Influence of B-site transition metal on NO oxidation over LaBO3 (B=Mn, Fe and Co) perovskite catalysts

Abstract

A comprehensive understanding of NO catalytic oxidation on different La-based perovskites LaBO3 (B=Mn, Fe, Co) enables to ultimately utilize the catalyst in the lean-burn NOx after treatment system. Here, we report a comparative study of the NO oxidation on LaBO3 (B = Mn, Fe and Co) surfaces by first-principles calculations though density functional theory (DFT). Based on the adsorption of NOx (x=1, 2 and 3) on the LaO and BO2 terminations of (001) surface, we find that the NOx adsorbates are bound stronger on the LaO terminations than BO2 ones. Infrared vibrational spectra and the NO oxidation reactions calculations suggest that BO2 surfaces are more active compared to LaO ones. The primary step for NO oxidation is the desorption of NO2* from the BO2 surfaces with a sequence of barrier 1.43eV, 1.60eV, 1.68 eV for CoO2, MnO2, and FeO2 terminations, respectively. Fundamentally, least charge transfer from CoO2 surface to NO2 ensures its smallest activation energy in contrast to the other two BO2 terminations. These findings provide insights into the influence of B-site transition metal and different terminations on NO oxidation activity of La-based perovskites which might be extended to design of other NO oxidation catalysts.