Electrodeposition organic electrolyte

Room-temperature ionic liquids are the promising electrolytes for the electrodeposition of various metals because they have the merits of both organic electrolytes and high-temperature molten salts. Ionic liquids can be used in a wide temperature range, so temperatures can be elevated to accelerate such phenomena as nucleation, surface diffusion and crystallization associated with the electrodeposition of metals. In addition the process can be safely constracted because ionic liquids are neither flammable nor volatile if they are kept below the thermal decomposition temperature of the organic cations. 

Because of its very negative standard electrode potential of — 1.7 Kh. aliuninum cannot be deposited from aqueous solutions. Therefore only molten salt and water-free inorganic or organic electrolyte systems are eligible for electrolytic deposition of aluminum. Only through the development of such nonaqueous systems [53, 54, 118, 217, 221] did it become possible to electrodeposit aluminum with the desired quality and properties. 

Titanium can likewise be electrodeposited from nonaqueous organic electrolytes. At circa 18 °C, 1-75 iim thick coatings are deposited from electrolytes containing dimethylsulfoxide (DMSO) [169]. The baths utilized do not exhibit high stability. Zirconium, hafnium, niobium, and aluminum are also expected to afford electroplated coatings from similar composite systems. Electroplating of titanium from electrolytes based on aromatic solvent mixtures has recently been reported [171]. 

Not only pure aluminum, but also aluminum alloys can be electrodeposited from organic electrolyte systems. Thus, codeposition of iron, nickel, and cobalt from systems composed of AlBrj, LiBr, and toluene have been reported. However, only a small content up to a maximum of 1.4% (for instance, iron) is reached [175]. 

A common method for the electrodeposition of Am is from isopropanol solutions containing small quantities of dilute acid stock solutions of Am ions. Aqueous deposition methods have also been employed, but the organic electrolyte medium is more advantageous in that it tends to produce more uniform coatings [151[. Zhi etal. prepared relatively thick targets of Am from a mixture of isopropanol and dilute (0.1 N) nitric acid stock solutions pf [152]. The electrolysis... 

Electrodeposition and dissolution of magnesium film were studied from the ionic liquid of [BmimJBF with 1 MMgfCFjSOj) at room temperature by Nuli et al. [176, 177]. It was shown that magnesium can be electrodeposited on Ag substrate and the deposits were dense. They also smdied the electrochemical magnesium deposition and dissolution on metal substrates in organic electrolyte... 

Electrodeposition of aluminum is severely limited by the necessity of using molten salt baths or anhydrous organic electrolytes. 

Nam, K. W., C. W. Lee, X. Q. Yang, B. W. Cho, W. S. Yoon, and K. B. Kim. 2009. Electrodeposited manganese oxides on three-dimensional carbon nanotube substrate Supercapacitive behaviour in aqueous and organic electrolytes. Journal of Power Sources 188 323-331. 

Y. Zhao and T.J. VanderNoot, Electrodeposition of aluminium from nonaqueous organic electrolytic systems and room temperature molten salts , Electrochimica Acta, 42, (1997), 3-13. 

Organic Electrolytes. One of the major drawbacks of any molten salt process for electrodeposition is the energy needed to maintain the system in its molten state. The energy that is added either by external heaters or by Joule heating must add to the cost of the final product. 

It has been pointed out that metals residing below the position held by manganese (and, therefore, much below hydrogen) in the electrochemical series (Table 6.11) cannot be electrodeposited from aqueous solutions of their salts. These metals are called base metals or reactive metals and can be electrodeposited only from nonaqueous electrolytes such as solutions in organic solvents and molten salts. As with an aqueous electrolyte, there is a minimum voltage which is required to bring about the electrolysis of a molten salt. 

Having identified the main features of electrochemistry, the remainder of this chapter will focus on the use of electrolytic cells and will use as examples the electrodeposition (or electroplating) of metals such as copper, zinc, iron, chromium, nickel and silver. The chapter will also consider the electrochemistry of some organic molecules. Electroanalysis will not be considered since a full description is not within the scope of this chapter. Eor those interested readers, there is a review on the topic [2],... 

O Brien. 1235 Ohmic drop, 811, 1089, 1108 Ohmic resistance, 1175 Ohm s law, 1127. 1172 Open circuit cell, 1350 Open circuit decay method, 1412 Order of electrodic reaction, definition 1187. 1188 cathodic reaction, 1188 anodic reaction, 1188 Organic adsorption. 968. 978. 1339 additives, electrodeposition, 1339 aliphatic molecules, 978, 979 and the almost-null current test. 971 aromatic compounds, 979 charge transfer reaction, 969, 970 chemical potential, 975 as corrosion inhibitors, 968, 1192 electrode properties and, 979 electrolyte properties and, 979 forces involved in, 971, 972 977, 978 free energy, 971 functional groups in, 979 heterogeneity of the electrode, 983, 1195 hydrocarbon chains, 978, 979 hydrogen coadsorption and, 1340 hydrophilicity and, 982 importance, 968 and industrial processes, 968 irreversible. 969. 970 isotherms and, 982, 983... 

---