Electrochemical deposition experimental procedure

The electrochemical characterization of platinum alloys is performed by cyclic voltammetry, with a careful cycling procedure of no more than three profiles. Moreover, the upper potential limit of the scan has to be recorded with care, and is defined by that of the less noble component of the alloy. The scan potential value has to be always lower than 0.05 V s 1 to avoid large pseudocapa-citive currents that promote surface enrichment on the platinum. The electrochemical description of the surface can be also performed on single crystal alloys. Besides this type of characterization, it is also possible to use the same experimental setup for surface alloy preparation by a potential-controlled deposition. Better cleanliness can be achieved with the help of a UHV chamber as studied for the Sn/Pt(l 11) surface alloy that shows the same structure as that of the bulk after annealing [51]. 

The monolayers described so far have all been grown by self-assembly processes, where ligand-stabilized metal nanopartides are deposited on innocent surfaces from solution, followed by a more or less rapid evaporation of the solvent. Depending on the concentration and other experimental conditions, those procedures may occasionally also result in multilayers, or even in small 3-D microcrystals. Self-assembly processes can, however, also be supported by chemical, electrochemical, magnetic, or mechanical effects some examples of these are provided in the following subsections. 

Many of the procedures applied in this field are modifications of chemical engineering techniques, mainly in the area of solid-solid or solid-liquid separation. The more advanced techniques are washing procedures, of which the fine-grained residues are eventually deposited. With respect to acid extraction procedures, there are many experimental designs, but few practical applications. Electrochemical procedures are in progress, in particular for in-situ-reclamation of metal-rich areas. 

Electrochemical procedures have also progressed considerably. In particular, anodic electropolymerization has been tested in a great variety of experimental conditions in organic and acid media. The procedure constitutes a well established method for depositing doped or undoped thin polyphenylene films on platinum or other metals. The linearity and the DP of the PPP chains are very poor in organic media, but are much improved in acidic media (melt salts in the presence of Lewis acids, superacid media), or when the electrosynthesis is carried out at low temperature in SO2 with a Lewis acid (SbFs). 

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