Electrochemical Cell

An electrochemical cell is a part of electrochemistry. Electrochemistry deals with the relations between electrical and chemical phenomena. In these, electrochemical processes are used in various branches of industry. It is the most important process for the production of several chemicals. The production of various metals is based on the electrochemical method. The electrolysis of water manufactures hydrogen. It also plays a major role in the development of the electric automobile.

Electrochemical Cell 

An electrochemical cell is a device used to create electrical energy through the chemical reactions involved in it. The electrical energy supplied to electrochemical cells is used to smooth the chemical reactions. In the electrochemical cell, the involved devices have the ability to convert the chemical energy to electrical energy or electrical energy to chemical energy.

Electrochemical Cell Definition

An electrochemical cell is a device capable of either generating electrical energy from chemical reactions or facilitating chemical reactions for the generating of electrical energy.

Electrochemical Cell Example

A standard 1.5-volt cell is used to power many electrical appliances such as TV remotes, clocks and toys.

Features of Electrochemical cells

• There is no evolution of heat.

• The solution remains neutral on both sides.

• The reaction stops after some time.

Electrochemical Cell Description

In order to induce a flow of electric charges, we place a strip of metal (the electrode) in a solution containing the same metal, which is in an aqueous state. The combination of an electrode and its solution is called a half cell. Within the half-cell, metal ions from the solution could gain electrons from the electrode and become metal atoms; or the metal atoms from the electrode could lose electrons and become metal ions in the solution. This is the redox process.

Voltmeter Is the device used to measure  the  cell potential. How readily electrons can flow from one electrode to another is measured using two half cells. For further flow of current, electrical neutrality is required in both half cells. Salt bridge is used to accomplish that. It is a glass tube, U shaped, filled with strong electrolyte in semi solid paste of strong electrolytes like KCl and KNO3 etc.

As indicated in the diagram, the anode is the electrode where oxidation occurs. Cu loses two electrons to form Cu+2. The cathode is the electrode where reduction occurs, Ag+ (aq) gains an electron to become Ag(s). We use a cell diagram to show all parts of an electrochemical cell and electrochemical representation. We can make a cell notation from this electrochemical representation or vice versa.

General Cell Notation of Electrochemical Cell

It is the symbolic representation of the two halves of the galvanic cells by using abbreviations and symbols of the elements.

Anode(oxidation) half reaction ||

Example -: Above electrochemical reaction cell notation

Cu(s)|Cu2+(aq) || Ag+(aq)|Ag(s)

Function of Salt Bridge in Electrochemical Cell

•   Salt bridge allows the flow of current by completing the circuit.

•    It assures electrical neutrality on both sides.

•   The salt bridge usually comprises the solution of a strong electrolyte known as KNO3, KCL etc. In most cases, KCI is preferred because the transport numbers of K+and Cl– are almost the same.

Features of Cathode and Anode

Types of Electrochemical Cell

1.     Voltaic cells: The galvanic cell is also called voltaic cells. The galvanic cells principle is used in modern batteries that we use today. The cell in which chemical energy is converted into electrical energy is called a galvanic cell. 

2.     Electrolytic cells: The reverse mechanism of a galvanic cell is an electrolytic cell. In an electrolytic cell, electrical energy is utilised for the motion of ions inside the electrolyte. Electrolysis is the process that takes place in an electrolytic cell for producing electrical energy. Thus electrical energy is consumed to produce chemical energy. As an electrolytic cell is the reverse of a galvanic cell in an electrolytic cell, the cathode is marked with the negative terminal and the anode is marked with a positive terminal. In electrolytic cells the redox reaction is not spontaneous as redox reactions happen only when electrical energy is passed through electrodes. This principle is mainly used in electroplating methods.

The above example electrochemical cell is a galvanic cell, so we will not discuss it again. Daniel’s cell is also an example of a galvanic cell.

In galvanic cells, the cathode acts as the positive electrode and the anode acts as the negative electrode. In galvanic cells, the half cells i.e. Electrochemical cells with one electrode are immersed in a solution in different containers. The electrodes are connected through salt bridges. When spontaneously the ions move from one electrode to the other electrical energy is produced. That energy can be used for some useful work.One of the examples of Galvanic cells is Non-rechargeable batteries .

Uses of voltaic cells

1. To get electrical power. 

2.To make the chargeable batteries

3. To make the solar cells which are rechargeable.

4. Galvanic cell batteries are also used in chargeable vehicles. 

Electrolytic Cell 

These are the type of electrochemical cells that drive a nonspontaneous reaction using electrical energy. These can decompose chemical compounds, like water, into hydrogen and oxygen. This decomposition takes place by the process called electrolysis. So, electrolytic cells need a DC power supply, two electrodes and an electrolyte to perform electrolysis.

The function of electrolyte and electrode

1. The electrolyte provides the path for the flow of electrons or ions inside the cell. The chemical reactions happening in the cell help to convert the chemical energy into electrical energy.

2. When driven by an external voltage applied to the electrodes, the ions in the electrolyte are attracted to an electrode with the opposite charge, where charge-transferring (also called redox) reactions can take place.

As mentioned above, electrolytic cells require the use of electricity. As opposed to galvanic cells, electrolytic cells require the electrodes to be placed in the same container. It makes use of both the cathode and anode. However, the charges are reversed here. The cathode is negatively charged, and the anode is positively charged. 

As a prerequisite of electricity, an external battery is connected to the system. 

The various aspects concerned with the electrolysis or working of an electrolytic cell are as follows:

• The electrons in the negative terminal move towards the cathode and act as reducing agents.

• The negative ions move towards the anode. They release electrons and act as oxidising agents.

• If ∆G is > 0 then non-spontaneous reaction will occur.

Uses of electrolytic cells

• Electroplating.

• Battery manufacturing.

• Electroplating or electrorefining.

• Oxygen production in spacecraft and submarines is prepared by electrolytic cells.

•  Hydrogen fuel is also produced by using electrolytic cells.

The uses of the galvanic and electrolytic cells are the application of electrochemical cells.

Conclusion

The electrolytic and galvanic cells are one of the main types of electrochemical cells with many uses in the modern world. From watch to television, we can see the use of galvanic cells everywhere. On the other hand, electrolytic cells are explored in many research activities and find wide applications in laboratories. Due to the discovery of these cells, the perspective towards electrolytic and galvanic cells has completely changed. They are very similar yet different in the way they function. They may use the common anode and cathode for their processes, but the implications differ in electrolytic and galvanic cells.Electroplating and electrorefining are the two very useful electrolytic cell applications widely used in industries.