Separate Hydrogen and Oxygen From Water Through Electrolysis




About: Buildin' not buyin'

Electrolysis a method of separating elements by pushing an electric current through a compound. It is used in various industrial applications such as removing copper from its ore. It is also used to separate hydrogen and oxygen from water. Electrolysis isn't the most efficient way to obtain hydrogen, but it is one of the easiest and cheapest ways to "homebrew" hydrogen.

Hydrogen is the most abundant element in the universe. With the "green-energy" craze and talk of powering our future oil-free economy on hydrogen, it has gotten much attention in the last few years. Learning about this potential fuel of the future is important and interesting. Besides, hydrogen is a powerful fuel, and blowing stuff up in the name of science is fun .

Step 1: Electrolysis of Water - an Explanation

This section is an explanation of the electrolysis of water, feel free to skip it if you don't find it interesting.

2H2O(l) = 2H2(g) + O2(g)

As everyone knows a water molecule is formed by two elements: two positive Hydrogen ions and one negative Oxygen ion. The water molecule is held together by the electromagnetic attraction between these ions. When electricity is introduced to water through two electrodes, a cathode (negative) and an anode (positive), these ions are attracted to the opposite charged electrode. Therefore the positively charged hydrogen ions will collect on the cathode and the negatively charged oxygen will collect on the anode.

When these ions come into contact with their respective electrodes they either gain or lose electrons depending on there ionic charge. (In this case the hydrogen gains electrons and the oxygen loses them) In doing so these ions balance their charges, and become real, electrically balanced, bona fide atoms (or in the case of the hydrogen, a molecule).

The reason this system isn't very efficient is because some of the electrical energy is converted into heat during the process. There have been reports of 50%-70% efficiency, but I doubt that is possible in a home environment. Anyway, enough with the boring stuff, lets go make some gas!

Step 2: Materials

****DISCLAIMER**** You are putting electricity into water. It has the potential to be dangerous. Do so at your own risk. Be smart about it. If you wouldn't touch it with your hands don't stick it in the water. If you're worried about it wearing rubber gloves will give some extra insulation. ****DISCLAIMER****

****DISCLAIMER**** Hydrogen is highly flammable and explosive (think Hindenburg). The amount we're making isn't extremely dangerous, but be careful. Flying shards of glass are never fun.****DISCLAIMER****

Separating Hydrogen and oxygen from water is really simple. It can be as easy as sticking two wires leading from a battery into water and watching the bubbles form. We however want to collect all the little bubbles, so its just slightly more complicated.

Things you will need:

@ (1) Med.Container - To hold water. Preferably clear so you can see whats going on.
@ (1 or 2) Gas Collecting Containers - A test tube, or an old soda bottle like me. Also clear. 2 if you want to collect both the hydrogen and the oxygen
@ (1) Power Source - I use a 12v 1000mA adapter, 9v batteries (in a series) and other sources work too. Bigger the power source, faster the bubbles form.
@ (2) Graphite Electrodes - Optional. You can stick a bare wire into the water, but it corrodes pretty quick. You can pull them out of a 6v Lantern Battery
@ Salt
@ Water

Step 3: Water and Salt

Water alone is not a very good conductor. You need to add some sort of electrolyte. Regular old table salt works fine. Add as much as will dissolve into the water, and don't worry about it if there is some sitting on the bottom, it really doesn't matter. Pour this salt/water solution into your med. container, and also fill your 1 or 2 gas collecting containers

Step 4: The Tricky Part

Ok, this is the tricky part. You need to flip the gas collecting container(s) upside down in the med. container, so that no air is trapped in the gas container(s). I do it by holding my thumb over the hole, and flip it really quickly. Its not a huge deal if air is trapped, your hydrogen just won't be pure.

Step 5: The Electrodes

Now take the two electrodes leading from your power source. The hydrogen will form on the positive electrode, and the oxygen on the negative. If you don't know which is which, turn on the power source and stick the electrodes in the water. The one with more bubbles is the hydrogen. Now stick the electrode underneath the gas collecting container. (turn off the power first) If you're having trouble making the gas collecting container stay up, and the electrode stay in the right place, tape it. Thats what I do anyway.

Step 6: Thats It!

Thats it! Turn it on, and watch it bubble. The amount of time it takes depends on how powerful your power source is. Stronger it is, faster it bubbles. Mine takes about 5 min for a test tube.

The electrodes do corrode if you don't have graphite, its pretty gross, but i don't think its dangerous. (don't quote me)

Here is a video of it bubbling:

Step 7: Further Ideas

When your gas collecting container is full, try lighting it. The hydrogen will give a very satisfying *POP*, and the oxygen won't do anything.

