Potassium promoted macro-mesoporous Co₃O₄-La_0.88Sr_0.12CoO_3−δ nanotubes with large surface area: A high-performance catalyst for soot removal

The construction of porous perovskite nanotubular materials with a good intrinsic activity, as well as a greater dispersion of the active sites is an effective strategy to obtain a high-performance catalyst used in soot removal. Thence, macro-mesoporous Co₃O₄-La_0.88Sr_0.12CoO_3−δ nanotubes with large specific surface area (154.4 m²·g⁻¹) from the acid etching of the porous La_0.6Sr_0.4CoO_3−δ nanotubes, are supported by 5% K through bubbling method following calcination for soot combustion. The relationship between the specific surface area and K dispersion and their effect on the activity are studied by a series of isothermal kinetic measurements combined with the characterizations and activity evaluation results. It can be found that the greater the amount is of K⁺ incorporated into perovskite lattice, the better the dispersion of K, as well as the La₂O₂CO₃ formed on the catalyst surface, thus leading to the enhanced performance in the soot catalytic combustion. As a result, the 5% K supported macro-mesoporous Co₃O₄-La_0.88Sr_0.12CoO_3−δ nanotubes after acid etching show good activity and stability, where the T₅₀ is 338 °C (5% O₂ + 500 ppm NO + 6% H₂O) with a good CO₂ selectivity (above 99%), the activate energy is 78.1 kJ·mol⁻¹, and the turnover frequency is 5.14 × 10⁻⁴ s⁻¹.