For hydrogen to become a serious contender for replacing fossil fuels, the manufacturing thereof has to be further investigated. One such process, the membrane based Hybrid Sulfur (HyS) process, where hydrogen is produced from the electrolysis of SO2, has received considerable interest recently. Since H2SO4 is formed during SO2 electrolysis, H2SO4 stability is a prerequisite for any membrane to be used in this process. In this study, pure as well as blended polybenzimidazole (PBI), partially fluorinated poly(arylene ether) (sFS) and nonfluorinated poly(arylene ethersulfone) (sPSU) membranes were investigated in terms of their acid stability as a function of acid concentration. Membranes were characterized using weight change, TGA, GPC, SEWEDX and IEC. While a general stability was observed at 30 and 60 wt% H2SO4, the blended sFS-PBI and sPSU-PBI showed the highest stability throughout. According to the VI curve obtained for the SO2 electrolysis, the sPSU-PBI blend membrane performed slightly better than Nafion (R) 117. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.