PEFCs

PEFCs, or proton exchange membrane fuel cells, generate electricity from hydrogen and oxygen using a solid polymer electrolyte membrane that conducts protons. Hydrogen at the anode is oxidized to produce protons and electrons. Electrons flow through an external circuit to the cathode, while protons pass through the membrane to the cathode, where they react with oxygen and electrons to form water and heat. The membrane must stay hydrated, so humidified gas feeds are used. PEFCs consist of a membrane electrode assembly with the polymer membrane, catalyst layers, and gas diffusion layers, between bipolar plates. The stack design enables scalable power for vehicles, stationary power, or portable systems. They operate at low temperatures (about 60-80°C), allowing rapid startup and high power density; water is the main byproduct.

Electrical efficiency at the cell level typically ranges from 40% to 60%, with higher system efficiency when excess heat is recovered in combined heat and power. Advantages include quiet operation, fast response, and low emissions when hydrogen is clean. Challenges include high material costs (platinum catalysts), durability under thermal cycling, water and humidity management, and sensitivity to impurities such as CO. Materials research targets reduced platinum loading, more durable membranes, and cheaper catalysts. Applications include transportation (fuel-cell electric vehicles), stationary and backup power. The outlook emphasizes continued cost reduction and integration with renewable hydrogen, improving robustness for wide deployment.