Density Functional Calculations and IR Reflection Absorption Spectroscopy on the Interaction of SO₂ with Oxide-Supported Pd Nanoparticles

Abstract

A systematic study on the interaction of sulfur dioxide (SO2) on BaO-supported Pd nanoparticles has been carried out using suitable models and state-of-the-art density functional (DF) calculations. Detailed information concerning the structure and energetics of the different conformations of adsorbed SO2 is provided as a function of coverage together with calculated infrared reflection absorption spectroscopy (IRAS) spectra. SO2 may adsorb on Pd(111) in several conformations, some active, η2-SbOa and η1-Sb, and others inactive in IRAS, η3-SaOaOa. SO2 is found to attach stronger to Pd nanoparticle edges and corners, a fact intimately related to catalyst poisoning by site blocking. On Pd nanoparticles, SO2 is found to preferably adopt adsorption conformations that depend on the specific region on the nanoparticle, thus adding site specificity to vibrational recognition. Molecular beam experiments and IRAS have been performed on a single-crystal-based Pd/BaAl2x O1+3x /NiAl(110) model NO x storage and reduction catalyst and its individual components. SO x formation on the oxide components, evolution of a SO2 multilayer, and adsorption of SO2 on BaO or Pd nanoparticles is linked to DF calculations. The effect of cation intermixing in the oxide support and overlap of absorption bands on the unequivocal discrimination of signals are discussed.

Kinetics of the sulfur oxidation on palladium: A combined in situ x-ray photoelectron spectroscopy and density-functional study

“…24 More details of the model, the slab representing the surface, as well as of the isolated SO x (x = 1-4) species, and the S and O atoms can be found elsewhere. 8,36 To allow for a comparison with previous studies 8,25,[36][37][38][39] calculations have been carried out using the Perdew-Wang 40 (PW91) exchange-correlation functional.…”

“…2,45 Finally, the notation of different adsorption sites used throughout the study follows that suggested earlier. 8,25,[36][37][38][39] In short, for any given species and adsorption mode, η x and μ y keys denote that x atoms of the molecule (η x ) are bound to y surface Pd atoms (μ y ).…”

“…7 Once the fuel is burned, atomic sulfur or SO x (x = 1-4) are formed and can attach to the catalyst palladium phase, thus leading to the poisoning of the catalyst, reducing its lifetime and effectiveness. 8,9 Therefore, a major goal in the technical operation of catalysts is to minimize this poisoning. 10,11 One way to achieve this is by the removal of sulfur in the early processing of the used feedstocks by hydrodesulfurization methods, even though a complete removal is, unfortunately, not possible.…”

Explaining Cu@Pt Bimetallic Nanoparticles Activity Based on NO Adsorption

“…Pt NPs are typicallyu sed as the active phase in NSR, [16,17] with very high activities and essentially ac ompleteN Oc onversion. However,t hey display certain drawbacks, including i) al ow selectivity towards N 2 species, ii)susceptibility towards sulfur poisoning owing to the competitive adsorption of SO x speciesa nd/or their perturbation effecto nt he Pt electronic structure, [17][18][19] and iii)the high cost of the preciousP t. Quite interestingly,t he Cu@Pt NPs maintain the high reactivity of Pt NPs with am uch better N 2 selectivity,u pt o9 3%,a nd remain stable under the catalytic workingt emperature of 360 8C. In contrast, Pt@CuN Ps showed very little NO conversion,apriori,o wing to the Cu-rich shell structure, and the N 2 selectivity wasf ound to drop over time until meeting that of the CuPt alloy.…”

Regeneration of sulfur-poisoned Pd-based catalyst for natural gas oxidation

“…From the theoretical perspective, density functional theory (DFT) based calculations have been carried out to investigate the poisoning mechanism of SOx 4) on Pd catalysts [15 18]. Using infrared absorption spectroscopy (IRRAS), X-ray photoelectron spectroscopy (XPS), and DFT calculations, Luckas et al reported the adsorption and reactivity of SO2 on Pd/BaO, Pd(111) [15], and oxygen pre-covered Pd(100) surfaces [16]. The energetically preferred adsorption orientation of SO2 on Pd(100) was the molecular plane perpendicular to the Pd surfaces, and the oxidation of SO2 led to SO3…”