Electrolysis Cell Research Articles

Diffusion-Bonded Unitized Anode Assemblies for PEM Electrolysis Stacks

Hydrogen generation via proton exchange membrane (PEM) water electrolysis is in the midst of a technological renaissance aimed at achieving cost parity with steam reforming within the decade. Reaching that plateau will require substantial system cost reductions accompanied by increased performance of the cell stack module. Many proposed improvements to the cell stack draw from the established principles of electrochemical and manufacturing engineering, targeting lower component resistances while lowering part count and enhancing ease of assembly, respectively.The PEM electrolyzer anode assembly (comprising the porous transport layer (PTL) and the anode flow field) is suited for just such a revision. In practice, the anode PTL is positioned on a metallic bipolar plate that is machined or embossed with a flow field, or the PTL is joined to an assemblage of thin macroporous media that serves as a flow field1. In both cases, the interfacial resistances between the subcomponents of the assembly are non-negligible and are conventionally mitigated by applying noble metal coatings, typically Pt.In this contribution, we investigate alternatives to conventional assemblies via diffusion bonding. Using thermal treatments, the porous transport layer is joined to the anode flow field, yielding a robust, atomic-scale metallurgical bond. We demonstrate the manufacturing of large-format assemblies in multiple configurations, using either stacked microporous media or grooved plates, meeting tight tolerances for thickness across their span. We also show that the bulk-like character imparted to the assembly obviates the need for antipassivation coatings at the critical interfaces between components, evinced by low series resistance in both ex situ and in situ electrolysis cell tests.References(1) Dristy, M. E. Proton Exchange Membrane Electrochemical Cell System. US7270908B2, September 18, 2007.

Coating Titanium Transport Layers for Enhanced Short and Long Term Performance in PEM Water Electrolysis Cells

The ageing of titanium porous transport layers (PTL) affects the longevity of polymer electrolyte membrane water electrolysis systems by the formation and thickening of a weakly conductive oxide layer. The evolving oxygen on the anode in combination with the high electrical potential provides a challenging environment in which a low electrical contact resistance to the catalyst layer (CL) needs to sustain over a long period. One previous approach is a precious metal coating of the PTL with platinum or iridium [1], which can prevent oxidation of the titanium. A cost-effective alternative is a hydrochloric acid treatment, which forms titanium hydride (TiH). [2] Titanium nitride (TiN) promises better electrical conductivity with similar corrosion resistance, but has not yet been tested as a coating. The same is true for niobium, which performed well as a coating for stainless steel bipolar plates. [3] In our studies, all these candidates face the same conditions aside an untreated PTL in one unique series of measurements. All types are repeated three times to ensure reproducibility. The mean polarization curves (figure 1 left) show that the two precious metals, iridium and platinum, significantly improve the cell voltage at a current density of 2A/cm² by 80mV and 95mV, respectively. Titanium hydride achieves an even higher reduction of 100mV without the use of precious metals. The high frequency resistance plots in figure 1 right determine that the improvement of up to 20% or 30mΩ∙cm² is attributable to a reduced contact resistance to the CL. This assumption is proven by the fact that a PTL that is only coated with iridium on the side facing the CL behaves identically to a PTL that is coated on both sides. The ohmic losses in contact with the BPP are therefore negligible in these experiments. Titanium nitride and niobium coated PTLs behave in the same way as the reference measurement. In addition to the measurements shown, long-term experiments (>1000 hours) are currently running for all types of coating, and corrosion measurements in sulphuric acid are being carried out in parallel. The joint results will determine the suitability of the various coatings for long-term use in electrolysers.[1] Liu, C., Shviro, M., Gago, A. S., Zaccarine, S. F., Bender, G., Gazdzicki, P., Morawietz, T., Biswas, I., Rasinski, M., Everwand, A., Schierholz, R., Pfeilsticker, J., Müller, M., Lopes, P. P., Eichel, R.-A., Pivovar, B., Pylypenko, S., Friedrich, K. A., Lehnert, W., Carmo, M., Exploring the Interface of Skin-Layered Titanium Fibers for Electrochemical Water Splitting. Adv. Energy Mater. 2021, 11, 2002926. https://doi.org/10.1002/aenm.202002926[2] Bystron, T., Vesely, M., Paidar, M. et al. Enhancing PEM water electrolysis efficiency by reducing the extent of Ti gas diffusion layer passivation. J Appl Electrochem 48, 713–723 (2018). https://doi.org/10.1007/s10800-018-1174-6[3] Stiber, S., Hehemann, M., Carmo, M., Müller, M., Ayers, K.E., Capuano, C., Danilovic, N., Morawietz, T., Biswas, I., Gazdzicki, P., Heger, J.-F., Gago, A.S. and Friedrich, K.A. (2022), Long-Term Operation of Nb-Coated Stainless Steel Bipolar Plates for Proton Exchange Membrane Water Electrolyzers. Adv. Energy Sustainability Res., 3: 2200024. https://doi.org/10.1002/aesr.202200024 Figure 1

