Fuel cell

A fuel cell is an electrochemical device that converts the chemical energy of a fuel, most often hydrogen, directly into electricity. When hydrogen is the fuel, the only products are electricity, water and heat. A fuel cell resembles a battery, but it does not run down or need recharging as long as fuel keeps flowing in.

History of the fuel cell

In 1800 the British scientists William Nicholson and Anthony Carlisle described splitting water into hydrogen and oxygen with electricity. In 1839 the Welsh scientist and jurist William Robert Grove reversed that process. He placed two platinum electrodes in separate glass cylinders, one filled with hydrogen and one with oxygen, and immersed them in dilute sulfuric acid. The cell produced a small voltage, so he linked several in a series, and he called the device a gas battery. It is regarded as the first fuel cell.

In 1889 the chemist Ludwig Mond and his assistant Carl Langer built a hydrogen-oxygen cell with thin, perforated platinum electrodes. They struggled with liquid electrolytes and soaked a porous material in the electrolyte instead. The best-known early use came in spaceflight. Francis Thomas Bacon designed an alkaline hydrogen-oxygen cell, and a version of it powered the Apollo missions.

The Smithsonian’s National Air and Space Museum notes that the Apollo Command Module drew its primary electric power from three fuel cells housed in the Service Module. Each combined hydrogen and oxygen to make electricity and water, and the crew drank the water. Each power plant contained 31 cells in series, with a normal output of 563 to 1,420 watts and a maximum of 2,300 watts.

How a fuel cell works

A fuel cell has two electrodes, a negative anode and a positive cathode, with an electrolyte between them. In a hydrogen fuel cell, hydrogen is fed to the anode and air to the cathode. A catalyst at the anode splits hydrogen molecules into protons and electrons. The electrons travel through an external circuit, and that flow is the electric current. The protons move through the electrolyte to the cathode, where they combine with oxygen and the electrons to form water and heat.

One cell produces less than 1 volt, which is too little for most uses, so cells are combined in series into a stack that may contain hundreds of cells. In the polymer electrolyte membrane design, the heart of the cell is a membrane electrode assembly. Its membrane looks like kitchen plastic wrap and passes only positively charged ions while blocking electrons. Catalyst layers of nanometer-sized platinum particles on carbon sit on either side. Bipolar plates stack the cells and carry channels for fuel and air.

Types of fuel cells

Fuel cells are classified mainly by their electrolyte, which sets the temperature, the catalyst and the fuel they need. The U.S. Department of Energy describes several types:

Polymer electrolyte membrane (PEM) cells run at about 80 degrees Celsius, start quickly and suit vehicles, but they need a platinum catalyst that carbon monoxide can poison. Direct methanol cells burn liquid methanol and are used for portable power. Alkaline cells use potassium hydroxide, were among the first developed and were the first widely used in the U.S. space program, but they are sensitive to carbon dioxide.

Phosphoric acid cells were the first to be used commercially and are about 37 to 42 percent efficient at making electricity alone, rising above 85 percent when waste heat is also used. Molten carbonate cells run at about 650 degrees Celsius and can approach 65 percent efficiency when coupled with a turbine, but corrosion shortens their life. Solid oxide cells use a ceramic electrolyte, reach about 60 percent efficiency, and operate at up to 1,000 degrees Celsius.

Applications of fuel cells

Fuel cells can power systems as large as a utility station and as small as a laptop. PEM cells are used mainly in transportation, including cars, buses and heavy-duty trucks, and in some stationary roles. Phosphoric acid cells serve mostly as stationary generators, and a few have powered city buses. Direct methanol cells supply phones and laptops. The Department of Energy also lists long-term storage for the electricity grid, using reversible systems, as an application. Fuel cell cars and trucks compete with the battery electric vehicle.

Fuel cell vs. battery and combustion engine

A battery holds its reactants inside and runs down as they are used up. A fuel cell is fed from outside, so it keeps working while fuel is supplied. The Department of Energy also compares fuel cells with combustion, noting that combustion-based power plants typically run at around 33 percent efficiency, below the 37 to 42 percent of a phosphoric acid fuel cell plant making electricity alone and the 60 percent or more possible with other designs. Because a fuel cell has no combustion step, it also avoids many of the pollutants that burning fuel produces. Lithium-ion batteries, covered in a separate entry on the lithium-ion battery, store electricity instead of generating it from a fuel, so the two technologies often serve different roles.

Advantages and disadvantages of fuel cells

Fuel cells convert fuel directly to electricity at efficiencies that can exceed 60 percent. A hydrogen fuel cell emits only water where it operates, with no air pollutants that cause smog. With few moving parts, fuel cells are quiet.

The drawbacks are mostly about cost, durability and the fuel. Platinum catalysts raise the price, and the Department of Energy lists corrosion and short cell life as the main obstacle for molten carbonate designs, which now last about 40,000 hours, or roughly five years. Hydrogen has the highest energy per mass of any fuel, but because it is so light it holds little energy by volume. Gas storage typically needs tanks at 350 to 700 bar, and liquid storage needs cryogenic temperatures, since hydrogen boils at minus 252.8 degrees Celsius.

The emissions of the whole system also depend on where the hydrogen comes from. It can be released from natural gas, coal or biomass by heat and chemical reactions, or made by splitting water with electricity in an electrolyzer. The clean operation of the cell itself therefore does not settle the question of the fuel’s overall footprint.

Editorially reviewed by Specialty Digest Editorial TeamLast reviewed November 4, 2026Researched and drafted with AI assistanceReport an issue