A fuel cell is an electrochemical device that directly converts chemical energy into electricity. It parts from a reactive fuel (usually hydrogen) and an oxidizer (in many cases oxygen) to produce water, electricity (DC) and heat.
It has several parts:
Electrodes (anode, where the H2 is reduced and cathode, where H+ reacts with O2)
Electrolyte (separate the gases, allowing the passage of H+ ions to the cathode and separate e-)
Bipolar plates (separate the cells, “lead” the gases and evacuate the H2O)
The reactions that take place in each of the electrodes are:
Anode reaction: H2 –>2H+ + 2e- Cathode reaction: ½ O2 + 2H+ + 2e- –> H2O Global reaction: H2 + ½ O2 –> H2O
On the anode side, hydrogen dissociates into protons and electrons. The protons are leaded through the membrane to the cathode, but the electrons are forced to go through an external circuit (producing power) because the membrane is electrically isolated. In the cathode catalyst, oxygen molecules react with electrons (leaded through the external circuit) and protons forming water. In this case, the only waste product is water vapor or liquid water.
FUEL CELLS TYPES
Fuel cells are classified primarily by the kind of electrolyte they use. This determines the kind of chemical reactions that take place in the cell, the kind of catalysts required to enable the reaction, the temperature range in which the cell operates, and the fuel required. These characteristics, in turn, affect the applications for which these cells are most suitable.
There are several types of fuel cells, each with its own advantages, properties and potential applications, as summarized in the following table:
FUEL CELLS APPLICATIONS
Fuel cells comprise a wide variety of applications:
Portable, oriented to small electrical devices, increasingly abundant around us (computers, Smart phones, small appliances).
Stationary systems, after using the hydrogen as storage system it can be used to generate electricity and heat to businesses, hospitals, residential areas and power generators in emergency cases when the main supply fails.
Transport applications, the use of hydrogen as fuel in fuel cells for electric vehicles of all kinds (cars, buses, ships) are contemplated, appearing with increasing frequency, prototypes and test models powered by these technologies. It is expected even marketing these vehicles for the coming years.
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