2019 Volume 18 Issue 1 Pages 70-77
NOx reduction reactions, occurring in the three-way catalyst, are highly sensitive to the reaction condition: The reaction is inactive in both too low and too high temperature conditions, as well as high O2 partial pressure condition. In the present theoretical study, we performed kinetic analyses of the NO-CO-O2 model reaction system, taking place on Rh(111) surface, on the basis of density functional theory calculations. The temperature/pressure dependences were incorporated into account by coverage dependent reaction and activation free energies. The kinetic analyses revealed the existence of peak temperature for NO reduction reaction as well as the switching of N + NO and N + N reaction mechanisms with respect to the temperature. The analyses for the surface coverages of intermediate species revealed that the coverages of N ad-atom and NO ad-molecule species are the crucial factor for the activity and selectivity of NO reduction reactions.