Fuel Cell – IGCSE Chemistry Definition
IGCSE Chemistry definition of fuel cell: a device producing electricity from a fuel (e.g. hydrogen) and oxygen without combustion. Covers advantages and the hydrogen fuel cell.
Published by IGCSEChemistry.com.my
Chemistry teaching team: K. S. Tan (15+ years teaching IGCSE Chemistry) and Ms Yash (10+ years teaching IGCSE Chemistry) and Ms Kartini (15+ years teaching IGCSE Chemistry).
Mapped to Cambridge IGCSE Chemistry 0620 (2026–2028). Last updated 2026-08-19.
A fuel cell is a device that produces electricity directly from a chemical reaction between a fuel and oxygen, without burning the fuel. The hydrogen fuel cell is the main example on the 0620 syllabus and is tested as a Supplement topic on Papers 2 and 4, often in the context of alternative energy and environmental chemistry.
The 0620 definition
A fuel cell is an electrochemical device that converts the chemical energy of a fuel (such as hydrogen) and an oxidant (oxygen) directly into electrical energy. Unlike a battery, it does not run down — it continues to produce electricity as long as fuel and oxygen are supplied.
The hydrogen fuel cell
How it works
- Hydrogen gas (H₂) is supplied to the anode
- At the anode, hydrogen is oxidised: 2H₂ → 4H⁺ + 4e⁻
- Electrons flow through the external circuit (this is the electrical current)
- At the cathode, oxygen is reduced: O₂ + 4H⁺ + 4e⁻ → 2H₂O
- Overall reaction: 2H₂ + O₂ → 2H₂O
The only product is water — no carbon dioxide, no pollutants.
Advantages and disadvantages
| Advantages | Disadvantages |
|---|---|
| Only product is water — no CO₂ emissions during use | Hydrogen is difficult and expensive to store (highly flammable, low density, needs high pressure or very low temperature) |
| More efficient than combustion engines | Hydrogen production may use fossil fuels (unless from renewable electrolysis) |
| Continuous operation as long as fuel is supplied | Fuel cells are currently expensive to manufacture |
| Quiet operation | Infrastructure for hydrogen refuelling is limited |
Fuel cells vs batteries
| Feature | Fuel cell | Battery |
|---|---|---|
| Fuel supply | External — continuous feed | Internal — chemicals stored inside |
| Duration | As long as fuel is provided | Runs down when chemicals are used up |
| Products | Water (for hydrogen fuel cell) | Various chemical waste |
| Recharging | Not needed — just add more fuel | Rechargeable batteries need electricity to reverse the reaction |
Worked exam question
A hydrogen fuel cell is used to power a car. (a) Write the overall equation for the reaction in the fuel cell. (1) (b) State one advantage and one disadvantage of using a hydrogen fuel cell compared to a petrol engine. (2) (c) Explain why hydrogen fuel cells are sometimes described as “not completely pollution-free.” (1)
Mark scheme
(a) 2H₂ + O₂ → 2H₂O [1]
(b) Advantage: no carbon dioxide / no pollutant gases produced (only water) [1]; Disadvantage: hydrogen is difficult/expensive to store / highly flammable / limited refuelling stations [1]
(c) The production of hydrogen (e.g. by electrolysis) may require electricity generated from fossil fuels, which produces CO₂ [1]
Common exam mistakes
- Saying fuel cells produce no pollution at all. The fuel cell itself produces only water, but producing the hydrogen fuel may involve fossil fuels, so the overall process may not be pollution-free.
- Confusing fuel cells with electrolysis. Electrolysis uses electricity to decompose a compound. A fuel cell produces electricity from a chemical reaction. They are essentially the reverse of each other.
- Forgetting to balance the overall equation. 2H₂ + O₂ → 2H₂O requires the 2 in front of H₂ and H₂O.
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