Key Concepts of Electrochemical Cells

Electrochemical cells are devices that convert chemical energy into electrical energy or vice versa. They play a crucial role in various applications, from powering batteries to facilitating electrolysis, showcasing the fascinating interplay between chemistry and electricity.

1. Galvanic (voltaic) cells

   • Convert chemical energy into electrical energy through spontaneous redox reactions.
   • Consist of two half-cells, each containing an electrode and an electrolyte.
   • Generate a positive voltage (emf) that can be harnessed to do work.

2. Electrolytic cells

   • Use electrical energy to drive non-spontaneous chemical reactions.
   • Require an external power source to facilitate the reaction.
   • Commonly used in processes like electroplating and electrolysis.

3. Concentration cells

   • Operate based on differences in concentration of the same species in two half-cells.
   • Generate voltage due to the tendency of ions to move from high to low concentration.
   • Often used to study thermodynamic principles in electrochemistry.

4. Fuel cells

   • Convert the chemical energy of fuels (like hydrogen) directly into electrical energy.
   • Operate continuously as long as fuel and oxidant are supplied.
   • Known for high efficiency and low environmental impact compared to combustion engines.

5. Standard hydrogen electrode (SHE)

   • Serves as a reference electrode with a defined potential of 0 volts.
   • Consists of a platinum electrode in contact with hydrogen gas and an acidic solution.
   • Used to measure the standard electrode potentials of other half-reactions.

6. Daniell cell

   • A type of galvanic cell that uses zinc and copper electrodes.
   • Zinc acts as the anode (oxidation) and copper as the cathode (reduction).
   • Produces a standard cell potential of approximately 1.1 volts.

7. Lead-acid battery

   • A rechargeable battery commonly used in vehicles and backup power systems.
   • Composed of lead dioxide (PbO2) and sponge lead (Pb) electrodes in sulfuric acid.
   • Provides high current output and is relatively inexpensive.

8. Lithium-ion battery

   • Widely used in portable electronics and electric vehicles due to high energy density.
   • Operates through the movement of lithium ions between the anode and cathode.
   • Offers advantages like lightweight, rechargeable, and low self-discharge rates.

9. Mercury cell

   • A type of primary battery that uses mercury oxide and zinc.
   • Known for its stable voltage output and long shelf life.
   • Used in small devices like watches and hearing aids, but environmental concerns limit its use.

10. Leclanche cell (dry cell)

    • A type of electrochemical cell that uses a paste electrolyte, making it portable and leak-proof.
    • Composed of a zinc anode and a carbon cathode with manganese dioxide as a depolarizer.
    • Commonly used in household batteries, such as AA and AAA batteries.