How does electrolysis split water into hydrogen and oxygen?

Electrolysis uses electricity to drive a chemical reaction that would not happen on its own. In water electrolysis, electrons are supplied at the cathode to produce hydrogen gas, while oxygen forms at the anode. Pure water conducts poorly, so an electrolyte is usually added to help the current flow. The basic chemistry was understood in the early 19th century and later became important in hydrogen production. The process is a key route to making green hydrogen when the electricity comes from low-carbon sources.