Hydrogen
Hydrogen (H2) is being explored as a fuel for passenger vehicles. It can be used in fuel cells to power electric motors or burned in internal combustion engines (ICEs).
It is an environmentally friendly fuel that has the potential to dramatically reduce our dependence on imported oil, but several significant challenges must be overcome before it can be widely used.
Benefits
Produced Domestically. Hydrogen can be produced domestically from several sources, reducing our dependence on petroleum imports.
Environmentally Friendly. Hydrogen produces no air pollutants or greenhouse gases when used in fuel cells; it produces only nitrogen oxides (NOx) when burned in ICEs.
https://www.fueleconomy.gov/feg/hydrogen.shtml