For more than two centuries, humanity uses the energy of chemical reactions between different substances to produce a direct current.
Principle of operation.
The oxidation-reduction reaction occurs between the substances, having the properties of an oxidizer and a reducing agent, is accompanied by the release of electrons, whose motion constitutes an electric current. However, to use its energy, it is necessary to create conditions for the passage of electrons through the external circuit.
Therefore, all chemical sources have two electrodes:
an anode on which occurs oxidation;
a cathode performs the recovery of substance.
Electrodes are placed at a distance into container with an electrolyte – substance conducting electric current.
The principle of conversion of chemical energy into electrical energy.
The electrodes are placed in separate vessels connected by a salt bridge, through which is created the movement of ions by the internal circuit. When the outer and inner circuit are separated, on the electrodes occur two processes: the transition of ions from the metal of electrode into electrolyte and the transition of ions from electrolyte into the crystal lattice of the electrodes.
The rates of these processes are the same and on each electrode are accumulated the voltage potentials of opposite signs. If connect them through the salt bridge and attach the load – there is an electrical circuit. At the internal contour the electric current is generated by movement of ions between the electrodes through the electrolyte and salt bridge. At the external circuit occurs motion of the electrons in the direction from the anode to the cathode.
Almost all oxidation-reduction reactions are accompanied by electric power generation. However, its value depends on many factors including the volume and weight of used chemicals, the materials used for the manufacture of electrodes, the type of electrolyte, the ion concentration, structure.
Most often in the modern chemical power sources, are used:
For the material of anode (reductant) – zinc (Zn), lead (Pb), cadmium (Cd) and certain other metals;
For the material of cathode (oxidant) – lead oxide PbO2, manganese oxide, MnO2, nickel oxide hydroxide NiOOH and others;
Electrolytes based on solutions of acids, alkali or salts.