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: Ionic liquids are steadily attracting interests throughout a recent decade and their application is expanding into various fields including electrochemistry due to their unique properties such as non-volatility, inflammability, low toxicity, good ionic conductivity, wide electrochemical potential window and so on. These features make ionic liquids become an alternative solution for electrodeposition of metals that cannot be electroplated in aqueous electrolytes. In this review, we classify investigated metals into three categories, which are light (Li, Mg), refractory (Ti, Ta) and noble (Pd, Pt, Au) metals, rather than covering the exhaustive list of metals and try to update the recent development in this area. In electrodeposition of light metals, granular fine Li particles were successfully obtained while the passivation of electrodeposited Mg layers is an obstacle to reversible deposition-dissolution process of Mg. In the case of refractory metals, the quality of Ta and Ti deposit particles was effectively improved with addition of LiF and pyrrole, respectively. In noble metal category, EMIM TFSA ionic liquid as an electrolyte for Au electrodeposition was proven to be effective and BMP TFSA ionic liquid developed a smooth Pd deposit. Pt nanoparticle production from ionic liquid droplet in aqueous solution can be cost-effective and display an excellent electrocatalytic activity.Journal of the Korean Electrochemical Society. 01/2012; 15(3).
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ABSTRACT: The electrodeposition of black chromium coatings from ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate with chromium chloride, and the chemical composition of the deposits are discussed in this article. The UV–Vis spectra recorded for chromium(III) species in 1-butyl-3-methylimidazolium tetrafluoroborate suggest that along with the chromium(III) complexes containing three ligands, there are some amounts of chromium species containing four ligands in the bath employed. The cathodic process of chromium electrodeposition in the employed ionic liquid is complicated by the electrochemical reduction of water molecules, which is followed by chemical disintegration of tetrafluoroborate ions. The surface morphology of black chromium films deposited potentiostatically (–1.5 to −2.0 V) at 85 °C shows nodules and microcracks increasing in size with cathodic potential. Analysis of the X-ray photoelectron spectra recorded from surface to depth of the deposit has shown that the black oxide-rich chromium coating consists of chromium in both oxide and metallic states with small impurities of other elements (fluorine, boron, carbon and nitrogen) and the surface is covered with a thin layer of organic substances. The results of this study show that 1-butyl-3-methylimidazolium tetrafluoroborate may be considered as a promising substitute of toxic Cr(VI) baths for black chromium plating.Journal of Applied Electrochemistry 01/2011; 41(1):107-114. · 1.84 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). · 4.20 Impact Factor