Three-dimensionally ordered macroporous Fe-doped ceria catalyst with enhanced activity at a wide operating temperature window for selective catalytic reduction of NOx

Abstract

A series of three-dimensional ordered macroporous (3DOM) Ce-Fe composite oxides are synthesized for selective catalytic reduction of NOx by CO. The optimized 3DOM Ce0.6Fe0.4O2 catalyst has nearly 90% NO conversion at a relatively low temperature (200 °C) and high catalytic activity in a wide operating temperature window of 200–700 °C. Adding appropriate amount of Fe into pure cerium can form Ce-Fe solid solution, which can promote the reduction performance and further improve oxygen vacancies and active oxygen species. Meanwhile, the introduction of Fe further improves the specific surface area and pore volume of the 3DOM structure, which provides more active sites and improves the more effective contact between the reaction gas and the catalyst. Moreover, surface Fe2O3 can be used as a storage site for nitrite and nitrate and promote the adsorption of NOx species, which can be further desorbed/converted/dissociated. It can be seen that the reduction of NO by CO follows the Eley-Rideal (E-R) mechanism, which can be proved by in situ DRIFTS. There is no doubt that the coexistence of Ce-Fe solid solution and Fe2O3 in 3DOM Ce0.6Fe0.4O2 catalyst is the key reason for the excellent catalytic activity of NO + CO reaction.