Electrochemistry

Introduction

Electrochemistry is a branch of chemistry that has been introduced by the contributions made by the English chemist John Daniel and the physicist Michael Faraday. John Daniel invented the primary cell and Michael Faraday introduced the laws of electrochemistry. Nernst introduced the electromotive force and put forward an equation that is now known as the Nernst equation. Electrochemistry deals with the study of electron movement. And it also deals with the relationship between electrical and chemical energy. Spontaneous chemical reactions taking place in the electrochemical systems produce a large amount of electrical energy. And the study of this electrical energy is a major part of electrochemistry.

The advancement in the technology field helped in the discovery of the branch of chemistry, electrochemistry. The invention of the voltaic pile by the scientist Alessandro Volta in the year 1800 led to the discovery of electrochemistry. It deals with electricity for the first time. Then Benjamin Franklin studied this topic further and which leads to the discovery of static electricity too. As voltaic pile produces electricity, it introduced a new advancement that chemical energy itself can produce electrical energy. Humphry Davy later introduced the voltaic battery with the help of some metals. Then in 1806 electrical theory of chemical affinity was also introduced.

Oxidation and Reduction

The oxidation and reduction processes are together known as redox. And this type of reaction involves the transfer of electrons between two species. In such reactions, the oxidation number of two chemical substances may increase or decrease. They are present for the proper functioning of many systems even in our nature such as the respiration process, photosynthesis, corrosion, combustion, etc.

And the chemical compound’s oxidation number is used for the representation of the number of electrons, lost or gained. For a single element, the oxidation state is always zero. If a chemical compound undergoes loss of electrons, it is said that the compound has undergone oxidation. So, the loss of electrons is represented by the term oxidation. While if a chemical compound gains an extra electron, it is said that it has undergone reduction. So, if a chemical compound loses electrons it is reduced. The oxidation state increases if it undergoes oxidation while the oxidation state reduces or decreases if it undergoes reduction. The chemical compound in which oxidation brings is called the reducing agent while the chemical compound in which reduction brings is called the oxidizing agent.

The subsequent reaction illustrates the process of oxidation.

$$\mathrm{Na\:\rightarrow\:Na^{+}\:+\:e^{-}}$$

And in the following reaction represents the process of reduction.

$$\mathrm{Cl\:+\:e^{-}\:\rightarrow\:Cl^{-}}$$

Electrochemical Cell

The device that is capable of producing electricity by some chemical reactions taking place in a system for the one that produces chemical energy by the electric current is the electrochemical cell. The device that produces electrical energy by chemical reactions is voltaic or galvanic cells. While the one that produces chemical energy by the electrolysis reaction is the electrolytic cell. Generally, comprises two half cells. And are consists of an electrode and electrolyte system.

A salt bridge is also used for connecting these two systems. The electrodes are metallic components that are good conductors of electricity that act as a passage for the flow of current in between the non-metallic materials. While electrolytes are material that contains ions that lie between two types of electrodes. A salt bridge is used for connecting two half cells where oxidation and reduction are taking place. Lithium-ion batteries and galvanic cells are examples of electrochemical cells.

Types of Electrochemical Cells

Based on the type character of electrochemical cells they are generally two types. And are

• Electrolytic cell

• Galvanic cell or voltaic cell

The features of these two electrochemical cells are tabulated below.

Electrolytic cell	Galvanic cell or voltaic cell
It involves the conversion of electrical energy to chemical energy.	Transformation of chemical energy to electrical energy.
It generally contains a single compartment.	It generally consists of two compartments and a salt bridge.
Non-spontaneous redox chemical reactions are taking place.	Spontaneous redox chemical reactions are taking place.
The production of electrons is taking place by the supply of external electrical energy.	No external energy is needed for electron generation.

How is an Electrochemical Cell Represented?

From the International Board of Chemistry, there is a general representation of the electrochemical cells. It includes,

• The oxidation half-cell reaction is first represented in which the metal is represented first not the ions. For example, $\mathrm{Zn/Zn^{2+}(0.1M)}$.

• A salt bridge is represented after the oxidation has a cell as ||.

• The reduction half-cell reaction is then represented by the metallic ion first and then the metal that is reduced. For example,$\mathrm{Cu^{2+}(0.1M)/Cu}$..

• So, the electrochemical cell can be represented as,

$$\mathrm{zn/Zn^{2+}(0.1M)\:\:\rVert\:Cu^{2+}(0.1M)/Cu}$$

Functioning of Daniel Cell or Voltaic Cell

The electrochemical cell which transforms the chemical energy into electrical energy is the Daniel cell or voltaic cell. Redox chemical reactions taking place in this cell leads to the formation of an electric current. There are two types of cell electrodes in this cell they are cathode and anode. The electrode at which oxidation takes place or the loss of electrons occurs is an anode and the one in which gain of electrons or reduction takes place is a cathode. Thus, a potential difference is developed between these two electrodes. And a current flow will occur. This current is then detected by using a voltmeter. In this way, galvanic or voltaic cells generate electricity.

Electrochemical Cell and Gibbs Energy of the Reaction

The multiplication of electric potential and the total charge is electrical work done. The passage of charges reversible leads to the formation of maximum work. The reversible work done by a galvanic cell is equal to the value of decreasing Gibbs energy. The Gibbs energy of a reaction is therefore given by the equation,

$$\mathrm{\Delta\:rG\:=\:-nFE_{cell}}$$

For example, in the following reaction,

$$\mathrm{Zn(s)\:+\:Cu^{2+}(aq)\:\rightarrow\:Zn^{2+}(aq)\:+\:Cu(s)}$$

$$\mathrm{\Delta\:rG\:=\:-2FE_{cell}}$$

Since the charge is two.

Conclusion

Electrochemistry is an important branch of chemistry that deals with the flow of electrons through redox reactions. A redox process is a chemical reaction in which two chemical species undergo an oxidation and reduction process. The loss of electrons is given by the name oxidation and the gain of electrons is given by the name reduction. An electrochemical cell is a device that generates electricity by chemical reactions or produces chemical reactions from electricity. So, there are two types of galvanic cells: Daniel cell and electrolytic cell. An electrolytic is a cell that converts electrical energy to chemical reactions while a galvanic cell converts chemical reactions into electrical energy. Both have varying applications depending on their purpose.

FAQs

1. What are some of the real-life applications of galvanic cells?

Some important applications of the galvanic cells are their use in batteries, the process of electroplating, fuel cells, etc.

2. What are the uses of electrolytic cells?

The use of electrolytic cells is mainly in the generation of gases such as Oxygen and Hydrogen by the supply of electricity.

3. What are the advantages of electrochemistry?

It has many advantages in which the technique or the device of electrochemical applications are very simple, fast process, and very cheap. So, it is present in many fields.

4. What are electrochemical sensors?

Electrochemical sensors can detect the presence of the target gases by the oxidation and reduction process with the help of an electrode system by detecting the electric current produced.

5. Who is the father of modern electrochemistry?

The chemist Allen Bard is the father of modern electrochemistry through his contribution to the field of electrogenerated chemiluminescence.