The following uses for hydrogen are gathered from a number of sources as well as from anecdotal comments. I would be delighted to receive corrections as well as additional referenced uses.
One of hydrogen's isotopes, tritium (3H) is radioactive. Tritium is produced in nuclear reactors and is used in the production of the hydrogen bomb. It is also used as a radioactive agent in making luminous paints and as a tracer isotope.
- commercial fixation of nitrogen from the air in the Haber ammonia process
- hydrogenation of fats and oils
- methanol production, in hydrodealkylation, hydrocracking, and hydrodesulphurization
- rocket fuel
- production of hydrochloric acid
- reduction of metallic ores
- for filling balloons (hydrogen gas much lighter than air; however it ignites easily)
- liquid H2 is important in cryogenics and in the study of superconductivity since its melting point is only just above absolute zero