Activated Carbon Production from Coconut Husks for Supercapacitors

Why in the News?

Researchers at Government College for Women, Thiruvananthapuram, have developed a way to make activated carbon from coconut husks, which are a common leftover from farming in Kerala. This activated carbon is well-suited for making supercapacitors.

Back2Basics: Supercapacitors

Supercapacitors, also known as ultra-capacitors or electrochemical capacitors, are energy storage devices that bridge the gap between conventional capacitors and batteries.
They store energy through the electrostatic separation of charges rather than through chemical reactions as in batteries.
This allows supercapacitors to charge and discharge much faster than batteries.

Key Characteristics:

High Power Density: Supercapacitors can deliver and accept charge much more rapidly than batteries.
Long Cycle Life: They can endure millions of charge-discharge cycles without significant degradation.
Wide Operating Temperature Range: Supercapacitors perform well in a broad range of temperatures, making them suitable for various applications.

Structure and Components:

Electrodes: Made of materials like activated carbon, carbon aerogels, or graphene, which have high surface areas.
Electrolyte: The medium that allows ionic conductivity between the electrodes, typically a liquid or gel.
Separator: A porous membrane that prevents electrical contact between the electrodes but allows ionic movement.

What is Activated Carbon?

Activated Carbon, also known as activated charcoal, is a highly porous form of carbon.
It is processed to have small, low-volume pores with increased surface area available for adsorption or chemical reactions.
It is widely used for purification, decontamination, and as a filtration medium.
Key Characteristics:
- High Surface Area: Due to its extensive network of pores, activated carbon has a very high surface area, typically ranging from 500 to 1500 m²/g.
- Porosity: The structure includes micropores, mesopores, and macropores, allowing it to adsorb a variety of molecules.

How is it produced?

Activated carbon is produced from carbonaceous source materials such as coconut shells, peat, wood, coir, lignite, coal, and petroleum pitch.
The production involves two main steps:

Carbonization: The raw material is subjected to high temperatures (600-900°C) in an inert atmosphere (usually nitrogen or argon) to remove volatile components.
Activation/Oxidation: The carbonized material is treated with oxidizing agents (such as steam or carbon dioxide) at high temperatures (800-1000°C) to develop a porous structure.

Types:

Powdered Activated Carbon (PAC): Finely ground carbon particles primarily used in liquid phase applications.
Granular Activated Carbon (GAC): Larger particles used in both liquid and gas phase applications, such as water and air filtration.
Extruded Activated Carbon (EAC): Cylindrical pellets used mainly for gas phase applications due to their low pressure drop and high mechanical strength.
Impregnated Activated Carbon: Activated carbon treated with chemicals to enhance its adsorption capacity for specific contaminants.

Applications:

Water Treatment: Removes contaminants like chlorine, odors, and organic compounds from drinking water.
Air Purification: Adsorbs volatile organic compounds (VOCs), odors, and airborne pollutants.
Medical Uses: Used in poisoning cases to absorb toxins in the gastrointestinal tract.
Industrial Processes: Utilized in the recovery of solvents, purification of gases, and in gold purification.
Food and Beverage: Helps in decolorization and purification processes in sugar, wine, and juice production.

About Coconut Husk-Derived Activated Carbon

Coconut husk-derived activated carbon is a sustainable and efficient green solution for high-performance supercapacitors.
This material is readily available, low-cost, and eco-friendly.
It was produced by Microwave-Assisted Method designed at the Centralised Common Instrumentation Facility (CCIF) at the college.

Importance of Supercapacitors

Energy Storage: Supercapacitors have significantly higher capacitance and energy storage capacity compared to conventional capacitors.
Search for Ideal Material: Finding the ideal supercapacitor electrode material has been a significant challenge in sustainable energy storage solutions.

Research Findings:

Efficiency: Prototype supercapacitors made from coconut husk-derived activated carbon are four times more efficient than existing supercapacitors.
Cost-Effective and Efficient: Activated carbon produced using this technology is inexpensive and exhibits exceptional supercapacitor capability.