In situ exsolution of Co/CoO_x core-shell nanoparticles on double perovskite porous nanotubular webs: A synergistically active catalyst for soot efficient oxidation

The PrBa_0.5Sr_0.5Co_0.2Fe_1.8O_5+δ double perovskite porous nanotubular webs are prepared by a simple electrospinning technique following calcination. It shows better catalytic activity compared with the bulk PrBa_0.5Sr_0.5Co_0.2Fe_1.8O_5+δ prepared by citrate method, due to its larger specific surface area and higher utilization of active sites. On basis of this, introducing multiple active sites is conducive to enhancing the catalytic activity. In this work, the PrBa_0.5Sr_0.5Co_0.2Fe_1.8O_5+δ double perovskite porous nanotubular webs are further reduced at 750 °C in a 10% H₂/N₂ gas flow, which can give rise to the in situ exsolution of Co core-shell nanoparticles and obtain double active sites. Meanwhile, series of related catalysts are also prepared for comparison, and the physicochemical properties of these catalysts are studied by a lot of characterization techniques. The catalytic performance for soot combustion is evaluated by a temperature programmed oxidation test, which can simulate the soot combustion process. Turn of frequency (TOF) and activation energy (E_a) are calculated by isothermal studies to further evaluate the activity of the as-prepared catalyst. Among all the prepared catalysts, the PrBa_0.5Sr_0.5Co_0.2Fe_1.8O_5+δ porous nanotubular webs after reductive treatment at 750 °C in H₂ atmosphere exhibits the best catalytic activity for soot combustion, showing the lowest activation energy and the highest TOF values. Furthermore, its catalytic activity is significantly promoted compared with the bulk-type catalyst. Firstly, it may be associated with the synergistic effects of sufficient Co core-shell nanoparticles and oxygen vacancies in double perovskite functioned as active sites. Secondly, the structure of porous nanotubular webs can make full use of these active sites.