An Electrochemical Cell is an experimental system capable of either generating electrical energy from two half-cells, or facilitating the chemical reaction between two half-cells through the introduction of electrical energy.
Each electrochemical cell is composed of two half-cells each with its own electrode and electrolyte. Essentially, one half-cell will be oxidized (lose electrons), while the other will be reduced (gain electron). These half cells have their electrodes connected to facilitate this reaction. Another feature of an electrochemical cell is the presence of a salt bridge to provide ionic contact between the two half-cells (other than the electrodes) in order to prevent the solutions from mixing, and disrupting the function of the electrochemical cell.
For example, consider the following electrochemical cell:
Cu2+(aq) + 2e- --> Cu(s)
Zn(s) --> Zn2+(aq) + 2e-
Cu(s) and Zn(s) are the electrodes
Zn2+(aq) and Cu2+(aq) are the electrolytes
The overall redox reaction is:
Cu2+(aq) + Zn(s) --> Cu(s) + Zn2+
Eventually, the reaction will reach an equilibrium state with a characteristic electrical potential, which is dependent on both the reducing and oxidizing strength of the respective half-cells. Thus, understanding the intricacies of electrochemical cells will help gain better appreciation of electrochemistry.
Title Image Credit: Wikimedia Commons