MIT10_626S11_lec20

MIT10_626S11_lec20 - IV. Transport Phenomena Lecture 20:...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
IV. Transport Phenomena Lecture 20: Warburg Impedance Notes by ChangHoon Lim 1. Warburg impedance for semi-infinite oscillating diffusion Warburg (Ann. Physik. 1899) is credited with the first solution to the diffusion equation with oscillating concentration at the boundary, which is related to the diffusional (or mass transfer) impedance of electrochemical systems. An interesting point made in the first part of the class is that the very same mathematical model and impedance formula also holds for capacitive charging of a porous electrode with constant electrolyte concentration (i.e. no diffusion) modeled by an RC transmission line, and this effect is often mistaken for diffusional impedance. We start by linearizing the equations for transport and electrochemical reactions to describe the response to a small oscillating voltage. Suppose equation, ) and for linear response (e.g. Nernst Also, assume quasi-equilibrium reactions at x=0 and linear diffusion. Alternating current: Therefore, Hence, ( as ) Thus, impedance is ,
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
x 0 L x 0 L Now, C=C 0 is imposed on x=L , not at the infinity. At low frequency ( ), FLW acts like a resistor. This situation is depicted in above figure. Solve
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 11/27/2011 for the course CHEMICAL E 20.410j taught by Professor Rogerd.kamm during the Spring '03 term at MIT.

Page1 / 7

MIT10_626S11_lec20 - IV. Transport Phenomena Lecture 20:...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online