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.
Hydrogen is the most common fuel, but hydrocarbons such as natural gas and alcohols like methanol are sometimes used. Fuel cells are differnt from batteries in that they require a constant source of fuel and oxygen/air to sustain the chemical reactions; however, fuel cells can produce electricity continuously for as long as these inputs are supplied.
There are many types of fuel cells, but they all consist of an anode, a cathode and an electrolyte that allows charges to move between the two sides of the fuel cell.
Electrons are drawn from the anode to the cathode through an external circuit, producing direct current electricity.
Fuel cells come in a variety of sizes. Individual fuel cells produce relatively small electrical potentials, about 0.7 volts, so cells are "stacked", or placed in series to increase the voltage and meet the application's requirements.
In addition to electricity, fuel cells produce water, heat and, depending on the fuel source, very small amounts of nitrogen dioxide and other emissions.
The energy efficiency of a fuel cell is generally between 40-60%, or up to 85% efficiency in cogeneration if waste heat is captured for use.
The most important design features in a fuel cell are:
The electrolyte substance. The electrolyte substance usually defines the type of fuel cell. The fuel that is used. The most common fuel is hydrogen. The anode catalyst breaks down the fuel into electrons and ions. The anode catalyst is usually made up of very fine platinum powder. The cathode catalyst turns the ions into the waste chemicals like water or carbon dioxide. The cathode catalyst is often made up of nickel but it can also be a nanomaterial-based catalyst.