Electrolysis is a process where you use electrical energy (electricity) to make a chemical reaction happen that wouldn't happen otherwise. Electrolysis is often used to break a chemical compound down into the elements that make it up. Here, we'll look at the electrolysis of water into hydrogen and oxygen, and the electrolysis of sodium chloride into sodium and chlorine. In electrolysis, electrons get pushed by a battery into the cathode (the site of reduction), and they get pulled by a battery from the anode (the side of oxidation).