How efficient can fuel cells be when converting fuel into useful energy?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Diagram of a proton exchange membrane (PEM) fuel cell showing labeled layers, including flow field plates, electrodes, and the proton exchange membrane, with arrows indicating hydrogen and oxygen inputs, electricity generation, and water and heat as outputs. — fuel cell Proton exchange membrane (PEM) fuel cell
The proton exchange membrane is one of the most advanced fuel cell designs. Hydrogen gas under pressure is forced through a catalyst, typically made of platinum, on the anode (negative) side of the fuel cell. At this catalyst, electrons are stripped from the hydrogen atoms and carried by an external electric circuit to the cathode (positive) side. The positively charged hydrogen ions (protons) then pass through the proton exchange membrane to the catalyst on the cathode side, where they react with oxygen and the electrons from the electric circuit to form water vapour (H₂O) and heat. The electric circuit is used to do work, such as power a motor.

Fuel cells are inherently high-efficiency devices because they convert chemical energy directly into electrical energy, bypassing the thermal limitations of combustion-based systems. While an internal-combustion engine is typically limited to efficiencies of 40 percent or less, fuel cells can convert fuel into useful energy at efficiencies as high as 60 percent.1

This superior efficiency means that fuel cells require less fuel and smaller storage containers to meet a specific energy demand, making them particularly advantageous for applications where fuel supply is costly or logistically difficult, such as in space missions.1