Write down two forms of hydrogen which are used as a energy donor

Hydrogen Economy: Hydrogen can be used as a source of energy. It involves the production of large quantites of hydrogen electrically and its storage in liquid form in vacuum insulated cryogenic tanks (maintain at low temperature) and used in space programmes.
(ii) Advantage of hydrogen as an auto mobile fuel.
(a) It produces greater energy per unit mass of fuel due to high calorific value.
(b) It is pollution free.
© Combustion products of hydrogen in presence of air will be ${{H}_{2}}$O and traces of oxides of nitrogen.