Concept: A fuel cell is a device that converts chemical potential energy (energy stored in molecular bonds) into electrical energy. A PEMFC (Proton Exchange Membrane Fuel cell) uses hydrogen gas (H2) and oxygen gas (O2) as fuel. The products of the reaction in the cell are pure water, high electricity, and less heat. They are also known as polymer electrolyte membrane (PEM) fuel cells. PEMFCs have attracted great attention due to their numerous advantages, such as high power density, high energy conversion efficiency, fast startup, low sensitivity to orientation, and environmental friendliness. Working: In PEMFCs, the fuel (hydrogen, H2) enters at the anode. There, a chemical reaction causes the hydrogen molecules to separate into positive hydrogen ions (H+ or protons) and electrons (e−). This reaction releases heat. The positive hydrogen ions pass through the electrolyte made of a polymer membrane and travel to the cathode. The electrons remain behind and thereby give the anode a negative charge, creating a voltage difference between the anode and the cathode. Because electrons travel from negative to positive, the electrons follow an external circuit from the anode to the cathode. At the same time, oxygen (O2) enters the fuel cell at the cathode and combines there with the electrons, which have traveled through the external circuit, and the positive hydrogen ions, which have traveled through the electrolyte, to produce water (H2O) at the cathode.