The hydrogen fuel cell works in a way that is similar to a battery. It has two electrodes, an anode and a cathode, which are separated by a membrane. Hydrogen passes over one electrode, while oxygen passes over the other. The hydrogen reacts to a catalyst on the electrode anode which turns the hydrogen gas into negatively charged electrons (e-) and positively charged ions (H+). The electrons are then used as electrical energy when they flow out of the cells.