Chemistry Reference
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troublesome and time-consuming to separate
the desired product from an electrolytic
solution containing a large amount of
supporting salts. Moreover, supporting salts are
usually not recovered and recycled, and become
waste after electrolysis. In general, supporting
salts are very soluble in polar solvents, but,
depending on the starting organic substrates,
some are not soluble in polar solvents, only in
non-polar solvents. As mentioned previously,
the correct choice of supporting salt and
electrolytic solvent is not easy. In sharp
contrast, electrolysis using solid polymer
electrolytes (SPE) does not require an
electrolytic solution, therefore these problems
are readily solved [2,3].
6.1.1 Principle of SPE Electrolysis
By chemical plating, fine metal particles are
deposited on the surface of ion-exchange
membranes like Nafion®, and then a wire
mesh electrode or porous electrode made of the
same metal is pressed on the opposite surface of
the membrane to provide an SPE composite
electrode, which has dual roles of electrode and
supporting salt.
The general advantages of the SPE electrolysis
system for organic synthesis can be described as
follows: (i) to economize the separation and
recycling of a supporting salt and (ii) to avoid
any contamination or side reaction with a
supporting electrolyte. There are two types of
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