First principles and experimental study of NH3 adsorptions on MnOx surface

The oxidative abstraction of hydrogen from adsorbed ammonia is the first step in selective catalytic reduction (SCR) and NH3 adsorptions on the MnO, surfaces played a significant role in the mechanism of SCR with NH3. NH3 adsorptions on the Mn203 (2 2 2), Mn304 (2 1 1) and Mn02 (1 1 0) surfaces were investigated by the density functional theory (DFT) method. With more negative adsorption energy values, the Mn203 (2 2 2) and Mn304 (2 1 1) surfaces tended to be the favorable adsorption sites for NH3 molecule. In addition, the shorter Mn N bonds indicated that NH3 adsorptions took place easily on Mn203 (2 2 2) and Mn304 (2 1 1) surfaces. According to the ammonia temperature programmed desorption (NH3-TPD) performance, Mn203 and Mn304 showed significantly higher amount of desorbed NH3, which was in good agreement with the DFT study. Meanwhile, the NH3-SCR performances of Mn203 and Mn304 for NO conversion below 433 K show higher performance than that of Mn02. Crown Copyright 2013 Published by Elsevier B.V. All rights reserved.