Abstract
Changing the supporting electrolyte cation from tetrabutylammonium to 1-butyl-3-methylimidazolium is known to significantly increase the apparent heterogeneous electron transfer rate constants (k 0 value at the formal reversible potential, (E F 0)) associated with the [SVW11O40]3-/4- (VV/IV) and [SVW11O40]4-/5- (WVI/V) processes in aprotic organic media. In this study, supporting electrolytes containing 7 different cations, namely 1-ethyl-3-methylimidazolium ([EMIM]+), 1-butyl-3-methylimidazolium ([BMIM]+), 1-butyl-1-methylpyrrolidinium ([Py14]+), tetraethylammonium ([TEA]+), tetrapropylammonium ([TPA]+), tetrabutylammonium ([TBA]+) and tetrahexylammonium ([THA]+), have been investigated in order to provide a systematic account of the influence of the electrolyte cations on the rate of polyoxometalate (POM) electron transfer at a platinum disk electrode. Fourier transformed alternating current (FTAC) voltammetry has been used for the measurement of fast kinetics and DC cyclic voltammetry for slow processes. The new data reveal the formal reversible potentials and electron-transfer rate constants associated with the VV/IV (k V 0) and WVI/V (k W 0) processes correlate with the size of the supporting electrolyte cation. k V 0 and k W 0 values decrease in the order, [EMIM]+ >[BMIM]+ >[Py14]+ ≈[TEA]+ >[TPA]+ >[TBA]+ >[THA]+ for both processes. However, while k V 0 decreases gently with increasing cation size (k 0 =0.1 and 0.002cms-1 with [EMIM]+ and [THA]+ electrolyte cations, respectively), the decrease in k W 0 is much more drastic (k 0 =0.1 and 2×10-6 cms-1 for [EMIM]+ and [THA]+, respectively). Possible explanations for the observed trends are discussed (e.g., ion-pairing, viscosity, adsorption and the double-layer effect), with inhibition of electron-transfer by a blocking "film" of electrolyte cations considered likely to be the dominant factor, supported by a linear plot of ln(k 0) vs. ln(d) (where d is the estimated thickness of the adsorbed layer on the electrode surface) for both the VV/IV and WVI/V processes.
| Original language | English |
|---|---|
| Pages (from-to) | 193-201 |
| Number of pages | 9 |
| Journal | Journal of Electroanalytical Chemistry |
| Volume | 819 |
| DOIs | |
| Publication status | Published - 15 Jun 2018 |
Keywords
- Cation dependence
- Electron transfer kinetics
- Fourier transformed ac voltammetry
- Polyoxometalates
- Propylene carbonate
Cite this
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Electrolyte cation dependence of the electron transfer kinetics associated with the [SVW11O40]3-/4- (VV/IV) and [SVW11O40]4-/5- (WVI/V) processes in propylene carbonate. / Li, Jiezhen; Bentley, Cameron L.; Ueda, Tadaharu; Bond, Alan M.; Zhang, Jie.
In: Journal of Electroanalytical Chemistry, Vol. 819, 15.06.2018, p. 193-201.Research output: Contribution to journal › Article › Research › peer-review
TY - JOUR
T1 - Electrolyte cation dependence of the electron transfer kinetics associated with the [SVW11O40]3-/4- (VV/IV) and [SVW11O40]4-/5- (WVI/V) processes in propylene carbonate
AU - Li, Jiezhen
AU - Bentley, Cameron L.
AU - Ueda, Tadaharu
AU - Bond, Alan M.
