Carbon monoxide induced ordering of adsorbates on the Rh(111) crystal surface: Importance of surface dipole moments

Mate, C. Mathew; Kao, C.-T.; Somorjai, Gábor A.

doi:10.1016/0039-6028(88)90019-2

Cited by 100 publications

(44 citation statements)

References 60 publications

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“…Work function lowering due to contamination is a well established phenomenon. [25][26][27] This barrier height lowering may be ascribed to dipole-dipole interactions and charge transfer induced by adsorption on electrode surfaces. 26,28 The second hypothesis concerns surface elastic deformations.…”

Section: Discussionmentioning

confidence: 96%

Tip-to-surface distance variations vs voltage in scanning tunneling microscopy

et al. 1999

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This paper presents an experimental and theoretical study of distance vs voltage characteristics of Au/Au tunnel junctions in air and UHV. Qualitative and quantitative results are compared with the classical models of Tersoff and Hamann and Simmons. To fit experimental conditions, the Simmons model has been extended in three dimensions using a hyperboloidal tip. However, a large discrepancy between theoretical and experimental quantitative results has been found in air because of barrier height lowering due to electrode contamination. An experimental rescaling factor is used in the modified Simmons model to fit any s(V) curve with high accuracy. These results are mainly interpreted in terms of gold surface elastic deformations. ͓S0163-1829͑99͒11635-7͔

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Section: Discussionmentioning

confidence: 96%

Tip-to-surface distance variations vs voltage in scanning tunneling microscopy

et al. 1999

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“…The work function of the Au(l 11), Pt(lll) and Rh(l 11) faces are 5.3 (± -0.2) (82-84), 6.1 eV (±0.06) (85) and 5.2 (± -0.2) eV (86)(87)(88)(89), respectively. Recall also that from among these three surfaces only Au(l 11) has no vacancies in d band.…”

Section: Discussionmentioning

confidence: 99%

Adsorption of Bisulfate Anion on the Au(111), Pt(111), and Rh(111) Surfaces

Thomas

Sung

Wiȩckowski

1997

ACS Symposium Series

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We report on adsorption of bisulfate anion on the Au(111), Pt(111), and Rh(111) electrodes in sulfuric acid media using electrochemistry, Auger electron spectroscopy, low energy electron diffraction and core--level electron energy loss spectroscopy. The key observations for the bisulfate adsorbate on all surfaces studied are: (i) the oxygen-to-sulfur ratio is 4, (ii) the S(LMM) Auger electron transitions and S2p energy loss spectra show signatures characteristic of the sulfate anion, (iii) the spectral data are typical of the S 6+ valency in the adsorbate. These results indicate that no decomposition or dehydration of the adsorbed anion occur in UHV. On Pt(111) and Rh(111) the maximum anion coverage is very close to 1/3 of the monolayer (ML). This is in an excellent agreement with the Me(111)(√3 x √3)R30° from electron diffraction. For Au(111), the maximum coverage is 1/5 ML while the diffraction data indicate a diffuse Au(√3 x √3)R30° structure. Whereas in the specific case of the Au(111) electrode the low energy electron diffraction data provide only an indirect basis for structural assignment of the sulfate adsorbate, we may conclude from these data that the structure of bisulfate on gold is different from that on Pt(111) and Rh(111). The core level energy loss spectra show that the electron density on surface sulfur is higher than in the salt, evidently due to backdonation of electrons from the substrate to the adsorbate. To complete the description of the anion-surface chemical bond requires the assessment of the electron donation contribution to the bond. This will be interrogated in a separate study.Anions, together with cations and solvent molecules, are building blocks of the boundary layer that develops in the interface between metal and electrolytic solution. When specifically adsorbed, they alter the charge distribution at the interface and the

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“…Numerous studies of the co-adsorption of CO and organics have been conducted on various metals in the surface science literature [95][96][97][98][99][100]. These studies are often conducted at low temperatures and UHV conditions, so the surface is not in equilibrium with the gas phase.…”

Section: Coadsorption Of Carbon Monoxide and Ethylene On Pt Catalystsmentioning

confidence: 99%

The Synthesis, Characterization and Catalytic Reaction Studies of Monodisperse Platinum Nanoparticles in Mesoporous Oxide Materials

Rioux

2006

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A catalyst design program was implemented in which Pt nanoparticles, either of monodisperse size and/or shape were synthesized, characterized and studied in a number of hydrocarbon conversion reactions. The novel preparation of these materials enables exquisite control over their physical and chemical properties that could be controlled (and therefore rationally tuned) during synthesis. The ability to synthesize rather than prepare catalysts followed by thorough characterization enable accurate structure-function relationships to be elucidated. Pt nanoparticles (1.7-7.1 nm) are synthesized by solution phase reduction methods in which Pt precursors are reduced in protic solvents in the presence of a surface templating polymer, which serves to stabilize the metal nanoparticles in solution. Particle size can be controlled during synthesis by altering either the PVP: Pt salt ratio, reaction media and by seeded growth methods. After Pt nanoparticles are synthesized, their size and morphology are confirmed with transmission electron microscopy and x-ray diffraction. Low power sonication in either aqueous or 2 organic solvent was utilized to disperse Pt nanoparticles within the mesoporous metal oxide matrix. This method of catalyst synthesis is named capillary inclusion (CI). An alternative approach to catalyst synthesis combines the hydrothermal synthesis of mesoporous silica with Pt nanoparticle synthesis in the same solution. Synthesis under neutral conditions led to a catalyst in which the nanoparticles were highly dispersed throughout the catalyst matrix. This method of catalyst synthesis called nanoparticle encapsulation (NE) ensured that Pt nanoparticles were located on the internal pore surface of the mesoporous silica. Catalysts were characterized by transmission electron microscopy (TEM), x-ray diffraction (XRD), small angle x-ray scattering (SAXS) and physical adsorption to determine metal particle size and mesoporous structure. The surface chemistry of the nanoparticle surface was studied by infrared spectroscopy, selective gas adsorption (chemisorption) and catalytic reactivity studies. During nanoparticle synthesis, PVP is added to the solution to stabilize the platinum nanoparticles against aggregation. This polymer remains bound to the nanoparticle surface after catalyst synthesis and must be removed before catalytic reactions.Calcination of the catalyst at high temperature (623-723 K) for long time periods (24-36 hours) followed by reduction was initially used to clean the Pt surface. While calcination-reduction treatment is a standard procedure for catalyst activation, the need for long treatments was due to the high molecular weight (~55,000) of the surfacestabilizing polymer. Polymer removal was confirmed by selective gas adsorption, infrared spectroscopy investigation of CO adsorption as well as ethylene hydrogenation.Metallic surface area determined by chemisorption was not in agreement with XRD or TEM results and turnover rates for ethylene hydrogenation results were lower than those 3 measured o...

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Carbon monoxide induced ordering of adsorbates on the Rh(111) crystal surface: Importance of surface dipole moments

Cited by 100 publications

References 60 publications

Tip-to-surface distance variations vs voltage in scanning tunneling microscopy

Tip-to-surface distance variations vs voltage in scanning tunneling microscopy

Adsorption of Bisulfate Anion on the Au(111), Pt(111), and Rh(111) Surfaces

The Synthesis, Characterization and Catalytic Reaction Studies of Monodisperse Platinum Nanoparticles in Mesoporous Oxide Materials

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