Bulk metal surfaces

Electrochemistry of proteins is another case where electrode size affects the electrochemical results. Direct adsorption of proteins, such as enzymes, onto bulk metal surfaces frequently results in denaturation of the... 

The term surface alloy is somewhat generic and may refer to a variety of different systems. Here, we apply it to those systems where ultra-thin metal layers (i.e. a few atomic layers thick) are deposited on a bulk metal surface and where the system is subsequently annealed in vacuum in order to obtain alloying in a surface region a few atoms thick. In these conditions it is possible to obtain single atomic layer binary phases, or multilayer surface alloy phases (also termed epitaxial alloys (for a general discussion of these surface alloys, see [5]. Relatively to the subject of the present paper, two Pt-Sn systems have been studied Sn-Pt(l 11) and Sn-Pt(lOO). The behavior and the structural properties of these systems will be discussed in detail in the following. 

Figure 10 Bar graphs of the ORR activities of UHV-prepared surfaces of Pt, P3M, and Pt3Co bulk metal surfaces. Current densities are per unit geometric area.

Analogous effects have also been discussed for the reactivity of different bulk metal surfaces, where the center of gravity of the d-band determines the bonding [350]. In this case, the effects on the reactivity are considerably smaller than in the case of clusters in the nonscalable size regime and are size independent. Additional factors that change the d-band structure for a particular element are strain effects and the crystallographic orientation of the respective surface plane (see Chap. 3). 

Underpotentially deposited ultra-thin layers of silver or copper on gold substrates are also suitable for monolayer assembly. Monolayers prepared on such surfaces are different from those that form on the parent bulk metal surfaces and show enhanced stability against thermal desorption or exchange with thiol-containing solutions91 92. 

In our relativistic density-functional study of mixed Pt-M nanoparticle surfaces is represented by a two-layer cluster with seven surface and three second-layer atoms, Ptio-nMn(7,3) [6]. The subnano cluster model does not simulate bulk surface properties because of its limited size and undercoordinated metal atoms. However, the model is suitable for simulating the properties of nanoscale particle catalysts, e.g., Pt-Ru alloy nanoparticles wife an fee surface. Catalytically much more active than bulk metal surfaces, these nanocrystals exhibit a transition from metallic to insulator properties [48]. The cluster model is also suitable for rough Pt-M electrode surfaces that exhibit a high surface density of reactive Pt-M sites [49]. 

The ATR-technique does not apply to studies of adsorbed molecules on well deflned bulk metal surfaces. This is due to the fundamental electrodynamic properties of metals, which do not allow the electric field to penetrate the metal to any significant extent at in-... 

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