O2 sensor response times

[Gary Peyton]

Well....OK.

I'm a physical chemist.  And I can tell you for sure that while platinum
may help some kind of electrical contact for something, it's there
primarily as a catalyst.  In chemistry, if you want to catalyse something
and you dont know how, you use platinum.  Its great for reductions and
oxidations, and just about everything else.  What I dont know, is what the
specific reactions are that are generating the voltage, because its not
just "all of 'em".  But I'll bet that is not too difficult to find out.

[short off-topic introductory section :]
Actually in my research group we study reactions very similar to combustion
reactions, but we do it in water, at room temperature, to destroy
pollutants.  We study kinetics (how fast?) and mechanisms (what detailed
chemical pathway?) of these reactions, to make info, conclusions, and
calculational tools available so cleaner, cheaper pollution cleanup
processes can be designed.
[told you it was short]

I'll see what I can find out so maybe I can pay a little lurking dues.

Gary Peyton
 
At 06:27 PM 03/27/2000 -0800, you wrote:
>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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======================================================================
Gary R. Peyton
Senior Professional Scientist
Watershed Science Section
Illinois State Water Survey
Illinois Department of Natural Resources
(217) 333-5905	FAX (217) 333-6540
===================================================================

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