Here's a Video (sorry for not wearing a shirt =0 ):


For a bigger and better explosion, put both electrodes into the gas collecting container. Hydrogen needs oxygen to burn, and the ratio of 2:1 is the best ratio. That is what we get when splitting water. You will get a much more powerful explosion.

I've personally always wanted to make a model rocket powered on hydrogen. I know that there is one that is sold on the market, but I don't remember what its called. I'll look for it.

T3Hprogrammer and Kiteman suggest using baking soda rather than salt as an electrolyte. Table Salt (NaCL) has the potential of producing chlorine gas and sodium hydroxide when introduced to electricity.

JakeTobak suggests using platinum electrodes instead of graphite as graphite will chip, splinter, and corrode. They're as cheap as a couple dollars, and can be found on Ebay (thanks Kiteman)

Further Reading:

@ Homemade Hydrogen by Theodore Grey
@ Fuel from Water: Energy Independence with Hydrogen by Michael A. Peavey via
@ Water Car - How to Turn Water Into Hydrogen Fuel via

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822 Discussions

John TH

6 months ago

Why cant this be used to propelling a auto?


9 months ago

Query. Couldn't a solar panel be used to charge the battery which is then connected to the electrodes? Granted it may not generate huge amounts of hydrogen, but if it runs continuously with no ongoing cost for the electricity, wouldn't this generate an almost inexhaustible supply of hydrogen (...and oxygen) that could be used for whatever purpose? Just asking.


11 months ago

And what about prespitate for long time operation


8 years ago on Introduction

One thing people need to keep in mind with this kind of setup is that you are not going to get the kind of flow required to do any kind of work that will help MPG. These HHO system type things are sold on ebay with plans etc. The amount of work and energy required to get a substantial amount of gas is...substantial. I don't have a degree in physics, but used to run a machine that was designed to make pure O2 for submarines. It required 1050 amps of DC current to produce 120scfh with double that for Hydrogen which we disposed of overboard. The amount of gas produced from a 12 volt source is not enough to help your car. It's a cool science experiment for school, but that's about it. Former MM2(SS) A-gang type. (google what that is. I also used to run the CO2 scrubbers and COH2 burners for atmosphere control.)

15 replies

Reply 1 year ago

Of course, you are going to have a circuit breaker in the system to protect the wiring.

If using 14 gauge, that means you'd use a 15 amp breaker. At 120 VAC, that would be about 1800 watts.

If using 12 gauge, that means a 20 amp breaker. At 120 VAC, that would be 2,400 watts.

Things like the water heater use 10 gauge and require a 30 amp breaker. At 120 VAC, that would be 3,600 watts.

For each gauge wire above, the amperage would trip the breakers for the corresponding wire gauges immediately. Even the main breaker of houses around here can handle only 200 amps.

To play with that kind of amperage, and assuming 10 gauge wires, you'd have to be running no more than about 34 volts, but you'd have to go there without any breakers.

[amps x volt = watts]


Reply 7 years ago on Introduction

Not true. You can't even flow 1050 amps down a regular home wiring because it only handles 20 amps.
Go study some more would ya


Reply 6 years ago on Introduction

are you familiar with the inverse relationship between voltage and amperage? I can have a power source that is only a few volts that is 100 amps; or something could put out only a few amps that is 120 volt. Solar panels put out DC current which is typically converted to AC power and manipulated to usable 120volt/15 amp circuits. Your remark "Go study some more would ya" is meant to be inflammatory, and I don't appreciate it...


Reply 6 years ago on Introduction

AMPS x VOLTS = Watts

100 amps x 10 volts = 1000 watts
10 amp x 100 volts = 1000 watts

Nothing you can do will change the relationship between amps and volts

Amps is NOT power
Volts is NOT power

In order to get power - you need both and they both are related.


Reply 6 years ago on Introduction

I aint tryin to do nothin, except maybe explain to you how amps and volts are inversely related (as you seem to demonstrate so well in your post above). you are the one who saw my post of 7 solar panels generating up to 1050 amps and became rude. You may want to add one (or 2) more lines to your example above for a group of 7 solar panels collectively generating 1050 amps:
"100 amps x 10 volts = 1000 watts
10 amp x 100 volts = 1000 watts"
1050 amp x 1 volts = 1050 watts Hmmmm... OR
1 amp x 1050 volts = 1050 watts
-now, go to your menards store and buy yourself an electricity book...
PS-the relationship between amps and volts is tweeked everyday in our world it is nothing new; If you think your public utility powerplant is producing 20 amps of 120 volt current to your house, so that it don't trip your 20amp breaker, then I aint got nothin more for ya; 'cept you might wanna go to your menards store and see what kinda books they got on the shelf there for ya.


