An electrolysis cathode is the node at which cations, the positively charged ions of an electrolysis decomposition, gather. Electrolysis refers to the process of passing a direct electric current through a chemical solution consisting of positive and negative ions. It is performed by placing two electrodes, each a conductor of electricity attached to an external power source, in a chemical solution in order to produce the desired result — a separation of the solution into its basic ions. The electrodes are the cathode and the anode, the anode being the node at which anions, negatively charged ions, gather.
The electrolysis cathode is usually made from silicon, graphite or a metal such as copper, steel or lithium iron phosphate. The purpose of the cathode is to give out electrons, causing it to have an overall negative charge that attracts all cations contained in the solution. The process by which these cations migrate to the electrolysis cathode is known as reduction. Together with oxidation, the process by which anions migrate to the anode, reduction allows the decomposition of a solution to occur.
Electrolysis and, by extension, the notion of the electrolysis cathode, was first pioneered by William Nicholson and Anthony Carlisle in 1800. Nicholson and Carlisle wished to replicate an earlier experiment by Alessandro Volta, an Italian scientist who discovered that a current can be produced using two metals attached to any conductor — muscle tissue or brine, for instance. Following Volta's findings, Nicholson and Carlisle set up their experiment in a similar manner using metal plates, a conductor, and an electroscope to measure changes in electrical charge.
It was difficult to establish and maintain contact between the plates and the electroscope, so Nicholson and Carlisle used water as a binding agent. As they conducted the experiment, they were shocked to find that the water was decomposing into positive hydrogen ions that appeared as hydrogen gas and negative oxygen ions, which proved to be oxygen gas. Inadvertently, the two British scientists had just discovered the chemical process of electrolysis and denoted the importance of the electrolysis cathode.
There are many commercial and industrial uses for an electrolysis cathode. These uses include recharging rechargeable batteries; producing large quantities of hydrogen gas, chlorine solution and sodium hydroxide through salt water electrolysis; and electroplating various materials in order to make them stronger and more reliable. Without this important electrode, many chemical processes on which modern industries depend would not exist.