Electrochemistry : characterizing the electrode-electrolyte

Click For Summary

Discussion Overview

The discussion focuses on the characterization of the electrode-electrolyte interface in electrochemistry, particularly regarding the modeling of a metallic electrode in an aqueous solution and the estimation of the electrical double layer (EDL) capacitance in different ionic environments.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant references a model from "Modern Electrochemistry" suggesting that a metallic electrode in an aqueous solution can be represented as a resistance and capacitor in parallel, with specific values for EDL capacitance.
  • Another participant questions the order of magnitude of the capacitance value, seeking clarification on whether it should be in microfarads or picofarads per square centimeter.
  • A different participant confirms that the value of µF/cm² is appropriate for differential capacitance.
  • Concerns are raised about the use of deionized water, with one participant noting that the absence of ions could lead to a less pronounced EDL.
  • One participant indicates they are working with streaming current data using deionized water as the fluid.
  • Another participant emphasizes that the EDL involves ions and water dipoles, suggesting that the lack of ions in deionized water could significantly affect the EDL characteristics.

Areas of Agreement / Disagreement

Participants express differing views on the appropriateness of using a specific capacitance value in deionized water, with some questioning the implications of the absence of ions on the EDL. The discussion remains unresolved regarding the impact of these factors on the model.

Contextual Notes

There are limitations regarding the assumptions made about the ionic concentration and its effect on the EDL capacitance, as well as the potential differences in behavior between AC and DC currents in this context.

Florent
Messages
3
Reaction score
0
Hello guys (and gals),

I have mostly a background in Physics, but I've recently had to get some knowledge on electrochemistry, and more precisely on electrode-electrolyte interface.

From "Modern Electrochemistry 2A : Fundamentals of Electrodics" by Bockris I gathered that in the case of a metallic electrode plunged in an aqueous solution (with ultradilute concentration of inorganic ions) with a DC current, I can pretty much model it with a resistance and capacitor in parallel as an equivalent electrical circuit with the resistor being the interfacial resistance and the capacitor being the EDL capacitance.

From what I gathered, the capacitance of the EDL of a metallic electrode is generally estimated to be around 20µF/cm² in solutions with millimolar to molar concentration of ions with AC current. Can I safely take this value (or this order of magnitude) for my electrode in deionized water and DC or am I missing an important parameter that can change everything ?

Hope I'm making sense :p
Cheers !
 
Chemistry news on Phys.org
μF or pF/cm2?
 
µF/cm² for differential capacitance at least
 
Last edited:
Florent said:
deionized water
??!
 
Yes, I'm working on streaming current and on the data with deionized water as fluid
 
EDL involves ions and water dipoles, no ions, much less pronounced EDL.

At least that would be my line of thinking.
 

Similar threads

Definition of Absolute Electrode Potential
  • · Replies 2 ·
Replies
2
Views
2K
Understand pH Meter Functioning: An Electric Potential Difference
  • · Replies 8 ·
Replies
8
Views
4K
Detailed electrochemistry question
  • · Replies 5 ·
Replies
5
Views
3K
Electrochemists brain teaser-copper electrolysis
  • · Replies 1 ·
Replies
1
Views
3K
Graduate Can we measure the effective mass of charge carriers using a centrifuge?
  • · Replies 24 ·
Replies
24
Views
5K
Graduate What is a Capacitor: Definition, Summary & Equations
  • · Replies 1 ·
Replies
1
Views
2K
Could New Materials Propel China's Industry to Bill Gates-Level Success?
  • · Replies 4 ·
Replies
4
Views
10K
Graduate Are both velocity and jerk of charges responsible for magnetic fields?
  • · Replies 9 ·
Replies
9
Views
4K