DalisAndy - 22-5-2015 at 16:23
When performing electrolysis, what is the best cathode and anode you can use if you want to get near 100% yield. I'm going to electrolyze aqueous
sodium chloride and possibly Borax for fun. I was think about using pencil lead as my cathode and anode. Also is there any relationship between the
speed of the reaction and any electrical properties I.E voltage current etc.
j_sum1 - 22-5-2015 at 18:32
Anode and cathode choice is highly context specific.
Platinum is the go-to for almost all applications. Or at least it would be if it wasn' t so darned expensive.
For chlorate and perchlorate cells (which is what it sounds like you are doing) mixed metal ocide (MMO) anodes are recommended. But MMO will be killed
if electrolysing sulfuric acid (as I found the hard way) For other applications you might get away with graphite. But watch for erosion. Graphite
powder makes a mess. I have not had much success with pencils. Electrodes from batteries are ok. You might try scourging electrodes from a welder's
supply. Relatively cheap.
For cathodes it depend on what reaction is occurring there. Generally the cathode is under less stress than the anode. But then it will often plate
with whatever you are making. It reall depends on what you are trying to do.
edit: "matteries" Thumbs too big for phone.
[Edited on 23-5-2015 by j_sum1]
DalisAndy - 22-5-2015 at 20:05
Ok thank you. So a carbon rod would work then? I'm buy a chemistry set with one in it. Or I can make one from compressed sucrose and sulfuric acid.
Also when preforming electrolysis on sulfate salts, would hydrogen, sulfur dioxide and oxygen be created an the anode? And would igniting that gas
mixture create sulfuric acid?
[Edited on 23-5-2015 by DalisAndy]
j_sum1 - 22-5-2015 at 20:52
Sugar and sulfuric acid I think will give amorphous carbon and not graphite. It won't conduct.
PbO2 is a better anode for sulfates. You get oxygen at the anode and if you are depositing a metal at the cathode you will get H2SO4 in solution.
violet sin - 22-5-2015 at 21:58
to get 100% yield of? with what equipment? under what conditions? not trying to knock you down a peg, just be a little more clear. I see that you
mention salt for chlorate production I assume, but borax(?) just for fun.
I fully get the just for fun idea, I tried a great many things just to see what would happen. but some times you find that it was/could be dangerous(
copper salts, ammonia, nitrate ions in aqueous solution). I did a lot of the experimenting with copper electrochem. making copper hydroxide with
copper electrodes and magnesium sulfate( epsom salt) as the electrolyte additive for conductivity. electrode spacing, size, shape and number of 'em-
all changed the output of copper and how hot the cells got.
if you have a junk D-cell battery and can remove the center graphite electrode in one piece, use that for the anode, and a stainless steel nail works
for the cathode. simple suggestion.
there is plenty of info on the site electochem related 
start here..
Tutorial for making a miniature chlorate cell: http://www.sciencemadness.org/talk/viewthread.php?tid=14531
technochemistry sub-forum: https://www.sciencemadness.org/whisper/forumdisplay.php?fid=...
Thoughts On Anodes: https://www.sciencemadness.org/whisper/viewthread.php?tid=50...
not all the threads have a huge number of responses, but the subjects are quite varied. maybe use google to search the site. pretty easy to do,
search: "subject site:www.sciencemadness.org"
personally I LOVE electrochem,.. you can use things like a hacked ATX powersupply from a junked (often free) computer. or a nice bench top power
supply from ebay. some AC converters (walwart's) for charging a cellphone/answering machine/printer etc. can be used, and there are also cheap power
supplies on ebay that are really affordable and offer decent amperage.
simply put, the voltage/amperage do different things. amperage is amount of electrons dumped across to do the work = number of workers helping,
voltage is the potential difference pushing them through. preferred reactions usually have a range of voltage at which they are most effective, too
low = not gonna happen/low effective usage, too high and you promote side/alternate reactions.
some other reading
wiki-overpotential: http://en.wikipedia.org/wiki/Overpotential
wiki-Electrolytic cell: http://en.wikipedia.org/wiki/Electrolytic_cell
wiki-Electroplating: http://en.wikipedia.org/wiki/Electroplating
wiki-Electrode potential: http://en.wikipedia.org/wiki/Electrode_potential
wiki-Standard electrode potential (data page): http://en.wikipedia.org/wiki/Standard_electrode_potential_%2...
hope that is enough to get ya started