Electrodeposition of metals from supercritical fluids

Abstract

Electrodeposition is a widely used materials-deposition technology with a number of unique features, in particular, the efficient use of starting materials, conformal, and directed coating. The properties of the solvent medium for electrodeposition are critical to the technique's applicability. Supercritical fluids are unique solvents which give a wide range of advantages for chemistry in general, and materials processing in particular. However, a widely applicable approach to electrodeposition from supercritical fluids has not yet been developed. We present here a method that allows electrodeposition of a range of metals from supercritical carbon dioxide, using acetonitrile as a co-solvent and supercritical difluoromethane. This method is based on a careful selection of reagent and supporting electrolyte. There are no obvious barriers preventing this method being applied to deposit a range of materials from many different supercritical fluids. We present the deposition of 3-nm diameter nanowires in mesoporous silica templates using this methodology.electrochemistry ͉ nanomaterials

Electrochemistry in supercritical fluids: A mini review

“…Organic co-solvents form a single phase with scCO 2 and considerably improve the solubility of ionic species. This mixed solvent phase has been largely documented in the field electrodeposition [3,18,22], with Bartlett et al recently reviving interest in SCFs as electroplating media. Their research efforts have demonstrated that the unique mass transport properties and lack of surface tension in supercritical media permit the formation of well-defined nano-structured electrodeposits [3].…”

Steady-state macroscale voltammetry in a supercritical carbon dioxide medium

“…In general, it is understood that the better electrolytes for scCO 2 electrochemistry are highly fluorinated salts and consist of bulky ions. Anions such as tetrakis(pentafluorophenyl)borate (TFPB À ) and tetrakis(3,5-trifluoromethyl phenyl)borate are often used in liquid-liquid electrochemistry to pump protons from a water phase into an organic phase, 12,13 but have also been applied to scCO 2 electrodeposition processes as reported recently by Bartlett et al [14][15][16] In 1996, Abbott and co-workers 17 reported the high solubility of long chain ammonium alkanes in non-polar solvents, presenting tetra(decyl)ammonium tetraphenylborate (TDATPB) as a suitable electrolyte for scCO 2 studies. 5 Chanfreau et al used the latter electrolyte more recently in the electrocarboxylation of benzyl chloride in pressurised CO 2 .…”

The voltammetry of decamethylferrocene and coboltacene in supercritical difluoromethane (R32)

“…This cell is specially designed and has been described in the literature [32]. The steel cell consists of two parts, the top part contains seven 1/16 inch female SSI type fittings through which a thermocouple, a CO 2 /R32 feeding line and the 5 electrodes could be fed and sealed.…”