This document provides an overview of an active learning assignment on fuel cells. It discusses the basic components and workings of a fuel cell, including the electrodes, electrolyte, and catalyst. It also describes the reactions that take place in fuel cells to convert chemical energy to electrical energy. Finally, it outlines the main types of fuel cells, classified based on their electrolyte: alkaline, molten carbonate, phosphoric acid, proton exchange membrane, and solid oxide fuel cells. For each type it provides details on operating temperature, efficiency, applications, and other characteristics.

1. Active Learning Assignment
Subject : EEE(2110005)
Topic Name: Principle and types of
Fuel cells
Branch : Computer Engineering
Division :
Prepared by :
Enrollment : Guided by :
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2. INTRODUCTION:
What is fuel cell ?
 Fuel cell is a device that converts the chemical energy from
fuel into electrical energy through a chemical reaction with
oxygen.
 Every fuel cells has two electrodes, one positive and one
negative called anode and cathode respectively.
 Every fuel cell also has an electrolyte which carries electrically
charged particles from one electrode to the other and a
catalyst which speeds up the reaction at the electrodes.
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3.  In general hydrogen atoms enter a fuel cell at the anode
where chemical reaction strip them of their electrons. The
hydrogen atoms are now ionized and carry a positive
charge. The negative charged elections provide current to
external circuit through anode. Electrons again enters at the
cathode which have come from anode.
 Oxygen enters the fuel cell at the cathode. It combines
with electrons returning from the electrical circuit and
hydrogen ions that have travelled through the electrolyte
from the anode.
WORKING:
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4. 4

5. CELL REACTIONS:
• 2H2 + 2O2− → 2H2O +
4e−
Anode
Reaction:
• O2 + 4e− → 2O2−
Cathode
Reaction
• 2H2 + O2 → 2H2O
Overall Cell
Reaction: 5

6. TYPES OF FUEL CELLS:
There are following many types of fuel cells. They are basically
classified based on electrolyte used:
i. Alkaline fuel cell
ii. Molten carbonate fuel cell (MCFC)
iii. Phosphoric acid fuel cell (PAFC)
iv. Proton exchange membrane (PEM) fuel cell
v. Solid oxide fuel cell (SOFC) 6

7. • In this type of fuel cell a solution of potassium hydroxide (KOH)
in water is used as electrolyte.
• Efficiency is about 70% and operating temperature is 150ºC to
200ºC.
• Cell output range from 300W to 5kW.
• Alkali cells are used in Appolo spacecraft to provide both
electricity and drinking water.
• They require pure hydrogen and platinum electrodes.
1. ALKALINE FUEL
CELL
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8. • These cells use high temperature compounds of salt carbonates
i.e. 𝑁𝑎2 𝐶𝑜3 or Mg𝐶𝑜3 as the electrolyte.
• Efficiency ranges from 60% to 80% and operating temperature
is about 650ºC.
• Units with output up to 2 MW have been constructed.
• They use nickel electrodes which are inexpensive compared to
platinum used in other cells.
2. MOLTEN CARBONATE
FUEL CELL (MCFC)
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9. • These cells use phosphoric acid as electrolyte.
• Efficiency ranges from 40% to 80% and operating temperature
is between 150ºC to 200ºC.
• Existing phosphoric acid fuel cells have outputs up to 200 kW
and 11 MW units have been tested.
• Platinum electrode-catalysts are need and internal must be able
to withstand the corrosive acid.
3. PHOSPHORIC ACID
FUEL CELL (PAFC)
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10. • These cells work with a polymer electrolyte in the form of thin,
permeable sheet.
• Efficiency is about 40% to 50% and operating temperature is
about 80ºC.
• Cell outputs ranges from 50 to 250 kW.
• These solid flexible electrolyte does not leak or crack.
• These cells operate at a low enough temperature to make them
suitable for homes and cars.
4. PROTON EXCHANGE
MEMBRANE (PEM) FUEL
CELL
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11. • These fuel cells use a hard ceramic compound of metal (like
calcium or zirconium) oxides (𝑂2) as electrolyte.
• Efficiency is about 60% and opening temperature is about
1000ºC.
• Cell output is up to 100 kW.
• At such high temperature a reformer is not required to extract
hydrogen from the fuel and waste heat can be recycled to make
additional electricity.
5. SOLID OXIDE FUEL
CELL (SOFC)
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