A hydrogen fuel cell device that processes pure hydrogen to create an electrical current. In most common implementations, hydrogen is placed on one side of a gas-permeable barrier from ordinary air. Oxygen atoms in the air can cross the barrier but cannot carry their electrons across. The electrons are transferred to a conductor and flow around to the other side of the barrier as electricity that can be harnessed and stored. When the oxygen and hydrogen atoms meet, they bond to form water. The only emissions of a hydrogen fuel cell are electricity and pure water. Fuel cell electric vehicles (FCEVs) like the Toyota Mirai use hydrogen fuel cells for the energy to drive their electric motors.
