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# Fuel cell

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a device that converts the chemical energy from a fuel into electricity through a chemical reaction with oxygen or another oxidizing agent - from MSE-HUST k54

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### Fuel cell

1. 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
2. 2. 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”.
3. 3. designA block diagram of a fuel cell
4. 4. clasificationBased on types of electrolyte: polymer electrolyte membrand fuel cell alkaline fuel cell phosphoric acid fuel cell molten carbonat fuel cell solid oxides fuel cell
5. 5. Case study: polymer electrolite membran fuel cell (PEMFC)
6. 6. reactions-Anode : H2 --- 2H+ +2e- *E =0 VSHE (standard hidrogen electrode)-Cathode: 1/2O2 +2H+ +2e- --->H2O *E0=1.229 VSHEOverall reaction: H2 +1/2O2 -- H2O *E0=1.229 VSHE
7. 7. 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]
8. 8. 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
9. 9.  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.
10. 10. 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:
11. 11.  The thermal efficiency of the fuel cell ( in terms of the actual cell voltage): Based on the higher heating value of hydrogen: