How can We Use Water to run Cars?

Huge amounts of polluting gases are being released into the earth’s atmosphere by the large scale burning of fossil fuels or natural fuels found under the earth. These gases are the main culprits behind the phenomenon of global warming and other climatic changes.

In order to find cleaner fuels, scientists around the world are trying to find a fuel or source of energy which produces little or no pollution on being burnt.

Quite amazingly, there is a way to run a car that gives out nothing but water. The secret is a gas called hydrogen.

The fuel cell

Water is made out of two gases, hydrogen and oxygen, joined together. If you pass electricity through water, you can split it back into those two gases. But that splitting needs energy — it does not come free. Scientists hope to do it using clean power, like solar.

The hydrogen is then stored in the car, which carries a gadget called the fuel cell. Take a close look at any cell, and you will see it has two sides. One is marked ‘+’ (the anode) and the other ‘-’ (the cathode). A fuel cell is like that. Hydrogen is passed in at one side and oxygen from the air at the other. With the help of a catalyst (something that enables a chemical reaction), the hydrogen gives up a stream of electrons. This stream of electrons is nothing but electricity, and it runs the car’s motor.

How can We Use Water to run Cars? [Illustration by Shinod AP]

Here is the clever part. When the hydrogen reunites with oxygen, it forms water all over again. So the only thing coming out of the car is pure clean water — no smoke, no polluting gases.

A fuel-cell car runs on hydrogen and gives back water. Hydrogen is a clean way to carry energy, but making it still takes energy first. That is why scientists are working hard to make it cheap and green. Real hydrogen cars are already on the roads, like the Toyota Mirai and the Hyundai Nexo. But they are still costly, and there are few places to refuel, so it will take time before they are everywhere.

Editor’s note: This story was updated in 2026 to explain hydrogen fuel cells more clearly — water itself is not a fuel; hydrogen is, and it has to be made using energy.