How to Make Hydrogen by Electrolysis
Electrolysis is the process in which electricity is used to separate water molecules into hydrogen and oxygen gases. Electric current is passed through distilled water with some sort of electrolytes added to assist the current. The molecular bonds of the water are broken, and the hydrogen is collected at the cathode while the oxygen is collected at the anode. In a chemistry lab, a Hoffman apparatus is used to perform this experiment, but you can do it at home as long as you have a container to collect the hydrogen.
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Things You'll Need
- Battery or other source of DC power
- Distilled water
- Electrolytes
- Electrodes
- Two containers to collect hydrogen and oxygen (plastic soda or water bottles will work)
- Large container, about the size of an infant bathtub, for the water
Instructions
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Fill the large container 2/3 to 3/4 full of distilled water. Add electrolytes to the water. Do not use table salt, but most any other salt or other ion-producing molecules will work.
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Place the electrodes inside the collection bottles. Submerge the bottles in the water until they are filled and rest them against the side so they are at an angle with the bottoms above the water surface.
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Connect the power source to the electrodes. Bubbles will begin to form around the electrode. The gases will displace the water in the bottles.
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Disconnect the power before the water level in the bottles falls below the electrodes. Cap the bottles while keeping the tops underwater. There will be some water left in the bottles, but the gases will be either hydrogen or oxygen.
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Tips & Warnings
Hydrogen is formed twice as fast as oxygen, so the bottle with the larger volume of gas is the hydrogen.
Do not use table salt--sodium chloride, or NaCl---as your electrolyte. The chlorine ions will be attracted to the electrodes and form chlorine gas. Chlorine gas can be deadly.
