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Tafel plot for an anodic process . The Tafel equation is an equation in electrochemical kinetics relating the rate of an electrochemical reaction to the overpotential. [1] The Tafel equation was first deduced experimentally and was later shown to have a theoretical justification. The equation is named after Swiss chemist Julius Tafel.
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 overpotential.
where and are constants (for a given reaction and temperature) and are called the Tafel equation constants. The theoretical values of the Tafel equation constants are different for the cathodic and anodic processes. However, the Tafel slope can be defined as:
The Tafel equation for a single electrode is: = Where: the plus sign under the exponent refers to an anodic reaction, and a minus sign to a cathodic reaction: overpotential, V; A: "Tafel slope", V
In operating batteries and fuel cells, charge transfer coefficient is the parameter that signifies the fraction of overpotential that affects the current density.This parameter has had a mysterious significance in electrochemical kinetics for over three quarters of the previous century [citation needed].
Using the Tafel equation, one can obtain kinetic information about the kinetics of the electrode material such as the exchange current density and the Tafel slope. [6] OER is presumed to not take place on clean metal surfaces such as platinum, but instead an oxide surface is formed prior to oxygen evolution.
This plot will give a straight line with a slope equal to ρ*. Similar to the Hammett ρ value: If ρ* > 1, the reaction accumulates negative charge in the transition state and is accelerated by electron withdrawing groups. If 1 > ρ* > 0, negative charge is built up and the reaction is mildly sensitive to polar effects.
Tafel is a surname, and may refer to: Albert Tafel (1876–1935) German geographer, doctor and explorer; Edgar Tafel (1912–2011), American architect; Gustav Tafel (1830–1909), German-born colonel in the Union Army; Julius Tafel (1862–1918), German chemist; Tristan Tafel (born 1990), Canadian freestyle skier; Tafel may also refer to: Tafel ...