On the electrodeposition of titanium in ionic liquids
ABSTRACT The ability to electrodeposit titanium at low temperatures would be an important breakthrough for making corrosion resistant layers on a variety of technically important materials. Ionic liquids have often been considered as suitable solvents for the electrodeposition of titanium. In the present paper we have extensively investigated whether titanium can be electrodeposited from its halides (TiCl(4), TiF(4), TiI(4)) in different ionic liquids, namely1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([EMIm]Tf(2)N), 1-butyl-1-methylpyrrolidinium bis(trifluoromethyl-sulfonyl)amide ([BMP]Tf(2)N), and trihexyltetradecyl-phosphonium bis(trifluoromethylsulfonyl)amide ([P(14,6,6,6)]Tf(2)N). Cyclic voltammetry and EQCM measurements show that, instead of elemental Ti, only non-stoichiometric halides are formed, for example with average stoichiometries of TiCl(0.2), TiCl(0.5) and TiCl(1.1). In situ STM measurements show that-in the best case-an ultrathin layer of Ti or TiCl(x) with thickness below 1 nm can be obtained. In addition, results from both electrochemical and chemical reduction experiments of TiCl(4) in a number of these ionic liquids support the formation of insoluble titanium cation-chloride complex species often involving the solvent. Solubility studies suggest that TiCl(3) and, particularly, TiCl(2) have very limited solubility in these Tf(2)N based ionic liquids. Therefore it does not appear possible to reduce Ti(4+) completely to the metal in the presence of chloride. Successful deposition processing for titanium in ionic liquids will require different maybe tailor-made titanium precursors that avoid these problems.
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ABSTRACT: xxiii, 168 p. : ill. ; 30 cm. PolyU Library Call No.: [THS] LG51 .H577M ABCT 2009 Lee Ruthenium oxo complexes are potential electrocatalysts for a number of oxidation reactions. However, the electro-generation of ruthenium oxo species is kinetically slow on electrode surface which limits their applications. In this study, we investigated some factors associated with the promotion of the electro-generation of ruthenium oxo species on electrodes. The synthesis and characterization of [RuII(tpy)(MBP)(H2O)]3+, [RuII(tpy)(MBHP)(H20)]3+, [RuII(tpy)(dppa)(H2O)]2+ and [RuII(tpy)(dpha)(H2O)]2+ (tpy= 2,2':6,'2"-terpyridine, MBP= 1 -methyl-1 -(3-N, N'-bis(2-pyridyl)propylammo) pyrrolidinium, MBHP= 1 -methyl-l-(6-N, N'-bis(2-pyridyl)hexylamino)pyrrolidinium, dppa= (2,2'-dipyridyl)-n-propylamine and dpha= (2,2'-dipyridyl)-n-hexylamine) and the electrochemical properties of these complexes are the focuses of study in this project. The structures of [RuII(tpy)(MBP)(H2O)]3+ and [RuII(tpy)(dppa)(H2O)]2+ have been determined by X-ray crystallography. The effect of anions (including perchlorate, trifluoroacetate, trifluoromethanesulfonate, sulfate, tetrafluoroborate and hexafluorophosphate) on the rate of electro-generation of ruthenium oxo species was investigated. Among the anions investigated, perchlorate was found to promote the electro-generation of ruthenium oxo species. However, only the perchlorate anions alone is not sufficient to promote the oxidation of RuIII-OH to RuIV=O. It was found that in addition to perchlorate, the presence of an alkyl chain on the amine nitrogen of the 2,2'-dipyridylamine (dpa) is essential to speed up the electrochemical formation of RuIV=O species. The perchlorate anions have no effect in promoting the electrochemical oxidation of [RuIII(tpy)(dpa)(OH)]2+ which contains no alkyl tail on the amine nitrogen. The effect of the length and nature of the tail tagged on the 2,2'-dipyridylamine ligand on the rate of electro-generation of ruthenium oxo species was therefore also investigated. All the complexes [RuII(tpy)(MBP)(H2O)]3+, [RuII(tpy)(MBHP)(H2O)]3+, [RuII(tpy)(dppa)(H2O)]2+ and [Run(tpy)(dpha)(H2O)]2+containing either a cationic or a neutral tail on the 2,2'-dipyridylamine ligand showed an enhancement of the rate of oxo formation. A comparison of the cyclic voltammograms of [RuII(tpy)(dpa)(H2O)]2+, [RuII(tpy)(dppa)(H2O)]2+ and [RuII(tpy)(dpha)(H2O)]2+ suggested that a longer alkyl chain length can promote better formation of RuIV=O species. A mechanism involving the association of ruthenium complexes through hydrogen bonding between the perchlorate anion and the C-H hydrgoens on the alkyl chain, which can promote the formation of pre-associated [RuIII-OH...HO-RuIII] species, was proposed. Hydrogen bonding between the perchlorate anion and the C-H hydrogens on the alkyl chain were confirmed by the X-ray structure of the ruthenium complexes with the perchlorate anions. M.Phil., Dept. of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, 
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ABSTRACT: Direct electrodeposition of macroporous tin is achieved in a water- and air-stable room-temperature ionic liquid, namely, 1-ethyl-3-methylimidazolium-dicyanamide. This is the first example showing that tin nanowires interweaving into a porous structure can be obtained in ionic liquid without using any additive and template. The nanostructures, with great uniformity, high porosity, and good adhesion, were prepared by galvanostatic deposition at a current ranging from 0.3 to 1.2 mA cm(-2). Electrodeposition experiments performed in the 1-ethyl-3-methylimidazoliun-tetrafluoro borate ionic liquid under a similar condition generated granular tin rather than tin wires. (C) 2008 The Electrochemical Society.Electrochemical and Solid-State Letters 01/2008; 11(11). DOI:10.1149/1.2978089 · 2.32 Impact Factor
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ABSTRACT: The electro-deposition of titanium from two different classes of ionic liquids has been studied. Gold ions in solution have been used as an additive in order to provide a stable nucleation site for titanium to deposit on via a co-deposition process. Despite evidence from previous literature, it was found that it was not possible to reduce titanium from the +4 state to titanium (0) due to problems of redox cycling and solubility of reduced titanium species in the various ILs trialled. It was however found that gold was a very effective nucleating agent for these reduced titanium species and that successful mixed Ti(n+)/gold electro-deposits were obtained. The content of titanium in these species could be varied according to the conditions and IL used.Physical Chemistry Chemical Physics 01/2008; 10(38). DOI:10.1039/b803650k · 4.49 Impact Factor