Fig. 2: Operation and design of proton exchange membrane fuel cells.
From: Hydrogen as the nexus of future sustainable transport and energy systems
a, During the operation of a proton exchange membrane fuel cell (PEMFC), the fuel (hydrogen) is introduced at the anode side and is oxidized at the anode catalyst layer, releasing electrons (e−) and protons (H+). The electrons travel through an external circuit creating an electric current, whereas the protons migrate through the electrolyte to the cathode side. Concurrently, air is supplied to the cathode side, providing oxygen that reacts with the incoming protons and electrons at the cathode catalyst layer to form water. This reaction at the cathode also releases heat. Excess fuel exits the system, ensuring that the fuel cell does not flood with reactants. The arrows indicate the direction of reactant flow and electron movement, with the electric current resulting from the flow of electrons being directed out of the cell to power an external load. b, Representation of the key components of a PEMFC, highlighting both current technology and future possibilities, including the bipolar plates with integrated flow channels or fields, gas diffusion layers, and catalyst layers on both the anode and cathode sides, with the proton exchange membrane (PEM) positioned centrally. Part b is adapted from ref. 18, Springer Nature Limited.
