Uses of Hydrogen as a fuel :
Hydrogen releases large quantities of heat on combustion.
On a mass for mass basis, hydrogen can release more energy than petrol(about three times). Moreover, pollutants will be less than in petrol.
[The only pollutants will be the oxides of dinitrogen. This, of course, can be minimized by injecting a small amount of water into the cylinder to lower the temperature so that the reaction between nitrogen and oxygen may nit take place.]
Energy released on combustion of dihydrogen in liquid state is 285 kJ(/mole) and in gaseous state is 286 kJ(/mole).
A cylinder of compressed hydrogen weighs about 30 times as much as a petrol containing the same amount of energy. Also, hydrogen gas is converted into liquid state by cooling to 20 K.This would require expensive insulated tanks.
Advantage of hydrogen economy is that energy is transmitted in the form of dihydrogen gas and not as electric power.
In 2005, a pilot project using dihydrogen as fuel was launched, for the first time in the history of India.
Nowadays, it is also used in fuel cells for generation of electric power.