Hydrogen–oxygen fuel cells
Hydrogen–oxygen fuel cells
- A fuel cell uses hydrogen and oxygen to make electricity directly.
- The only chemical product is water.
$$2\text{H}_2 + \text{O}_2 \rightarrow 2\text{H}_2\text{O}$$
Practice
The only chemical product of a hydrogen–oxygen fuel cell is:
Hydrogen and oxygen combine to make water only — no polluting gases.
Fuel cell vs petrol engine
| Fuel cell | Petrol engine | |
|---|---|---|
| product | water only | carbon dioxide + pollutants |
| air | clean | adds pollution |
| fuel storage | hydrogen hard/dangerous to store | petrol easy to store |
- Advantages: only product is water (no air pollution); efficient.
- Disadvantages: hydrogen is hard to store/transport; making it may use fossil fuels.
Practice
A key advantage of a fuel cell over a petrol engine is that it:
The fuel cell's only product is water; a petrol engine makes carbon dioxide and pollutants.
Practice
A disadvantage of fuel cells is that hydrogen is hard and dangerous to store.
Hydrogen is flammable and needs high pressure to store, which is a real drawback.
You've got it
Key idea
- a fuel cell: $2\text{H}_2 + \text{O}_2 \rightarrow 2\text{H}_2\text{O}$ — electricity with water as the only product
- + clean and efficient; − hydrogen is hard to store and may be made from fossil fuels
- beats a petrol engine on pollution, loses on fuel storage