The document discusses fuel cells, which are devices that convert chemical energy from fuels like hydrogen into electricity with minimal air pollution emissions. It details various types of fuel cells, particularly the polymer electrolyte membrane fuel cell (PEMFC), including their reactions, thermodynamic principles, and efficiency. The document also outlines applications of fuel cells in power systems and portable electronics.

1. Seminar: Fuel cells
Class: Materials Science Engineering
Teacher : Phạ m Ngọ c Diệ u Quỳnh
Student: Hoàng Văn Tiế n
Hanoi 6-6-2012

3. What is fuel cell ?
-A fuel cell is a device that converts the
chemical energy from a fuel into electricity
through a chemical reaction with oxygen or
another oxidizing agent.
-Fuels: +Hydrogen ( the most common fuel.)
+Hydrocarbons : natural gas,alcohols ..…..
-Air pollution emissions almost “equal zero”.

4. design
A block diagram of a fuel cell

5. clasification
Based on types of electrolyte:
 polymer electrolyte membrand fuel cell
 alkaline fuel cell
 phosphoric acid fuel cell
 molten carbonat fuel cell
 solid oxides fuel cell

6. Case study: polymer electrolite membran fuel cell (PEMFC)

8. reactions
-Anode : H2 --- 2H+ +2e-
*E =0 VSHE (standard hidrogen electrode)
-Cathode: 1/2O2 +2H+ +2e- --->H2O
*E0=1.229 VSHE
Overall reaction: H2 +1/2O2 -- H2O
*E0=1.229 VSHE

9. Electrochemical Aspects
-The standard free energy change of the fuel cell reaction is
indicated by the equation :
∆G = –nFE-
The value of ∆G corresponding :
*∆G= −229 kJ/mol,
*n = 2,
*F = 96500 C/g.mole electron,
⇒ E = 1.229 V.
The enthalpy change ∆H for a fuel cell reaction:
∆H = –nFEt
-Nernst equation :
E = E0+ (RT/2F) ln [PH2/PH2O] + (RT/2F) ln [PO2 1/2]

10. Thermodynamic Principles
-The maximum electrical work obtainable in a fuel cell
operating at constant temperature and pressure is
given by the change in the Gibbs free energy of the
electrochemical reaction:
W = ∆G = –nFE
-The difference between ∆G and ∆H is proportional to
the change in entropy ∆S:
∆G = ∆H – T∆S

11.  The effect of temperature and pressure on
the cell potential:
− ∆V: change in volume,
∆S : entropy change,
E :cell poten-tial,
T:temperature,
P :reactant gas pressure,
n :the number of electrons transferred,
F: Faraday’s constant.

12. Fuel Cell Efficiency
 the efficiency :
 The ideal efficiency of a fuel cell operating
irreversibly:
 The thermal efficiency of an ideal fuel cell operating
reversibly on pure hydrogen and oxygen at standard
conditions:

13.  The thermal efficiency of the fuel cell ( in
terms of the actual cell voltage):
 Based on the higher heating value of
hydrogen:

14. Advantages and
disadvantages

15. Applicaions
-Power:
Type 212 submarine with fuel cell propulsion of the German Navy in dry dock

18. Other applications
 Providing power for base stations or cell sites
 Distributed generation
 An uninterrupted power supply (UPS)
 Base load power plants
 Fuel cell APU for Refuse Collection Vehicle
 Hybrid vehicles, pairing the fuel cell with either an ICE or a battery.
 Notebook computers for applications where AC charging may not be
readily available.
 Portable charging docks for small electronics (e.g. a belt clip that
charges your cell phones or PDA).
 Smartphones, laptops and tablets.
 Small heating appliances.

19. References
 www.wikipedia.org
 Nice, Karim and Strickland,Jonathan. "How
Fuel Cells Work: Polymer Exchange
Membrane Fuel Cells". How Stuff Works,
accessed August 4, 2011
 www.fuelcells.org
 www.fuelcellenergy.com
 onlinelibrary.wiley.com