Grove's discovery didn't get a lot of use until the 1960s, when fuel cells were employed to provide electricity and water for the Gemini and Apollo spacecraft. Today they do the same for the space shuttle missions. In principle, a fuel cell works like a battery. It produces electricity by combining hydrogen and oxygen electrochemically, without combustion. However, unlike a battery, a fuel cell doesn't run down or require recharging.
Oxygen passes over one electrode, while hydrogen passes over the other.
Along the way, a few of these electrons can be used to power any electrical device, like a motor. At the second electrode, the hydrogen and electrons combine with oxygen to form water. The PEM fuel cell converts hydrogen and air into useful electricity and water with no emissions and greater efficiency than a fossil fueled generator. There are also various ways to get hydrogen to use in a fuel cell. The cleanest way to obtain hydrogen is by passing an electric current through water, thereby splitting it into its components, hydrogen and oxygen.