Density Functional Theory Analysis of Elementary Reactions in NOx Reduction on Rh Surfaces and Rh Clusters

作者：Deushi Fumiko; Ishikawa Atsushi; Nakai Hiromi^*

来源：Journal of Physical Chemistry C, 2017, 121(28): 15272-15281.

DOI：10.1021/acs.jpcc.7b04526

The reduction of NOx is crucial for reducing air pollution from vehicle exhaust. In the presence of Rh-based catalysts, the dissociation of NO and the formation of N2O and N-2 constitute the important elementary steps of NOx reduction. The present study used density functional theory (DFT) to investigate the catalytic performances of the Rh(111) surface and Rh-55 and Rh-147 clusters toward these elementary reactions. The NO dissociation reaction was found to have minimum activation barriers (E-a) of 0.63, 0.68, and 1.25 eV on Rh-55, Rh-147, and Rh(111), respectively. Therefore, it is the fastest on small Rh clusters. In contrast, the N-2 formation reaction is relatively inefficient on small clusters, with corresponding E-a values of 2.14, 1.79, and 1.71 eV. Because of the stronger binding of N atoms to the Rh clusters than to the Rh surface, N-2 formation through the recombination of N atoms has a higher E-a value on Rh clusters. The calculated reaction rate constants confirmed that small Rh clusters are less reactive for N-2 formation than Rh(111), especially at low temperatures. Our results also suggest that N2O formation is largely endothermic and, thus, thermodynamically unfavored.

• 出版日期2017-7-20