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Fuel cell and its working

Short answer

A fuel cell is an electrochemical device that converts hydrogen and oxygen directly into electricity, heat, and water. At the anode, H2 splits into H+ and e-; H+ cross the electrolyte while e- flow externally. At the cathode, O2 combines with them to form water. Overall: 2H2 + O2 → 2H2O.

What is a fuel cell? Explain briefly how it works (how does a hydrogen fuel cell function?).

A fuel cell is an electrochemical device that converts the chemical energy of a fuel (usually hydrogen) and an oxidant (oxygen or air) directly into electricity, heat and water, without combustion. It works as long as fuel is supplied, unlike a battery, which stores a fixed amount of energy.

Construction

Two electrodes (anode and cathode) separated by an electrolyte, with a catalyst (platinum) on each electrode.

  H2 in --> [ANODE | ELECTROLYTE | CATHODE] <-- O2/air in
              (-)       H+  ->       (+)
                 \__ e- through load __/
  Output: electricity + water + heat

Working of a hydrogen fuel cell (PEM type)

  1. Hydrogen is fed to the anode. The catalyst splits it into protons and electrons: Anode: 2H₂ → 4H⁺ + 4e⁻
  2. The electrolyte (a proton-exchange membrane) lets only H⁺ pass to the cathode. The electrons cannot pass through the membrane and take the external circuit, producing DC current.
  3. At the cathode, oxygen combines with the protons and returning electrons to form water: Cathode: O₂ + 4H⁺ + 4e⁻ → 2H₂O
  4. Overall: 2H₂ + O₂ → 2H₂O + electricity + heat

One cell gives about 0.6–0.8 V, so many cells are stacked in series to form a stack with higher voltage.

Features

  • Efficiency 40–60% (higher with heat recovery), quiet, no moving parts.
  • Pollution-free at the point of use (only water).
  • Used in vehicles, backup power, space missions and portable devices.

✓ Answer checked by Claude Opus 5.5 (high effort)

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