A Path to Significant Reduction of the Interfacial Contact Resistance of Sintered Titanium Porous Transport Layers in Advanced Proton Exchange Membrane Water Electrolyzers

Abstract

Proton exchange membrane water electrolyzers (PEMWEs) are a leading industry solution to large scale production of green hydrogen, and as a form of energy storage [5]. The PEMWEs have the advantages of having greater energy efficiency, higher product purity, and are environmentally friendly. Within the construction of a PEMWE stack, there are many catalysts coated membranes (CCMs) sandwiched between anode porous transport layers (PTLs) and cathode Gas Diffusion Layers. The PTL is constructed of sintered titanium powder or fibers. The Ti-PTL is on the anode side of a PEMWE cell where the water diffuses towards the CCM. The anode half-cell reaction or oxygen evolution reaction (OER) occurs on this side of the cell. This is important as the PTL is in contact with the bipolar plate (BPP) and the anode catalyst layer [9]. A key aspect plaguing the PEMWEs is the highly oxidative and corrosive environment that is typically observed on the anode side. This significantly affects the interfacial contact resistance (ICR) of the components as the corrosion can cause the ohmic resistance of the PTL to increase. In order to combat the corrosion in the PTLs, in this work we use two thin film deposition methods, Physical Vapor Deposition (PVD) and Vacuum Sputtering, to deposit protective metal layers on top of the state-of-the-art Ti PTLs [2]. The explored metal coatings of interest are Platinum (Pt) and Gold (Au) [9]. For the purposes of these experiments, Au and Pt coatings with various thicknesses are deposited on Ti-PTLs by using either PVD or vacuum spattering method. As deposited thin films are characterized by scanning electron microscopy (SEM), digital optical microscopy, and inductively coupled plasma (ICP) analysis. Also, the in-plane conductivity and the ICR of all samples of interest are measured before and after the electrochemical tests by using the 4-probe method and in-house build setup for ICR measurements. The optimal deposition parameters for fabrication of thin, continuous and smooth Pt and Au protective coatings that result in minimum ICR and improved in-plane conductivity of the PTLs of interest are identified, and the results will be reported at the ECS 241 meeting. References: [1] Mo, Jingke, Steen, Stuart, Kang, Zhenye, Yang, Gaoqiang, Taylor, Derrick A., Li, Yifan, Toops, Todd J., Brady, Michael P., Retterer, Scott T., Cullen, David A., Green, Johney B., and Zhang, Feng-Yuan. Study on corrosion migrations within catalyst-coated membranes of proton exchange membrane electrolyzer cells. United States: N. p., 2017. Web. [2] Rojas, Nuria & Sevilla, Gema & Sánchez-Molina, Margarita & Amores, Ernesto & Bueno, Rebeca & Almandoz, Eluxka & Cruz, Marlon & Colominas, Carles. (2018). Materials selection for bipolar plates in PEMWE. [3] Oluwatosin Ijaodola, Emmanuel Ogungbemi, Fawwad Nisar. Khatib,Tabbi Wilberforce, Mohamad Ramadan, Zaki El Hassan, James Thompson andAbdul Ghani Olab. Evaluating the effect of metal bipolar plate coating on the performance of proton exchange membrane fuel cells. Energies, MDPI AG, 5 Oct. 2021 [4] Sigrid Lædre, Ole Edvard Kongstein, Anders Oedegaard, Frode Seland, and Håvard Karoliussen. Measuring In Situ Interfacial Contact Resistance in a Proton Exchange Membrane Fuel Cell. Journal of the Electrochemical Society, 166 (13) F853-F859 (2019) [5] Peter Holzapfela, Melanie Bühler, ChuyenVan Phamc, Friedemann Hegge, Thomas Böhm, David McLaughlin, Matthias Breitwieser, Simon Thielead. Directly coated membrane electrode assemblies for proton exchange membrane water electrolysis. Electrochemical Communications, volume 110, January 2020, 106640. [6] S. Stiber, N. Sata, T. Morawietz, S. A. Ansar, T. Jahnke, J. K. Lee, A. Bazylak, A. Fallisch, A. S. Gago and K. A. Friedrich. A high-performance, durable and low-cost proton exchange membrane electrolyser with stainless steel components. Journal, Energy & Environmental Science [7] Chang Liu, Marcelo Carmo, Guido Bender, Andreas Everwand, Thomas Lickert, James L. Young, Tom Smolinka, Detlef Stolten, Werner Lehnert, Performance enhancement of PEM electrolyzers through iridium-coated titanium porous transport layers, Electrochemistry Communications, Volume 97, 2018, Pages 96-99, ISSN 1388-2481, [8] Gago, Aldo & Ansar, Asif & Gazdzicki, Pawel & Wagner, Norbert & Arnold, Johannes. (2014). Low Cost Bipolar Plates for Large Scale PEM Electrolyzers. ECS Transactions. 64. 10.1149/06403.1039ecst. [9] Novel components in Proton Exchange Membrane (PEM) Water Electrolyzers (PEMWE): Status, challenges and future needs. A mini review, Electrochemistry Communications, Volume 114, 2020, 106704