title: Phase behaviour and conductivity study of electrolytes in supercritical hydrofluorocarbons.
abstract: The purpose of this work was to characterise supercritical hydrofluorocarbons (HFC) that can be used as solvents for electrodeposition. The phase behaviour of CHF(3), CH(2)F(2), and CH(2)FCF(3) containing [NBu(n)(4)][BF(4)], [NBu(n)(4)][B{3,5-C(6)H(3)(CF(3))(2)}(4)] and Na[B{3,5-C(6)H(3)(CF(3))(2)}(4)] was studied and the conditions for forming a single supercritical phase established. Although all three HFCs are good solvents for [NBu(n)(4)][BF(4)] the results show that the CH(2)F(2) system has the lowest p(r) for dissolving a given amount of [NBu(n)(4)][BF(4)]. The solubility of Na[B{3,5-C(6)H(3)(CF(3))(2)}(4)] in CH(2)F(2) was found to be unexpectedly high. Studies of the phase behaviour of CH(2)F(2) containing [NBu(n)(4)][BF(4)] and [Cu(CH(3)CN)(4)][BF(4)] showed that the copper complex was unstable in the absence of CH(3)CN. For CHF(3), [Cu(hfac)(2)] was more soluble and more stable than [Cu(CH(3)CN)(4)][BF(4)] and only increased the phase-separation pressure by a moderate amount. Studies of the conductivity of [NBu(n)(4)][B(C(6)F(5))(4)], [NBu(n)(4)][B{3,5-C(6)H(3)(CF(3))(2)}(4)], [NR(f)Bu(n)(3)][B{3,5-C(6)H(3)(CF(3))(2)}(4)] (R(f) = (CH(2))(3)C(7)F(15)), and Na[B{3,5-C(6)H(3)(CF(3))(2)}(4)] were carried out in scCH(2)F(2). The results show that these salts are more conducting than [NBu(n)(4)][BF(4)] under the same conditions although the increase is much less significant than that reported in previous work in supercritical CO(2) + CH(3)CN. Consequently, either [NBu(n)(4)][BF(4)] or the corresponding BARF salts would be suitable background electrolytes for electrodeposition from scCH(2)F(2).
authors.affiliation: School of Chemistry, University of Southampton, Southampton, SO17 1BJ, UK. pnb@soton.ac.uk
authors.forename: Philip N
authors.initials: PN
authors.lastname: Bartlett
authors.forename: David C
authors.initials: DC
authors.lastname: Cook
authors.forename: Michael W
authors.initials: MW
authors.lastname: George
authors.forename: Jie
authors.initials: J
authors.lastname: Ke
authors.forename: William
authors.initials: W
authors.lastname: Levason
authors.forename: Gillian
authors.initials: G
authors.lastname: Reid
authors.forename: Wenta
authors.initials: W
authors.lastname: Su
authors.forename: Wenjian
authors.initials: W
authors.lastname: Zhang
mesh_terms: D004553:Electric Conductivity; D004573:Electrolytes / Q000737:chemistry*; D006845:Hydrocarbons, Fluorinated / Q000737:chemistry*
chemical_list: D004573:Electrolytes; D006845:Hydrocarbons, Fluorinated