Fuel Cells

Full Notes:

What Is a Fuel Cell?

A fuel cell is an electrochemical device that converts fuel into electrical energy via a redox reaction. Unlike a combustion engine, it does not burn the fuel but instead allows the electrons to flow through a circuit, generating electricity.

Key Features of Fuel Cells

• Reactants: fuel (e.g., hydrogen or methanol) and oxygen.
• Products: typically water and carbon dioxide (for methanol fuel).
• Redox reactions occur at the electrodes.
• No combustion — energy is released electrically, not as heat.

Advantages of Fuel Cells

• High efficiency: directly converts chemical to electrical energy.
• Low emissions: hydrogen fuel cells produce only water.
• Quiet and reliable: no moving parts.

Limitations of Fuel Cells

• Hydrogen storage and transport can be challenging.
• Methanol produces CO₂, though less than fossil fuels.
• Fuel cells can be expensive and may have limited lifespan.

Hydrogen Fuel Cell (Acidic Conditions)

Hydrogen is oxidized at the anode and oxygen is reduced at the cathode.

• Anode (oxidation): H₂ → 2H⁺ + 2e⁻
• Cathode (reduction): O₂ + 4H⁺ + 4e⁻ → 2H₂O
• Overall reaction: 2H₂ + O₂ → 2H₂O

Clean reaction as only water is produced. Used in electric vehicles and space technology.

Methanol Fuel Cell (Direct Methanol Fuel Cell)

Methanol is oxidized to carbon dioxide (CO₂) at the anode and oxygen is reduced at the cathode.

• Anode (oxidation): CH₃OH + H₂O → CO₂ + 6H⁺ + 6e⁻
• Cathode (reduction): 1.5O₂ + 6H⁺ + 6e⁻ → 3H₂O
• Overall reaction: CH₃OH + 1.5O₂ → CO₂ + 2H₂O

Methanol is easier to handle and store than hydrogen. Used in portable electronics and experimental vehicles.

Summary

• Fuel cells use redox reactions of fuels and oxygen to produce electricity.
• Hydrogen fuel cells produce only water, while methanol cells also produce CO₂.
• They are efficient, clean, and reliable but face challenges with cost and fuel storage.
• Unlike primary cells, fuel cells work continuously with a supply of reactants.