Real-World Examples of Anode and Cathode in Devices

Anodes and cathodes are the working heart of countless devices and processes. Here are some common real-world examples, split into discharging (galvanic) and charging (electrolytic) types.

Galvanic Cells (Discharging - Produce Energy)

In these devices, the anode is the negative (`-`) terminal and the cathode is the positive (`+`) terminal.

• Lithium-Ion Battery (in your Phone/Laptop)
  • Anode (`-`): Graphite (carbon), where lithium atoms are stored and oxidized (lose electrons).
  • Cathode (`+`): A lithium metal oxide (like Lithium Cobalt Oxide, LiCoO₂), where lithium ions are accepted and reduced (gain electrons).
• Alkaline Battery (AA, AAA)
  • Anode (`-`): Zinc (Zn) powder.
  • Cathode (`+`): Manganese Dioxide (MnO₂) paste.
• Car Battery (Lead-Acid)
  • Anode (`-`): Porous Lead (Pb) plates.
  • Cathode (`+`): Lead Dioxide (PbO₂) plates.
• Corrosion (Rusting of Iron)
  • Anode: The spot on the iron (Fe) metal where it oxidizes (rusts) to form Fe²⁺.
  • Cathode: A nearby spot on the iron, where oxygen (O₂) and water are reduced to hydroxide (OH⁻).

Electrolytic Cells (Consuming Energy)

In these processes, an external power source is used. The anode is the positive (`+`) terminal and the cathode is the negative (`-`) terminal.

• Recharging a Battery (e.g., your Phone)
  • Anode (`+`): The Lithium Cobalt Oxide (LiCoO₂) - it is forced to oxidize (lose electrons).
  • Cathode (`-`): The Graphite - it is forced to reduce (gain electrons), storing lithium atoms for the next use.
• Electroplating (e.g., Silver-plating a spoon)
  • Anode (`+`): A bar of pure Silver (Ag). It is oxidized, and silver ions (Ag⁺) dissolve into the solution.
  • Cathode (`-`): The Spoon. Silver ions (Ag⁺) from the solution are reduced onto the spoon's surface, forming a silver plate.
• Electrolysis of Water (Producing H₂ and O₂)
  • Anode (`+`): Electrode where water (H₂O) is oxidized to produce Oxygen gas (O₂).
  • Cathode (`-`): Electrode where water (H₂O) is reduced to produce Hydrogen gas (H₂).