Both batteries and fuel cells are electrochemical devices. As such both have a positively charged anodeand a negatively charged cathode and an ion-conducting material called an electrolyte. Fuel cells are classified by their electrolyte material. Electrochemical devices generate electricity without combustion of the fuel and oxidizer, as opposed to what occurs with traditional methods of electricity generation.

Fuel cell construction generally consists of a fuel electrode (anode) and an oxidant electrode (cathode) separated by an ion-conducting membrane. Oxygen passes over one electrode, and hydrogen over the other, generating electricity, water and heat. Fuel cells chemically combine the molecules of a fuel and oxidizer without burning or having to dispense with the inefficiencies and pollution of traditional combustion.

Fuel Cells vs. Traditional Electricity Methods
In traditional methods of generating electricity, the fuel and air are burned, generating a high-temperature gas. In the case of a coal-burning power plant, heat is transferred from this hot gas to high pressure liquid water that is boiled. In the case of a gasoline, diesel or gas turbine engine, the hot gas itself is at high pressure. The high-pressure steam, or hot gas, is expanded in a mechanical device (e.g., cylinder, turbine) and ultimately turns an electrical generator. In a fuel cell, the same basic chemical reactions occur, but generate electricity directly as an electrochemical device and therefore, never goes through the step of being a high-temperature gas through normal burning. This direct conversion of chemical energy to electrical energy is more efficient and generates much less pollutants than traditional methods that rely on combustion.

Which is Better?
As mentioned above, the direct conversion of fuel and air to electricity is much more efficient than internal combustion engines and other methods of generating electricity. Therefore, fuel cells can generate more electricity from the same amount of fuel. Furthermore, by skipping the combustion process that occurs in traditional power-generating methods, the generation of pollutants during the combustion process is avoided. Some of the pollutants that are significantly lower for fuel cells are oxides of nitrogen and unburned hydrocarbons, (which together cause ground-level ozone), and carbon monoxide (a poisonous gas).

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