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Author Topic: Hydrogen Production!  (Read 7615 times)

Offline Life

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Hydrogen Production!
« on: 31/01/2006 19:32:40 »
If anyone (In the UK) watches scrapheap challenge, you might have seen a team producing hydrogen gas once. They had it connected so that when the generator was on, the hydrogen emitting tube could be lit to give a footlong constant flame!

I know this is done by the electrolysis of water but to get a steady stream of hydrogen being produced like that im guessin you would need alot of power. Now i understand why it must be DC but i dont know what voltage/current should be used.

For obvious reasons mains supply cannot be used so does anyone know what type of power source would suffice?

Thanx


 

another_someone

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Re: Hydrogen Production!
« Reply #1 on: 31/01/2006 21:30:09 »
quote:
Originally posted by Life

If anyone (In the UK) watches scrapheap challenge, you might have seen a team producing hydrogen gas once. They had it connected so that when the generator was on, the hydrogen emitting tube could be lit to give a footlong constant flame!

I know this is done by the electrolysis of water but to get a steady stream of hydrogen being produced like that im guessin you would need alot of power. Now i understand why it must be DC but i dont know what voltage/current should be used.

For obvious reasons mains supply cannot be used so does anyone know what type of power source would suffice?

Thanx



I don't imagine that the voltage you would require would be that much, but if you want a steady stream, then I would have thought you would want a power source that could deliver some significant power.  I could well imagine that a 12 volt lead acid batter would suffice, but something like an alkaline battery simply would not have the current capacity.

The current would also depend upon the resistance between the electrodes, which would mean that the closer the electrodes are to each other, and the larger the area of each electrode, the lower the resistance, and so the higher the current for a given voltage.
 

Offline daveshorts

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Re: Hydrogen Production!
« Reply #2 on: 31/01/2006 22:42:39 »
If I remember rightly the voltage you need to split water is around 2-3V although the internal resistance of the cell you build will probably be considerable, so to get an appreciable current you will need a bit higher voltage.

We built a piece of electrolysis kit to act as an expample to kids - I think it may have featured on the radio program a couple of times - That uses a about 10cm of platinum wire as the contacts uses a couple of amps and about 8-9V to produce 50ml of hydrogen in about 5mins.

 To make much more you will need very high currents, and to get reasonable efficiencies some sort of membrane that will allow the ions to move through but not gasses, so you can get the electrodes very close to each other and reduce the internal resistance.

The current is directly related to the amount of gas you produce you will get about 1/2 ml of hydrogen/second for every amp you can put through the cell. You will be able to increase this by increasing the voltage, (until bad side reactions start happening).
 

Offline ukmicky

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Re: Hydrogen Production!
« Reply #3 on: 01/02/2006 03:15:14 »
Isn't there a chenmical which can be added to the water which improve's and makes the electrolysis reaction process work better, i remember reading about it but can remember what it was called.  The germans used the chemical in ww11 to aid the production of heavy water through electrolysis
 
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« Last Edit: 01/02/2006 03:24:12 by ukmicky »
 

Offline Soul Surfer

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Re: Hydrogen Production!
« Reply #4 on: 01/02/2006 10:51:54 »
Done it when I was a kid with torch batteries etc.  

Remember you have to keep the gases seperate from the positive and negative electrodes because with water you get hydrogen from the negative electrode or Cathode and oxygen from the positive electrode or Anode. If you mix the gases together you don't get a nice flame when you light it you get one helluva bang!

Any Ionic substance will help conductivity but it's best to use an acid if you want clean hydrogen and not get it mixed up with other things  sulphuric acid should be OK and thats the one the books tell you.  You could also use a salt as long as the metal is above hydrogen in the electreochemical series.  common salt sodium chloride will do as well in dilute solutions but I think if you use strong solutions and high currents you can get chlorine from the other electrode and this is nasty.

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Offline Life

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Re: Hydrogen Production!
« Reply #5 on: 01/02/2006 18:20:43 »
O right, ill give it till the weekend to get sorted and il have a go with my car battery as a power source.

So if i understood (soul_surfer) correctly, using a salt of copper (e.g. CuSo4) wouldnt leave me with hydrogen as a product. Not sure on this, but would the copper be displaced by hydrogen, leaving me with a precepitate of copper in a dilute sulphuric acid solution? If this is the case, i am guessing that it wouldnt be possible to heat and condense the liquid down to a conc. solution? Sorry, im changing subject, i always get carried away with myself..

so.. to make this hydrogen..

