Electrochemical cell

An electrochemical cell is a device that generates electrical energy from chemical reactions. Electrical energy can also be applied to these cells to cause chemical reactions to occur. Electrochemical cells which generate an electric current are called voltaic or galvanic cells and those that generate chemical reactions, via electrolysis for example, are called electrolytic cells. Both galvanic and electrolytic cells can be thought of as having two half-cells: consisting of separate oxidation and reduction reactions. When one or more electrochemical cells are connected in parallel or series they make a battery. Primary cells are single use batteries. Galvanic cell A galvanic cell (voltaic cell) named after Luigi Galvani (Alessandro Volta) is an electrochemical cell that generates electrical energy from spontaneous redox reactions. A wire connects two different metals (ex. Zinc and Copper). Each metal is in a separate solution; often the aqueous sulphate or nitrate forms of the metal, however more generally metal salts and water which conduct current. A salt bridge or porous membrane connects the two solutions, keeping electric neutrality and the avoidance of charge accumulation. The metal's differences in oxidation/reduction potential drive the reaction until equilibrium. Key features: spontaneous reaction generates electric current current flows through a wire, and ions flow through a salt bridge anode (negative), cathode (positive) Galvanic cells consists of two half-cells. Each half-cell consists of an electrode and an electrolyte (both half cells may use the same or different electrolytes). The chemical reactions in the cell involve the electrolyte, electrodes, and/or an external substance (fuel cells may use hydrogen gas as a reactant). In a full electrochemical cell, species from one half-cell lose electrons (oxidation) to their electrode while species from the other half-cell gain electrons (reduction) from their electrode. A salt bridge (e.g.