O2 sensor response times

[Garfield Willis]

On Mon, 27 Mar 2000 17:35:30 -0800 (PST), Orin <orin at diy-efi.org> wrote:

>Heywood pg 301:  "Equilibrium is established in the exhaust gases
>by the catalytic activity of the platinum metal electrodes."
>
>So yes, there are other reasons.

Yes, but that's in a place where contact of the platinum with the
exhaust gases catalyzes/oxidizes the HC and CO gas components (namely,
in a CAT). Are you saying that this effect is part of the operation of
the O2 sensor? If so, it's never mentioned in any of the papers AFAIK. 

But since I've admitted I'm a total putz in this electrochemical realm,
I CAN see how the fact that gas components (H, HC, CO) seem to like
platinum, certainly might dispose it for use as the outer electrodes.
It's just that this is not the area normally mentioned where the
recombination of oxygen ions with the gas components occurs, which
affects the pumping current. It's always depicted as occuring in the
porous ZrO2 portion, where the oxy ions are either removed or supplied
to the sample of exhaust gas. But then again, these devices are referred
to as galvanic cells, which generally require dissimilar
metals/semiconductors. So does that mean the ZrO2 is one such material,
and the platinum makes up the other "plates" of this sorta battery.
Ouch, my head is beginning to hurt; if only I'd payed attention in
Chemistry class.

I know there is at least one physical chemist lurking behind the
curtain; maybe you could lift the veil on this stuff for us, eh?

TIA,
Gar


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