Overview
This lecture explains how hydrogen oxygen fuel cells work, details their structure and reactions, and discusses their main advantages and disadvantages.
What is a Fuel Cell?
- A fuel cell is an electrochemical cell that converts chemical energy from a fuel and oxygen into electrical energy.
- The most common type is the hydrogen oxygen fuel cell, which generates water and electrical energy from hydrogen and oxygen.
Structure of a Hydrogen Oxygen Fuel Cell
- The cell has a central electrolyte, typically potassium hydroxide, allowing ions to move.
- Two porous carbon electrodes (anode = negative, cathode = positive) with catalysts are placed on either side.
- Hydrogen enters the anode compartment (left); oxygen enters the cathode compartment (right).
- Electrons flow from anode to cathode through an external wire, generating electricity.
- Water and heat exit from the cathode side after the reaction.
How the Fuel Cell Works
- Hydrogen gets oxidized at the anode, losing electrons to form hydrogen ions (H₂ → 2H⁺ + 2e⁻).
- Electrons flow via the wire to the cathode; hydrogen ions travel through the electrolyte.
- At the cathode, oxygen reacts with hydrogen ions and electrons to make water (O₂ + 4H⁺ + 4e⁻ → 2H₂O).
- The movement of electrons through the wire provides usable electrical energy.
Key Reactions and Exam Points
- The cell’s overall reaction: 2H₂ + O₂ → 2H₂O.
- The two half-equations show oxidation at the anode and reduction at the cathode.
- Oxidation means hydrogen atoms lose electrons; this creates a potential difference to drive electron flow.
Pros and Cons of Hydrogen Oxygen Fuel Cells
- Pros: Only produces water as waste, uses abundant reactants, less polluting, lasts longer than batteries, and easier disposal.
- Cons: Hydrogen gas is bulky to store, explosive with air, and hydrogen production often uses fossil fuels.
Key Terms & Definitions
- Electrochemical cell — device converting chemical energy to electrical energy via redox reactions.
- Electrolyte — solution allowing ions to move, completing the circuit.
- Anode — electrode where oxidation occurs (loses electrons).
- Cathode — electrode where reduction occurs (gains electrons).
- Half-equation — shows either oxidation or reduction part of a redox reaction.
Action Items / Next Steps
- Review reaction equations for fuel cells.
- Compare the structure of fuel cells to electrolysis cells.
- Visit the recommended website for questions, flashcards, and exam practice.