Reply 6 years ago on Introduction

I do understand that the utility company supplies lots of amps to your home - I also understand that a typical home IS FUSED at 100 or 200 amps. After those fuses, there are branches of 20 amp fuses.
A typical home requires 10KVA for peak and an RMS value somewhat lower in the 4KVA arena.
Your 1050 amps is crazy - Even if you had that, you would require a copper conductor with diameters in the range of 5 inches diameter.
YOU WILL NEVER GENERATE 1050 AMPS from your solar toys.

I design computerized weld controllers which control up to 25,000 amps at 10 - 5 volts. The conductors are very short and very large diameters. I also design Rogowski coils (you'll have to Google that since the detail is not available at Menards) to measure the high currents.

So, I hope you can realize that after 35 years in the electrical design arena, I know just a little bit about electricity.

Now, if you ever get off your high horse, I can even tell you how to design a solar system that actually works..


Reply 4 years ago

But you don't know enough to see that the diagrams above are incorrect. Anode is positive, not negative and H2 comes from the cathode!


Reply 5 years ago on Introduction

Hmmm, looking back on this; I am thinking I must have meant to say 1050 watts instead of amps. It makes more sense that way. Guess I better get on down to Menards and see if I can't find me an electricity


Reply 6 years ago on Introduction

PS-how many amps you get out of 7 solar panels would depend on whether you lined them up in series or parallel. Just like flashlight batteries (also dc power), if they are all connected together like a train (in series) the voltage increases with each battery but the amps stay the same. If each battery is routed to the load separately (parallel) the voltage stays the same but the amps go up. Solar cells are a dc power source, they behave alot like batteries; and people who don't respect them get killed very easily because the amps do accumulate to dangerous levels. Didn't grace your post with a response sooner cause you teeed me off...


Reply 4 years ago on Introduction

grapenut -- just came across this post. Average Solar panel is rated 250 watts and around 30-40 volts. So the max amp you can get from one panel is around 8 amps. 7 panels will give you 56 amps. Amperage you can get depends on the source -- a 12 volt car battery can deliver over 400 amps for abort 30 seconds - known as cranking amperage . So alanwms is right in a way.


Reply 4 years ago on Introduction

Thanks for the info LaksmanD. I am no solar expert for sure. You may enjoy reading all of the posts between alanwms & I. In the end I conceded, I may have gotten amps mixed up with something else.


Reply 6 years ago on Introduction

OK then - Go ahead and flow 1050 amps down your house wiring. Should work fine with those 20 amp breakers. Maybe you can find 1050 amp breakers at Menards?

Amps drawn from a source are purely dependent on the load - For instance, if you connect nothing to batteries - regardless of how they are connected, nothing flows.

More current will flow from series devices assuming the same load, and in fact a double voltage creates a quadruple power since both the current and voltage are doubled. Amps x volts = watts.


Reply 6 years ago on Introduction

"OK then - Go ahead and flow 1050 amps down your house wiring. Should work fine with those 20 amp breakers. Maybe you can find 1050 amp breakers at Menards?"
-I already explained this below; but solar panels are not wired directly to circuit breakers. The power has to be converted from DC to useable 15amp 115volt circuits before going to the breaker box. You do not seem to be well informed enough, to be so critical... Who's goin to menards now?

"Amps drawn from a source are purely dependent on the load - For instance, if you connect nothing to batteries - regardless of how they are connected, nothing flows."
-interesting that you choose to use a battery as your analogy. I challenge you to get more than 2 amps out of a short circuited, single, C cell, battery. Likewise a solar panel will only put out what it will put out, I don't care what you or the "load" want to take from it. Your logic/theory about amps drawn being "purely dependent on the load" is probably taught in tech schools across the land for people working off the grid which is a seemingly/relatively limitless source of power. -Who's goin to menards now??

"More current will flow from series devices assuming the same load, and in fact a double voltage creates a quadruple power since both the current and voltage are doubled. Amps x volts = watts."
-OK now you introduce another word into the discussion; "current" without clearly defining it. Current is the flow of electrons typically among electricians referred to in volts, but more scientifically referred to in amps. It can be ACurrent or DCurrent. Anywhoo; you aint gettin 4x the current(energy) out of a battery unless you are usin 4x the batteries. 4, 1.5vdc batteries in series will give you 4x the volts or 6 volts.
4 batteries in series=4x the volts
4batterries in parallel=4x the amps
which of course equals alan goin to menards to get whatever kind of batteries he is talkin about ...