Evaluation of complex multi-physics phenomena at gas diffusion electrodes during high-pressure water electrolysis with AEMs

Abstract The alkaline water electrolysis is a well-established process for producing green hydrogen from renewable energy sources. Hereby, electrochemical gas compression can be realized with water electrolysis and ion pumping membranes, to avoid costly mechanical compression. In this experimental study we researched an electrolyzer cell with a strong metal structure, for internal pressure difference of up to 100 bar. Micro-porous gas diffusion electrodes containing non-precious nickel catalysts as well as different separators, alkaline membranes and AEMs have been investigated in the range of 300 to 800 mA cm− 2. For one preferred AEM, characteristics are shown for hydrogen pressures between 20 and 80 bars, while the anode remains at ambient 1 bar. Impedance spectroscopy diagrams are used to display the individual cell components: the ohmic resistance of the AEM and the complex impedances of both electrodes. Therewith we could visualize the complex multi-physics phenomena and show that the oxygen electrode works as a Wartburg-element, especially due to higher diffusion rates and therewith entropy production during bubble formation.