One of the most promising alternatives is hydrogen fuel cells, which use hydrogen to directly generate electricity via a reaction with oxygen, but the race is still very open as to which hydrogen ...
If pure hydrogen is used as a fuel, fuel cells emit only heat and water as a byproduct. Hydrogen-powered fuel cells are also far more energy efficient than traditional combustion technologies.
In a hydrogen-oxygen fuel cell, hydrogen and oxygen are used to produce a voltage. Water is the only product. The overall reaction in a hydrogen-oxygen fuel cell is: ...