Thanks to Chris Ford for suggesting this post.
How do hydrogen cars work? This video looks at how hydrogen (H2) can be used to power a vehicle. An on-board storage tank sends the hydrogen to the fuel cell stack, where the electrons are separated from the hydrogen via a platinum catalyst, and the energy is then used to propel the car. The electrons return to the fuel cell where they then combine with positively charged hydrogen atoms and oxygen atoms to form H2O, and the reaction is complete. The water then flows out the exhaust pipe, with no harmful emissions.