U.S. Department of Energy - Energy Efficiency and Renewable Energy

Fuel Cell Technologies Office – Fuel Cells

Basics

Photo of a fuel cell stack

A fuel cell uses the chemical energy of hydrogen to cleanly and efficiently produce electricity with water and heat as byproducts. (How much water?) Fuel cells are unique in terms of the variety of their potential applications; they can provide energy for systems as large as a utility power station and as small as a laptop computer.

Fuel cells have several benefits over conventional combustion-based technologies currently used in many power plants and passenger vehicles. They emit no emissions at the point of operation, including greenhouse gases and air pollutants that create smog and cause health problems. On a life-cycle basis, if pure hydrogen is used as a fuel, fuel cells emit only heat and water as byproducts.

How Does a Fuel Cell Work?

A fuel cell is a device that uses a fuel and oxygen to create electricity by an electrochemical process. A single fuel cell consists of an electrolyte and two catalyst-coated electrodes (a porous anode and cathode). While there are different fuel cell types, all fuel cells work similarly:

  • A fuel (such as hydrogen) is fed to the anode where a catalyst separates hydrogen's negatively charged electrons from positively charged ions (protons).

  • At the cathode, oxygen combines with electrons and, in some cases, with species such as protons or water, resulting in water or hydroxide ions, respectively.

  • For polymer electrolyte membrane and phosphoric acid fuel cells, protons move through the electrolyte to the cathode to combine with oxygen and electrons, producing water and heat.

  • For alkaline, molten carbonate, and solid oxide fuel cells, negative ions travel through the electrolyte to the anode where they combine with hydrogen to generate water and electrons.

  • The electrons from the anode cannot pass through the electrolyte to the positively charged cathode; they must travel around it via an electrical circuit to reach the other side of the cell. This movement of electrons is an electrical current.

View our fuel cell animation to see this process in action.

For more technology basics information, visit our Education section.