(Invited) Comparison of Catalyst-Coated Electrodes vs. Catalyst-Coated Membranes in PEM Water Electrolysis Cells

The PEM (Proton-Exchange Membrane or Polymer Electrolyte Membrane) cell concept [1] is used in fuel cells and water electrolysis cells. PEM water electrolysis is a compact, efficient and flexible technology for the production of “green-hydrogen” from renewable (intermittent) energy sources. The unit cell (Figure 1) is made of several adjacent functional layers: (i) the proton-conducting polymer membrane (1); (ii) two catalysts layers (CLs) for hydrogen/oxygen evolution containing platinum group metals or PGMs (2;2’); (iii) a porous transport layer used for mass transport of reactants/products and electricity distribution (3;3’); (iv) water flow fields for water circulation (4;4’); bipolar plates (5;5’). From a practical viewpoint, the CLs can be deposited on either side of the interfaces formed between the polymer membrane and the porous transport layer: (i) on the supporting porous transport layers to form catalyst-coated electrodes which are then hot pressed against the bare membrane to form membrane – electrode assemblies; (ii) directly onto the membrane to form catalyst-coated membranes (CCM).The aim of this paper is to evaluate the efficiency and durability of both concepts, drawing on recent advances in manufacturing techniques to reduce the loading of PGM catalysts.[1] W.T. Grubb Jr., Batteries with Solid Ion-Exchange Electrolytes. Journal of the Electrochemical Society. 106 (1959) 275-279.[2] C. Rozain, P. Millet, Electrochemical characterization of Polymer Electrolyte Membrane Water Electrolysis Cells, Electrochimica Acta, 131 (2014) 160-167. Figure 1. Schematic diagram showing the cross-section of a PEM water electrolysis cell [2]. Figure 1

(Invited) PEM Water Electrolysis Stack Development and Related Characterization Tools

For decades, proton-exchange membrane (PEM) water electrolysis (WE) has been mainly used for oxygen generation in anaerobic environments. Over the past two decades, however, it has been increasingly used for hydrogen generation in the industrial sectors at various scales. The PEMWE technology is also considered a key in the ongoing energy transition, if the process of hydrogen generation by means of WE is linked to renewable energy sources, such as wind, solar, etc.The following key elements enable the operation of a PEM WE plant for hydrogen production: a PEM-based WE stack and the balance of plant. The related system includes, but not limited to such key modules as the water and oxygen management systems, hydrogen gas management system, water input system, safety system, power electronics and electrolysis cell stack power supply, control system, and some other.A WE stack comprises several cells connected in series with electrically conductive bipolar plats and end plates. General design principles for the stack involve reducing efficiency losses, while aiming at lower costs and increase in durability. WE stacks should be designed in such a way, that an even current distribution is maintained, the water feed is optimized, suitable compression ratios are achieved, and preferably high discharge pressure of hydrogen can be enabled. For the stack level, in simple terms, efficiency is benchmarked by the total applied voltage, which includes the Nernst potential, anode and cathode overpotentials, and ohmic overpotentials due to the membrane ionic resistance and interfacial resistance at given current density. Overpotential represents inefficiencies in a cell stack, and some of stack design efforts focus on reducing these overpotential contributions. However, a compromise has to be found between (a) costs reduction challenges (that are often associated with the reduction of PGM-based catalyst loading, attempts to replace Ti as a key material for the bipolar plates, and the less expensive SPE membrane), (b) sufficient durability, (c) performance of the stack, (d) increase in power density of a stack.This talk will focus on the WE stack, and its subcomponents review, as well as characterization methods for both, a single cell and a stack and also challenges of the large-scale stack manufacturing. The key components of the WE stack include ion-conductive solid polyelectrolyte membranes (SPE), anode and cathode catalyst layers (CL), bipolar plates and current collectors/ gas diffusion layers (porous transport layers).In order to gain fundamental understanding of the relationships between electrical loses, degradation of the stack components and strategies to increase power density of the stacks, advanced characterization and modelling tools need to be used. These include, but not limited to electrochemical impedance spectroscopy (EIS), current interrupt (CI), dynamic compression measurements with piezoelectric senor plates, current mapping, gas cross-over analysis, computational fluid dynamics (CFD) simulations modelling, various visualization tools, etc. For example, CFD could assist in understanding and improving fluid flow dynamics in a WE stack as it is a complex challenge that requires a detailed examination of the geometry, channel design, and operating conditions within the stack. As for EIS, the usage of the distribution of relaxation times (DRT) approach would potentially allow to focus on the direct analysis of the data rather focusing on the equivalent circuit development.Approximately 15 years ago the South African Government approved a national program HySA: Hydrogen South Africa, which resulted in the development of the expertise and capacity to conduct research, development, and earlier commercial activities around green hydrogen production by means of water electrolysis. These activities include the development of local IP at the components, stack, and system levels.

