The hydrogen is used as a precursor in combination with oxygen in the air. Input Fuel Cell fuel cells or chemical process to generate electricity (and the rest is water).
Hydrogen is used as a substrate with oxygen in the air fed into the Fuel Cell or fuel cells. Then, through a chemical process to generate electricity. (The rest of the water).
Use of hydrogen as a feedstock with oxygen in the air. Fuel input Cell or fuel cells. Then through a chemical process to generate electricity (and have left is water).