Chemisorption of CO on Sm overlayers and SmRu alloy films on Ru(001)
TL;DR: In this article, the chemisorption of CO on Sm-covered Ru(001) and SmRu surface alloy has been investigated by XPS and TPD techniques and two molecular CO states are found: one is a chemisoric CO on Ru atoms and the other is a weakly adsorbed CO associated with Sm2Ox.
Abstract: The chemisorption of CO on Sm-covered Ru(001) and SmRu surface alloy has been investigated by XPS and TPD techniques. Sm-induced CO dissociation occurs on the Ru(001) surface. Sm is partly oxidized and agglomerated due to the dissociation of CO. Two molecular CO states are found: one is a chemisorbed CO on Ru atoms and the other is a weakly adsorbed CO associated with Sm2Ox. The latter is characterized by a new intense feature at 538.5 eV in the O 1s spectrum. The top layer of the SmRu surface alloy on Ru(001) is decomposed due to the selective oxidation of Sm by oxygen from CO. The CO TPD from the SmRu surface alloy film shows an additional feature at 345 K that is attributed to CO molecules from Ru Sm2Ox interfacial sites.
Citations
More filters
[...]
TL;DR: In this paper, the effects of V 2 O 5 component on the activity of Pt catalytic oxidation of methanol were investigated in 1.0 M KOH solution by cyclic voltammetry, chronoamperometry and chronopotentiometry.
Abstract: The Vulcan carbon-supported vanadium oxide (V 2 O 5 ) was prepared by solid-state reaction under intermittent microwave heating (IMH) method. Pt nanoparticles were dispersed by microwave-assisted polyol process over Vulcan carbon and V 2 O 5 /C. The catalyst samples were characterized by PXRD, TEM, CO-TPD and electrochemical methods. The TEM images showed homogeneous dispersion of ∼3 nm size Pt metal crystallites embedded over Vulcan carbon support. The activities of Pt/C and Pt–V 2 O 5 /C for electrochemical oxidation of methanol were studied in 1.0 M KOH solution by cyclic voltammetry, chronoamperometry and chronopotentiometry. The influence of V 2 O 5 component on the activity of Pt–V 2 O 5 /C was screened for catalytic oxidation of methanol. The results show that Pt–V 2 O 5 (4:3)/C composite catalyst performed better than Pt/C catalyst for methanol oxidation. The temperature programmed desorption (TPD) with CO was carried out to assess the CO tolerance of Pt–V 2 O 5 /C electrocatalyst. The formation of oxygen-containing species at lower potential can transform CO-like poisoning species on Pt to CO 2 in the presence of V 2 O 5 which helps in regenerating active sites on Pt for further electrochemical oxidation of methanol. The enhanced electrode response is attributed to synergistic effect between Pt and V 2 O 5 .
75 citations
[...]
TL;DR: In this paper, the effect of covering of SmOx blocks some sites on the surface and suppresses adsorption of the typical CO species with an uptake at about 500 K, while a novel desorption peak centered at 260 K emerges in the CO TDS.
Abstract: SmOx modified Rh(1 0 0) surfaces have been in-situ prepared by depositing metallic Sm and subsequently oxidizing under controlled conditions, and the interaction between the lanthanide oxide and transition metal has been characterized by means of X-ray photoelectron spectroscopy (XPS) and high-resolution electron-energy-loss spectroscopy (HREELS) as well as thermal desorption spectroscopy (TDS). As evidenced, the adsorption of CO on the modified surfaces shows some different features to the original surface of Rh(1 0 0). The covering of SmOx blocks some sites on the surface and consequently suppresses adsorption of the typical CO species with an uptake at about 500 K, while a novel desorption peak centered at 260 K emerges in the CO TDS. Correspondingly, the XP spectrum exhibits a new C 1s peak at 287.9 eV and O 1s peak at 532.6 eV. The intensity of the low temperature peak varies with the coverage of SmOx, which shows an actual correlation to the perimeter sites of SmOx particles on the surface.
20 citations
[...]
TL;DR: In this paper, the authors summarize the recent progress from their laboratory which explored the possibility of developing Pt-MoO3/C and Pt-Nb2O5/C electrocatalysts in acidic media, and Pt−V2O4/C in alkaline media for direct electro-oxidation of methanol.
