1. A fuel cell converts chemical energy directly into electricity through electrochemical reactions between hydrogen and oxygen without combustion. 2. There are several types of fuel cells that differ in their electrolyte material including polymer electrolyte membrane fuel cells, alkaline fuel cells, phosphoric acid fuel cells, molten carbonate fuel cells, and solid oxide fuel cells. 3. Each fuel cell type has advantages and disadvantages for different applications depending on factors like operating temperature, catalyst requirements, and fuel used.

1. G.SURAJ
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2. A fuel cell is an electrochemical cell that
converts the chemical energy from a fuel
into electricity through an electrochemical
reaction of hydrogen fuel with oxygen or
another oxidizing agent.

3. Fuel Oxygen
Combustion
Products
+
Heat

4. Fuel Oxygen
Oxidation
Products
+
Electricity

5. 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.
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.
Electrolyte
 Proton exchange membrane.
 Specially treated material, only conducts positively charged ions.
 Membrane blocks electrons.
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.

6.  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
 Make their way through the external circuit (doing useful work such
as turning a motor) and return to the cathode side of the fuel cell.
 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).

9.  Fuel cells are classified primarily by
the kind of electrolyte they employ.
 This classification determines the kind
of electro-chemical reactions that take
place in the cell, the kind of catalysts
required, the temperature range in which
the cell operates, the fuel required, and
other factors.
 These characteristics, in turn, affect
the applications for which these cells are
most suitable.
 There are several types of fuel cells
currently under development, each with its
own advantages, limitations, and potential
applications.

10.  Polymer Electrolyte Membrane
fuel cell(PEMFC)
 Direct Methanol fuel cell (DMFC)
 Alkaline fuel cell (AFC)
 Phosphoric acid fuel cell (PAFC)
 Molten-carbonate fuel cell (MCFC)
 Solid-oxide fuel cell (SOFC)
 Reversible Fuel Cells

11. 1. Polymer electrolyte membrane (PEM) fuel cells—also called proton
exchange membrane fuel cells—deliver high power density and offer
the advantages of low weight and volume compared with other fuel
cells.
2. PEM fuel cells use a solid polymer as an electrolyte and porous
carbon electrodes containing a platinum or platinum alloy catalyst.
They need only hydrogen, oxygen from the air, and water to operate. T
3. PEM fuel cells operate at relatively low temperatures, around 80°C
(176°F). Low-temperature operation allows them to start quickly (less
warm-up time) and results in less wear on system components,
resulting in better durability.
4. PEM fuel cells have a practical efficiency of 60%. Power output is in
the range of 5-200 kW. They are ideal for transportation and portable
power.
5. PEM fuel cells are particularly suitable for use in passenger vehicles,
such as cars and buses.

13. At the anode:
H2 = 2H+ + 2e-
At the cathode:
1/2O2 + 2H+ + 2e- = H2O
Overall cell reaction:
l/2O2 + H2 = H20

14. 1. Direct methanol fuel cells (DMFCs),
however, are powered by pure
methanol, which is usually mixed with
water and fed directly to the fuel cell
anode.
2. Direct methanol fuel cells do not have
many of the fuel storage problems
typical of some fuel cell systems
because methanol has a higher energy
density than hydrogen—though less
than gasoline or diesel fuel.
3. DMFCs are often used to provide power
for portable fuel cell applications such
as cell phones or laptop computers.

15.  DMFC
ELECTRO CHEMICAL
EQUATION :
Anode (Oxidation)
CH 3OH + 6OH − →5H2O + 6 e −
+ C O 2
Cathode (Reduction)
3/ 2 O 2 + 3H2O + 6 e − → 6OH-
Overall reaction
C H 3 O H + 3/ 2 O 2 → 2 H 2 O
+ C O2

16. 1. Alkaline fuel cells (AFCs) were one of the first fuel cell technologies
developed, and they were the first type widely used in the U.S. space
program to produce electrical energy and water on-board spacecraft.
2. These fuel cells use a solution of potassium hydroxide in water as
the electrolyte and can use a variety of non-precious metals as a
catalyst at the anode and cathode.
3. A key challenge for this fuel cell type is that it is susceptible to
poisoning by carbon dioxide (CO2).
4. The operating temperature of AFCs is about 70°C and their power
output is 10-100 kW.
5. They have been widely used for space and defense applications,
where pure hydrogen is used.
6. Their excessive cost and sensitivity to CO2 , have restricted their
research and development, no matter their high efficiency and power
density.

