Bimetallic surfaces

Chang SC, Ho Y, Weaver MJ. 1992. Applications of real-time infrared spectroscopy to electrocatalysis at bimetallic surfaces. I. Electrooxidation of formic acid and methanol on bismuth-modified platinum (111) and platinum (100). Surf Sci 265 81-94. 

Ross PN. 1998. The science of electrocatalysis on bimetallic surfaces. In Lipkowski J, Ross PN Jr, editors. Electrocatalysis. New York Wiley-VCH. pp. 43-74. 

The key parameters of the electronic structure of these surfaces are summarized in Table 9.3. The calculated rf-band vacancy of Pt shows no appreciable increase. Instead, there is a shght charge transfer from Co to Pt, which may be attributable to the difference in electronegativity of Pt and Co, in apparent contradiction with the substantial increase in Pt band vacancy previously reported [Mukerjee et al., 1995]. What does change systematically across these surfaces is the J-band center (s ) of Pt, which, as Fig. 9.12 demonstrates, systematically affects the reactivity of the surfaces. This correlation is consistent with the previous successes [Greeley et al., 2002 Mavrikakis et al., 1998] of the band model in describing the reactivity of various bimetallic surfaces and the effect of strain. Compressive strain lowers s, which, in turn, leads to weaker adsorbate-surface interaction, whereas expansive strain has the opposite effect. 

Koper MTM, Lukkien JJ, Jansen API, van Santen RA. 1999. Lattice gas model for CO electrooxidation on Pt-Ru bimetallic surfaces. J Phys Chem B 103 5522-5529. 

LischkaM, Mosch C, Gross A. 2007. Tuning catalytic properties of bimetallic surfaces Oxygen adsorption on pseudomorphic Pt/Ru overlayers, Electrochim Acta 52 2219. 

Shubina TE, Koper MTM. 2002. (Juantum-chemical calculations of CO and OH interacting with bimetallic surfaces. Electrochim Acta 47 3621-3628. 

Bimetallic surfaces are well known for showing radically different chemistry from the individual components and the catalysis industry frequently makes use of these properties to tune catalysts, a recent example is the alloying of... 

J. A. Rodriguez, The chemical properties of bimetallic surfaces importance of ensemble and electronic effects in the adsorption of sulfur and S02, Prog. Surf. Sci., 2006, 81, 141. 

The surface reaction of the chemisorbed hydrogen and tetraethyltin (a controlled surface reaction) was used to produce bimetallic surface species with direct Sn-Pt interaction, which were decomposed in a hydrogen atmosphere in a subsequent step (Scheme 7.21).308... 

Mazzone G, Rivalta I, Russo N, Sicilia E (2008) Interaction of CO with PdAu(lll) and PdAu(100) bimetallic surfaces a theoretical cluster model study. J Phys Chem C 112 ... 

CM = -Wzim- It should be noted that the Budd-Vannimenus theorems are obeyed by the electron density n(z) which is the exact solution to the jellium problem, and not necessarily by any approximate (e.g., variational) solution. There are extensions of the Budd-Vannimenus theorems to a bimetallic surface.74... 

The first deals with small islands of silver on a ruthenium substrate. One may look at this sample as a, perhaps somewhat far-fetched, model of a supported catalyst or a bimetallic surface. As metal layers are almost never in perfect registry with the substrate, they possess a certain amount of strain. Goodman and coworkers [46] used these strained metal overlayers as model systems for bimetallic catalysts. Here we look first at the electronic properties of the Ag/Ru(001) system as studied by UPS. 

These two features exemplify the behavior of interface states, which are states that are not seen for either component of a bimetallic surface alloy but which exist because of the abrupt change in electronic properties at the interface. 

As was previously mentioned, PtRu alloys exhibit improved performance over pure Pt alloys.117,118 This is primarily a result of the ability of Ru to dissociate H20 for reaction with CO adsorbed on Pt sites.115,116 That CO oxidation on pure Ru is unfavorable indicates that on the bimetallic surface, CO is oxidized only on the Pt sites.119 Thus, CO is oxidized on Pt sites adjacent to Ru sites, where water is activated.120,121 This is known as a bifunctional mechanism. In addition, the presence of Ru atoms reduces the adsorption energy of CO on neighboring Pt atoms, lowering the activation energy of CO oxidation.122 This effect is purely electronic and is less significant than the bifunctional effect of Ru.123 One significant limitation of PtRu is the weak adsorption of methanol on Ru, particularly at room temperature.117,124 The weak adsorption severely hinders methanol decomposition, which is evident in Fig. 7 by the drop in current density for PtRu electrodes with high Ru composition.125... 

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