Page 59 - MODERN ELECTROCHEMISTRY

4 CHAPTER 1

Fig. 1.1. A way to divide the two quite different aspects of the field of electro-
chemistry. In this book, the point of view is presented that the electrodic area
should be the realm associated with electrochemistry. Ionics is a necessary
adjunct field (just as is the theory of electrons in metals and semiconductors,
which is adequately dealt with in books on the solid state).

The last part of ionic electrochemistry, ionics, is about “pure electrolytes.” A few
decades back this electrochemistry would have been all about high-temperature liquids
(liquid common salt at 850 °C was the role model). However, this has changed, and
the temperatures for eliminating the solvent have decreased considerably. Some
molten salts are now room temperature liquids. At the other end of the temperature
scale are the molten silicates, where large polyanions predominate. These are impor-
tant not only in the steel industry, where molten silicate mixtures form blast furnace
slags, but also in the corresponding frozen liquids, the glasses.
The other half of electrochemistry, electrodics, in vol. 2 has surpassed ionics in
its rate of growth and is coming into use in enterprises such as the auto industry, to
obtain electrochemical power sources for transportation. Such a change in the way we
power our cars is seen by many as the only way to avoid the planetary warming caused
by the emitted by internal combustion engines.
Our discussion of electrodics starts with a description of the interfacial region
between the metal and solution phases. This is the stage on which the play is to be
performed. It involves the kinetics of electrons moving to and fro across areas with
immensely strong electric field strengths (gigavolts per meter) that are unavailable in
the laboratory. This is the heart of electrochemistry—the mechanism of electrically
controlled surface reactions.
Electrons are quantal particles and much basic electrochemistry in the past few
decades has been quantal in approach, so a simplified description of the current state
of this field is given.
After this, the text moves to the main applications of electrochemistry. There is
the conversion of light to electricity and the photosplitting of water to yield pure
hydrogen as a storage medium for electricity produced from solar light. Some organic
reactions are better carried out under electrochemical conditions, because one can vary
the energy of the available electrons so easily (i.e., by changing V in Tafel’s law). The
stability of materials (corrosion protection) is indeed a vast area, but the basic
mechanisms are all electrochemical and deserve a whole chapter. There are two other