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Re: Electolysis of water



Bernard Cleyet wrote:

p.s. seems to me if one uses an electrolyte that has a high
conductivity there will be little Joule heating.

Therefore nearly all electric energy will be used to do work,
as indicated by JohnD. Please scroll to the end of this message.

Ludwik Kowalski wrote:

I have a question. Consider an electrolytic cell with ideal
electrodes (Pt, to simplify chemistry) in a weak solution of
a salt in water. The current is flowing through it and two
gases (H2 and O2) are bubbling.

Part of the supplied electric energy is thermalized (becomes
heat) while the rest is used to do work (to break H2O
molecules). Thus electric energy goes in while heat and
bubbles are coming out at some constant temperature. I
suspect that the second law can be used to determine the
ideal possible efficiency (defined as work over electric
energy). But I have no idea how to do this. What is the
best possible efficiency at, say, 60 degrees C?

To further idealize the situation I would assume that tiny
droplets of water (at 60 C) are constantly added to the cell
to compensate for molecules escaping as bubbles. In that
way it will be a steady equilibrated process. JohnD said
my problem has nothing to do with the second law. Is this
because the input is not heat? Released heat is like friction
in mechanics, it can be reduced to nearly nothing. I suppose
that this is true and that those who decompose H2O work
above the 95% efficiency. Is this really true?
Ludwik Kowalski

This posting is the position of the writer, not that of SUNY-BSC, NAU or the AAPT.