Electrochemistry: Principles and Applications

Electrochemistry: Principles and Applications

Introduction:

Electrochemistry is the study of chemical processes that involve the transfer of electrons. It sounds esoteric, but electrochemistry has broad application, from the batteries that power your phone and electric cars to the production of ammonia, which is critical in the production of fertilizers.

Key Concepts:

• Oxidation and reduction reactions: The fundamental concept in electrochemistry is the transfer of electrons between different substances. Oxidation is the loss of electrons, while reduction is the gain of electrons.
• Galvanic cells: A galvanic cell is an electrochemical cell that converts chemical energy into electrical energy. In a galvanic cell, spontaneous oxidation-reduction reactions occur, and electrons flow from the anode (oxidation) to the cathode (reduction), generating a current.
• Electrolysis: Electrolysis is the process of using an electric current to drive a non-spontaneous chemical reaction. In electrolysis, the anode and cathode are reversed compared to a galvanic cell, and the anode is the site of oxidation, while the cathode is the site of reduction.
• Faraday’s laws: These laws describe the relationship between the amount of substance produced or consumed in an electrolysis reaction and the amount of electricity that passes through the electrolyte. The first law states that the amount of substance produced or consumed in an electrolysis reaction is directly proportional to the amount of charge passed through the electrolyte. The second law states that the amounts of different elements produced or consumed in an electrolysis reaction are proportional to their atomic weights.

Equations and Formulas:

• Nernst equation: This equation relates the standard electrode potential of an electrochemical cell to the concentration of the reactants and products. E = E° – (RT/nF)ln(Q), where E is the actual electrode potential, E° is the standard electrode potential, R is the gas constant, T is the temperature, n is the number of electrons transferred, F is the Faraday constant, and Q is the reaction quotient.
• The half-cell reactions: In electrochemistry, a half-cell is one of the two compartments in an electrochemical cell. The half-cell contains an electrode in contact with an electrolyte. The half-cell reaction is the oxidation-reduction reaction that takes place at an electrode in a half-cell. For example, in a galvanic cell with a Zn electrode and a Cu electrode, the half-cell reactions are Zn → Zn2+ + 2e- (oxidation at the anode) and Cu2+ + 2e- → Cu (reduction at the cathode).
• Coulomb’s law: Coulomb’s law describes the interaction between two charged particles. The force between two charged particles is proportional to the product of their charges and inversely proportional to the square of the distance between them. F = k(q1q2)/r2, where F is the force, q1 and q2 are the charges on the particles, r is the distance between the particles, and k is Coulomb’s constant.

Examples:

• Corrosion: Corrosion is an electrochemical process that can have severe consequences, such as weakening or failure of structures. The corrosion of iron is a well-known example of electrochemical corrosion. In the presence of water and oxygen, iron undergoes oxidation to form iron oxide (Fe2O3), which is commonly known as rust.
• Electroplating: Electroplating is a process by which a metal coating is deposited on a metal object. Electroplating is used for decorative purposes, to provide a protective coating, or to improve the properties of a material. In electroplating, the metal to be deposited (the cathode) is immersed in a solution containing dissolved ions of the metal to be deposited. An electric current is passed through the solution, causing the metal ions to be reduced and deposited onto the cathode.
• Redox flow batteries: Redox flow batteries are a type of rechargeable battery that uses two electrolytes instead of solid electrodes and an electrolyte. The electrolytes are pumped through separate chambers, where they are oxidized and reduced, generating electricity. Redox flow batteries have attracted attention as a potential energy storage solution for renewable energy sources, such as solar and wind power.

References:

• Bard, A. J., & Faulkner, L. R. (2000). Electrochemical methods: fundamentals and applications (2nd ed.). New York: Wiley.
• Compton, R. G., & Banks, C. E. (2010). Understanding Voltammetry (2nd ed.). Imperial College Press.
• Telford, R. N., & Schlag, E. W. (2014). Electrochemistry: A Reformulation of Basic Concepts (2 ed.). New York, NY: Springer.