Theory of nitride oxide adsorption on transition metal (111) surfaces: a first-principles investigation

Abstract

In this work, we report a density functional theory study of nitric oxide (NO) adsorption on close-packed transition metal (TM) Rh(111), Ir(111), Pd(111) and Pt(111) surfaces in terms of adsorption sites, binding mechanism and charge transfer at a coverage of Theta(NO) = 0.25, 0.50, 0.75 monolayer (ML). Based on our study, an unified picture for the interaction between NO and TM(111) and site preference is established, and valuable insights are obtained. At low coverage (0.25 ML), we find that the interaction of NO/TM(111) is determined by an electron donation and back-donation process via the interplay between NO 5sigma/2pi* and TM d-bands. The extent of the donation and back-donation depends critically on the coordination number (adsorption sites) and TM d-band filling, and plays an essential role for NO adsorption on TM surfaces. DFT calculations shows that for TMs with high d-band filling such as Pd and Pt, hollow-site NO is energetically the most favorable, and top-site NO prefers to tilt away from the normal direction. While for TMs with low d-band filling (Rh and Ir), top-site NO perpendicular to the surfaces is energetically most favorable. Electronic structure analysis show that irrespective of the TM and adsorption site, there is a net charge transfer from the substrate to the adsorbate due to overwhelming back-donation from the TM substrate to the adsorbed NO molecules. The adsorption-induced change of the work function with respect to bare surfaces and dipole moment is however site dependent, and the work function increases for hollow-site NO, but decreases for top-site NO, because of differences in the charge redistribution. The interplay between the energetics, lateral interaction and charge transfer, which is element dependent, rationalizes the structural evolution of NO adsorption on TM(111) surfaces in the submonolayer regime.

Direct Work Function Measurement by Gas Phase Photoelectron Spectroscopy and Its Application on PbS Nanoparticles

“…The extents of the electron transfer depend critically on the coordination number (adsorption sites) and TM d-band filling. 54 Thus, the work function changes on these surfaces are very sensitive to the adsorption sites. With the help of gas phase core level information, we can not only determine the chemical states of adsorbates and underlying surface but also provide additional structural information of adsorption sites at different coverages.…”

The Effect of Gamma-Al2O3Support on the NO Adsorption on Pd4Cluster

“…27 For adsorption of NO on an extended surface at low coverage the interaction is determined by electron donation and back-donation involving the 5σ/2π* antibonding orbital of the NO molecule and the d-bands of the transition metal, with a net charge transfer from the transition metal to the adsorbed NO. 29 However, the extent of the interaction via the back-donation process is strongly dependent on the coordination mode of the NO molecule. On a flat surface, the preferential adsorption occurs on a hollow-site.…”

“…13 The adsorption of NO on the supported catalyst surface has been investigated by both experimental 7,[14][15][16][17][18][19][20] and theoretical procedures. [21][22][23][24][25][26][27][28][29] NO adsorbs on small Pd clusters through its nitrogen atom in a tilted orientation, preferentially in the hcp threefold and bridge sites, 27 although the relative binding energies are strongly dependent on the size and geometry of the cluster employed. 27 For adsorption of NO on an extended surface at low coverage the interaction is determined by electron donation and back-donation involving the 5σ/2π* antibonding orbital of the NO molecule and the d-bands of the transition metal, with a net charge transfer from the transition metal to the adsorbed NO.…”

“…On a flat surface, the preferential adsorption occurs on a hollow-site. 29 Adsorption on the energetically less favorable top-site results in tilted orientation with the NO bent to the metal surface.…”

Atomistic Theory of Ostwald Ripening and Disintegration of Supported Metal Particles under Reaction Conditions

“…The mechanism presented could apply for various metal−oxide systems and chemical environments. For instance, NO molecules, which interacts strongly with transition metals, 79 could also induce the disintegration of supported Rh particles. 37 The formation of Rh-nitrosyl complexes was found in the reaction between NO and CO, and was suggested to be responsible for the observed redispersion.…”