Interface noble metal atoms

See also the main entry -+ underpotential deposition. Refs. [i] Haissinsky M (1933) J Chim Phys 30 27 [ii] Frumkin AN (1934) Zh Fiz Khimii 5 240 [iii] Kolb DM (1978) Physical and electrochemical properties of metal monolayers on metallic substrates. In Gerischer H, Tobias CW (eds) Advances in electrochemistry and electrochemical engineering, vol. 11. Wiley New York, p 125 [iv] Conway B (1984) Progr Surf Sci 16 1 [v] Ye S, Uosaki K (2003) Atomically controlled electrochemical deposition and dissolution of noble metals. In BardAJ, Stratmannn M, Gileadi E, Urbakh M (eds) Thermodynamics and electrified interfaces. Encyclopedia of electrochemistry, vol. 1. Wiley-VCH, p 471 [vi] Adzic R (2003) Electrocatalysis on surfaces modified by metal monolayers deposited at underpotentials. In Bard AJ, Stratmannn M, Gileadi E, Urbakh M (eds) Thermodynamics and electrified interfaces. Encyclopedia of electrochemistry, vol. 1. Wiley-VCH, p 561... 

If in the case of aluminized silicone we were able to evidence a drastic difference between sputtering and evaporation, it happens not to be the case for aluminized PET (13). Our preliminary results on this latter polymer indeed show no marked differences between the two deposition processes, both giving strong chemical interaction. By contrast we have also observed that with noble metals such as Au, no chemical interaction is taking place with silicone substrate with both deposition processes. This tells us that the nature of the polymer substrate and of the metal are most important for the interfacial and adhesive properties. The fundamental parameter seems to be the reactivity of both constituents of the interface. It has been confirmed by Pireaux et al. that the carboxylic function is one of the most reactive surface entity (14) and indeed for PET, the adsorption site for the Al atoms is found to be the carboxylic function (13). During this interaction, Al is oxidized and the diffusion of O into the Al film can occur. 

Chapter 3, by Rolando Guidelli, deals with another aspect of major fundamental interest, the process of electrosorption at electrodes, a topic central to electrochemical surface science Electrosorption Valency and Partial Charge Transfer. Thermodynamic examination of electrochemical adsorption of anions and atomic species, e.g. as in underpotential deposition of H and metal adatoms at noble metals, enables details of the state of polarity of electrosorbed species at metal interfaces to be deduced. The bases and results of studies in this field are treated in depth in this chapter and important relations to surface -potential changes at metals, studied in the gas-phase under high-vacuum conditions, will be recognized. Results obtained in this field of research have significant relevance to behavior of species involved in electrocatalysis, e.g. in fuel-cells, as treated in chapter 4, and in electrodeposition of metals. 

The process of surface electrooxidation is an electrochemical situation in which the electrons are lost in the outer layer of the metal/solution interface. During the process, the metal atom undertakes the formation of either a metallic cation or a surface oxide. The electron loss goes with an increase in the electron density by the oxidizing agent. The formation of a soluble species on non-noble metals containing oxygenated molecules or the formation of noble metal oxides is probably one of the most studied topics in this field. 

Wippermann developed a galvanic deposition of noble metals on carbon for usage in fuel cells [3]. Noble metal cluster such as platinum ion deposits on carbon particles which is in the contact interface of conducting carbon and electrolyte due to delivery of electrons via contact interface. Schindler developed the deposition of metal cluster on various metals and semiconductor substrate [3]. By cathodic accumulation of metal atoms on a conducting STM tip due to anodic dissolution, local enrichment can be achieved which allows localized cathodic deposition. Kolb applies localized deposition on the metal cluster on substrate by direct transferring of atoms from the STM tip [4]. 

As a fundamental basis for all STM studies, electrode-electrolyte interfaces must be prepared reproducibly, and methods must be established to observe these interfaces accurately. Well-defined single crystalline surfaces must be exposed to solution to understand surface structure-reactivity relationships on the atomic scale. Efforts have succeeded to produce extremely well-defined, atomically flat surfaces of various electrodes made of noble metals, base metals, and semiconductors without either oxidation or contamination in solution. 

Noble metal quantum clusters. Chemistry of gold-sulphur interface on monolayer protected clusters (MFCs) has long attracted research interest. These materials have a nanosized metal core containing hundreds or thousands of atoms with monolayers of surfactants/ligands on its surface. The metal core made of dense packing of metal atoms forming nanocrystals with specific lattice planes on its surface. 

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