NEW SOLID MEDIUM FOR ELECTROCHEMISTRY AND ITS APPLICATION TO DYE-SENSITIZED SOLAR CELLS - Energy Research Developments: Tidal Energy, Energy Efficiency and Solar Energy - page 110

Figure 3. The hardness of the polysaccharide solids measured by the hardness meter (Type 00 and Type
E2)[5].
Since the hardness is not an absolute value, it was compared with materials around us.
The hardness of a 2 wt% agarose solid was one third of a conventional rubber eraser, and that
of a 3 wt% κ-carrageenan involving 0.1 M KCl (M = mol dm -3 ) half of a rubber eraser.
It is interesting that the solid surface is superhydrophilic: the contact angle with water is
almost zero degree. The water inside of the solid is evaporated the same as a liquid water, and
after standing under ambient conditions the solid looses all the water to become a very hard
and dry solid.
Solid Medium for Electrochemistry
Overview for Electrochemistry in Solid
The electrochemical behavior of redox molecules in polymer films and gels has been
investigated [16-25], but such behavior has usually been studied by using a modified
electrode coated with a polymer film or gel in the presence of an outer electrolyte solution.
For a few examples, entirely solid state voltammetry was also achieved, but by using a
microelectrode array [23,24] composed of working, counter and reference electrodes because
of a slow ionic or molecular diffusion in the solid matrices. The apparent diffusion coefficient
( D app ) of a redox substrate in the films or solids coated on an electrode was very small [17-
25], usually of the order of less than 10 -7 cm 2 s -1 , and the largest value was of the order of 10 -6
cm 2 s -1 at a carrageenan film (2 mm thick) coated Pt gauze electrode in the presence of an
outer aqueous electrolyte solution [16]. Another example of solid state votammetry is a report
on the electrochemistry of Prussian blue in silica sol-gel electrolytes [26], but Pt gauze
working and counter electrodes for a 1 mm thick silica solid were used; the system was
different from a conventional three electrodes electrochemical measurement. Moreover, it is
well known that solid electrolytes have been used for various sensors, electrochromic devices,
etc. [27,28]. However, in spite of these activities in solid electrolytes, there has been almost
no work, to our knowledge, using a solid medium for conventional electrochemical