Origin of the superior activity of surface doped SmMn2O5 mullites for NO oxidation: A first-principles based microkinetic study

Using first-principles based microkinetic analysis, we conduct a comprehensive investigation on the NO oxidation process on SmMn2O5 mullite's active surface under experimentally relevant conditions. The influencing factor for NO oxidation activity is identified and Mars-van Krevelen (MvK) and Eley-Rideal (ER) mechanisms are found to contribute to the high activity of pristine SmMn2O5 mullites in high and low temperature regions, respectively. We further study the activity of surface (Ba/Sr/La) doped SmMn2O5. It is found that surface doping of Ba primarily destabilizes the nitrite (NO*) species to promote NO oxidation performance via MvK mechanism. Due to the stronger ability of O-2 (O*(2)) dissociation along the ER route, Sr and La doped mullites are predicted to have greatly enhanced reaction activity in a wide temperature region. Our study gives insight into the NO oxidation ability of pristine and surface doped SmMn2O5 that are beneficial for further optimization of mullite based catalyst performance. (C) 2018 Elsevier Inc. All rights reserved.