Interface Engineering: On the Impact of Micro-Porous Layers on Polymer Electrolyte Water Electrolysis Performance

Abstract

In polymer electrolyte water electrolysis (PEWE), operational cost represents the main cost fraction. Losses induced by kinetic, ohmic as well as mass transport overpotentials limit cell efficiency and in turn lead to lower volumetric power density and higher energy consumption.The interplay of porous transport layer bulk/surface properties1,2, providing thermal and electrical conductivity as well as fluid management between bipolar plates and catalyst layer, and cell efficiency is a disputed question in literature. Governing design parameters for porous transport layers, as well as fundamental limiting process haven’t been addressed so far. This study aims to close the gap between fundamentals and highly efficient PTL microstructure design. A novel class of hierarchically structured porous transport layers is fabricated based on sintering of economically viable Ti powder, see Figure 1..A series of four different PTL materials including three different MPL types was analysed. Structural properties, characterized by laboratory and synchrotron based X-ray tomographic microscopy (XTM) were correlated to in-depth electrochemical analysis. Performance of the novel PTLs was probed by comparison to state-of-the-art PTL materials and stack technology. The superior surface properties of the microporous-layer enabled the use of ultra-thin membranes with Ti PTLs for the first time. To elucidate the MPL effect and reveal the mechanism of partial catalyst utilization3,4, the catalyst layer conductivity was studied as function of hydration state and ionomer content.Reference1 S. A. Grigoriev, P. Millet, S. A. Volobuev and V. N. Fateev, International Journal of Hydrogen Energy, 2009, 34, 4968-4973.2 T. Schuler, R. De Bruycker, T. J. Schmidt and F. N. Büchi, Journal of The Electrochemical Society, 2019, 166, F270-F281.3 Z. Kang, J. Mo, G. Yang, S. Retterer, D. Cullen, T. Toops, J. Green Jr, M. Mench and F.-Y. Zhang, Energy and environmental science, 2017, 10, 166-175.4 T. Schuler, T. J. Schmidt and F. N. Büchi, Journal of The Electrochemical Society, 2019, 166, F555-F565.Figure 1. XTM rendering of hierarchically structured porous transport layer. Figure 1