(Invited) Understanding Potential Losses and pH Distribution in Electrochemical Nitrate Reduction Reaction to Ammonia

Electrochemical nitrate reduction reaction (NO3 -RR) to ammonia is a promising route to eliminate one of the major pollutants in surface and groundwater. When powered by renewable electricity, electrolysis provides a sustainable method to generate ammonia from nitrate ions, facilitating the transition from a linear to a circular economy. Optimizing the physical and chemical properties of electrolysis cells is crucial to make this process economically viable for widespread implementation. Here, we explore how the choice of current density, conductivity, pH, inter-electrode distance, membrane, catalyst, and buffer solution affect nitrate removal performance and efficiency. We develop a modeling framework to investigate the cell characteristics and fluid dynamics during electrochemical NO3-RR using both laminar and bubbly flows. To obtain more precise results, we employed the bubbly flow model (i.e., Multi-phase Fluid) to take into account how gas production near the electrode surface affects liquid velocity, pH distribution, and, ultimately, potential losses. We exploit mass transfer theory to include the current density effect on migration and diffusion. In the absence of a buffer solution, the Nernstian loss became a significant portion of the polarization loss, which increased with current density. We identified the positive effect of the membrane on energy efficiency to be more significant at smaller inter-electrode distances. This study provides insights into the origin of potential losses and pH distribution, enabling electrochemical cell optimization for renewable fuel synthesis. Next, we will discuss our recent work on designing single atom alloys (SAAs) for selective conversion of low concentration nitrate ions in natural wastewater streams from Dairy farm into ammonia. We benchmarked the catalyst's selectivity, activity, and stability following standard protocols established in the field of nitrogen fixation, including control experiments by using an electrolyte that does not contain nitrate ions and performing experiments under the same operating conditions using nitrogen isotopes (i.e., 14NO3 -, 15NO3 -).

Distinguishing Electrochemical Processes in PEM Electrolysis By Impedance Modeling – Distribution of Relaxation Times

Proton exchange membrane (PEM) water electrolysis is a key technology in hydrogen production to provide capacity and flexibility for renewable energy power sources. Various research topics for electrolyzer development focus on cost reduction, performance optimization and lifetime extension with minimum platinum group metal (PGM) loading required [1]. Understanding degradation mechanisms in PEM electrolysis cells becomes necessary for developing mitigation strategies in dynamic durability tests, which facilitates the importance of advanced electrochemical characterization methods.Electrochemical impedance spectroscopy (EIS) is a commonly used diagnostic technique in electrochemical systems. For impedance interpretation, equivalent circuit model (ECM) can be an option with prior knowledge about the system and appropriate circuit elements to prevent overfitting. Alternatively, distribution of relaxation times (DRT) provides a model-free pathway to address electrochemical mechanisms with different time constants and it has been applied to fuel cells, batteries and capacitors in the past years [2, 3]. Impedance deconvolution by DRT, however, has not been well adapted for PEMECs. In this study, electrochemical processes are successfully identified from the DRT profile by varying membrane electrode assembly (MEA) compositions and different operational conditions. In a single cell testing, four main peaks in DRT results associated with (1) mass transport losses (2) reaction kinetic (3) ionic conductivity within the catalyst layer and (4) ohmic properties at the interface of membrane and catalyst layers can be separated and quantified. Examination of electron microscopy provides further explanation of different MEA characteristics in performance analysis. This study verifies DRT is a promising tool to better understand PEM electrolysis processes and will be applied to degradation mitigation in the future.

Evolution of 2PB/3PB Transport Pathways in Oxygen Electrodes during Degradation Test: A Perspective from Electro-Chemo-Mechanical Coupling on Microstructures

