An Electrochemical cell that converts chemical energy into electrical energy by a reaction of hydrogen fuel and oxygen (or other oxidizing agent)is called as a Fuel Cell. Fuel cells differ from batteries as they require continuous supply of fuel and oxidizer in them to sustain the chemical reaction. Unlike the batteries, they can operate for as long as fuel gets supplied to them.
They are a great alternative to regular sources of electrical energy production like the one's in Power houses, like thermal or nuclear power, as the byproduct generated in them is pure water.
They are famously used in space missions, eg in Apollo missions to the moon in late 1969-72, they powered the space capsules and provided clean drinking water(from the byproduct of reaction) t the astronauts on board the spacecraft.
The reactions that follows in them are:
1. At Anode :
2. At Cathode :
Net Reaction :