The RSPFC is a battery-like hydrogen/oxygen system which offers the possibility of splitting water by electrolysis, storing the gases hydrogen and oxygen and regenerating electricity by the fuel cell process. The most outstanding feature is the use of only one energy Conversion device for both processes, electrolysis and fuel cell operation. Membrane technology is the most suitable system for realization of this concept. Basic investigations concerning the best catalysts for the electrode reactions at electrode/membrane units have been carried out. The preparation of these units and the electrochemical characterization by half cell measurements and impedance measurements are reported as well as first experiences in reversibly operating small single cells.