The solid oxide electrolysis cell (SOEC) has garnered significant attention over the past decades for hydrogen generation integrated with intermittent renewable energy [1]. However, a major hurdle in the commercialization of SOEC is cell degradation when operated beyond 1000 hours [2]. SOEC degrades two times more quickly than the same cell operated in fuel cell mode [3]. Perovskite oxygen electrodes (OEs), such as La1-xSrxCo1-yFeyO3-δ (LSCF), exhibit flexible oxygen stoichiometry [4-6] depending on the operating conditions. The delamination failure in perovskite OEs arises from a mismatch between the slower O2 evolution rate at the surface and the rapid O2 current in the bulk from the electrolyte (EL), which causes variations in oxygen stoichiometry. This variation in oxygen stoichiometry enhances bonding, contracts lattice volume, and leads to chemical stress at the OE/EL interface [7].In this research, we aim to construct an electro-chemo-mechanically coupled model with synthetic microstructures (Fig.1a) to explore the intricate interactions between delamination at the OE/EL interface and oxygen ion transport pathway evolution. The Dream 3D software will be utilized for microstructure generation, Matlab for mesh preparation, and Comsol for Multiphysics simulation. We will examine two OE configurations known for achieving high electrocatalytic activity [8]: single layer and bilayer OEs . For the single layer configuration, La0.6Sr0.4Co0.4Fe0.6O3 (LSCF) [9, 10] serves as the sole electrode material. For bilayer OEs, we incorporate SrTa0.1Co0.9O3 (SCT) [11, 12] as the capping layer for electrocatalytic activity, with LSCF acting as the supporting backbone. The evolution of two transport pathways (Fig.1b&c), double phase boundary (2PB) and tripe phase boundary (3PB), in different configurations during long-term degradation tests will be evaluated by coupling the models with experimental polarization curves and electrochemical impedance spectra. The investigations will focus on the effects of delamination resulting from lattice volume variations on shifting of transport pathways (Fig.1d) in different OE configurations. References Nechache, A. and S. Hody, Alternative and innovative solid oxide electrolysis cell materials: A short review. Renewable and Sustainable Energy Reviews, 2021. 149.Rashkeev, S.N. and M.V. Glazoff, Atomic-scale mechanisms of oxygen electrode delamination in solid oxide electrolyzer cells. International Journal of Hydrogen Energy, 2012. 37(2): p. 1280-1291.Moçoteguy, P. and A. Brisse, A review and comprehensive analysis of degradation mechanisms of solid oxide electrolysis cells. International Journal of Hydrogen Energy, 2013. 38(36): p. 15887-15902.Adler, S.B., Chemical Expansivity of Electrochemical Ceramics. Journal of the American Ceramic Society, 2001. 84(9): p. 2117-2119.Atkinson, A. and T.M.G.M. Ramos, Chemically-induced stresses in ceramic oxygen ion-conducting membranes. Solid State Ionics, 2000. 129(1): p. 259-269.Bishop, S.R., K.L. Duncan, and E.D. Wachsman, Defect equilibria and chemical expansion in non-stoichiometric undoped and gadolinium-doped cerium oxide. Electrochimica Acta, 2009. 54(5): p. 1436-1443.Cook, K., J. Wrubel, Z. Ma, K. Huang, and X. Jin, Modeling Electrokinetics of Oxygen Electrodes in Solid Oxide Electrolyzer Cells. Journal of The Electrochemical Society, 2021. 168(11): p. 114510.Laguna-Bercero, M.A., H. Monzón, A. Larrea, and V.M. Orera, Improved stability of reversible solid oxide cells with a nickelate-based oxygen electrode. Journal of Materials Chemistry A, 2016. 4(4): p. 1446-1453.Mogensen, M.B., M. Chen, H.L. Frandsen, C. Graves, J.B. Hansen, K.V. Hansen, A. Hauch, T. Jacobsen, S.H. Jensen, T.L. Skafte, and X. Sun, Reversible solid-oxide cells for clean and sustainable energy. Clean Energy, 2019. 3(3): p. 175-201.Jiang, S.P., Challenges in the development of reversible solid oxide cell technologies: a mini review. Asia-Pacific Journal of Chemical Engineering, 2016. 11(3): p. 386-391.Huang, K. and Y. Wen, Electrochemical Performance of New Bilayer Oxygen Electrode for Reversible Solid Oxide Cells. ECS Meeting s, 2021. MA2021-03(1): p. 138-138.Huang, K., Method to Make Isostructural Bilayer Oxygen Electrode. 2020, University of South Carolina: US. Figure 1

(Invited) Novel Polymer and Membrane Development Strategies for Water Electrolysis

