Electrodeposition of metals

Typically, electroplating metals and metal alloys is less sophisticated than the corresponding metal oxide or chalcogenide electrodeposition. Further, dense and highly stable deposits are usually obtained. The two-step synthesis approach is more versatile, in a sense that after identifying a synthesis route to a nanostructured metal, various ceramics can be produced by thermal oxidation under an appropriate atmosphere. In fact more porous and sophisticated structures, such as hollow nano-spheres, nanotubes, and nano-peapods, can be synthesized based on the nanoscale Kirkendall effect (NKE) occurring during thermal oxidation [2-5]. 

Parts of this chapter were previously published and are reprinted/adapted with permission from American Chemical Society, Copyright 2013 [1]. 

Scherer, Double-Gyroid-Structured Functional Materials, Springer Theses, DOI 10.1007/978-3-319-00354-2 6, 

Thomas Schubert, SherifZein El Abedin, Andrew P. Abbott, KatyJ. McKenzie, Karl S. Ryder, and Frank Endres 

Between 1980 and about 2000 most of the studies on the electrodeposition in ionic liquids were performed in the first generation of ionic liquids, formerly called room-temperature molten salts or ambient temperature molten salts . These liquids are comparatively easy to synthesize from AICI3 and organic halides such as Tethyl-3-methylimidazolium chloride. Aluminum can be quite easily be electrode-posited in these liquids as well as many relatively noble elements such as silver, copper, palladium and others. Furthermore, technically important alloys such as Al-Mg, Al-Cr and others can be made by electrochemical means. The major disadvantage of these liquids is their extreme sensitivity to moisture which requires handling under a controlled inert gas atmosphere. Furthermore, A1 is relatively noble so that silicon, tantalum, lithium and other reactive elements cannot be deposited without A1 codeposition. Section 4.1 gives an introduction to electrodeposition in these first generation ionic liquids. 

In the 1990s John Wilkes and coworkers introduced air- and water-stable ionic liquids (see Chapter 2.2) which have attractive electrochemical windows (up to 3 V vs. NHE) and extremely low vapor pressures. Furthermore, they are free from any aluminum species per se. Nevertheless, it took a while until the first electrodeposition experiments were published. The main reason might have been that purity was a concern in the beginning, making reproducible results a challenge. Water and halide were prominent impurities interfering with the dissolved metal salts and/or the deposits. Today about 300 different ionic liquids with different qualities are commercially available from several companies. Section 4.2 summarizes the state-of-the-art of electrodeposition in air- and water-stable ionic liquids. These liquids are for example well suited to the electrodeposition of reactive elements such as Ge, Si, Ta, Nb, Li and others. 

Section 4.3 is devoted to electrodeposition in a special class of deep eutectic solvents/ionic liquids which are based on well-priced educts such as e.g. choline chloride. The impressive aspect of these liquids is their easy operation, even under air, as well as their large-scale commercial availability. One disadvantage has to be mentioned the choline chloride-based liquids especially are currently not yet 

Electrodeposition from Ionic Liquids. Edited by F. Endres, D. MacFarlane, A. Abbott Copyright 2008 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim ISBN 978-3-527-31565-9 

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Electrodeposition of Metals. Citric acid and its salts are used as sequestrants to control deposition rates in both electroplating and electroless plating of metals (153—171). The addition of citric acid to an electroless nickel plating bath results in a smooth, hard, nonporous metal finish. 

Section 6.2.1 offers literature data on the electrodeposition of metals and semiconductors from ionic liquids and briefly introduces basic considerations for electrochemical experiments. Section 6.2.2 describes new results from investigations of process at the electrode/ionic liquids interface. This part includes a short introduction to in situ Scanning Tunneling Microscopy. 

Electrodeposition of metals that can also be obtained from water... 

Electrodeposition of metals from ionic liquids Endres 3... 

Although the mechanisms discussed above are still topics of debate, it is now firmly established that the electrodeposition of conducting polymers proceeds via some kind of nucleation and phase-growth mechanism, akin to the electrodeposition of metals.56,72-74 Both cyclic voltammetry and potential step techniques have been widely used to investigate these processes, and the electrochemical observations have been supported by various types of spectroscopy62,75-78 and microscopy.78-80... 

