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Proton exchange membrane fuel cell

Short answer

In a PEMFC, hydrogen at the anode is split (H2 -> 2H+ + 2e-) by platinum; protons migrate through the polymer membrane, electrons flow through external load. At the cathode, 0.5 O2 + 2H+ + 2e- -> H2O. Operates at 60–80°C, ~0.6–0.7 V per cell, requires pure hydrogen and platinum catalyst.

How does a Proton Exchange Membrane Fuel Cell (PEMFC) work?

A Proton Exchange Membrane Fuel Cell (PEMFC), also called polymer electrolyte membrane fuel cell, is a low-temperature (60–80 °C) fuel cell that converts the chemical energy of hydrogen and oxygen into electricity, heat and water. Its electrolyte is a solid polymer membrane (for example Nafion) that conducts protons.

Construction

  • Membrane (PEM): thin polymer sheet, conducts H⁺ ions only, and must be kept moist.
  • Catalyst layers: platinum on carbon on each side.
  • Gas diffusion layers and bipolar plates with flow channels to supply gases and collect current.
  • Many cells are stacked in series.
 H2 -> [Anode|  PEM  |Cathode] <- O2/air
        Pt      H+ ->      Pt
          \__ e- -> load __/
 Exhaust: H2O + heat

Working

  1. Hydrogen enters the anode side; platinum splits it: Anode: H₂ → 2H⁺ + 2e⁻
  2. Protons pass through the membrane to the cathode; electrons cannot, and take the external circuit, producing current.
  3. At the cathode, oxygen, protons and electrons combine to form water: Cathode: ½O₂ + 2H⁺ + 2e⁻ → H₂O
  4. Overall: H₂ + ½O₂ → H₂O (+ electricity and heat). Cell voltage is about 0.6–0.7 V in use (1.23 V theoretical).

Features

  • Efficiency 40–60%, fast start-up, compact and quiet.
  • Used in cars, buses, backup power and portable power.
  • Needs pure hydrogen (CO poisons platinum) and costly platinum, with water management of the membrane.

✓ Answer checked by Claude Opus 5.5 (high effort)

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