Fuel Cells
Definition and meaning of Fuel Cells in chemistry.
Fuel cells are electrochemical devices that generate electricity directly from the reaction between a fuel, typically hydrogen, and an oxidant, typically oxygen, without combustion.
In more detail
In a proton exchange membrane fuel cell, hydrogen gas is oxidized at the anode into protons and electrons. The electrons travel through an external circuit to perform electrical work, while the protons migrate through a solid polymer electrolyte to the cathode, where they recombine with oxygen and the returning electrons to form water. Because this is a direct electrochemical conversion rather than a heat engine, fuel cells are not limited by Carnot efficiency and can achieve higher energy-conversion efficiencies than combustion-based generators. Unlike a battery, a fuel cell does not store its reactants internally; it keeps producing electricity as long as fuel and oxidant are continuously supplied.
Key facts
| Overall reaction | 2H2 + O2 → 2H2O |
|---|---|
| Field | Physical Chemistry |
| Anode half-reaction | H2 → 2H+ + 2e− |
| Cathode half-reaction | O2 + 4H+ + 4e− → 2H2O |
A hydrogen-oxygen proton exchange membrane fuel cell used in fuel-cell electric vehicles carries out the overall reaction 2H2 + O2 → 2H2O, producing electric current along with water and heat as byproducts.
Frequently asked questions
How does a fuel cell differ from a battery?
A fuel cell requires a continuous external supply of fuel and oxidant to generate electricity, whereas a battery stores its reactants internally and stops producing current once they are consumed (unless it is rechargeable).
What is produced when a hydrogen fuel cell operates?
A hydrogen-oxygen fuel cell produces electrical current, water, and heat, with water being the only chemical byproduct, which is why it is considered a clean power source.