1. Il use two 2 close contacts (possibly copper?)
2. In a saturated brine solution
3. With a membrane separating the two gases
4. Powered by a lead acid car battery..

Right!

When it was done on scrapheap challenge the contacts emmitted a bright light and the water bubbled quite vigorousely! It never occured to me that they may have been using a 12V Lead Acid battery because i assumed that 12Volts wouldnt be enough. I didnt realise that it is current that affects hydrogen production.

I'll give it a go on the weekend and keep you guys posted..



P.S.
As you know im quite new to this forum (to be honest its the 1st one ive registered with) and am surprised at how informative and helpful you guys are.. thanx
 

Offline rosy

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Re: Hydrogen Production!
« Reply #6 on: 01/02/2006 19:04:27 »
1. Il use two 2 close contacts (possibly copper?)

I think if you want to use the cell for any length of time you'll probably find that the copper oxidises on the surface of one electrode and your yield goes down, but it should work for a bit.

2. In a saturated brine solution
If you want to eliminate the risk of getting chlorine instead of oxygen, magnesium sulphate is a better bet if you can get it. But I'm not sure where you'd get it other than chemical suppliers, just because I think it's mainly chemists that use it.

3. With a membrane separating the two gases
4. Powered by a lead acid car battery..
 

Offline daveshorts

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Re: Hydrogen Production!
« Reply #7 on: 01/02/2006 22:10:12 »
I think the positive electrode doesn't want to be copper as the copper will ionise and become Cu+ before you produce oxygen. Graphite will work, but when I have tried propelling pencil leads before they fell to pieces, this could be something to do with the glue. You may do better with very soft pencil leads as they probably have more graphite and less glue.
 

another_someone

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Re: Hydrogen Production!
« Reply #8 on: 01/02/2006 23:17:35 »
I would have thought a better source of graphite would be somewhere you can buy brushes for electric motors.

Is not magnesium sulphate the same as epsom salts?  Is that not commonly available from pharmacists, and maybe gardening shops?
 

Offline rosy

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Re: Hydrogen Production!
« Reply #9 on: 01/02/2006 23:28:58 »
According to wikipedia, yes.
http://en.wikipedia.org/wiki/Epsom_salts
 

Offline Soul Surfer

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Re: Hydrogen Production!
« Reply #10 on: 01/02/2006 23:36:27 »
Straight acids are probably best. Battery acid is another possible commercially avaiable electrolyte and you can get carbon rods out of the middle of disposable batteries.

I tried to look up electrochemistry in a modern inorganic cemistry textbook and found it remarkably lacking in information compared with an old (1939) school text book that I have.

Using copper sulphate would precipitate copper that's what electroplating is all about.

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Offline rosy

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Re: Hydrogen Production!
« Reply #11 on: 01/02/2006 23:42:51 »
Yes... copper is too stable in its elemental form. Which is why I suggested magnesium sulphate. Magnesium ions are really pretty stable in solution.
We use it for CHaOS because it has the same sort of properties in terms of increasing conductivity as the acids, without the safety issues if you spill it.
 

Offline Life

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Re: Hydrogen Production!
« Reply #12 on: 02/02/2006 15:21:57 »
Epsom Salts! yeh i should have known that.. I was thinkin the same (where am i going to get MgSO4 from). I dont have a disposable amount of Sulphuric acid so il go with the epsom salts..

right, il have a look for graphite rods but if unsuccessful, i think i should be able to use pencil lead somehow..
 

Offline Life

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Re: Hydrogen Production!
« Reply #13 on: 07/02/2006 11:22:25 »
Oryte all, tried electrolysis with the lead acid battery in my car but with no success. I got more bubbles of H" being produced using a 9V battery! any suggestions..
 

Offline Engdave

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Re: Hydrogen Production!
« Reply #14 on: 08/02/2006 03:20:10 »
Does the production have to be by electrolysis?
A fairly economical method is to use aluminium pop or beer cans and hydrochloric acid. this can often be purchased as Muriatic acid or as a swimming pool Ph corrector. Put crushed up cans in a plastic container that can have gas collected from it, add water and then some acid. If you get too heavy handed the mixture will get hot and the reaction rate will increase.
 

Offline Life

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Re: Hydrogen Production!
« Reply #15 on: 08/02/2006 16:04:52 »
yer im trying to do it by electrolysis..
Although it requires high power, i like the fact that H2 can be produced continousely and cheaply using water as a fuel..
 

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Re: Hydrogen Production!
« Reply #15 on: 08/02/2006 16:04:52 »

 

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