45. Fuel Cells: Hydrogen-Oxygen Cell

1. Key Definitions

• Fuel Cell: An electrochemical cell that converts the chemical energy of a fuel and oxygen into electrical energy.

• Potential Difference: A difference in charge between the two electrodes that drives the flow of electrons through a circuit.

2. Structure of the Hydrogen-Oxygen Fuel Cell

• Electrolyte: A solution (often potassium hydroxide) that allows ions to move through it.

• Electrodes: Made of porous carbon and contain a catalyst to speed up the reaction.

  • Anode (Negative): On the left side.

  • Cathode (Positive): On the right side.

  • Note: This is the opposite of electrolysis (where the anode is positive and the cathode is negative).

• Inlets: Hydrogen enters the anode compartment; Oxygen enters the cathode compartment.

• Outlet: Water and heat leave through the cathode compartment.

3. How it Works

1. Oxidation at the Anode: Hydrogen gas enters and is oxidized. Each hydrogen atom loses an electron to become a hydrogen ion (H⁺).

2. Movement: The electrons travel through the external wire (generating electricity), while the H⁺ ions move through the electrolyte to the cathode.

3. Reduction at the Cathode: Oxygen gas enters and reacts with the H⁺ ions and the incoming electrons to form water (H₂O).

4. Discharge: The water produced leaves the cell as the only waste product.

4. Chemical Equations

• Anode Half Equation (Oxidation): H₂ → 2H⁺ + 2e⁻

• Cathode Half Equation (Reduction): O₂ + 4H⁺ + 4e⁻ → 2H₂O

• Overall Equation: 2H₂ + O₂ → 2H₂O

5. Evaluation (Pros & Cons)