A hydrogen fuel cell uses hydrogen and oxygen to produce a potential difference. Describe how a hydrogen fuel cell works and give one advantage of using a hydrogen fuel cell compared with a non-rechargeable alkaline battery.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
A hydrogen fuel cell supplies hydrogen gas to the anode where it is oxidised to protons and electrons. The protons pass through the electrolyte to the cathode, while the electrons travel through an external circuit, giving a potential difference. At the cathode the protons, electrons and oxygen from the air combine to form water.
One advantage is that the cell can keep producing electricity as long as hydrogen and oxygen are supplied, so it does not run out like a non‑rechargeable alkaline battery and only produces water as a by‑product.
One advantage is that the cell can keep producing electricity as long as hydrogen and oxygen are supplied, so it does not run out like a non‑rechargeable alkaline battery and only produces water as a by‑product.
Examiner tips
- Use the words ‘oxidised’, ‘electrolyte’, ‘external circuit’ and ‘water’ to show understanding of the cell process.
- Mention that the cell can operate continuously and that water is the only waste product to gain the advantage mark.
Common mistakes
- Mixing up the roles of anode and cathode, or saying the hydrogen is reduced instead of oxidised.
- Failing to state that the cell can run continuously or that water is the only by‑product.
Mark scheme (4 marks)
- Hydrogen (fuel) is supplied from an external source / hydrogen is oxidised electrochemically within the fuel cell
- Oxygen (or air) is also supplied from an external source
- The reaction between hydrogen and oxygen produces a potential difference (electricity)
- One advantage: the fuel cell can operate continuously as long as fuel is supplied / does not run out like a non-rechargeable battery / only produces water as a by-product (no harmful waste / more environmentally friendly)
Key terms in this question
fuel cell · potential difference · non-rechargeable · alkaline battery
Related
- All AQA GCSE Chemistry (8462) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
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