A system for energy generation or storage on an electrochemical basis includes at least one flow cell, each flow cell including two half-cells through which differently charged electrolyte liquids (21, 22) flow and which are separated by a membrane, at least one electrode being disposed in each of these half-cells, and a tank for each of the electrolyte liquids. A common gas volume (23) connecting the tanks is provided, and at least one catalyst (24) for reducing a positive reaction partner of then redox pair in contact with the positive electrolyte liquid (22) and also with the common gas volume (23) is disposed in the tank for the positive electrolyte liquid (22).