<P> Jan Rudolph Deiman and Adriaan Paets van Troostwijk used, in 1789, an electrostatic machine to make electricity which was discharged on gold electrodes in a Leyden jar with water . In 1800 Alessandro Volta invented the voltaic pile, and a few weeks later William Nicholson and Anthony Carlisle used it for the electrolysis of water . When Zénobe Gramme invented the Gramme machine in 1869 electrolysis of water became a cheap method for the production of hydrogen . A method of industrial synthesis of hydrogen and oxygen through electrolysis was developed by Dmitry Lachinov in 1888 . </P> <P> A DC electrical power source is connected to two electrodes, or two plates (typically made from some inert metal such as platinum, stainless steel or iridium) which are placed in the water . Hydrogen will appear at the cathode (where electrons enter the water), and oxygen will appear at the anode . Assuming ideal faradaic efficiency, the amount of hydrogen generated is twice the amount of oxygen, and both are proportional to the total electrical charge conducted by the solution . However, in many cells competing side reactions occur, resulting in different products and less than ideal faradaic efficiency . </P> <P> Electrolysis of pure water requires excess energy in the form of overpotential to overcome various activation barriers . Without the excess energy the electrolysis of pure water occurs very slowly or not at all . This is in part due to the limited self - ionization of water . Pure water has an electrical conductivity about one millionth that of seawater . Many electrolytic cells may also lack the requisite electrocatalysts . The efficiency of electrolysis is increased through the addition of an electrolyte (such as a salt, an acid or a base) and the use of electrocatalysts . </P> <P> Currently the electrolytic process is rarely used in industrial applications since hydrogen can currently be produced more affordably from fossil fuels . </P>

Where did the hydrogen in the water come from in this reaction