PEM technology is the most efficient water electrolysis technology and the technology of choice for hydrogen fuel cells. As such, this technology will be crucial in the breakthrough of green hydrogen. AlterPEM proposes a novel electrolysis system consisting of a fluorine-free membrane, coated as thin layer on top of ultrathin metallic nanomesh (NM) electrodes with no or lean PGM catalyst, resulting in a cheaper, gap-less NM-Membrane Electrode Assembly (MEA). Nickel NM electrodes have been successfully implemented in alkaline electrolyzers by imec already. To withstand the acidic conditions during operation in PEM, the NM will need to be acid resistant, protected and made catalytic by ALD coatings (consortium partners imec and UGent). Consortium partner KU Leuven has experience with pH-resistant polymer membrane development and with membranes for electrochemical technologies. To develop the fluorine-free membrane, they can build further on experience in membranes developed for redox flow batteries and filtration.