Investigation of Anion Exchange Membrane Water Electrolysis Efficiencies at Cell Level Using Online Mass Spectrometry

In the future, water electrolysis (WE) will play a decisive role in the energy-efficient and sustainable production of green hydrogen. In this respect, anion exchange membrane water electrolysis (AEMWE) is a promising technology that combines the advantages of the already established alkaline and acidic water electrolysis systems. The alkaline environment makes it possible to replace precious metal catalysts with nickel or iron as cost-effective alternatives. At the same time, using an anion-conducting membrane instead of a porous separator enables higher current densities and flexible operation.1 In direct comparison to proton exchange membrane water electrolysis (PEMWE), durability and stability are still the main problems of AEMWE, but significant progress has been made in recent years. Electrochemical cell tests lasting a year and longer are available for the commercial AEMs Sustainion®2 and Aemion+®3. In addition, piperidinium-based membranes have now also been tested for 1000 hours.4 While the stability improvements of AEMWE are going in the right direction, the question remains to what extent the high efficiencies achieved in PEMWE can be matched. For the latter, the individual contributions to the cell voltage5, 6 and the expected gas permeations7, 8 at different current densities have already been studied in detail – an understanding that is still missing for AEMWE systems. Consequently, in this work, we want to give an insight into AEMWE efficiencies for a standard cell configuration. For this purpose, we used the novel PiperION® membrane and a scalable non-noble NiFe-LDH catalyst from Matteco as the anode catalyst in a self-designed 5 cm² cell setup. Furthermore, we set the focus on implementing product gas analysis using online mass spectrometry to investigate the faradaic efficiency and draw a conclusion on the gas-crossover mechanisms of the novel technology. Tracking the weight of our electrolyte reservoirs during operation additionally allowed us to analyze the water drag. Both phenomena were examined over a wide range of current densities from 0 to 5 A cm-2 at 70 °C and 1 M KOH to provide currently missing information for AEMWE development. References H. A. Miller, K. Bouzek, J. Hnat, S. Loos, C. I. Bernäcker, T. Weißgärber, L. Röntzsch and J. Meier-Haack, Sustainable Energy Fuels, 4(5), 2114–2133 (2020). B. Motealleh, Z. Liu, R. I. Masel, J. P. Sculley, Z. Richard Ni and L. Meroueh, Int. J. Hydrog. Energy, 46(5), 3379–3386 (2021). M. Moreno-González, P. Mardle, S. Zhu, B. Gholamkhass, S. Jones, N. Chen, B. Britton and S. Holdcroft, Journal of Power Sources Advances, 19, 100109 (2023). C. Hu, J. Y. Lee, Y. J. Lee, S. H. Kim, H. Hwang, K. Yoon, C. Park, S. Y. Lee and Y. M. Lee, Next Energy, 1(3), 100044 (2023). M. Suermann, T. J. Schmidt and F. N. Büchi, ECS Trans., 69(17), 1141–1148 (2015). M. Bernt and H. A. Gasteiger, J. Electrochem. Soc., 163(11), F3179-F3189 (2016). M. Bernt, J. Schröter, M. Möckl and H. A. Gasteiger, J. Electrochem. Soc., 167(12), 124502 (2020). P. Trinke, B. Bensmann and R. Hanke-Rauschenbach, Int. J. Hydrog. Energy, 42(21), 14355–14366 (2017).