Introduction: Solar Electrolytic Cell

Hello, everyone! This is actually my first Instructable for the Chemical Reactions challenge, but I also want to help those looking for ways to use green energy or who are just looking for a fun project. Today I'll be showing you how to make a Solar Electrolytic Cell that splits water into hydrogen and oxygen. Good luck and enjoy!!

Step 1: Materials

Here's what you'll need for this project:

- Solar Cell (preferably 1.2V or higher; you can probably get one off Amazon for $7; the one I'm using is a 6V I got from Radioshack for $16)
- Cup or container (sorry that mine is so dark, it was all that I had)
- Wire
- Capacitor (optional; you can get one by harvesting a disposable camera)
- Soldering Iron & Solder (optional; makes things WAY easier though)
- Tape

Step 2: Fill It Up

First off, fill your cup or container with water. I used a tiny bottle so I could carry it around.

Step 3: Set the Capacitor (optional)

Wire up the capacitor by wrapping the wires or soldering them and place the wires in the water. Then, tape the capacitor to the cup or container. What's cool about the capacitor is that while it's in the water, even in total darkness, it prevents the hydrogen and oxygen from recombining into water by keeping the electricity released when the two recombine in place.

Step 4: Set the Solar Cell

Put the wires of the solar cell in the water and place the assembly in a well-lit area. Solar cells can sometimes conduct electricity using artificial light from light bulbs instead of sunlight. Soon the cell will produce an electric current and begin to split the water by means of a process called electrolysis. Electrolysis is a type of decomposition reaction caused by adding electricity. The electricity splits the water into hydrogen and oxygen, hydrogen forming on the negative wire, and oxygen forming on the positive.

Step 5: Watch the Bubbles Form!!

After a few minutes, bubbles should begin to form on the wires, hydrogen on the negative and oxygen on the positive. After about 20 minutes, it should be covered in bubbles. If you remove the assembly and hook wires up to the water, electricity should be released as the water recombines, but I was unable to show it because I don't have a multimeter. I might redo the experiment with a more advanced assembly. If anyone else has tried my experiment and did use a meter, please post it in the comments! I'm happy to have help in building on this project!


f.3 made it!(author)2012-09-06

I like this I'ble it sounds grand. One question though if you will. Everyone else talks about salt or baking soda water mixture to be able to make electrolysis possible. I don't remember you saying anything about that so how is yours possible with plain water?

lmfny made it!(author)2012-10-30

Pure water (i.e., distilled) will not conduct electricity, so it will not work. However, plain tap water has some electrolytes in it to conduct the electricity and will work. I do not recommend using salt, because chlorine gas will be produced at the cathode rather than hydrogen. If you truly want hydrogen at the cathode and oxygen at the anode, then use epsom salts (magnesium sulfate). It's safe, cheap and very effective.

ARVash made it!(author)2013-02-09

To be fair it also produces hydrogen. The chlorine gas concentration isn't very high, but yes.

kretzlord made it!(author)2011-11-06

A nice, scalable, concept. Do you have any applications for this yet? Also, i'm not an expert on electrolysis, but i'm fairly certain that for the water to recombine, you need to add energy (ie heat), or have a catalyst (as seen in hydrogen cars).

*fun idea* adjust your water container to accept a balloon on the top so you can fill it with a perfect molar ratio of H and O. When the balloon fills up, tie the end, then tape on a piece of cannon fuse. Light. Release. Plug your ears. and only do that under competent adult supervision....

tzq33tdq made it!(author)2012-01-09

i heard platnium wire works to make the elecricity. im making something like this but it will have a switch for input or output. or a valve that goes to a torch/hydrogen engine/genorator that runs on compressed air/hydrogen/any compressed gas.

f.3 made it!(author)2012-09-06

Platinum wire is expensive stuff but if you are able to do this please let me know, send me a link or something. Good luck to you.

GASSYPOOTS made it!(author)2012-03-23

can i haz AA versionz?

pabs129 made it!(author)2012-03-17

please reply me soon.i m in a hurry to make a hydrogen related project

pabs129 made it!(author)2012-03-17

how can i store the liberated hydrogen separately in a container without oxygen

ironsmiter made it!(author)2011-11-06

Once the gases split, you don't need ANY electricity to keep them from reverting to water. So the capacitor is a frivolous add on for this circuit.

The 2 H2O(l)→2 H2(g)+O2(g) reaction , when reversed, produces HEAT energy aka it's flaming gasses! No measurable electricity produced.
Although the chemical reaction SEEMS simple enough... there are actually a few half-reactions involved, that prevent a true two-way reaction. That's why you need flame/spark to reverse the equation. It is just for the sake of simplicity and brevity, that we write the equation the way we do.

Also note, PURE water(distilled, de-ionized) will NOT work, especially at the low voltages produced though consumer grade solar-voltaic cells.

Final experimenters note.
Never EVER run this with the cap on.
When the water being split is in an enclosed container, what you have is a BOMB! :-)
Sure, that can be fun in and of itself, but you need to treat it as such.

To help stave off arguments... here's the half-reactions ACTUALLY involved(well, ONE of them, as best explained by
2 H2O(l) → O2(g) + 4 H+(aq) + 4e−
2 H+(aq) + 2e− → H2(g)

techno+guy made it!(author)2011-11-19

If running it with a cap on makes it a bomb, then when it explodes does it explode with fire or does the bottle just rupture from the pressure?

ironsmiter made it!(author)2011-11-26

possibly BOTH.

initially, you would just have the gasses building up pressure, till the vessel ruptured.
The severity of the rupture is directly proportional to the container.
Small film canister, with the press on lid, not much worry. after a few psi, it'll just go "pop" and the lid will partially come off. Screw-on-lids, glass jars, metal containers... all a fair bit worse, when the give up their structural integrity.

then you have a concentrated ball of highly flammable gas, and pure oxygen, waiting for the least little spark, heat, or flame, to turn into a proper explosion.
This danger increases, the larger your container, and the greater pressure.
these qualities allow MORE gas to build up before the potential explosion.
More gas = bigger boom = more dangerous :-)

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