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Ask a scientist
In this feature, NRC scientists answer questions about biology, chemistry, physics, astronomy and other science topics.
Lars Rose is a visiting worker from the Department of Materials Engineering at the University of British Columbia.
Location: NRC Institute for Fuel Cell Innovation, Vancouver, British Columbia.
Research: Development of solid oxide fuel cells that operate at relatively “low” temperatures of up to 600°C, in order to reduce the cost and increase the durability of the cells.
Question: What is a fuel cell and how does it work?
Answer: A fuel cell is a clean energy technology that converts a fuel into an electric current. Unlike disposable or rechargeable batteries, fuel cells are replenished by an external fuel source and can therefore operate continuously without significant downtime. Fuel cells are also lighter and less toxic than batteries since they do not contain heavy metals, like lead, that are found in some batteries.
There are five main types of fuel cells, of which three are commercially produced on a large scale: proton exchange membrane (PEM) or low temperature fuel cells (so called because they operate between room temperature and 140°C), molten carbonate fuel cells (MCFCs), which operate at approximately 600°C, and solid oxide fuel cells (SOFCs), which operate at up to 1000°C.
Did you know?
NASA uses fuel cells aboard spacecraft to produce electricity. The “exhaust” is clean enough to be used as drinking water for the crew.
Fuel cells can power virtually any device that requires energy by replacing a battery or motor. Today, you can find fuel cells in laptops, mobile phones and MP3 players. Fuel cells are also being used to power forklifts, boats and buses, as well as the electronics aboard airplanes.
How a fuel cell works
Fuel cells have three main components: 1) an electrolyte, which is sandwiched between 2) an anode (positive electrode) and 3) a cathode (negative electrode). On the cathode side, you supply air (which contains oxygen) and, on the anode side, a fuel source. Depending on the fuel cell, this fuel could be virtually anything. PEM fuel cells mostly run on hydrogen or methanol. But solid oxide fuel cells can run on hydrogen, gasoline, methane, butane, ethylene glycol, carbon monoxide — even “garbage” such as old rubber tires. Molten carbonate fuel cells also run on many different types of fuel, but require carbon dioxide to operate.
If you combine oxygen and fuel in the presence of an ignition source, the typical result is a fire. This happens in engines. But in a fuel cell, an electrochemical reaction occurs. To keep the fuel and oxygen from directly contacting each other, the electrolyte acts as a separating wall. You slowly “trickle” specific ions through the wall to produce electricity. (For PEMs, you trickle protons; in MCFCs, you trickle carbonate ions; and in SOFCs, you trickle oxygen ions.) In the case of hydrogen fuel, the only by-product is water, which makes hydrogen the cleanest fuel available. If you use a fuel other than hydrogen, carbon dioxide is also produced — although much less than would be produced if you burned the fuel instead. One of the main advantages of fuel cells is that they can convert any fuel into electricity very efficiently. 
Did you know?
Fuel cells are being developed to replace nuclear power stations and coal-fired power plants, and serve as diesel backup generators. These fuel cells can use any fuel to create energy and heat — for example, the toxic exhaust fumes from large-scale car paint-shops, which would otherwise have to be burned and chemically cleaned, or the biogas produced in waste from beer breweries. Breweries often pay high prices to have their waste water treated municipally, but the waste could be used to power and heat their own production plants instead, saving money in the long run and reducing their environmental footprint.
