Silver-modified NiCo2O4 nanosheets monolithic catalysts used for catalytic soot elimination

Abstract

Highly active spinel-derived monolithic catalysts loading Ag (xAg/NiCo-NS) have been successfully designed and synthesized and used to catalytic soot elimination. The crossed macro-porous of NiCo2O4 nanosheets and the three-dimensional porous structure of Ni foam not only provides a convenient gas mass transfer channel, but also provides a large number of contact points between soot and catalyst. After loading Ag on the NiCo-NS, the catalytic performance for soot oxidation is improved remarkably. Among the xAg/NiCo-NS catalysts, the 4.5Ag/NiCo-NS sample has the highest catalytic performance with the lowest T50 (333 °C), which is 50 °C lower than that of the NiCo-NS catalyst and lower than that of other prove metal catalysts (Pt/Pd/Au) in the atmosphere of 500 ppm NO/10 % O2/N2. The metal-support interaction between Ag and NiCo-NS weakens the Co-O bond, increases the amount of surface oxygen vacancies and improves the intrinsic activity determined by turnover frequency (TOF) of the catalyst. Moreover, Ag can also adsorb and activate gaseous oxygen to produce the low-temperature active oxygen species (O2−), which can promote the soot combustion in the low temperatures. Based on the catalytic performance for soot oxidation and activation Energy (Ea), the reaction paths for the catalytic combustion of soot on Ag/NiCo-NS are identified.