Electrochemistry and Its Applications
Science & Technology › Chemistry – Basic Concepts and Atomic Structure · Topic 6.6
Electrochemistry is the branch of chemistry that studies the link between chemical reactions and electricity. It covers galvanic or voltaic cells, which turn the energy of a spontaneous redox reaction into electrical energy, and electrolytic cells, which use electrical energy to drive a non-spontaneous reaction, called electrolysis. In every cell, oxidation occurs at the anode and reduction at the cathode. Michael Faraday stated the laws of electrolysis in 1834. A battery is a set of cells. Primary batteries such as dry cells cannot be recharged, secondary batteries such as lead-acid and lithium-ion batteries can be recharged, and fuel cells make electricity continuously from a fuel such as hydrogen. Applications include electroplating, metal extraction and refining, batteries, and corrosion prevention.
5 min read · UPSC Prelims · Science & Technology · Chemistry – Basic Concepts and Atomic Structure
At a Glance
- Oxidation at Anode
- Reduction at Cathode
- Faraday’s laws 1834
- Rechargeable battery Lead-acid, lithium-ion
- Fuel cell Hydrogen and oxygen give water
- Exam link UPSC Prelims, Science & Technology: Chemistry – Basic Concepts and Atomic Structure
Where Does It Fit?
This is the sixth topic of the macro on chemistry. It links redox reactions to energy storage and industry, and ties to the energy topics of the later macros. Previous topic: Acids, Bases and Salts. Next topic: Characteristics of Solutions.
How Do Galvanic and Electrolytic Cells Differ?
| Feature | Galvanic cell and electrolytic cell |
|---|---|
| Energy change | Chemical energy to electrical energy, versus electrical energy to chemical energy |
| Reaction | Spontaneous, versus forced by an external source |
| Anode | Negative electrode in a galvanic cell and positive electrode in an electrolytic cell. Oxidation occurs at the anode in both |
| Cathode | Positive in a galvanic cell and negative in an electrolytic cell. Reduction occurs at the cathode in both |
| Example | Daniell cell of zinc and copper, versus electrolysis of molten sodium chloride or of water |
| Use | Batteries, versus electroplating and extraction of metals |
What Are the Types of Batteries?
- Primary cells: the dry cell of zinc, graphite and manganese dioxide, invented by Georges Leclanche, powers torches and clocks, but cannot be recharged.
- Lead-acid battery: a secondary cell with lead and lead dioxide plates in sulphuric acid, used in vehicles and inverters. It gives high current and is rechargeable.
- Nickel-cadmium and nickel-metal hydride: older rechargeable cells for tools and electronics.
- Lithium-ion battery: light and with high energy density, it is used in phones, laptops and electric vehicles. John Goodenough, Stanley Whittingham and Akira Yoshino received the Nobel Prize in Chemistry in 2019 for it.
- Sodium-ion and solid-state batteries: newer designs that use cheaper materials or solid electrolytes and are under development.
- Fuel cells: hydrogen is oxidised at the anode and oxygen reduced at the cathode to give water and electricity, with no carbon dioxide emitted, as in the use of hydrogen in vehicles and in space missions.
What Are Faraday’s Laws and Applications?
| Item | Detail |
|---|---|
| First law | The mass of a substance deposited or released at an electrode is proportional to the electric charge passed |
| Second law | For the same charge, masses of different substances are proportional to their equivalent weights |
| Electroplating | Coating an object with a thin layer of a metal such as nickel, chromium, silver or gold by making the object the cathode |
| Electrorefining | Impure copper is made the anode and pure copper the cathode in copper sulphate solution |
| Extraction | Sodium, magnesium and aluminium are obtained by electrolysis, as in Haematite (Fe2O3) Aluminium ore Bauxite Concentration for sulphide ores Froth flotation Aluminium extraction Electrolysis in cryolite Iron…">Metallurgical Processes and Extraction of Metals |
| Chlor-alkali process | Electrolysis of brine gives chlorine, hydrogen and sodium hydroxide |
What Else Should You Remember and Why Does It Matter?
- Electrode potential: the tendency of a metal to lose electrons, measured against the standard hydrogen electrode, which has a potential of zero.
- Corrosion as an electrochemical process: rusting of iron is a galvanic process in which one area acts as anode and another as cathode. Galvanising and sacrificial anodes of zinc or magnesium protect iron.
- Electrolytes: substances such as salts, acids and bases that conduct current in solution or when molten, as in Characteristics of Solutions.