Abstract: An important research target in DMFCs is to find better catalyst materials that are cheaper, less-prone to poisoning and more catalytically active. In this context, metal oxides with good catalytic properties and stronger interaction with Pt nanoparticles can generate active interfacial regions for electrocatalysis. Pt catalysts promoted by certain metal oxides show enhanced methanol electro-oxidation activity and CO tolerance behavior. In this paper we summarize the recent progress from our laboratory which explored the possibility of developing Pt–MoO3/C and Pt–Nb2O5/C electrocatalysts in acidic media, and Pt–V2O5/C electrocatalyst in alkaline media for direct electro-oxidation of methanol. The oxide electrocatalysts have been prepared by a fast and efficient method of loading the metal oxide on carbon black (Vulcan XC-72) employing an intermittent microwave heating (IMH) method. These materials are found to achieve higher activity and stability towards methanol electro-oxidation.
19 citations
[...]
TL;DR: The effect of preadsorbed Sm atoms on CO adsorption has been studied over the Ru(001) surface, employing temperature-programmed desorption and photoemission spectroscopy as discussed by the authors.
Abstract: The effect of preadsorbed Sm atoms on CO adsorption has been studied over the Ru(001) surface, employing temperature-programmed desorption and photoemission spectroscopy. It was found that the pres...
12 citations
[...]
TL;DR: In this paper, the authors review the preparation and reaction properties of ordered SmRh surface alloys and SmO x /Rh(1/0/0) model catalyst which have been systematically investigated by low energy electron diffraction (LEED), Auger electron spectroscopy (AES), X-ray photoelectron spectroscope (XPS), high-resolution electron energy loss spectrography (HREELS), and temperature desorption spectrograms (TDS).
Abstract: In this paper we review the preparation and reaction properties of ordered SmRh surface alloys and SmO x /Rh(1 0 0) model catalyst which have been systematically investigated by low energy electron diffraction (LEED), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), high-resolution electron energy loss spectroscopy (HREELS) and temperature desorption spectroscopy (TDS). The growth of Sm on Rh(1 0 0) at room temperature follows the Stranski-Krastanov mode. Thermal treatment of the Sm films on Rh(1 0 0) leads to the formation of ordered SmRh surface alloys. An “inverse” SmO x /Rh(1 0 0) model catalyst is produced under controlled oxidation of the SmRh surface alloy. CO adsorption on the SmRh alloy and SmO x /Rh(1 0 0) surfaces gives rise to five TDS characteristic features originating from different adsorption sites. Both the site blocking of SmO x and the electron transfer between SmO x and Rh substrate significantly affect the CO adsorption. Acetate decomposition on both Rh(1 0 0) and the SmO x /Rh(1 0 0) surfaces are found to undergo two competitive pathways that yields either (i) CO(a) and O(a) or (ii) CO 2 (g) and H 2 (g) at high temperature. The reactive desorption of acetic acid on SmO x /Rh(1 0 0) is dramatically different from that on Rh(1 0 0). A rapid decomposition of acetic acid to produce CO(g) and CO 2 (g) can be observed only on SmO x /Rh(1 0 0), where CO(g) becomes the predominant product at 225 K, indicating a strong promotional effect of SmO x in the selective decomposition of acetate. Finally, we briefly describe the future outlook of research on rare earth oxide/metal model catalysts.
9 citations
References
More filters
[...]
TL;DR: In this paper, the authors investigated the adsorption of CO on Ru(001) with IR reflection-absorption spectroscopy and the results correlated with LEED and thermal desorption measurements.
