NEW SOLID MEDIUM FOR ELECTROCHEMISTRY AND ITS APPLICATION TO DYE-SENSITIZED SOLAR CELLS - Energy Research Developments: Tidal Energy, Energy Efficiency and Solar Energy - page 112

Impedance spectra of a 5 mM Fe(CN) 6 3- were measured in 2 wt% agarose and κ-
carrageenan solids, and in an aqueous solution containing 0.5 M KCl at the rest potentials
(figure 5).
Figure 5. Impedance spectra of 5 mM Fe(CN) 6 3- in 2 wt% agarose (squares), 2 wt% κ-carrageenan
(triangles), and aqueous solution (diamonds) containing 0.5 M KCl at the rest potentials [3]:. Frequency
range is from 20 kHz to 100 mHz (25 data points per spectrum).
All the spectra (figure 5a) show liner relations characteristic for a diffusion-controlled
process in the bulk phase at low frequencies (< 30 Hz). However, at high frequencies (figure
5b) semi-circles are clearly seen in theκ-carrageenan solid and in an aqueous solution, while
the impedance spectrum in the agarose solid is slightly different showing a larger semi-circle.
These semi-circles at high frequencies are determined both by the capacitance ( C dl ) in the