A fuel cell is an electrochemical device that converts the chemical energy of a fuel directly into electrical energy through a redox reaction. Unlike conventional batteries, fuel cells do not run down as long as fuel and oxidant are supplied. They are essential in IB Chemistry Topic 9 (Redox Processes) because they demonstrate practical applications of galvanic cells, electron flow, and redox chemistry on an industrial scale. Fuel cells also highlight sustainability, efficiency, and modern energy technologies.
What Is a Fuel Cell?
A fuel cell is an electrochemical cell that continuously converts the energy of a supplied fuel (often hydrogen) and an oxidant (usually oxygen) into electricity through spontaneous redox reactions.
Key features:
- Works like a galvanic cell
- Produces electricity continuously
- Requires constant input of reactants
- Emits minimal pollutants
- Highly efficient
Fuel cells are clean, reliable, and capable of powering vehicles, buildings, and portable devices.
How a Fuel Cell Works
A typical fuel cell contains:
- Anode (oxidation site)
- Cathode (reduction site)
- Electrolyte to carry ions
- Catalyst (often platinum)
- External circuit for electron flow
Fuel is supplied to the anode, and oxygen is supplied to the cathode.
1. Oxidation at the anode
Hydrogen gas is a common fuel.
Anode reaction:
H₂ → 2H⁺ + 2e⁻
Hydrogen molecules split into:
- Protons that move through the electrolyte
- Electrons that travel through the external circuit
2. Electron flow produces electricity
Electrons released at the anode flow through the external circuit to the cathode, generating usable electrical energy.
3. Reduction at the cathode
Oxygen undergoes reduction:
O₂ + 4H⁺ + 4e⁻ → 2H₂O
4. Water is produced
The only product in a hydrogen–oxygen fuel cell is water, making it environmentally friendly.
Overall Reaction of a Hydrogen Fuel Cell
Combine the anode and cathode equations:
2H₂ + O₂ → 2H₂O
This is the classic fuel cell reaction and is spontaneous.
Because it is a redox reaction, the fuel cell behaves like a galvanic cell.
Types of Fuel Cells
IB Chemistry focuses mainly on hydrogen fuel cells, but there are several types:
1. PEM (Proton Exchange Membrane) Fuel Cells
- Most common
- Use polymer electrolyte membrane
- Operate at moderate temperatures
2. Alkaline Fuel Cells (AFCs)
- Use KOH electrolyte
- High efficiency
- Used in space missions
3. Solid Oxide Fuel Cells (SOFCs)
- Use ceramic electrolytes
- High-temperature operation
- Suitable for large-scale power generation
4. Molten Carbonate Fuel Cells (MCFCs)
- Operate at very high temperatures
- Industrial applications
Hydrogen fuel cells are favored for IB-level study due to their simplicity and clean operation.
Advantages of Fuel Cells
Fuel cells offer several important benefits:
1. High efficiency
They convert chemical energy directly into electrical energy without combustion.
2. Clean emissions
Hydrogen fuel cells produce only water as a byproduct.
3. Continuous operation
Unlike batteries, fuel cells do not need recharging—just refueling.
4. Quiet and reliable
Few moving parts mean less noise and mechanical wear.
5. Sustainable potential
They can use hydrogen from renewable sources like electrolysis powered by solar energy.
Limitations of Fuel Cells
Despite their advantages, there are challenges:
1. Hydrogen storage
Hydrogen must be compressed or liquefied, which is difficult and costly.
2. Production of hydrogen
Most hydrogen today is made from fossil fuels, though renewable methods exist.
3. Catalyst cost
Platinum catalysts are expensive.
4. Durability issues
PEM membranes and catalysts degrade over time.
5. Infrastructure
Hydrogen fueling stations are limited.
These issues slow widespread adoption, but research continues rapidly.
Fuel Cells vs Batteries
Feature Fuel Cell Battery Reactants Supplied continuously Stored internally Operation time Unlimited with fuel Limited by charge Products Often water Heat + chemical byproducts Use case Vehicles, power plants Phones, laptops, cars (EVs)
Fuel cells excel in long-duration energy applications.
Common IB Misunderstandings
“Fuel cells store energy.”
No—they convert incoming fuel into electricity.
“Fuel cells burn hydrogen.”
They do not burn; they use redox chemistry.
“Fuel cells and batteries are identical.”
Fuel cells require continuous fuel; batteries do not.
“Fuel cells always produce CO₂.”
Hydrogen fuel cells produce no CO₂.
FAQs
Why are fuel cells more efficient than combustion engines?
They avoid the energy losses from heat and mechanical steps.
Can fuel cells power cars?
Yes—many hydrogen-powered vehicles use PEM fuel cells.
Why do fuel cells need catalysts?
To speed up oxidation and reduction reactions at the electrodes.
Conclusion
A fuel cell is an electrochemical device that converts chemical energy into electrical energy through a spontaneous redox reaction. With continuous fuel supply, high efficiency, and clean emissions, fuel cells are an important technology in sustainable energy and a key concept in IB Chemistry. Understanding their structure and operation helps students connect redox chemistry to real-world applications.