Water electrolysis processes play a crucial role in transitioning to a climate-friendly society. They facilitate the integration of renewable energy, offer a clean and versatile energy carrier, decarbonize industries, improve energy storage and grid stability, and support the development of sustainable transportation solutions. As technology advances and economies of scale are realized, electrolysis is expected to play an increasingly significant role in the clean energy landscape, contributing to a more sustainable and resilient future.Various water-splitting electrolysis processes currently exist, including alkaline, solid oxide, proton exchange membrane (PEM), anion exchange (AEM), acidic-alkaline amphoteric, microbial, and photoelectrochemical methods [1]. In our research group, we are actively involved in membrane development for both PEM and AEM water electrolysis.In PEM electrolysis membrane development, our group explores several approaches, such as (a) aromatic main-chain block copolymers[2],(b) acid-base blend membranes using sulfonated and partially fluorinated aromatic polyether, polybenzimidazole, and a PSU-derived basic polymer[2], (c) poly(fluorene)-based sulfonated ionomers, (d) sulfonated and phosphonated poly(pentafluorostyrene) polymers with flexible side groups, and (d) nanophase-separated block copolymers based on phosphonated[3] or sulfonated pentafluorostyrene and octylstyrene. Additionally, we investigate (e) H+-conductive fiber-mat reinforced perfluorosulfonic acid (PFSA) polymers[4].The development of anion exchange membranes in our research group includes (a) polystyrene-based side chain anion exchange polymers and their blends with polybenzimidazole[5], (b) polynorbornene-based optionally ionically and covalently crosslinked anion exchange polymers and membranes, (c) side chain anion exchange polymers and membranes prepared by polyhydroxyalkylation[6], and (d) anion exchange blend membranes made from polydiallyldimethylammonium salts and polybenzimidazole.This contribution highlights the application of two polymer types in PEM and AEM membrane water electrolysis, respectively:(A) PEM Water Electrolysis (PEMWE): Membranes from PEM types (a) and (b) demonstrated good performance. PEM (a) achieved 2.2 V@6 A/cm2, and PEM (b) reached 2.26 V@6 A/cm2 (compared to Nafion212: 2.26 V@6 A/cm2)[2]. These performances were accomplished with non-optimized membrane-electrode assemblies using Nafion as the electrode ionomer. Further performance improvements are expected with optimized electrodes containing the same ionomers as used in the membrane.(B) AEM Water Electrolysis (AEMWE): Blend membranes from AEM type (a) exhibited excellent alkali stability (no conductivity decrease after 1000 hrs of storage in 1M KOH@85°C) and good AEMWE performance (CuCo anode catalyst, 1M KOH, 70°C, 2 V@3 A/cm2)[5]. Type (c) AEMs were applied to a seawater electrolysis cell at 60°C, achieving a performance of 2 V@1 A/cm2 using completely noble metal-free catalysts in both the anode and cathode[6].[1] M. F. Ahmad Kamaroddin, N. Sabli, T. A. Tuan Abdullah, S. I. Siajam, L. C. Abdullah, A. Abdul Jalil, A. Ahmad, Membranes 2021, 11.[2] J. Bender, B. Mayerhöfer, P. Trinke, B. Bensmann, R. Hanke-Rauschenbach, K. Krajinovic, S. Thiele, J. Kerres, Polymers 2021, 13.[3] S. Auffarth, M. Wagner, A. Krieger, B. Fritsch, L. Hager, A. Hutzler, T. Böhm, S. Thiele, J. Kerres, ACS Materials Lett. 2023, 5, 2039.[4] M. S. Mu'min, M. Komma, D. Abbas, M. Wagner, A. Krieger, S. Thiele, T. Böhm, J. Kerres, Journal of Membrane Science 2023, 685, 121915.[5] L. Hager, M. Hegelheimer, J. Stonawski, A. T. S. Freiberg, C. Jaramillo-Hernández, G. Abellán, A. Hutzler, T. Böhm, S. Thiele, J. Kerres, J. Mater. Chem. A 2023.[6] M. L. Frisch, T. N. Thanh, A. Arinchtein, L. Hager, J. Schmidt, S. Brückner, J. Kerres, P. Strasser, ACS Energy Lett. 2023, 8, 2387.

Design and Performance Evaluation of a Specialized Bubbler System for Accurate and Repeatable Solid Oxide Electrolysis Cell (SOEC) Testing

Accurate assessment of Solid Oxide Electrolysis Cell (SOEC) performance demands standardized testing conditions, particularly in stable steam delivery. Fluctuations in steam concentration and flow rate can significantly impact measured open-circuit voltage (OCV) and polarization behavior. Although direct steam injection is straightforward, it is often hindered by instability resulting from intermittent liquid water flux, pressure fluctuations, and fractional distillation effects. Bubbler humidification systems have the potential to offer consistent steam, but tailored designs for SOEC testing are currently absent.This study introduces a specialized bubbler system designed to deliver stable steam to SOEC test stands accommodating both oxygen-conducting (O-SOEC) and proton-conducting (H-SOEC) cells. The bubbler components include a refill water reservoir, a level control module, heating elements, pressure relief valves, check valves, tubing, and fittings integrated with the test stand. The system humidifies the sweep gas, transporting steam to the cell test fixture situated within a high-temperature furnace.The design process involved meticulous considerations of materials compatibility, hydrogen safety, and overtemperature protection. All wetted components employ stainless steel, glass, or PTFE materials in their construction construction. Redundant thermocouples ensure safe process temperatures with automated overtemperature shut off. The refill reservoir and bubbler headspace operate near ambient pressure, facilitated by an exhaust line vent sized for minimal backpressure.In various executed O-SOEC tests, the bubbler maintained OCV stability within ±5 mV over several hundred hours for each cell operating at 750°C, eliminating spikes caused by steam fluctuations observed with direct injection methods. This facilitates precise electrochemical analysis and determination of area-specific resistance losses. Polarization curves align with expected behavior based on the Nernst equation. The system has demonstrated safe and stable functionality for over thousands of hours across various operating conditions.The bubbler design presents researchers with notable advantages over existing steam supply options for SOEC test stands, addressing performance, safety, and flexibility concerns. Online instrumentation enables closed-loop control of steam conditions, enhancing stability. Standardization of test equipment is crucial for quality results, and this work contributes progress toward reproducible protocols in the international SOEC community. The modular bubbler approach, integrated with safety features, also signifies safer methodology choices for lab-scale experimental research.

