ELECTROCHEMISTRY(fuel cells)

fuel cells(rechargeable)

fuel cells are means by which chemical energy can be converted into electrical energy. when gaseous fuels such as hydrogen and oxygen are allowed to undergo a reaction, electrical energy can be obtained.

use of fuel cells

in space vehicles

electrodes

the electrodes are hollow tubes made of porous compressed carbon impregnated with platinum, which acts as a catalyst. at the electrodes, hydrogen is oxidized to water and oxygen is reduced to hydroxide ions.

electrolyte

the electrolyte is koh.

reactions

[H + 2OH arrow 2H2O + 2e ] x 2 anode

O + 2H2O + 4e arrow 4OH cathode

2H + O arrow 2H O overall reaction

operated at high temperature

This fuel cell is operated at a high temperature so that the water formed as a product of the cell reaction evaporates and may be condensed and used as drinking water for an astronaut. A number of these cells are usually connected together so that several kilowatts of power can be generated.

advantages

The fuel cell produce electricity and pure water during space lights. Fuel cell are light, portable and sources of electricity. Many fuel cells do not produce pollutants. Fuel cells are very efficient. They convert about 75% of fuels bond energy into electricity.

other cell reactions

2NH + 3/2 O arrow N + 3H O

N H + O arrow N + 2H O

CH + 2O arrow CO + 2H O