TY - JOUR
T1 - Phase behaviour and conductivity of supporting electrolytes in supercritical difluoromethane and 1,1-difluoroethane
AU - Han, Xue
AU - Ke, Jie
AU - Suleiman, Norhidayah
AU - Levason, William
AU - Pugh, David
AU - Zhang, Wenjian
AU - Reid, Gillian
AU - Licence, Peter
AU - George, Michael W.
N1 - Publisher Copyright:
© 2016 the Owner Societies.
PY - 2016
Y1 - 2016
N2 - We present investigations into a variety of supporting electrolytes and supercritical fluids probing the phase and conductivity behaviour of these systems and show that they not only provide sufficient electrical conductivity for an electrodeposition bath, but match the requirements imposed by the different precursors and process parameters, e.g. increased temperature, for potential deposition experiments. The two supercritical fluids that have been explored in this study are difluoromethane (CH2F2) and 1,1-difluoroethane (CHF2CH3). For CH2F2, the phase behaviour and electrical conductivity of eight ionic compounds have been studied. Each compound consists of a cation and an anion from the selected candidates i.e. tetramethylammonium ([N(CH3)4]+), tetrabutylammonium ([N(nC4H9)4]+), 1-ethyl-3-methylimidazolium ([EMIM]+) and 1-butyl-3-methylimidazolium ([BMIM]+) for cations, and tetrakis(perfluoro-tert-butoxy)aluminate ([Al(OC(CF3)3)4]-), chloride (Cl-), trifluoromethyl sulfonimide ([NTf2]-) and tris(pentafluoroethyl)trifluorophosphate ([FAP]-) for anions. For CHF2CH3, [N(nC4H9)4][BF4] and [N(nC4H9)4][B{3,5-C6H3(CF3)2}4] have been investigated for comparison with the previously measured solubility and conductivity in CH2F2. We have found that [N(nC4H9)4][Al(OC(CF3)3)4], [N(nC4H9)4][FAP] and [N(CH3)4][FAP] have much higher molar conductivity in scCH2F2 at similar conditions than [N(nC4H9)4][BF4], a widely used commercial electrolyte. Additionally, scCHF2CH3 shows potential for use as the solvent for supercritical fluid electrodeposition, especially at high temperatures since high density of this fluid can be achieved at lower operating pressures than similar fluids that can be used to produce electrochemical baths with comparable conductivity.
AB - We present investigations into a variety of supporting electrolytes and supercritical fluids probing the phase and conductivity behaviour of these systems and show that they not only provide sufficient electrical conductivity for an electrodeposition bath, but match the requirements imposed by the different precursors and process parameters, e.g. increased temperature, for potential deposition experiments. The two supercritical fluids that have been explored in this study are difluoromethane (CH2F2) and 1,1-difluoroethane (CHF2CH3). For CH2F2, the phase behaviour and electrical conductivity of eight ionic compounds have been studied. Each compound consists of a cation and an anion from the selected candidates i.e. tetramethylammonium ([N(CH3)4]+), tetrabutylammonium ([N(nC4H9)4]+), 1-ethyl-3-methylimidazolium ([EMIM]+) and 1-butyl-3-methylimidazolium ([BMIM]+) for cations, and tetrakis(perfluoro-tert-butoxy)aluminate ([Al(OC(CF3)3)4]-), chloride (Cl-), trifluoromethyl sulfonimide ([NTf2]-) and tris(pentafluoroethyl)trifluorophosphate ([FAP]-) for anions. For CHF2CH3, [N(nC4H9)4][BF4] and [N(nC4H9)4][B{3,5-C6H3(CF3)2}4] have been investigated for comparison with the previously measured solubility and conductivity in CH2F2. We have found that [N(nC4H9)4][Al(OC(CF3)3)4], [N(nC4H9)4][FAP] and [N(CH3)4][FAP] have much higher molar conductivity in scCH2F2 at similar conditions than [N(nC4H9)4][BF4], a widely used commercial electrolyte. Additionally, scCHF2CH3 shows potential for use as the solvent for supercritical fluid electrodeposition, especially at high temperatures since high density of this fluid can be achieved at lower operating pressures than similar fluids that can be used to produce electrochemical baths with comparable conductivity.
UR - http://www.scopus.com/inward/record.url?scp=84971357183&partnerID=8YFLogxK
U2 - 10.1039/c6cp00466k
DO - 10.1039/c6cp00466k
M3 - Article
AN - SCOPUS:84971357183
SN - 1463-9076
VL - 18
SP - 14359
EP - 14369
JO - Physical Chemistry Chemical Physics
JF - Physical Chemistry Chemical Physics
IS - 21
ER -