Novel Ru-Based PEM Electrolysis Catalyst – Development from the Nano- to the Industrial-Scale

For the de-fossilization of sectors like chemicals, steel, and transportation, green H2 generated via water electrolysis provides a path towards net-zero. The broad use of H2 across hard-to-abate sectors confirms the urgent need for green hydrogen at scale.Within water electrolysis, there are several competing technologies: the so-called solid oxide electrolysis cell (SOEC), alkaline water electrolysis (AEL) and polymer electrolyte membrane electrolysis (PEM EL). Here, the latter shows significant benefits, such as high current density operation (> 2 A/cm2) and thus a smaller footprint, highly dynamic operation mode, high gas purity, and generation of pressurized hydrogen. However, at present, PEM EL requires precious metal catalysts; in particular, the O2 evolution on the anode currently relies on iridium, a metal which is rather scarce and expensive [1].To meet the demand of iridium with respect to the announced increase in electrolyzer capacities in the multi-GW range, material innovation to reduce the use of this precious metal must be implemented. Successful catalyst and electrode developments have already been demonstrated in the BMBF funded project Kopernikus P2X, whereby loadings of approx. 0.3 mg/cm2 (< 0.1 g/kW1) have been achieved without any significant losses in activity over time [2, 3].Here, we present a material innovation in the form of Ru-based electrocatalysts with a significantly reduced Ir content. This ruthenium-iridium oxide can be adjusted in a wide range of Ir content down to less than 15 wt.% (Ir). Consequently, iridium-based electrode loadings of less than 0.1 mg/cm2 and mass activities of about 3,500 A/g are feasible. Moreover, in accelerated degradation tests those mixed-oxides have demonstrated the often-missing stability by showing low degradation rates, similar to that of pure IrO2, in up to 30,000 potential-induced stress cycles.This achievement stems from a remarkable screening approach that combines synthesis, characterization and testing at the nanoscale at Mattiq, and on industrial scale in the multi-gram range at Heraeus Precious Metals GmbH & Co. KG. Remarkably the alignment of degradation testing on both scales showcases the power of the applied method, providing a blueprint for high throughput screening for future material developments, both within water electrolysis and beyond.

Synergistic Electrocatalysts Impact Efficient and Durable Oxygen Evolution Catalysis for Proton Exchange Membrane Water Splitting

