Objective of the Course
Familiarity with the Processes in Electrochemical
Reactions
Understanding the factors affecting the rates of
reactions
Approaches to measure rate processes
Theoretical basis
Experimental techniques
Applications of the various tec
Previous Lecture
Overview of electrochemical reaction processes
Potential due to a charge
VAB= WAB/Q Joule Coloumb-1
Concept of capacitance of system
C= Q/V Coulomb Volt-1
Calculating the surface charge given the potential
Interfacial potential arisi
k= A expcfw_ -G*/RT
G* = Go* + nF (dGo*/dE) (E-Eo)
Potential Dependent Rate Constant
G* = Go* + nF (dGo*/dE) (E-Eo)
Substituting for G*
k= A exp cfw_-(Go* +nF (dG/dE) (E-Eo) )/RT
Let us define (dGo*/dE) = ; is called the transfer
coefficient; sometimes it
Oxygen Evolution
Acid: 2H2O = O2 + 4 H+ + 4 e- Eo = 1.23 V
Alkaline: 4OH- = O2 +2 H2O + 4eEo = 0.41 V
Electrolysis of Water to make hydrogen
Recharging of Metal Air Batteries
Regenerative Fuel Cells
Anodes in Electroplating
Perovskite Structure
CaTiO3, A=
I/Io=(Cox/C*ox) expcfw_-()nF/RT
expcfw_ (1-)() nF/RT
(Cred/C*red)
I/Io= (1- I/I lim ox) expcfw_-()nF/RT-(1- I/I lim red)
expcfw_ (1-)() nF/RT
Linear Case I. When the overpotential is very small,
i.e. ,
< (RT/nF ) ; = 0.052 V for n=1 and =0.5, then
the ex
I = Io sin t
where = 2f ; f is the frequency, s-1 and
is the angular frequency in radians s-1,
Io is the amplitude ( maximum value).
sin (/2) = 1; sin ( ) = 0; sin ( 3/2) = -1 and sin( 2) = 0.
V= R * Io sin t = Vo sin t
The amplitude of the voltage is gi
I=
C* cfw_1-exp (E-Eeq)*nF/RT nFAD1/2/2t1/2
E - Eeq = RT/nF ln (C*- I*2 t1/2/ nFA D1/2)/C*
Linear and Spherical Diffusion
Various types of Microelectrodes evaluated by
Kolthoff and Laitinen
JACS 61 (1939) 3344
JACS 61 (1939) 3344
Calculation of Diffusion
Previous Lecture:
Response of RC circuits to sinusoidal current
Impedance of a capacitor: (- 1/C); phase shif
Magnitude of impedance and Phase Angle for
any circuit
Properties of impedance- complex number like.
Analysis of Zmag and data
Zmag vs. fre
Spectro-Electrochemical Response is affected by
many properties of the electrode/solution interface
the bulk of the electrode
the surface i) of the free electron gas ii) of surface states; iii) of
the bound electrons, if the electrode is a metal;
the s