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
Seawater electrolysis faces unique and fundamental chemical challenges, such as the suppression of highly detrimental halogen chemistries [1], that poison the current state-of-the-art anode catalyst and accelerate the degradation of the membrane [2]. The technically favored solution path is to address these issues by developing a new selective catalyst and possibly by limiting operating conditions [3]. Therefore, developing a facile and cost-effective way to design highly active, selective, and and stable seawater-splitting catalysts is of great importance for research and industry [4]. In this work, hexagonal NiFe-layered double hydroxide (LDH) nanosheets were synthesized by one-step solvothermal reactions. As synthesized NiFe-LDH catalyst exhibits high activity, selectivity, and stability towards the oxygen evolution reaction (OER) in alkaline electrolyte, delivering current densities of 10 mA/cm2 at low overpotentials of 359 mV, with no significant degradation observed during RDE testing at constant voltage of 1.57 V for 72 hours in 1.0 M KOH electrolyte. In addition, in order to fabricate catalyst coated electrode (CCE), the nanostructured NiFe-LDH catalyst was homogeneously sprayed onto a platinized titanium porous transport layer (PTL) using an ultrasonic spray coating system. As prepared CCE is used as an anode and commercially available Raney nickel catalyst deposited on a nickel fiber frit is used as a cathode to assemble a MEA with Sustainion® X37-50 grade T anion exchange membrane (AEM) that was tested in alkaline seawater. Employing local seawater, the AEM electrolyzer cell demonstrated stable performance for over 1000 hours at a constant current density of 300 mA cm -2. Reference: [1] S.-C. Ke, R. Chen, G.-H. Chen, X.-L. Ma, Energy Fuels 2021, 35, 12948. [2] S. Dresp, F. Luo, R. Schmack, S. Kühl, M. Gliech, P. Strasser, Energy Environ. Sci. 2016, 9, 2020. [3] S. Dresp, F. Dionigi, S. Loos, J. Ferreira de Araujo, C. Spöri, M. Gliech, H. Dau, P. Strasser, Advanced Energy Materials 2018, 8, 1800338. [4] H. Koshikawa, H. Murase, T. Hayashi, K. Nakajima, H. Mashiko, S. Shiraishi, Y. Tsuji, ACS Catal. 2020, 10, 1886.
The metal layer deposition technologies have been revolutionized throughout the years. One of the most common forms of thin metal film deposition techniques is Physical Vapor Deposition (PVD). Within the category of PVD, there are many modifications based on the source of deposition. Among all PVD variations, the Electron Beam Physical Vapor Deposition (EB-PVD) has the advantages of higher deposition rates, the ability to deposit a wide range of high purity metals for high purity films, and the creation of continuous film layers. [1,3]. EB-PVD is better known as a thermal vaporization technique. Thermal Vaporization focuses on a source, in this case an Electron Beam (EB), which bombards the desired source material with electrons. The electron beam increases the temperature of the porous metal source until it reaches its vapor phase. The metal vapor is then condensed onto the surface of the substrate holder perpendicular to the source material. While EB-PVD is known for its advantages of higher material utilization efficiency, higher deposition rates, and better step coverage [1], it lacks in its ability to penetrate into the volume of Porous Transport Layer (PTL) or coat surfaces that are not perpendicular to the source. This is important as the PTL is in contact with a corrosive environment, which causes metal corrosion and degradation of the PTL at the surfaces that are not protected by the coating. A key aspect plaguing the thin film deposition techniques is the ability to penetrate deep into the volume of a PTL and provide full coating of the porous material, including surfaces not perpendicular to the source. In an attempt to find a solution to this challenging task, we explored the capability of the Reactive Spray Deposition Technology (RSDT) to deposit precious metal nanoclusters directly onto all surfaces in the volume of the sintered titanium material [2]. The studied metal coating of interest is Gold (Au). In this work, we have deposited Au coatings of various thicknesses onto the Ti-PTLs by using both EB-PVD and RSDT techniques. The Au thin film deposits are characterized by scanning electron microscopy (SEM), digital optical microscopy, inductively coupled plasma (ICP), and focused ion beam scanning electron microscopy (FIB-SEM) [2]. The optimal deposition parameters for thin and continuous Au films with precisely controlled thicknesses have been identified. In addition, the depth of penetration of the deposits in the volume of the PTL as a function of the deposition parameters have been studied in detail, and the results will be reported at the ECS 242 meeting. References: [1] Stagon, Stephen P., "Physical Vapor Deposition of Nanorods from Science to Technology" (2013). Doctoral Dissertations. 189. https://opencommons.uconn.edu/dissertations/189 [2] Garces, Hector F., et al. “Formation of Platinum (PT) Nanocluster Coatings on K-OMS-2 Manganese Oxide Membranes by Reactive Spray Deposition Technique (RSDT) for Extended Stability during CO Oxidation.” Advances in Chemical Engineering and Science, Scientific Research Publishing, 29 Oct. 2013, [3] “Electron Beam Physical Vapor Deposition.” Electron Beam Physical Vapor Deposition - an Overview | ScienceDirect Topics, https://www.sciencedirect.com/topics/materials-science/electron-beam-physical-vapor-deposition.
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