Tafel Curve in Electrochemistry

​
log
10
​​
k
0
​ (m/s)
-3
α
0.5
E
corr
(V)
0
The Tafel curve is widely used in electrochemistry, especially in the study of corrosion. Using the Tafel curve one can determine the corrosion potential
E
corr
or open circuit potential. The coefficient of charge transfer
α
can also be determined as the slope of the Tafel curve. This Demonstration shows the current-potential curve on the left and the Tafel curve,
log
10
(current)
vs
potential
on the right.

Details

The current-potential curve on the left obeys the Butler–Volmer equation for a kinetic-controlled reaction,
i=nFA
k
0
-
c
O
exp-α
nF
RT
(E-
E
0
)+
c
R
exp(1-α)
nF
RT
(E-
E
0
)
,
where
α
is the charge transfer coefficient,
n
is the number of electrons transferred,
F
is Faraday's constant,
T
is temperature,
R
is the gas constant,
c
O
and
c
R
are the concentrations of oxidant and reductant,
k
0
is the standard rate constant, and
E
0
is the standard potential or corrosion potential
E
corr
=
E
0
.
The
log
10
i
potential curve on the right is the Tafel curve.
For high overpotential
E>>
E
0
,
log
10
i=
log
10
(nFA
k
0
c
R
)+(1-α)
nF
RT
log
10
(exp[E-
E
0
])
.
So the anodic slope is
(1-α)
nF
RT
; as
α
increases, this slope decreases.
For large negative potential
E<<
E
0
,
log
10
(-i)=
log
10
(nFA
k
0
c
O
)+(-α)
nF
RT
log
10
(exp[E-
E
0
])
.
Thus the absolute value of cathodic slope is
α
nF
RT
; as
α
increases, the slope increases.
The Tafel slope can be used to calculate the charge transfer coefficient
α
and the corrosion potential
E
corr
=
E
0
.

External Links

Butler-Volmer Equation for Electrochemical Reaction

Permanent Citation

Quang-Dao Trinh
​
​"Tafel Curve in Electrochemistry"​
​http://demonstrations.wolfram.com/TafelCurveInElectrochemistry/​
​Wolfram Demonstrations Project​
​Published: June 8, 2011