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⚡ fuel cell · electrochemistry

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16.13 Fuel cells

Fuel cells provide a method in which chemical energy is converted to electrical energy. These cells use gaseous fuels like hydrogen and oxygen to produce electricity. A fuel cell is composed of two hollow tubes which act as electrodes. They are made of porous compressed carbon saturated with platinum which acts as a catalyst. The electrolyte used in this cell is aqueous potassium hydroxide.

Electron Flow Load Hydrogen Oxygen Hydrogen ions Water Anode Cathode Electrolyte (KOH) 
Electron Flow → Load → then to cathode
Hydrogen → Anode  |  Oxygen → Cathode
Hydrogen ions migrate through electrolyte
Water produced at cathode side

At the anode, hydrogen is oxidized to water:

H₂ + 2OH⁻ → 2H₂O + 2e⁻

At the cathode oxygen is reduced to hydroxide ions:

O₂ + 2H₂O + 4e⁻ → 4OH⁻

Overall reaction:

2H₂ + O₂ → 2H₂O
📝 MEMORY TIP: “Anode Oxidation = lose electrons (H₂ → water) ; Cathode Reduction = gain electrons (O₂ → OH⁻). Remember ‘AOR’ – Anode Oxidation Releases electrons.”

The fuel cell produces electricity and water continuously provided the reactants are continuously supplied. They are very efficient because they convert 75% of the bond energy of fuels to electricity.

Advantages & Disadvantages

✅ 1. Zero emission (only water), no CO₂, NOₓ, SOₓ.
✅ 2. Higher efficiency (≈75%) than fossil fuels.
✅ 3. Less noise pollution.
✅ 4. Hydrogen from renewables (solar/wind) – sustainable.
❌ 1. Very expensive (H₂ production by electrolysis).
❌ 2. Hydrogen highly inflammable → special storage/transport.
❌ 3. Less durable than petrol/diesel engines.
✍️ QUICK CHECK (16.5): Fuel cells and electric motors are less durable than petrol/diesel engines.

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