[CobraJet]

So if the fuel cell is gas> electro-chemical reaction> electrical energy, what type of gas is used to charge into the cell?

[Hodar]

This depends largely on which Fuel Cell design is used. There are some that use water and air, others use natural gas, some use diesel, some have used Sunflower oil. Granted, the Sunflower Oil was a messy, ugly and not practical solution - but it proved a concept that it COULD be done.

The hyperlink above is to Wikipedia - which lists 22 types of Fuel Cells. What may be practical for a RV or truck, may not be practical for your laptop, or your cell phone. Cost, output power, size ane efficiency vary. But generally, they are all much more efficient than what we have now.