Mesoporous LaCoO₃ perovskite oxide with high catalytic performance for NO_x storage and reduction

A mesoporous LaCoO₃ perovskite oxide (LaCoO₃-Meso) with three-dimensionally ordered helical interwoven structure was synthesized by a nano-casting method using KIT-6 as the hard template. The obtained LaCoO₃-Meso with high surface area was tested for its catalytic performance in the NO_x storage and reduction (NSR) reaction and compared with a sample synthesized by the conventional sol-gel method. The LaCoO₃-Meso showed a significant advantage for NO_x storage, with a NO_x storage capacity 2 times higher than the regular sample. LaCoO₃-Meso also exhibited improved NSR catalytic performance in the 150-450 °C temperature range, especially within 350-400 °C, where the NO_x conversion was raised for 40%. The results of X-ray photoelectron spectroscopy and X-ray absorption fine structure measurements suggested the presence of a high concentration of oxygen defects on the LaCoO₃-Meso surface. Further results provided by temperature programmed reduction and temperature programmed desorption indicated that the oxygen defects not only increase the amount of trapped NO_x, but also improve the low-temperature redox performance of the catalyst. The lower stability of NO_x species adsorbed on oxygen defects promotes the NO_x release step in the NSR reaction and benefits the regeneration of storage sites.