Chemistry Reference
In-Depth Information
•
study of unstable intermediates and its thermodynamics;
•
study of the kinetics of electron transfer, also in non-aqueous solution;
•
organic electrosynthesis at the electrode-electrolyte interface;
•
bioelectrochemistry;
•
studies at inorganic metal complexes towards structure,
chemical
formula and reactivity;
•
(electro)catalysis;
•
development of a wide range of sensors for electroanalysis.
The studies and developments described in this topic focus on the latter
application, which is the development of sensors, with the aim of generat-
ing information from textile wet processes by immersing the developed
sensor in the process bath and measuring parameters such as temperature,
pH and concentration of the active compound. With this information, it is
possible to improve and optimise the envisaged processes.
1.2
What is an electrochemical reaction?
Electrochemical methods are useful for the determination of chemical
parameters, such as the concentration of analytes, through measurement of
electrical parameters (current, potential, resistance, impedance) of an elec-
trochemical cell. In this chapter, the relationship between electrical and
chemical parameters will be described qualitatively. In the following chap-
ters, this general approach will be discussed in more detail and applied to
specific problems.
An electrochemical reaction can be defined as a chemical reaction involv-
ing charge transfer through an interface. The most commonly known form
of charge transfer is the transfer of electrons over a solid electrode-liquid
electrolyte interface. In the simplest form, electrons can be transferred from
the electrode to a chemical substance in solution (reduction), or electrons
that were released from the chemical substance by oxidation can be taken
up by the electrode. This is generally given by Equation 1.1:
¨
Oe
+
n
-
R
[1.1]
with O and R being the oxidant and reductant, respectively and
n
being
the number of electrons transferred over the interface. From this equation,
it is clear that charge transfer (in this case, the electrons passing the
electrode-electrolyte solution interface) implies chemical transformations
(being the transformation of O to R, or the opposite). However, this charge
transfer also implies transport of charge or electrons, which in fact is an
electrical current - hence the electrical current can provide information
about the chemical transformation. This current can be positive or negative
depending on the direction of electron transfer (from or to the electrode).
It is also possible that two electrode processes occur at the same time in
