A half cell is a structure that contains an electrode and a surrounding electrolyte. A standard half cell, used in electrochemistry, consists of a metal electrode in a 1 molar aqueous solution of the metal's salt, at 298 Kelvin (25^o Celsius). The electrochemical series, which consists of standard electrode potentials and is closely related to the reactivity series, was generated by measuring the between the metal half cell in a circuit with a standard hydrogen half cell, connected by a salt bridge.

The half cell of a Daniell Cell: Zn + Cu+² -> Zn+² + Cu :Original equation Zn -> Zn+² + 2e- :Half Cell of Zn Cu+² - 2e- -> Cu :Half Cell of Cu

Electrolysis