Chemistry Reference
In-Depth Information
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Fundamentals of electrochemistry
P. WESTBROEK
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Introduction
A system of two electrodes connected to each other with an external circuit
providing an electrical current and immersed in an electrolyte solution
allows the conversion of chemical energy into electrical energy and vice
versa. Conversion of chemical energy into electrical energy is found in bat-
teries, fuel cells and corrosion reactions, while the conversion of electrical
energy to chemical energy is obtained in electroanalysis, electrolysis and
electroplating.
At the beginning of the twentieth century, there was a significant increase
in the use of electrochemical phenomena for electroanalytical purposes,
with potentiometry and polarography being the main methods. This growth
was based on the development of the electrochemical thermodynamics
theory by Faraday. For both methods, the relationships that describe them
reveal information from solution thermodynamics by measuring a poten-
tial or an electrical current. For polarography (not discussed in detail in this
topic), an additional phenomenon occurs, namely diffusion of species
from solution towards the electrode measuring the potential or electrical
current.
In the last four decades, a wide range of electrochemical transient
methods have been developed and offered the possibility of studying new
applications, chemical reactions and heterogeneous adsorption. In addition,
the dynamics and mechanism of electron-transfer processes were investi-
gated with the transition-state theory to the kinetics for electrochemical
reactions
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.This resulted in understanding not only the kinetics of electron
transfer, but also the (electro)chemical reaction steps preceding and fol-
lowing the electron-transfer step.
The most significant breakthrough of electrochemistry came with the
introduction of modern electronic equipment controlled by a computer
with suitable software. This allowed experiments under much more extreme
conditions which opened new fields of research and applications:
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