PEMFC

A proton exchange membrane fuel cell (PEMFC) is a type of fuel cell that converts chemical energy from hydrogen and an oxidant (typically oxygen from air) into electricity through an electrochemical reaction, using a solid polymer electrolyte known as a proton exchange membrane.

The cell stack comprises an anode, a cathode, and the polymer electrolyte membrane; catalysts (often platinum) on both electrodes; gas diffusion layers; and bipolar plates that route reactants and electrical current. Hydrogen is supplied to the anode, where it is oxidized to protons and electrons; protons pass through the membrane; electrons travel through an external circuit to the cathode, where oxygen combines with protons and electrons to form water.

PEMFCs operate at relatively low temperatures (about 60-80°C), offer high power density and rapid start-up, and can be fed with pure hydrogen or hydrogen-rich reformates, but require careful water management to keep the membrane hydrated. Impurities, particularly carbon monoxide, can poison catalysts; membranes and catalysts add to cost; durability and stack lifetime are ongoing challenges.

Applications include transportation (fuel cell electric vehicles and buses), stationary power systems, backup power, and portable devices. In combined heat and power installations, the high-quality heat is used with electricity; electrical efficiency can exceed 60% with heat recovery, depending on system design.

History and development: PEM technology traces to the 1950s-60s with NASA and General Electric; later commercialized in the 1990s-2000s. Ongoing research aims to reduce cost, improve durability, and enable non-precious metal catalysts to broaden adoption.