and a better dispersion of the active oxygen species, thence improving the catalytic activity of soot oxidation. As a result, porous perovskite-type La_0.6Sr_0.4CoO_3-δ nanotubes after nitric acid treatment for 4 h have the best activity and a good stability, with the T₅₀ of 442 °C (5% O₂) and 415 °C (5% O₂ + 500 ppm NO), and the E_a of 93.6 kJ mol mol^-1.