Pavlovic, M. G. Electrodeposition of Metal Powders with Controlled Particle Grain Size and Morphology 24... 

Fukami, K., Nakanishi, S., Yamasaki, H., Tada, T., Sonoda, K., Kamikawa, N., Tsuji, N., Sakaguchi, H. and Nakato, Y. (2007) General mechanism for the synchronization of electrochemical oscillations and self organized dendrite electrodeposition of metals with ordered 2D and 3D microstructures./. Phys. Chem. C, 111, 1150-1160. 

Electrodeposition of metals can be performed under different electrochemical modes. In the work mentioned in Ref. [18], it was performed in potentiostatic mode. The potential value for formation of platinum nanoparticles is —25 mV vs. SCE the deposition is performed from 2.5 mM solution of H2[PtCl6] in 50 mM KCl. The size of nanoparticles formed depends on the reduction charge. Continuous monitoring of the charge in potentiostatic mode is provided by different potentiostats, for example, by Autolab-PG-stat (EcoChemie, The Netherlands). Conditions for deposition of other metals should be selected according to their electrochemical properties. 

Finally, the presence of ultrasound in the electrodeposition of metals can produce both massive metal and metal colloid [75]. The reduction of AuCLt- at polycrystalline boron-doped diamond electrodes follows two pathways forming... 

Hyde ME, Compton RG (2002) How ultrasound influences the electrodeposition of metals. J Electroanal Chem 531 19-24... 

Electrodeposition of metal onto structured objects, such as circuits, is controlled in part by a template. At the same time, the deposit must fill all the recesses uniformly and seamlessly, the texture and crystal structure must fall within tolerances, and the quality of the features must be sustained over a large workpiece. The distribution of material within recesses or onto widely separated portions of the workpiece is subject to a limited number of macroscopic control-parameters such as applied potential and plating bath composition. Success therefore depends on exploitation of the natural pathways of the process. The spontaneous and unconstrained development of structure must be taken into consideration in the production of highly organized and functional patterns. 

Used industrially for the manufacture of phosphorus oxychloride, phosphorus pentachlor-ide, phosphites, organophosphorus pesticides, surfactants, gasoline additives, plasticizers, dyestuffs used as a chlorinating agent and catalyst. Used to prepare rubber surfaces for electrodeposition of metal. Used as an ingredient of textile finishing agents. 

Bruhn D, Dietz W, Muller K-J and Reynvaan C, EPA 86109265.8(1986) through ref (247) 248a. Dietz W (1986) Electrodeposition of metals from an electrolysis bath, Eur Pat Appl EP... 

Electro sorption at electrodes and its relevance to electrocatalysis and electrodeposition of metals. 

Generally, the reduction to the metallic state implies decomplexation of the bound ligands (hence, irreversible reduction), electrodeposition of metallic zinc on the electrode surface and consequently the anodic stripping process in the backscan. 

Walsh, F.C. and M.E. Herron, Electrocrystallization and electrochemical control of crystal growth fundamental considerations and electrodeposition of metals. Journal of Physics D Applied Physics, 1991. 24(2) p. 217. 

S.M. Kochergin and G.Ya. Vyaselva, Electrodeposition of Metals in Ultrasonic Fields, Consultants Bureau, New York, 1966. 

Figure 2.1. Electrolytic cell for electrodeposition of metal, M, from an aqueous solution of metal salt, MA.

In this chapter we derive the Butler-Vohner equation for the current-potential relationship, describe techniques for the study of electrode processes, discuss the influence of mass transport on electrode kinetics, and present atomistic aspects of electrodeposition of metals. 

In the electrodeposition of metals, a metal ion is transferred from solution into the ionic metal lattice. A simplified atomistic representation of this process is... 

Steps, or growth layers, are structure components for construction of a variety of growth forms in the electrodeposition of metals (e.g., columnar crystals, whiskers, fiber textures). We can distinguish between monoatomic steps, polyatomic microsteps, and polyatomic macrosteps. Only the propagation of polyatomic steps can be observed directly, in situ. 

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