Dear friends, As have been well studied by several researchers that the relaxation time of electric double layer (EDL) or triple layer on electrodes under AC electric field can be evaluated by λL/D, where λ is Debye length, L is the distance between two electrodes and D is diffusivity of ions. My question is, if this time scale can be applied to describe the time scale of EDL from the moment the solid (insulated) and liquid interface contact to that of finally equlibrium state? In other words, how long will that cost for the formation of EDL from very beginning to equilibrium state, please? Best regards
Hello,
Do you have a reference for the equation you mentioned ? Because at first sight I would rather write the time as \lambda^2/D.
Yes, the time scale ( λL/D ) can be found in the paper of Martin Bazant--"M. Z. Bazant, K. Thornton, and A. Ajdari, Diffuse-charge dynamics in electrochemical systems, Physical Review E 70, 021506 (2004)." But in the cited work, this time scale is used to describe the relaxation time of EDL on electrodes. I am wondering if it can be used to describe a highly nonequilibrium EDL on insulated wall that far from electrodes. Thanks,
Hello,
I had a rapid look on the paper. It is very long... but likely the main physics lies in the introduction part:
- blocking electrodes: tau= λ²/D
- non-blocking electrodes: tau = L²/D
λL/D is something intermediate.
Probably, due to these two limits, the response is non-linear (it probably depend on the applied voltage and on ion species, see electrochemical reactions), but in the limit of small voltage, electrodes should be blocking (tau= λ²/D). Spontaneous fluctuations should obey to this regime.
Hope that this comment will help you.
Didier
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