PEM Electrolysis

PEM electrolysis, short for proton exchange membrane electrolysis, splits water into hydrogen and oxygen using a semipermeable membrane, usually made from an ionomer such as the fluoropolymer Nafion, that conducts protons across it while blocking both a direct electronic pathway and the reactants themselves from passing straight through. Because it generally relies on expensive platinum group metal catalysts, a PEM electrolyzer costs more to build than other electrolyzer types, but it also runs more efficiently and can operate at higher current densities. Average working efficiency for PEM electrolysis today is around 80 percent, with efficiency expected to rise to between 82 and 86 percent before 2030 and a theoretical ceiling estimated as high as 94 percent.