How to make a lead-dioxide cathode?

[isaaclimdc]

Hi all,

I'm doing an experiment in which I am investigating the kind of effects that sulfation has on lead-acid batteries.

In order to do that, I have to build my own simple cell using lead and lead dioxide electrodes, both immersed in a solution of concentrated sulphuric acid. However, I don't know how I can go about doing this: how can I make a lead dioxide cathode from lead dioxide powder? Also, is PbO2 a conductor; if not, how do I coat a conductor electrode like graphite with lead dioxide?

This is a really important essay, so your help is greatly appreciated.

Thanks,
Isaac.

[chemisttree]

Why not coat a lead electrode with lead dioxide? The chemistry will happen at the surface.

[isaaclimdc]

yeah i was thinking of that... but how do i go about doing that?

[chemisttree]

I would think that would happen naturally if you applied the proper potential at high pH. I don't know if it would be stable once you switched to sulfuric acid.

[isaaclimdc]

okay now, maybe if i changed the setup, and instead of actually making the electrodes, i simply perform the reaction:

Pb + PbO2 + 2HSO4− → 2PbSO4 + 2H2O

I would use sheet lead, powder pbo2 and 6M sulphuric acid. What could I get out of this, both in terms of just the discharge reaction itself, and for the sulfation effect? Does it make sense to measure something like the enthalpy of the above reaction, then again with crystallised lead sulphate in it?

Thanks so much for your help, I really appreciate it.

[chemisttree]

Have you read the Wiki on lead batteries? Lead oxide is pressed as a paste into lead electrodes to form the lead oxide part of the circuit. If you sprinkle lead oxide onto a lead plate you will likely see galvanic pitting but I don't know if you will know anything about the effect of electrode sulfation on the 'battery'.

[isaaclimdc]

hmm yeah i have read that... sorry to ask.. but what about the chemical reaction

Pb + PbO2 + 2HSO4− → 2PbSO4 + 2H2O?

Can I get anything out of that?

[chemisttree]

Yes, you will make additional lead sulfate up to the point of saturation. It will then begin to ppt on all surfaces if you have the proper amount of lead sulfate and sulfuric acid to start with and you use enough lead oxide. How will you visualize it? How will it be measured?

[isaaclimdc]

i actually have no idea.. i only just thought of the idea. Basically, what I'm trying to get at is a way to measure the current/voltage/power/efficiency of the system before and after sulfation occurs.

for the reaction we're talking about, what do you think I can measure?