 The electrolysis of water is a simple method of producing hydrogen . A low voltage current is run through the water , and gaseous oxygen forms at the anode while gaseous hydrogen forms at the cathode . Typically the cathode is made from platinum or another inert metal when producing hydrogen for storage . If , however , the gas is to be burnt on site , oxygen is desirable to assist the combustion , and so both electrodes would be made from inert metals . ( Iron , for instance , would oxidize , and thus decrease the amount of oxygen given off . ) The theoretical maximum efficiency ( electricity used vs. energetic value of hydrogen produced ) is in the range 80 – 94 % . 
