Chemistry Reference
In-Depth Information
In this work, for the research on a laboratory scale, rotating-disc electrodes
72
were used, amongst others. For the transport coefficient of this configura-
tion, the following applies:
16
d
Ê
Ë
ˆ
¯
m
=
0 620
.
D
23
w
12
[1.51]
h
where (d/h) (m
2
s
-1
) represents the kinematic viscosity of the solution and
w is the angular rate (rad s
-1
) of the electrode. This electrode, which permits
change in the relation between k
0¢
and m, makes it possible to study, in an
efficient way, kinetic and transport parameters of electrode processes, on
condition that the value for k
0¢
is not greater than 5.10
-4
ms
-1
.
The field of predominantly kinetic influence (base of the voltammogram,
BV relation valid) and the field of a mixed influence of kinetics and trans-
port are suitable to determine parameters such as rate constant, reaction
order and transfer coefficients. The field controlled by transport (Equation
1.51 valid, in practice usually with c
O
•
or c
R
•
= 0) can lead to the diffusion
coefficient.
In the field of mixed influence, a combination of the BV relation with the
comparison for transport-determined current is valid. A number of variants
to these have been described in the literature. The most well known and
the most commonly used is presumably the relation deduced by Frumkin
and Tedoradze
72
:
11
1
12
i
=+
kin
(1.52)
i
Bw
The denominator of the first term of the right part represents the BV
current. The denominator of the second term represents the transport-
controlled current at the rotating-disc electrode; this is Equation 1.41 or
1.42, where m is replaced by the right part of Equation 1.51 and all the
terms, except for w
1/2
, are incorporated in the parameter B.
1.8
References
1. Bockris J.O'M., Reddy A.K. (eds),
Modern Electrochemistry 2
, Plenum Press,
New York, 1970.
2. Kissinger P.I., Heinemann W.R.,
Laboratory Techniques in Electroanalytical
Chemistry
, Marcel Dekker, New York, 1996.
3. Levich E.,
Physicochemical Hydrodynamics
, Prentice Hall, Englewood Cliffs,
New Jersey, 1962.
4. Compton R.G, Sanders G.H.W.,
Electrode Potentials
, Oxford Science Publica-
tions, Oxford, 1996.
5. Monk P.M.S.,
Fundamentals of Electroanalytical Chemistry
,Wiley, Chichester,
2001.
