| AVS 57th International Symposium & Exhibition | |
| Surface Science | Thursday Sessions |
| Session SS-ThM |
| Session: | Adsorption and Reactivity on Oxide Surfaces |
| Presenter: | T.S. Rahman, University of Central Florida |
| Authors: | T.S. Rahman, University of Central Florida S. Hong, University of Central Florida A. Karim, Brookhaven National Laboratory |
| Correspondent: | Click to Email |
We have used a combination of density functional theory (DFT) and kinetic Monte Carlo (KMC) simulations to calculate the reaction rates for the selective oxidation of ammonia on the RuO2(110) surface. We find that the overall energy barrier for NH3 + O → NH + H2O is 0.56 eV, while that for N + N → N2, and N + O → NO to be 0.27 and 0.14 eV, respectively. In accompanying KMC simulations, in which we include in addition to the above key processes, several intermediates and their reactions ( 18 processes), we find selectivity towards NO and N2 formation, as a function of O2 pressure range, in excellent qualitative and quantitative agreement with experiment [1]. As for the high reactivity of RuO2(110) we concur that hydrogen bonding between ammonia, and its intermediates, with adsorbed and substrate oxygen play a critical role by making H abstraction facile such that NH decomposition is a spontaneous, non-activated process. As for the high selectivity of RuO2(110) for ammonia oxidation, the significantly-restricted N diffusion caused by reaction intermediates present on the RuO2(110) surface severely affects the recombination rate for N+N → N2 while N+O → NO is much less affected by such reduced N diffusion due to dissociatively-adsorbing O2 species on RuO2(110). As a result, NO production is remarkably favored than N2 production even at low O2 pressure. These results highlight the important role of the chains of undercoordinated Ru atoms on this surface.
[1] Y.Wang, K. Jacobi, W.-D. Schoene, and G. Ertl, J. Phys. Chem. B 109, 7883 (2005).
Work supported in part by DOE Grant DE-FG02-07ER15842