Hydrogen Fuel Cell is electric; in more ways than one.
The hydrogen must be separated from water by electrolysis (very expensive energy wise).
The fuel cell generates electricity that will power a electric traction motor.
Personally I would prefer a natural gas (methane) fuel cell if I were to want to use such a thing to power a truck; Much more environmentally friendly.
Hydrogen is a waste product for many manufacturing processes.
Before we shipped most of the plastics industry overseas, that industry by itself vented enough hydrogen to be one third of what would be needed to switch to hydrogen.
Or.....you can mix lye and water and drop in aluminum - another costly method that also produces a lot of heat...
While hydrogen CAN be generated from water using this method, it almost never IS.
Almost all commercially used hydrogen is generated from fossil fuels, with the carbon released into the atmosphere exactly the same as if the fuel were just burned directly.
The only way hydrogen fuel cell becomes a truly zero-emissions system is if the hydrogen is provided through electrolysis of water, and the electricity used is from wind, hydro, nuclear or some other non-carbon source.