1. HYDROGEN
Is often seen as an environmentally friendly alternative to fossil fuels.
Some car manufacturers have developed cars that run on hydrogen rather than petrol or diesel.
There are two ways in which hydrogen is used to power cars:
Burning hydrogen directly in the engine. Water is the only product formed when hydrogen burns:
i.e. Hydrogen + Oxygen  Water
2H2 + O2  2H2O
There are no carbon dioxide emissions that could contribute to global warming.
In a hydrogen fuel cell, hydrogen reacts with oxygen without burning. The energy released is used to generate electricity, which is used to drive an electric motor.

2. PROBLEMS WITH HYDROGEN
At the moment, most hydrogen is made by reacting steam with coal or natural gas – both non-renewable resources.
Hydrogen can be made by passing electricity through water
Unfortunately most electricity is generated using coal and other fossil fuels, so pollustion from burning these fuels happens at the power stations.
Pollution therefore still occurs
However, some countries are producing hydrogen using electricity from renewable sources, such as geothermal energy in Iceland.

3. ADVANTAGES AND DISADVANTAGES OF HYDROGEN
Unlike petrol and diesel cars, hydrogen does not generate carbon dioxide when burnt
Hydrogen fuel cell are very efficient
DISADVANTAGES
Few filling stations sell hydrogen
Hydrogen must be compressed and liquefied, and then stored in tough, insulated fuel tanks
Atmospheric pollution may be generated during the production of hydrogen
Hydrogen fuel cells do not work at very low temperatures, and they may also require a platinum catalyst, which is very expensive and is prone to contamination by impurities.