Biomedical Engineering Reference
In-Depth Information
of
water
on
cyclic
voltammetry
of
the
electrolytes
[BMIM]
] [9]. For both of those ILs, a decrease
in the electrochemical window was observed with increasing
concentration of water. Also, under exposure of [BMIM][PF
[BF
] and [BMIM][PF
4
6
] to
water-saturated argon, the electrochemical window decreased
from ca. 4 to 2 V within less than 1 h. Even ppm levels of water
can affect the electrochemical response [32]. Hence, great
care must be taken in synthesis of ILs as well as in their
electrochemical studies. Viscosity of ILs ranges from ca. 30 cP
to 600 cP [5]. These relatively high values of viscosities
have strong influence on the conductivity of ILs and mass
transport in them. For conventional electrolytes conductivity is
proportional to the concentration of charge carriers. However,
in ILs the apparent cation-anion interaction makes it difficult
to exactly define the number of charge carriers. Hence, ILs
have much lower ionic conductivities than could be expected
when compared with some high-temperature molten salts [33].
High viscosities of ILs also result in relatively low self-diffusion
and difficulties in determination of the exact transport numbers.
6
Table 3.1
Physical properties important for electrochemical applications of
common ionic liquids (25
°
C)
Ionic
conductivity
[mS·cm
-1
]
Abbreviation
Viscosity
[cP]
Electrochemical
window [V]
Electrolyte
1-Butyl-3-
methylimidazolium
hexafluorophosphate
[BMIM][PF
]
312
1.4
3.2 (Pt)
6
[36]
[36]
[38]
Butylmethylpyrrolidinium
bis(trifluoromethylsulfonyl)
imide
[BMP][Tf
N]
85
2.2
5.5 (GC)
2
[39]
[39]
[37]
1-Butyl-3-
methylimidazolium
tetrafluoroborate
[BMIM][BF
]
52
3.9
4.6 (Pt)
4
[6]
[6]
[29]
1-Ethyl-3-
methylimidazolium
bis(trifluoromethylsulfonyl)
imide
[EMIM][Tf
N]
34
8.8
(GC)
2
[6]
[6]
[40]
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