Abstract: The adsorption of CO on Ru(001) has been investigated in the temperature range 80–400 K with IR reflection-absorption spectroscopy and the results correlated with LEED and thermal desorption measurements. The C-O frequency shifts continuously from 1984 cm−1 to 2061 cm−1 as a function of increasing coverage, which is attributed mainly to dipole-dipole coupling. No new bands were discovered in the spectrum. The frequency versus coverage relation is also clearly affected by the ordering of the adlayer into the 3 × 3 R 30° and 2 3 × 2 3 R 30° structures. Likewise the shape and half-width of the absorption band depend on the details of the ordering process. A linear relationship between coverage and integrated absorption intensity exists only below θ = 0.33; thereafter the absorption intensity falls, with the result that at saturation coverage the absorption per adsorbed molecule is only 35–40% of the absorption at θ = 0.33. This effect is also ascribed to strong lateral interactions in the adlayer. The intrinsic high resolution of the IR method is necessary for the careful study of these phenomena associated with position, shape and intensity of the absorption band.
415 citations
[...]
TL;DR: In this article, a variety of rare-earth (RE) compounds (oxides, sulfates and oxalates) have been studied by X-ray photoelectron spectroscopy.
Abstract: A variety of rare-earth (RE) compounds (oxides, sulfates and oxalates) have been studied by X-ray photoelectron spectroscopy. Except for Eu, the binding energies (BE's) of the RE 3 d and 4 d peaks for the sulfates and oxalates are respectively almost equal to and 1.3–3.1 eV higher than those for the oxides. In the Eu 3 d spectrum of europium(II) oxalate, distinct shake-down satellite peaks are present, and the BE's of these peaks are 10 eV lower than the parent ones. For the oxides, appreciable differences are found in the BE's of the O 1 s peaks, and a specific “inclined W” form is observed in plots of BE versus 1/ R (where R is the mean distance from the oxygen atom to the neighboring RE atom) and versus the RE oxidation-reduction potential (ORP). No characteristic differences are seen in the BE's (C 1 s , S 2 s and S 2 p ) of the other ligands.
368 citations
[...]
TL;DR: In this article, the Uv and x-ray photoelectron spectra of carbon monoxide and transition-metal (TM) carbonyl complexes have been studied and the systematic changes in these spectra were recorded as the number of metal atoms in the complexes was increased and as the bonding configuration of the CO changed.
Abstract: The uv and x-ray photoelectron spectra of carbon monoxide and transition-metal (TM) carbonyl complexes have been studied. The systematic changes in these spectra were recorded as the number of metal atoms in the complexes was increased and as the bonding configuration of the CO changed. The observations on TM carbonyl complexes are compared to the spectra of CO adsorbed on corresponding TM surfaces. We show this comparison for the electron binding energies, the shake-up spectra, the relative peak intensities, and the Auger-peak kinetic energies, as a function of the number of metal atoms in the TM carbonyl complexes. A single-metal-atom carbonyl complex reproduces nearly all of the features of the photoelectron spectra of adsorbed CO. However, there are subtle features of the photoelectron spectra of adsorbed CO, associated with molecular orbitals of CO which participate in the bonding to the substrates, which can only be reproduced by multimetal carbonyl complexes. Three or four metal atoms in a carbonyl complex are sufficient to reproduce the spectra associated with CO adsorbed on the corresponding semi-infinite TM solid.
213 citations
[...]
TL;DR: The interaction of carbon monoxide and sub-monolayer coverages of potassium on Ru(001) has been investigated with high resolution electron energy loss spectroscopy, LEED, Auger electron spectrograms, thermal desorption, and work function measurements as mentioned in this paper.
Abstract: The interaction of carbon monoxide and submonolayer coverages of potassium on Ru(001) has been investigated with high resolution electron energy loss spectroscopy, LEED, Auger electron spectroscopy, thermal desorption, and work function measurements. The adsorption of potassium on ruthenium at submonolayer coverages (θk≤0.15) is characterized by ionic, mutually repulsive potassium atoms as evidenced by a strong work function decrease (−4.3 eV), various LEED patterns and a large desorption energy (65 kcal/mol) at low coverage. The adsorption of CO on a potassium precovered surface (θk=0.10) is nondissociative and reversible with an initial increase in the activation energy for desorption from 40 kcal/mol for clean Ru(001) to 50 kcal/mol on the potassium precovered surface. The C–O bond is anomalously weak as evidenced from vibrational spectroscopy (EELS), where C–O stretch frequencies in the range of 1400 to 1970 cm−1 are found. Observation of the first vibrational overtone indicates a strong anharmonicity...
173 citations