- Electric vehicles: India supports battery production and electric mobility through schemes such as the production-linked incentive scheme for advanced chemistry cells, approved in 2021 for 50 gigawatt-hours of capacity.
- Battery recycling: used batteries contain lithium, cobalt and nickel, and India has rules for battery waste management, as in the critical minerals discussion.
- Green hydrogen: made by electrolysis of water using renewable power, as in the National Green Hydrogen Mission.
- Voltage units: a Daniell cell gives about 1.1 volts, and a lead-acid cell about 2 volts.
- Exam pattern: anode and cathode rules, battery types and uses of electrolysis.
- Standard cells: a standard hydrogen electrode is assigned zero volts, and the electromotive force of a cell is the difference between its electrode potentials.
- Conductors: metallic conductors carry current by electrons, while electrolytic conductors carry it by moving ions, and conductivity of an electrolyte rises with temperature.
- Mobile phones: a typical phone battery stores about 15 watt-hours, and the same chemistry in a larger pack powers an electric car.
As an analytical point, energy storage is the key to clean energy and electric transport. Better batteries and electrolysis are central to India’s targets of renewable power and reduced oil imports.
Why Is This Topic Important?
- Facts Cell types and electrodes asked
- Use Batteries and plating
- Policy ACC battery scheme
What Came Next?
The next topic covers the characteristics of solutions. Next topic: Characteristics of Solutions.
Key People and Terms
- Electrolysis Decomposition by electric current
- Anode Site of oxidation
- Cathode Site of reduction
- Redox Reduction and oxidation reaction
- Electrolyte Ionic conductor
- Fuel cell Cell fed by a fuel
Exam Corner
Points to Remember
- Anode: oxidation; cathode: reduction.
- Faraday’s laws: 1834.
- Li-ion Nobel: 2019.
- Lead-acid: secondary battery.
- Fuel cell product: water.
Do Not Confuse With
- Galvanic and electrolytic cell Produces versus uses electricity
- Primary and secondary cells Not rechargeable versus rechargeable
- Anode charge Negative in galvanic and positive in electrolytic
Memory Hook
An Ox, Red Cat: oxidation at anode, reduction at cathode; Faraday thirty-four, lead-acid recharges, Li-ion Nobel twenty nineteen.
Mains Angle
Questions link electrochemistry with energy transition. These points add depth.
- Cells Galvanic and electrolytic
- Storage Batteries
- Policy EV and hydrogen
A Question You May Face
An original practice question, not a past paper question.
“Explain the working of galvanic and electrolytic cells and discuss the role of batteries and fuel cells in India’s energy transition.”
How to Answer
- Cells Two types.
- Laws Faraday.
- Batteries Li-ion, fuel cell.
- Policy ACC scheme.
GS Relevance
Frequently Asked Questions
What is the difference between a galvanic cell and an electrolytic cell?
A galvanic cell turns the chemical energy of a spontaneous redox reaction into electrical energy, as in a battery, while an electrolytic cell uses electrical energy to drive a non-spontaneous reaction, as in electroplating. In both, oxidation takes place at the anode and reduction at the cathode.
What are Faraday's laws of electrolysis?
Faraday's first law says that the mass of a substance deposited or released at an electrode is proportional to the quantity of electric charge passed through the electrolyte. The second law says that for the same charge, the masses of different substances are proportional to their equivalent weights.
How does a lithium-ion battery work?
In a lithium-ion battery, lithium ions move through an electrolyte from the negative electrode to the positive electrode during discharge, while electrons flow through the external circuit and power the device. During charging the ions move back, and its light weight and high energy density make it suited to phones and electric vehicles.
What is a fuel cell?
A fuel cell is a device that produces electricity continuously from a fuel, usually hydrogen, and an oxidant, usually oxygen from air, through electrochemical reactions. Its only products are water and heat, so it is a clean source of power for vehicles and was used in space missions.
What is electroplating?
Electroplating is a process in which a thin layer of a metal such as nickel, chromium, silver or gold is deposited on an object by electrolysis. The object to be coated is made the cathode in a solution of a salt of the coating metal, and it is used to prevent corrosion and for decoration.
PYQ Practice — Statement Analysis
1 Oxidation takes place at the anode.
In all cells.
2 A lead-acid battery is a primary cell.
It is a rechargeable secondary cell.
3 Fuel cells running on hydrogen produce water.
With electricity.
4 Faraday stated the laws of electrolysis.
In 1834.
Past Mains Questions on This Topic
This topic comes under Chemistry – Basic Concepts and Atomic Structure. UPSC Mains questions asked on the matching syllabus topic, year-wise with marks:
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