Impedance analysis of multilayer polypyrrole electrodes

1
Impedance analysis of multilayer polypyrrole
electrodes

• Maria Grzeszczuk
• Faculty of Chemistry, University of Wroclaw, F.
  Joliot-Curie 14, 50-383 Wroclaw, Poland
• 39th Heyrovsky Discussions and 7th International
  Symposium on EIS
• ELECTROCHEMICAL IMPEDANCE ANALYSIS
• June 4 8, 2006, Trest Castle, Czech Republic

2
Topics

• Electrodeposition of polypyrrole
• Redox transformations and ion exchange properties
  of polypyrrole
• Electrical circuit analogs of thin film
  polypyrrole electrodes
• Impedance frequency dispersions predictions vs.
  observations
• Bulk and interfacial impedances of the single
  layer and multilayer electrodes a comparison
• Contribution of ions and electrons to interlayer
  charge transfer resistance
• On separation of nonfaradaic frequency dispersion
  from faradaic one

3
Thin film polypyrrole deposited on gold

• polypyrrole aqueous Na3AlF6
• polypyrrole aqueous Na2SiF6
• polypyrrole aqueous NaPF6
• polypyrrole aqueous NaCl

4
Potentiostatic deposition with mixed (2D 3D)
growth mechanismof polypyrrole phase
4,6SUBSTRATE ELECTRODE gold-1,4,5
polypyrrole-2,3 THICKNESS µm 0.18 -1 0.44
-2,4 0.71 -3,5
5
Mechanistic scheme of redox reactions / mass
exchange for polypyrrole electrode doped with
dianionic counterion in contact with aqueous
electrolyte under nitrogen 5
6
Electrical circuit analogs of E.W.and
corresponding frequency dispersion functions
1,3
7
Impedance spectra of thin layer polypyrrole
electrodes 1

8
The former spectrum corresponded to the secondary
counterion system polypyrrole (chloride)
hexafluorosilicate 1.The next slide shows
selection of spectra for the primary counterion
system polypyrrole hexafluoroaluminate (dark
symbols) and the corresponding secondary
counterion system polypyrrole(hexafluoroaluminate
) chloride (light symbols) 4circles
experiment, stars fit to a circuit model (A),
(C) -0.1V vs SSCE, (B), (D) 0.1V vs SSCE.

• Spectra on the left side
• Multilayer hexafluoroaluminate electrodes (A),
  (B)

• Spectra on the right side
• Single-layer hexafluoroaluminate electrodes (C),
  (D)

9
(No Transcript)
10
The next three (columnar) plots show results of
the impedance analysis of the multilayer
polypyrrole electrodes 4.
11
Relaxation time of transport function T RTW
a,c RTO b,dEdc 0.1 V (1,2,3) -0.1 V
(4,5,6) multi-stage deposition a,b single
stage deposition c,dElectrodeposition charge /
thickness3.00 mC / 0.18 µm (1,4) 7.49 mC /
0.44 µm (2,5) 11.97 mC / 0.71 µm (3,6)
12
Redox capacitance of transport function T RTW
a,c RTO b,dEdc 0.1 V (1,2,3) -0.1 V
(4,5,6) multi-stage deposition a,b single
stage deposition c,dElectrodeposition charge /
thickness3.00 mC / 0.18 µm (1,4) 7.49 mC /
0.44 µm (2,5) 11.97 mC / 0.71 µm (3,6)
13
Charge transfer resistance R RTW a,c RTO
b,dEdc 0.1 V (1,2,3) -0.1 V (4,5,6)
multi-stage deposition a,b single stage
deposition c,dElectrodeposition charge /
thickness3.00 mC / 0.18 µm (1,4) 7.49 mC /
0.44 µm (2,5) 11.97 mC / 0.71 µm (3,6)
14
Analysis of the interfacial resistance at
constantdc potential / redox state of polypyrrole

• ?Rct Rct,primary Rct,secondary
• ?Rct(multilayer) - ?Rct(singlelayer) gt 0

15
Contributions of nonfaradaic processes
16
(No Transcript)
17
Conclusions ? Layer-by-layer electrodeposition
of polypyrrole from electrolyte of a constant
composition results in charge/mass transport of
the resulting multilayer polymer electrode that
differs from the single-layer electrode of
similar thicknesses. ? The multilayer as
compared with the single-layer electrodes
prepared using similar total polymerization
charges slow down rates of charge transport
measured as Rct- and t-values. ? The most
significant effect of layer-by-layer deposition
concerns hindrance of the interlayer ion
transfer. ? The multilayer and single-layer
electrodes prepared using similar total
polymerization charges have similar charge
storage capabilities, i.e. similar
Credox-values. ? Consider to add the Gerisher
impedance into the frequency dispersion function
to account for contribution of chemical
reaction(s) to the redox processes of polypyrrole
and similar materials 7.
18
References
1 M. Grzeszczuk, G. Zabinska-Olszak, J.
Electroanal. Chem., 427 (1997) 169. 2 M.
Grzeszczuk, A. Kepas, G. Zabinska-Olszak,
Electrochim. Acta, 49 (2004) 2405. 3 M.
Grzeszczuk, Polish J. Chem., 78 (2004) 1423. 4
A. Kepas, M. Grzeszczuk, J. Electroanal. Chem.
582 (2005) 209. 5 A. Kepas, M. Grzeszczuk,
Electrochimica Acta, 51 (2006) 4167. 6 J.
Kalenik, A. Kepas, M. Grzeszczuk, submitted
(2006). 7 M. Grzeszczuk, R. Szostak, J.
Electroanal. Chem., 571 (2004) 51.