Quantum chemistry study of SCR-NH3 nitric oxide reduction on Ce-doped γFe2O3 catalyst surface

Abstract

The doping of Ce on γ-Fe2O3 catalyst surface can improve the NO removal catalytic activity and widen the temperature window of activity. However, the mechanism of promoting the De-NOx activity of γ-Fe2O3 catalyst by Ce doping has not been revealed. In this paper, therefore, the doping of Ce on γ-Fe2O3(001) surface and the adsorption behavior of NH3 and NO as well as the reaction pathway were studied by the density functional theory (DFT). The results show that the doping of Ce on γ-Fe2O3(001) surface can lead to the migration of electrons on the surface of catalyst and cause the dislocation of the surface lattice, so as to improve the surface acid activity. Thus, the Ce doping can increase the adsorbed energy of the modified γ-Fe2O3 catalyst to NO and NH3 and decrease the activation energy barrier of the rate determining step in SCR reaction. Furthermore, the effects of Ce doping will change with the concentration of the Ce doping, and the excellent SCR De-NOx efficiency will be obtained in the optimal doping amount. On the other hand, O2 makes an important effect. Which makes the activation energy barrier of the rate determining step under aerobic condition lower than that under anaerobic conditions, causes the surface active O to react with NO to form NO2 and perform a rapid SCR reaction. The Ce doping can promote the dissociation of O2 on the active cation site and reduce the activation energy barriers of above steps. Accordingly, the doping of Ce on γ-Fe2O3 catalyst surface can improve the SCR process.