NO dissociation and reduction by H2 on Pd(1 1 1): A first-principles study

Abstract Periodic density functional theory (DFT) calculations were carried out to elucidate the reaction mechanisms of NO reduction by H 2 and possible products on Pd(1 1 1). The results show that direct NO dissociation is unlikely due to high-energy barrier; alternatively, NO dimer exists on Pd(1 1 1) surface followed by the N–O bond scission to form N 2 O. The presence of H 2 promotes the NO dissociation. The N 2 formation pathway is NO + N → N 2  + O rather than N + N → N 2 . Besides, N 2 is formed preferentially than N 2 O from the coadsorbed state of NO + N. The NH 3 formation comes from the successive hydrogenation reactions of nitrogen and the NH formation is the rate-determining step. The microkinetic analysis further confirms that N 2 O is major at low temperature while N 2 becomes dominant as temperature increases. The selectivities toward N 2 and NH 3 shift to slightly lower temperature as H 2 /NO ratio increases.