AU - Zhang, Jie
PY - 2018/6/15
Y1 - 2018/6/15
N2 - Changing the supporting electrolyte cation from tetrabutylammonium to 1-butyl-3-methylimidazolium is known to significantly increase the apparent heterogeneous electron transfer rate constants (k 0 value at the formal reversible potential, (E F 0)) associated with the [SVW11O40]3-/4- (VV/IV) and [SVW11O40]4-/5- (WVI/V) processes in aprotic organic media. In this study, supporting electrolytes containing 7 different cations, namely 1-ethyl-3-methylimidazolium ([EMIM]+), 1-butyl-3-methylimidazolium ([BMIM]+), 1-butyl-1-methylpyrrolidinium ([Py14]+), tetraethylammonium ([TEA]+), tetrapropylammonium ([TPA]+), tetrabutylammonium ([TBA]+) and tetrahexylammonium ([THA]+), have been investigated in order to provide a systematic account of the influence of the electrolyte cations on the rate of polyoxometalate (POM) electron transfer at a platinum disk electrode. Fourier transformed alternating current (FTAC) voltammetry has been used for the measurement of fast kinetics and DC cyclic voltammetry for slow processes. The new data reveal the formal reversible potentials and electron-transfer rate constants associated with the VV/IV (k V 0) and WVI/V (k W 0) processes correlate with the size of the supporting electrolyte cation. k V 0 and k W 0 values decrease in the order, [EMIM]+ >[BMIM]+ >[Py14]+ ≈[TEA]+ >[TPA]+ >[TBA]+ >[THA]+ for both processes. However, while k V 0 decreases gently with increasing cation size (k 0 =0.1 and 0.002cms-1 with [EMIM]+ and [THA]+ electrolyte cations, respectively), the decrease in k W 0 is much more drastic (k 0 =0.1 and 2×10-6 cms-1 for [EMIM]+ and [THA]+, respectively). Possible explanations for the observed trends are discussed (e.g., ion-pairing, viscosity, adsorption and the double-layer effect), with inhibition of electron-transfer by a blocking "film" of electrolyte cations considered likely to be the dominant factor, supported by a linear plot of ln(k 0) vs. ln(d) (where d is the estimated thickness of the adsorbed layer on the electrode surface) for both the VV/IV and WVI/V processes.
AB - Changing the supporting electrolyte cation from tetrabutylammonium to 1-butyl-3-methylimidazolium is known to significantly increase the apparent heterogeneous electron transfer rate constants (k 0 value at the formal reversible potential, (E F 0)) associated with the [SVW11O40]3-/4- (VV/IV) and [SVW11O40]4-/5- (WVI/V) processes in aprotic organic media. In this study, supporting electrolytes containing 7 different cations, namely 1-ethyl-3-methylimidazolium ([EMIM]+), 1-butyl-3-methylimidazolium ([BMIM]+), 1-butyl-1-methylpyrrolidinium ([Py14]+), tetraethylammonium ([TEA]+), tetrapropylammonium ([TPA]+), tetrabutylammonium ([TBA]+) and tetrahexylammonium ([THA]+), have been investigated in order to provide a systematic account of the influence of the electrolyte cations on the rate of polyoxometalate (POM) electron transfer at a platinum disk electrode. Fourier transformed alternating current (FTAC) voltammetry has been used for the measurement of fast kinetics and DC cyclic voltammetry for slow processes. The new data reveal the formal reversible potentials and electron-transfer rate constants associated with the VV/IV (k V 0) and WVI/V (k W 0) processes correlate with the size of the supporting electrolyte cation. k V 0 and k W 0 values decrease in the order, [EMIM]+ >[BMIM]+ >[Py14]+ ≈[TEA]+ >[TPA]+ >[TBA]+ >[THA]+ for both processes. However, while k V 0 decreases gently with increasing cation size (k 0 =0.1 and 0.002cms-1 with [EMIM]+ and [THA]+ electrolyte cations, respectively), the decrease in k W 0 is much more drastic (k 0 =0.1 and 2×10-6 cms-1 for [EMIM]+ and [THA]+, respectively). Possible explanations for the observed trends are discussed (e.g., ion-pairing, viscosity, adsorption and the double-layer effect), with inhibition of electron-transfer by a blocking "film" of electrolyte cations considered likely to be the dominant factor, supported by a linear plot of ln(k 0) vs. ln(d) (where d is the estimated thickness of the adsorbed layer on the electrode surface) for both the VV/IV and WVI/V processes.
KW - Cation dependence
KW - Electron transfer kinetics
KW - Fourier transformed ac voltammetry
KW - Polyoxometalates
KW - Propylene carbonate
UR - http://www.scopus.com/inward/record.url?scp=85032390805&partnerID=8YFLogxK
U2 - 10.1016/j.jelechem.2017.10.028
DO - 10.1016/j.jelechem.2017.10.028
M3 - Article
VL - 819
SP - 193
EP - 201
JO - Journal of Electroanalytical Chemistry
JF - Journal of Electroanalytical Chemistry
SN - 1572-6657
ER -