Adsorption and decomposition of NO on stepped and K-deposited Pd surfaces: a comparison of NO stretching vibrational frequencies calculated by density functional theory and measured by infrared spectroscopy

Abstract

The adsorption and decomposition of NO have been investigated by using density functional theory (DFT) method at the generalized gradient approximation (GGA) level. We have performed calculations on adsorption energies, structures, and vibrational frequencies of NO on Pd(3 1 1) and K-deposited Pd(1 1 1) surfaces with full-geometry optimization, and compared them with the experimental data. Calculated NO stretching frequencies agree well with experimental ones, and precise determination of adsorption sites can be carried out. The most favorite adsorption on Pd(3 1 1) occurs at the bridge site parallel to step edge. Decomposition pathways also have been investigated with transition state search. We show that tilted adsorption structures play an important role in determining the reaction pathways for Pd(3 1 1). Coadsorption of K changes adsorption properties of NO drastically. Adsorption energy and bond length of NO become larger, whereas NO stretching frequency becomes lower. A tilted atop species also exists on K-deposited Pd(1 1 1) surface at larger NO exposure.