Sciencemadness Discussion Board - electrochemical H2O2? and also it's affinity for N

electrochemical H2O2? and also it's affinity for N

lmschers - 16-1-2011 at 01:50

I have searched the internet just a little bit and it seems as though you can make H2o2 via mono-polar electrolysis of dilute sodium hydroxide.

Wikipedia has a couple long passages on chemical processes, and then one small blurb on this "novel" electrochemical way to produce it.

Could I make sodium hydroxide with brine and two electrodes, and then take one electrode out of solution and then make H2o2?

I am curious also about the affinity that h2o2 has for nitrogen.
when copper is dissolved in nitric acid, orangeish-brown NO gas is released and the resulting solution is green.

If copper is dissolved in nitric acid with some added h2o2, the brown NO fumes are not produced, and the resulting solution is a very pretty blue. It is like blue copper sulfate, but not a crystal.

Can anyone help me understand what role the H2o2 plays in this oxidation process? What is some good literature in this area? Is there already a post on this subject that I should read?

thanks for any replies,
luke

condennnsa - 16-1-2011 at 02:28

Electrochemical H2O2 from NaOH sounds very interesting indeed!

hissingnoise - 16-1-2011 at 07:45

Quote: Originally posted by lmschers

Could I make sodium hydroxide with brine and two electrodes, and then take one electrode out of solution and then make H2o2?

The production of NaOH by electrolysis isn't trivial as it requires a mercury cathode!
The slow metathesis of NaCO3 and Ca(OH)2 in boiling solution produces NaOH and CaCO3.
As for electrolysis itself, I think it's a subject you should really read up on . . .

hissingnoise - 16-1-2011 at 08:19

Quote: Originally posted by lmschers

I am curious also about the affinity that h2o2 has for nitrogen.
when copper is dissolved in nitric acid, orangeish-brown NO gas is released and the resulting solution is green.

If copper is dissolved in nitric acid with some added h2o2, the brown NO fumes are not produced, and the resulting solution is a very pretty blue. It is like blue copper sulfate, but not a crystal.

I don't know why you think H2O2 has any affinity for N2 since O2 and N2 are difficult to combine!
Cu(NO3)2 is blue, crystalline and deliquescent; in solution with NO2 it's green, obviously!
H2O2 oxidises N2O4 in solution to N2O5, the colourless anhydride of HNO3.

lmschers - 16-1-2011 at 08:27

well, i'm reading davy and faraday, and i'm scoured the internet for a bunch of pictures of cells and other random info. i came here to try to find someone who has done this.

i don't believe that mercury is the only electrode that you can use for production of NaOH. i was going to use platinum and test out the decomposition at different levels of current. i also thought about just plain old graphite and then filtering out what dissolves. have you ever made any NaOH via electrolysis?

i'm reading posts in the forum and trying to catch up, if anyone has links to posts about H2O2, that would be helpful

[Edited on 16-1-2011 by lmschers]

lmschers - 16-1-2011 at 08:47

Quote: Originally posted by hissingnoise

hmm... well i watched this as far as N's affinity for h2o2.
i should clarify and say i'm talking about nitric acid.
http://www.youtube.com/watch?v=2yE7v4wkuZU

i poured some nitric acid and h2o2 on copper (there was also gold in the solution, they were computer pins) and got this solution in a bottle, which i'm posting. i poured just plain old nitric acid on some of the same kind of pins earlier and got green solution, if i dissolved along with h202, the solution was blue and clear and no NO2 gas was produced.

[Edited on 16-1-2011 by lmschers]

[Edited on 16-1-2011 by lmschers]

hissingnoise - 16-1-2011 at 09:59

Impure NaOH can be prepared by electrolysis of NaCl in a two-compartment cell connected by a salt bridge.
But if you think that electrolysis can proceed using a single electrode in an electrolyte you, and I'm trying to be diplomatic here, know fuck all about electrolysis.
This forum has the info you need - UTFSE and get reading!

not_important - 16-1-2011 at 10:56

Re Cu, HNO3, H2O2

Cu(s) + 4HNO3(aq) --> Cu(NO3)2(aq) + 2NO2(g) + 2H2O(l)

the subreaction is
Cu(s ) + 4 H+(aq ) + 2 NO3-(aq ) --> Cu2+(aq ) + 2 NO2(g ) + 2 H2O(l )

Adding H2O2 allows for the oxidation of the copper without consuming HNO3. In a similar fashion HCl + H2O2 will attack copper metal, while air/oxygen free hydrochloric acid will not react - copper is below hydrogen in the electrochemical series.

Adding the H2O2 also added a lot of water, the resulting solution of cupric nitrate is much more dilute, and does not contain NO2 is solution, thus the colour difference.

lmschers - 16-1-2011 at 11:59

@hiss thanks for your diplomacy, but it's not very good.
anyway, here's the blurb i'm talking about :
http://www.chemsystems.com/about/cs/news/items/PERP%200708_3...
An electrochemical process for the production of alkaline hydrogen peroxide has been developed by H-D Tech Inc., formerly a joint venture of Huron Technologies Inc. and Dow Chemical of Canada, but now wholly owned by Dow. The process employs a monopolar cell to achieve an electrolytic reduction of oxygen in a dilute sodium hydroxide solution.

i assumed that "monopolar" was analogous to "one electrode" but god knows what happens when i make assumptions. and yes, it sounds unusual and interesting to me, and that's why i'm asking around. it does sound too terribly simple (KISS comes to mind though). i'm also going to assume that you (like me) have not yet made either NaOH or H2O2 via electrolysis. so to start with, i'll just do it the hard way and grab some salt and see what happens.

@important
thanks for the equations

from what you're saying, since there's no NO2, and the HNO3 wasn't consumed, then there should still be nitric acid in the solution...?
that's about as far as my thinking got: no brown gas=N still in solution in some form
the bottle is gathering small bubbles and slight pressure over the course of a week.
still some peroxide i guess.
i'll try to electrolyze it with two copper electrodes and see what happens.
i'm hoping that like copper sulfate, i can suck up the metal and be left with acid.
(same color...8-)
that's best case scenario though.
we'll see. i'll experiment and post.

condennnsa - 16-1-2011 at 12:33

Here's a patent i came across on the subject http://www.freepatentsonline.com/4431494.pdf
Regarding the anode-cathode confusion here's a quote from the patent "An electrochemical cell having a platinum coated titanium anode and a carbon particle, packed bed cathode separated by a porous asbestos diaphragm was used to produce an alkaline peroxide solution. An aqueous sodium hydroxide electrolyte solution having a concentration of about 1.0 mole NaOH per liter of solution ..."

lmschers - 17-1-2011 at 03:40

@ condennnsa
thanks man, i checked out that patent and it referenced a guy named colin oloman in canada. it looks like he's at the top of the field.
i jumped on scifinder and searched for his documents and got a really in depth article from the journal of applied electrochemistry. there are a lot of diagrams and charts. i'm reading through that now. apparently he's also been electrolyzing carbon dioxide to formate.
it's easy to search for authors and i wasn't sure where to start so that helped a lot.

hissingnoise - 17-1-2011 at 04:00

Monopolar electrodes refers to anodes and cathodes connected directly to positive and negative . . .
Dipolar electrodes are unconnected electrodes placed between a cathode and anode so that they act as anode and cathode on opposing surfaces.
Electrolytic stepping stones - if you will . . .