A device that converts energy of combustion of fuels like hydrogen and methane, directly into electrical energy is known as

The device you are referring to is known as a "fuel cell." Fuel cells convert the chemical energy from fuels, such as hydrogen or methane, directly into electrical energy through an electrochemical reaction. They consist of an anode, a cathode, and an electrolyte. In the case of hydrogen fuel cells, hydrogen gas is supplied to the anode side, where it undergoes oxidation to produce protons and electrons. The protons pass through the electrolyte to the cathode, while the electrons travel through an external circuit, creating an electric current. At the cathode, oxygen is combined with protons and electrons to produce water and heat. Fuel cells are clean and efficient, emitting only water and minimal heat as byproducts.