Low-temperature water electrolysis can rapidly produce environmentally sustainable or green hydrogen, and is a prospective means of storing energy from renewable but intermittent power sources, such as wind and solar, in future clean energy infrastructure (1-4). Commercial water electrolysis either use liquid alkaline electrolyte or proton exchange membrane electrolyte (1). The proton exchange membrane water electrolysis (PEMWE) offers more advantages than the alkaline counterpart, such as higher purity of H2, lower resistance losses, more compact design, and what the most important is the compatible with the intermittent of the renewable energy (1-2). The grant challenge remaining in PEMWE is the development of the highly active, cost effective and stable catalysts for oxygen evolution reaction (OER), which is very sluggish requiring large amounts of precious metal as the catalysts, such as Ir, Ru and their oxides (1).In PEM water electrolysis cells, the catalysts should have high surface areas and high porosities that exposit sufficient active sites available to the reactants and electrolyte, as well as transferring the bubble out of the catalyst surface to ensure a fast mass transfer (5). Also, the OER is dependent on the inherent conductivity of the catalysts or the supports (1). For example, poor electronic conductivity within the catalyst layer will result in poor lateral conductivity across the catalyst layer, thus catalyst not in the vicinity of the porous transport layer will not participate in the reaction. To enable the widespread penetration of the PEMWE technologies, it is urgently to reduce the Ir loading to the sustainable level (~ 0.3 mg/cm2) compared with the current commercial usage (2-6 mg/cm2). Alternatively, to develop precious metal free catalyst with high efficiency and sustained durability (5).In this presentation, we will describe a method of preparing highly active yet stable synergistic electrocatalysts for oxygen evolution reaction for PEMWE. The new catalysts contain IrCoOx/ RuCoOx cluster and La&Li co-doped Co3O4 fiber which was derived from cobalt zeolitic imidazolate framework as precursor. The OER activities of the catalysts were first tested in O2 saturated acidic electrolyte by ring disk electrode (RDE), which displayed high mass activity 26-50 times that of commercial Ir and RuO2. The catalysts were fabricated into membrane electrode assemble and measured under real PEM water electrolysis condition. The cells demonstrated 2 A/cm2@1.76 V @0.25 ± 0.05 mgIr/cm2 loading, and negligible degradation after ~250 h chronoamperometric measurements at 2 A/cm2 (6), which meets the target set by US DOE for OER catalysts for PEMWE.The characterizations of the fresh and post-electrochemical samples were investigated by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), X-ray absorption near-edge structure (XANES), extended X-ray absorption fine structure (EXAFS), transmission electron microscopy (TEM), Raman spectroscopy and BET surface analysis. We also performed DFT simulation on the OER reaction pathways over Ir and Co sites of different facets parallelly on basis of the TEM results. The result reveals the synergy between Ir/Ru and Co resulting in the enhanced catalytic activities of both IrCoOx /RuCoOx and LaLi@Co3O4 toward OER.Acknowledgments:This work was supported by Overseas Outstanding Youth Fund project, shanghai Jiao Tong university, Shanghai, China; Shanghai Pujiang talent Plan, Shanghai, China; Argonne National Laboratory through Maria Goeppert Mayer Fellowship, US; State Key Laboratory of Metal Matrix Composites, shanghai Jiao Tong university, Shanghai, China. The works performed at Hydrogen research center, shanghai Jiao Tong university, and Argonne National Laboratory’s Center for Nanoscale Materials and Advanced Photo Source.Reference: K. Ayers et al., Annu. Rev. Chem. Biomol. Eng. 10, 219–239 (2019).M. Carmo, D. L. Fritz, J. Mergel, D. Stolten, Int. J. Hydrogen Energy 38, 4901–4934 (2013).M. T. M. Koper, J. Electroanal. Chem. 660, 254–260 (2011).R. D. L. Smith et al., Science 340, 60–63 (2013).Chong et al., Science 380, 609–616 (2023).Chong et al., Adv. Energy Mater. 2023, 2302306.

Long Term Durability Investigation of Cu-Doped La2NiO4 Oxygen Electrodes in Solid Oxide Electrolysis Cells

State-of-the-art oxygen electrodes in SOECs, lanthanum strontium cobalt iron oxide (LSCF) and lanthanum strontium cobalt oxide (LSC), contain strontium. Undesired reactivity and migration of Sr cations during long-term operation was found to be detrimental to the electrochemical performance as they triggered formation of multiple oxide phases, including insulating phases and electrode or barrier layer delamination. Developing alternative electrodes that are devoid of Sr is very important for long-term operation of SOECs.In this work, we synthesized and evaluated properties of La2NiO4-based compositions with a Ruddlesden-Popper structure. The Cu-doped La2NiO4 compositions made of nano-size particles exhibited an enhanced electrochemical performance when tested in SOECs during steam electrolysis for hydrogen production. Long-term durability of these electrodes was studied using planar Ni-YSZ electrode-supported cells with an active area of 1.5 (button cells) and 13 cm2 (2.5 cm x 5 cm cells). Compared to the Sr-containing electrodes, the La2Ni0.8Cu0.2O4 (LNCuO-20) demonstrated lower degradation rate at 1.3 Volt resulting in a current density over 1 A/cm2 at 750⁰C. Chrome and sulfur tolerance of these electrodes during long term operation will be discussed as well.

Enhancing Direct Eectrochemical CO2 Electrolysis By Introducing a-Site Deficiency for Dual-Phase Pr(Ca)Fe(Ni)O3-Δ Cathode

