How does an alkaline fuel cell work?
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.
Alkaline fuel cells function by utilizing an aqueous solution of potassium hydroxide or sodium hydroxide as an electrolyte.1
The process typically involves the following components and mechanisms:
- Fuel and Oxidizer: Hydrogen gas is generally used as the fuel, while oxygen (or oxygen from air) serves as the oxidizer.1
- Electrodes: These cells employ gas-diffusion electrodes constructed from carbon and a metal, such as nickel. These electrodes keep the fuel gas in controlled contact with the aqueous electrolyte.12
- Operation: The cells operate at temperatures below 100 °C (212 °F). As the chemical reaction proceeds, water is produced as a by-product and must be removed from the system, typically through evaporation from the electrolyte.1
Due to their efficiency, these fuel cells have been utilized in applications such as the U.S. space shuttle orbiters. Their design requires careful engineering to manage the corrosive nature of the hot alkaline electrolyte, which can damage structural seams and certain plastics.1