Hydrogen can serve as an energy vector and is expected to play a vital role in future sector coupling and deep decarbonization scenarios, for example for the production of transportation fuels. Water electrolysis using renewable electricity is a flexible, modular, and scalable technology for green hydrogen production. Improvement of the conversion efficiency is imperative to lower hydrogen cost. The aim of the proposed project is, on the one hand, to introduce new additive materials into thin proton exchange membranes to reduce hydrogen crossover and improve membrane stability. On the other hand, functional additives will be incorporated into anion exchange membranes (AEMs), which operate under alkaline conditions and offer the prospect of a lower use of critical raw materials. The new membranes will be characterized and validated in laboratory-scale single cells.