17.  AFC
Electro chemical
Equation:
Anode: H2 + 2(OH)- 
2H2O + 2 e-
Cathode: ½ O2 + HO2 +
2e-  2(OH)-
Over all Cell Reaction:
H2 + ½ O2 + CO2  H2O
Diagram of an Alkaline Fuel Cell.
1:Hydrogen 2:Electron flow 3:Load 4:Oxygen
5:Cathode 6:Electrolyte 7:Anode 8:Water
9:Hydroxyl Ions

18. 1. Phosphoric acid fuel cells (PAFCs) use liquid phosphoric
acid as an electrolyte—the acid is contained in a Teflon-
bonded silicon carbide matrix—and porous carbon
electrodes containing a platinum catalyst.
2. The PAFC is considered the "first generation" of modern
fuel cells.
3. PAFCs have an operating temperature of 200 °C. The power
output varies from 200 kW to 20 MW.
4. The main disadvantage is that it has no self-starting
capability, because at lower temperatures (40-50 °C)
freezing of concentrated Phosphoric Acid occurs.
5. PAFCs are more than 85% efficient when used for the co-
generation of electricity and heat but they are less efficient
at generating electricity alone (37%–42%).
6. PAFCs are also less powerful than other fuel cells, given the
same weight and volume. As a result, these fuel cells are
typically large and heavy. PAFCs are also expensive.

19.  PAFC
Electro Chemical
Equation :
Anode reaction:
2H2(g) → 4H+ + 4e‾
Cathode reaction:
O2(g) + 4H+ + 4e‾ → 2H2O
Overall cell reaction:
2 H2 + O2 → 2H2O

20. 1. Molten carbonate fuel cells (MCFCs) are currently being
developed for natural gas and coal-based power plants for
electrical utility, industrial, and military applications.
2. MCFCs are high-temperature fuel cells that use an electrolyte
composed of a molten carbonate salt mixture suspended in a
porous, chemically inert ceramic lithium aluminum oxide
matrix.
3. As they operate at high temperatures of 650°C (roughly
1,200°F), non-precious metals can be used as catalysts at the
anode and cathode, reducing costs.
4. Molten carbonate fuel cells, when coupled with a turbine, can
reach efficiencies approaching 65%, considerably higher than
the 37%–42% efficiencies of a phosphoric acid fuel cell plant.
5. When the waste heat is captured and used, overall fuel
efficiencies can be over 85%.
6 The primary disadvantage of current MCFC technology is
durability. The high temperatures at which these cells operate
and the corrosive electrolyte used accelerate component
breakdown and corrosion, decreasing cell life.

21.  MCFC
Electrochemical
Equation:
Anode:
H2 + CO3
2- H2O
+CO2 + 2 e-
Cathode:
½ O2 + CO2 + 2e- 
CO3
2-
Cell:
H2 + ½ O2 + CO2 
H2O + CO2

22. 1. Solid oxide fuel cells (SOFCs) use a hard, non-porous
ceramic compound as the electrolyte.
2. SOFCs are around 60% efficient at converting fuel to
electricity and operate at very high temperatures—as
high as 1,000°C (1,830°F).
3. High-temperature operation removes the need for
precious-metal catalyst, thereby reducing cost.
4. It also allows SOFCs to reform fuels internally, which
enables the use of a variety of fuels and reduces the
cost associated with adding a reformer to the system.
5. In addition, they are not poisoned by carbon
monoxide, which can even be used as fuel. This
property allows SOFCs to use natural gas, biogas, and
gases made from coal.
6. High-temperature operation has disadvantages. It
results in a slow startup and requires significant
thermal shielding to retain heat and protect personnel,
which may be acceptable for utility applications but
not for transportation.

23.  SOFC
Electrochemical
Equation:
Anode:
H2 + O2 H2O + 2 e
-
Cathode:
½ O2 + 2e-  O2-
Cell:
H2 + ½ O2  H2O

24. 1. Reversible fuel cells produce electricity from hydrogen and
oxygen and generate heat and water as byproducts, just like
other fuel cells. However, reversible fuel cell systems can
also use electricity from solar power, wind power, or other
sources to split water into oxygen and hydrogen fuel
through a process called electrolysis.
2. Reversible fuel cells can provide power when needed, but
during times of high power production from other
technologies (such as when high winds lead to an excess of
available wind power), reversible fuel cells can store the
excess energy in the form of hydrogen.
3. This energy storage capability could be a key enabler for
intermittent renewable energy technologies.

25. REVERSIBLE FUEL CELL
CONCEPT :
RFC SYSTEM INTEGRATED
INTO THE HOME :

27. COMPARISON CHART

29.  High Efficiency- when utilizing co-generation, fuel cells can
attain over 80% energy efficiency.
 Good reliability- quality of power provided does not degrade
over time.
 Noise- offers a much more silent and smooth alternative to
conventional energy production.
 Environmentally beneficial- greatly reduces CO2 and
harmful pollutant emissions.
 Size reduction- fuel cells are significantly lighter and more
compact.

30.  Expensive to manufacture due the high cost of catalysts
(platinum).
 Lack of infrastructure to support the distribution of
hydrogen.
 A lot of the currently available fuel cell technology is in
the prototype stage and not yet validated.
 Hydrogen is expensive to produce and not widely
available .