MadSci Network: Chemistry

Re: Can you decompose Hydrogen Peroxide into H2g and O2g?

Date: Thu Nov 4 23:25:15 1999
Posted By: Todd Holland, Grad student, Biophysics, University of Illinois at Urbana-Champaign
Area of science: Chemistry
ID: 941477360.Ch

Hi Kyle, 
Great idea! I thought that electrolysis of hydrogen peroxide should work, 
but I wasn't sure. Hydrogen peroxide slowly decomposes naturally over time, 
in what is called a redox reaction. Redox is short for Reduction-Oxidation. 
That means that it involves the transfer, or rearrangement of electrons. 
Electrochemistry also involves redox reactions, so it seemed logical to 
assume that a little electrical push might help speed up the sluggish 
hydrogen peroxide decomposition. I decided to try the experimental approach 
rather than look up a bunch of technical stuff to give you as an answer. I 
think that's the funnest part of science anyway. 

I stripped down the ends of a couple of wires that I took out of a phone 
cord that I wasn't using. Then I poured a little hydrogen peroxide into a 
small container (I actually used the plastic lid of a two liter bottle). I 
wrapped a rubber band around a double A battery, and put the end of one 
wire under it on each end of the battery (tape might work as well or 
better). Then I submerged the ends of the wires into the hydrogen peroxide 
solution. I didn't see anything from this, so I took your suggestion and 
tried adding an electrolyte. I poured a couple pinches of salt into the 
container, mixed, and tried it again. This time I did see bubbles 
accumulating around each wire end. I also noticed that the copper of my 
wire was actually being oxidized to Cu2+ ions. This caused a blue color to 
invade the rest of the solution around the negative electrode. 

I looked up the redox potential of the reaction in a chemistry textbook to 
see what size battery would be adequate before I tried this. The redox 
potential was only 0.77 V for the reaction, and the side of the battery 
said it generated 1 Volt. Also, if you want to avoid oxidizing the wires, 
try silver wires. They should hold up if you can find them. 

If you decide to collect the hydrogen and/or oxygen, PLEASE BE CAREFUL! I 
accidentally caused an explosion once by burning off hydrogen that I had 
collected during an electrolysis adventure at my grandparents' house. I was 
lucky that no one was hurt. If you decide to collect the gases, the 
hydrogen should collect at the negative electrode, and the oxygen at the 
positive. You can collect them by placing an inverted container filled with 
your electrolyte solution over each electrode. Make sure to get rid of any 
air bubbles. You can turn the container upside down as long as the mouth 
remains submerged; air pressure will hold the liquid in it. The gasses will 
collect in a pocket at the top. It will take a while to collect any 
appreciable amount, and I would advise against collecting much. Hydrogen 
gas is extremely flammable. I would definitely recommend that you don't 
burn it. After some of the hydrogen has burned off, air will flow back into 
the container and the ENTIRE CONTAINER WILL EXPLODE! That is what happened 
to me when I tried it. I had my hand on the jar when it happened, and was 
lucky that the glass didn't break and cut me, or worse. Have fun and be 

Todd Holland
Mad Scientist

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