A Simple in-situ Voltage Characterization Technique and Coating Methods for Developing Polymer Electrolyte Membrane Water Electrolysis Porous Transport Layer and Bipolar Plates
Authors: Jang Yujae , Kim Yangjae , Jeong Wonyeop , Cha Suk Won 
Published: December 2024

As climate change progresses, decarbonization becomes imperative, and hydrogen is gaining attention as a clean energy source alongside carbon [1]. Particularly, hydrogen obtained through electrolysis has the advantage of being carbon-free throughout the production process, known as green hydrogen. Currently, electrolysis is primarily conducted through alkaline and polymer electrolyte membrane methods. Polymer electrolyte membrane devices, operating effectively even at high pressures, offer advantages over alkaline electrolysis in efficiency and hydrogen production. Thus, polymer electrolyte membrane devices are essential for entering carbon neutrality [2]. However, the high voltage (~2V) and acidic operating environment in the operating condition causes component corrosion, forcing their uses of high price materials. The porous transport layer and bipolar plates of polymer electrolyte membrane devices utilize platinum-coated titanium [3]. Therefore, accurately measuring the voltage profile inside the device and replacing precious metal coated titanium can reduce device costs and offer commercial advantages. Although considerable research is ongoing, most studies require complex electrolyte solutions and custom membrane electrode assembly fabrication techniques.
This study proposes a simple technique using commercial products to evaluate internal voltage profile in polymer electrolyte membrane devices and introduces materials that can replace titanium. Membrane Electrode Assembly from HIAT and Porous Transport Layer from Mott is utilized, and similar to Z. Kang et al. [4], voltages of the PTL, Catalyst Layer (CL), and Bipolar Plate (BP) relative to the cathode were measured. 0.001x0.005 mm² gold wire (California fine wire Co.) is used to measure voltage during the voltage. In some studies, voltage profiles of PEMWE stack were measured by applying voltage to the MEA instead of the bipolar plate [5]. In this study, voltage profiles inside of the cell and stack was measured. By simply placing a gold wire between the component, the voltage profile during device operation was observed. The measurements revealed a voltage small drop within the proton exchange membrane.
On the other hand, the Ta-based stainless steel confirms the potential utilization of stainless steel coated materials as an alternative to titanium-based ones. According to Becker et al. [6], the voltage of the cathode during operation is approximately 0VvsRHE or less, and the bipolar plate's condition is electrochemically stable compared to the anode. Thus, a single-layer coating of PEALD TiN on stainless steel has been proposed for the cathode. On the contrary, the environment at the anode was harsher compared to the cathode, with a higher susceptibility to corrosion due to the application of high voltages (~2V). Therefore, a Ta based coating has been proposed for the anode. When conducting PEMWE experiments using Ta-coated stainless steel (SUS), it exhibited performance comparable to using Ti-based bipolar plates in both cell and stack performance. Moreover, in long-term performance, Ta-coated SUS demonstrated superior performance. Furthermore, coating Ta onto SUS PTL used in AEMWE confirmed the feasibility of replacing Ti-based PTL.
References.
[1] Y. Leng, P. Ming, D. Yang, C. Zhang, Stainless steel bipolar plates for proton exchange membrane fuel cells: Materials, flow channel design and forming processes, J. Power Sources. 451 (2020) 227783. https://doi.org/10.1016/j.jpowsour.2020.227783.
[2] S.Y. Kang, J.E. Park, G.Y. Jang, C. Choi, Y.H. Cho, Y.E. Sung, Directly Coated Iridium Nickel Oxide on Porous-Transport Layer as Anode for High-Performance Proton-Exchange Membrane Water Electrolyzers, Adv. Mater. Interfaces. 10 (2023). https://doi.org/10.1002/admi.202202406.
[3] H. Becker, E.J.F. Dickinson, X. Lu, U. Bexell, S. Proch, C. Moffatt, M. Stenström, G. Smith, G. Hinds, Assessing potential profiles in water electrolysers to minimise titanium use, Energy Environ. Sci. 15 (2022) 2508–2518. https://doi.org/10.1039/d2ee00876a.
[4] Z. Kang, S.M. Alia, M. Carmo, G. Bender, In-situ and in-operando analysis of voltage losses using sense wires for proton exchange membrane water electrolyzers, J. Power Sources. 481 (2021) 229012. https://doi.org/10.1016/j.jpowsour.2020.229012.
[5] A.J. McLeod, L. V. Bühre, B. Bensmann, O.E. Herrera, W. Mérida, Anode and cathode overpotentials under accelerated stress testing of a PEM electrolysis cell, J. Power Sources. 589 (2024). https://doi.org/10.1016/j.jpowsour.2023.233750.
[6] H. Becker, E.J.F. Dickinson, X. Lu, U. Bexell, S. Proch, C. Moffatt, M. Stenström, G. Smith, G. Hinds, Assessing potential profiles in water electrolysers to minimise titanium use, Energy Environ. Sci. 15 (2022) 2508–2518. https://doi.org/10.1039/d2ee00876a.