fenomena overpotensial hidrogen
TRANSCRIPT
Introduction
3
OVERPOTENTIAL?
The difference of equilibrium with applied
potential.
= Eapplied – Eequilibrium
Types of Overpotential
1. Concentration
2. Activation
Thermodynamics aspect
4
Polarization Curve
Tidak Perlu
Overpotensial
Aqueous Solution
Perlu
Overpotensial
Perlu
Overpotensial
Aqueous Solution Non Aqueous Solution
5
POLARIZATION CURVE
(I vs E)
Equilibrium reaction M+ + e- M which is
occured on the electrode surface will cause the
current which is depend on the potential given.
Condition 1
7
• For noble metal
• In general, metal has lower hydrogen
overpotential
• Electrolysis can be occurred with high
current efficiency.
9
Condition 2
Intermediate reactivity
For Ni, Zn, Cd dan Fe
Can be extracted with aqueous solution
electrolysis method
Hydrogen overpotential is higher
11
Condition 3
Very reactive metals
Cannot be extracted with aqueous solution
media
because ηH2 increase quickly
fused salt as used media
Kinetics aspect
12
Ion movement which is occurred slowly
cause the potential deviate from Nerst
formulation.
In Hydrogen : 2H+ + 2e- H2
Kinetics aspect
13
Mass Transfer-Controlled Reaction-Concentration Overpotential
Interfacial Reaction Rate Control-Activation
Overpotential
Kinetics aspect
15
I. H3O+ diffusion from Bulk Solution to double layer
II. H3O+ go through Double Layer
III. Decomposition
H3O+ H2O + H +
IV. Electrochemical
H3O+ + M + e- M-H + H2O
2 M-H 2M + H2
V. H2 (g) desorption from NBL
VI. H2 (g) diffusion from Bulk Solution menjauhi
electrode
References
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H. S. Ray A. Ghosh. 1991. Principles of Extractive Metallurgy : New Age International
Rosenqvist. Principles of Extractive Metallurgy.McGraw-Hill Kogakusha Ltd., Tokyo. 2nd ed. 1983.
Bard, A.J.; Faulkner, L.R. Electrochemical Methods: Fundamentals and Applications. New York: John Wiley & Sons, 2nd Edition, 2000 [http://en.wikipedia.org/wiki/Overpotential, Diakses tanggal 19 Maret 2012]
http://electrochem.cwru.edu/encycl/art-t01-tafel.htm [Diakses tanggal 19 Maret 2012]