fuel cells are devices which convert chemical energy from fuel into electricity through a chemical reaction with oxygen or other oxidizing agent.

1. FUEL CELLS

2. PRESENTED BY:
MAIRA PERVAIZ
SIDRA JAMEEL
QURAT-UL-AIN
ANEEQA ZUBAIR

3. WHAT IS A FUEL CELL?
 A device that generates electricity by a
chemical reaction
 Uses Oxygen or another oxidizing agent
 Another fuel, generally Hydrogen.
 Electrochemical process

4. HISTORY
 The first fuel cell was constructed in 1839 by British physicist and lawyer Sir
William Robert Groove.
 For many years little was done to develop fuel cells for commercial purposes.
 Recent advances in technology and electrochemistry have made the
scientists successful to introduce the fuel cell which are more efficient, than
thermal source of electrical energy.

5. COMPONENTS:
 An anode
 A Cathode
 An Electrolyte
 A Catalyst
 Fuel
 Oxidant

6. ANODE:
 Negative post of the fuel cell.
 Conducts the electrons that are freed from the hydrogen molecules so
that they can be used in an external circuit.
 Etched channels disperse hydrogen gas over the surface of catalyst.

7. CATHODE:
 Positive post of the fuel cell
 Etched channels distribute oxygen to the surface of the catalyst.
 Conducts electrons back from the external circuit to the catalyst
 Recombine with the hydrogen ions and oxygen to form water.

8. ELECTROLYTE:
 Proton exchange membrane.
 Specially treated material, only conducts positively charged
ions.
 Membrane blocks electrons.

9. CATALYST:
 Special material that facilitates reaction of oxygen and
hydrogen
 Usually platinum powder very thinly coated onto carbon
paper or cloth.
 Rough & porous maximizes surface area exposed to
hydrogen or oxygen
 The platinum-coated side of the catalyst faces the PEM.

10. WORKING:
 Pressurized hydrogen gas (H2) enters cell on anode side.
 Gas is forced through catalyst by pressure.
 When H2 molecule comes contacts platinum catalyst, it splits into two H+ ions and two
electrons (e-).
 Electrons are conducted through the anode
 On the cathode side, oxygen gas (O2) is forced through the catalyst
 Forms two oxygen atoms, each with a strong negative charge.
 Negative charge attracts the two H+ ions through the membrane,
 Combine with an oxygen atom and two electrons from the external circuit to form a water
molecule (H2O).

11. REACTIONS:
 Anode side (an oxidation reaction)
 2H2 => 4H++ 4e-
 Cathode side (a reduction reaction):
 O2 + 4H+ + 4e- => 2H2O
 Net reaction (the "redox" reaction):
 2H2 + O2 => 2H2O

12. TYPES:
 Alkaline fuel cells
 Solid oxide fuel cells
 Phosphoric Acid Fuel Cell
 Proton Exchange Membrane Fuel
Cells
 Molten Carbonate fuel cells

13. ALKALINE FUEL CELLS:
 Operates on compressed hydrogen and oxygen.
 Efficiency is about 70 percent, and operating
temperature is 50 to 100 degrees C.
 Used in Apollo spacecraft to provide both
electricity and drinking water.
 They require pure hydrogen fuel, however, and
have platinum electrode catalysts.

14. SOLID OXIDE FUEL CELLS:
 Uses a hard, ceramic compound of metal
oxides as electrolyte
 Efficiency is about 60 percent
 Operating temperatures are about 1,000
degrees C, so no reformer is required for
extracting hydrogen from fuel
 Utility applications

15. PHOSPHORIC ACID FUEL CELL:
 Uses phosphoric acid as the
electrolyte
 Efficiency ranges from 40 to 80
percent
 Typically used for stationary power
generation

16. PROTON EXCHANGE MEMBRANE FUEL CELLS:
 Work with a polymer electrolyte in
the form of a thin, permeable sheet
 Efficiency is about 40 to 50 percent
 Suitable for homes and cars

17. MOLTEN CARBONATE FUEL CELL:
 Uses high-temperature compounds of salt
carbonates as electrolyte
 Efficiency ranges from 60 to 80 percent, and
operating temperature is about 650 degrees
C
 Developed for natural gas and coal-based
power plants to generate power for industry
and military use

18. EFFICIENCY:
 The ability of a cell to convert chemical
energy of a fuel-oxidation reaction into
electrical energy is expressed in terms of
efficiency of the cell (Ԑ). It is defined as
Ԑ=∆F∆H × 100

19. EFFICIENCY OF H2– O2 FUEL CELL:
∆F° = -273.2 kJmole-ˡ
∆H° = -258.9 kJmole-ˡ
Ԑ = ∆F/∆H
= -273.2×100/-258.9
=83%

20. ADVANTAGES:
 Clean Energy Source
 High Efficiency
 Noise Reduction
 More reliable
 Flexible technology

21. DISADVANTAGES:
 Expensive
 Catalyst cost (usually platinum)
 Durability
 Safety Hazards associated with
Hydrogen
 Hydrogen is not readily available

22. APPLICATIONS:
 Stationary
 Transportation
 Consumer Electronics
 Providing power for base stations or cell sites
 Food preservation
 Small heating appliances
 Notebook computers
 Hybrid vehicles