Making pure hydrogen requires either electric separation, referred to as electrolysis, or chemical separation using metal and a hydrogen-based acid. Electrolysis uses a direct current passing through water, which breaks down the hydrogen and oxygen based on the electrode’s polarity, and is the preferred method.
Obtain a direct current source
Use a rectangular 9-volt battery, also called a transistor battery, and note the polarity on the terminals.
Make a solution of water and salt
Dissolve 1 tablespoon of table salt in a gallon of tap water. The salt helps conduct electricity, improving the result.
Create a collection system
Use a glass or ceramic bread baking pan, and fill it with the salted water. Take two small glass jars or test tubes and submerge them in the pan of water. Invert the jars, making sure no air is trapped inside.
Connect the battery
Use two wires and connect one to each pole on the battery. If possible use plastic insulated wire with about 1 inch exposed on either end.
Start the electrolysis
Place the positive wire under one jar and the negative wire under the other. Bubbles will form on the exposed wire and then rise. The positive electrode creates oxygen, while the negative electrode creates hydrogen. To stop the process, disconnect one or both wires from the battery.
Proceed with caution
Do not place both electrodes beneath a single container. Doing this creates a mix of oxygen and hydrogen gas, which can easily explode.