In
electrochemistry
Electrochemistry is the branch of physical chemistry concerned with the relationship between Electric potential, electrical potential difference and identifiable chemical change. These reactions involve Electron, electrons moving via an electronic ...
, partial current is defined as the
electric current
An electric current is a flow of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is defined as the net rate of flow of electric charge through a surface. The moving particles are called charge c ...
associated with (
anodic
An anode usually is an electrode of a polarized electrical device through which conventional current enters the device. This contrasts with a cathode, which is usually an electrode of the device through which conventional current leaves the devi ...
or
cathodic
A cathode is the electrode from which a conventional current leaves a polarized electrical device such as a lead-acid battery. This definition can be recalled by using the mnemonic ''CCD'' for ''Cathode Current Departs''. Conventional current ...
) half of the
electrode
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or a gas). In electrochemical cells, electrodes are essential parts that can consist of a varie ...
reaction
Reaction may refer to a process or to a response to an action, event, or exposure.
Physics and chemistry
*Chemical reaction
*Nuclear reaction
*Reaction (physics), as defined by Newton's third law
* Chain reaction (disambiguation)
Biology and ...
.
Depending on the electrode half-reaction, one can distinguish two types of partial current:
* cathodic partial current ''I
c'' (called also cathodic current): is the flow of
electrons
The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...
from the electrode surface to a species in solution;
* anodic partial current ''I
a'' (called also anodic current): is the flow of electrons into the electrode from a species in solution.
The cathodic and anodic partial currents are defined by
IUPAC
The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is ...
.
The partial
current densities
In electromagnetism, current density is the amount of charge per unit time that flows through a unit area of a chosen cross section. The current density vector is defined as a vector whose magnitude is the electric current per cross-sectional a ...
(''i
c'' and ''i
a'') are the ratios of partial currents respect to the electrode areas (''A
c'' and ''A
a''):
:''i
c = I
c/A
c''
:''i
a = I
a/A
a''
The sum of the cathodic partial current density ''i
c'' (positive) and the anodic partial current density ''i
a'' (negative) gives the
net current density ''i'':
[Electrochemistry Dictionary and Encyclopedia]
:''i = i
c + i
a''
In the case of the cathodic partial current density being equal to the anodic partial current density (for example, in a
corrosion
Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engine ...
process
[B. Elsener]
''Corrosion and durability of metals''
, p. 252.), the net current density on the electrode is zero:
[
:''ieq = ic,eq + ia,eq = 0''
When more than one reaction occur on an electrode simultaneously, then the total electrode current can be expressed as:]
Notes
References
* Bard, A.J. and Faulkner L.R. ''Electrochemical Methods: Fundamentals and Applications'' (2nd ed.), 2001 John Wiley & Sons Inc.
See also
* Exchange current density
In electrochemistry, exchange current density is a parameter used in the Tafel equation, Butler–Volmer equation and other electrochemical kinetics expressions. The Tafel equation describes the dependence of current for an electrolytic process to ...
Electrochemistry
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