High-temperature CO2 electrolysis via solid oxide electrolysis cells (CO2-SOECs) has drawn special attention due to the high energy convention efficiency, fast electrode kinetics, and great potential in carbon cycling. However, the development of cathode materials with high catalytic activity and chemical stability for pure CO2 electrolysis is still a great challenge. In this work, A-site cation deficient dual-phase material, namely (Pr0.4Ca0.6)xFe0.8Ni0.2O3- δ (PCFN, x=1, 0.95, and 0.9), has been designed as the fuel electrode for a pure CO2-SOEC which presents superior electrochemical performance. Among all these compositions, (Pr0.4Ca0.6)0.95Fe0.8Ni0.2O3- δ (PCFN95) exhibited the lowest polarization resistance of 0.458 Ω cm2 at open circuit voltage and 800℃. The application of PCFN95 as the cathode in a single cell yields an impressive electrolysis current density of 1.76 A cm-2 at 1.5 V and 800℃, which is 76% higher than that of single cells with stoichiometric Pr0.4Ca0.6Fe0.8Ni0.2O3- δ (PCFN100) cathode. The effects of A-site deficiency on materials’ phase structure and physicochemical properties are also systematically investigated. Such an enhancement in electrochemical performance is attributed to the promotion of effective CO2 adsorption, as well as the improved electrode kinetics resulting from A-site deficiency.

Introducing Platinum Cryoaerogel As a Low Loading Cathode Catalyst in PEM Water Electrolysis

An important cost factor for polymer electrolyte membrane water electrolysers is precious metals as the catalyst layers. Therefore, reducing of the platinum loading on the cathode side and the iridium on the anode is essential to reduce the overall costs of hydrogen production. Cryoaerogels from noble metal nanoparticles are a suitable, yet unexplored material for use as a catalyst in water electrolysis. They combine high porosity and surface area with an excellent catalytic activity at low loadings of noble metal.[1] Recently, we have succeeded in producing a carbon-based gas diffusion electrode (GDE) coated with platinum cryoaerogel as the catalyst. The mechanical connection to the carbon underneath as well as maintaining a high protonic conductivity in contact to the Nafion membrane allowed the application to the water electrolysis cell. The manufacturing includes an oven treatment, whose temperature is particularly decisive for the structure of the cryoaerogel. Figure 1 left shows the polarization curves of the samples pyrolyzed at 300°C, 350°C and 500°C compared to a commercial GDE (platinum loading of 0.5 mg/cm²). All measurements are repeated three times and showed good reproducibility, as indicated by the error bars on the graph. Among the different temperatures, 300°C is the optimum for the pyrolysis process as it showed the lowest voltages. The catalytic performance of the different samples can be correlated to the micro-structure of the cryoaerogel layer represented by the SEM images and the electronic-structure of the platinum as shown by X-ray photoelectron spectroscopy (XPS). Although in figure 1 the performance of the cryoaerogel catalyst layers is not better than the commercial GDE, however, the platinum loading is significantly reduced by 70% (0.15 mg/cm2). Moreover, the reproducibility of the measurements proofs the possibility of using cryoaerogels in the full water electrolysis cell.[1] Müller, D., Zámbó, D., Dorfs, D., Bigall, N. C., Cryoaerogels and Cryohydrogels as Efficient Electrocatalysts. Small 2021, 17, 2007908. https://doi.org/10.1002/smll.202007908 Figure 1

Theoretical Understanding of Stability of the Oxygen Electrode in a Proton-Conductor Based Solid Oxide Electrolysis Cell

The oxygen electrode in a proton-conductor based solid oxide cells is often a tripleconducting material that enables the transport and exchange of electrons (e), oxygen ions (O2), and protons (H+), thus expanding active areas to enhance the oxygen electrode activity. In this work, a theoretical model was developed to understand stability of triconducting oxygen electrode by studying chemical potentials of neutral species (i.e., μO2 , μH2 , and μH2O) as functions of transport properties, operating parameters, and cell geometry. Our theoretical understanding shows that (1): In a conventional oxygen-ion based solid oxide cell, a high μO2 (thus high oxygen partial pressure) exists in the oxygen electrode during the electrolysis mode, which may lead to the formation of cracks at the electrode/electrolyte interface. While in a proton-conductor based solid oxide cell, the μO2 is reduced significantly, suppressing the crack formation, and resulting in improved performance stability (2). In a typical proton-conductor based solid oxide electrolyzer, the dependence of μO2 on the Faradaic efficiency is negligible. Hence, approaches to block the electronic current can improve the electrolysis efficiency while achieving stability (3). The difference of the μO2 (thus pO2 ) between the oxygen electrode and gas phase can be reduced by using higher ionic conducting components and improving electrode kinetics, which lead to further improvement of electrode stability.

Development of an Onboard Urea Electrolyser to Reduce NOx Emissions in Vehicles By Enhancing the Selective Catalytic Reduction with the Produced H2 and NH3

In the persistent pursuit of reducing nitrogen oxide emissions from diesel exhaust, challenges arise in achieving optimal performance at lower temperatures, especially in urban driving conditions. This research focuses on a pragmatic approach – development of an onboard urea electrolyser using diesel exhaust fluid (DEF) as the hydrogen-rich carrier. The primary goal is to enhance the NOx reduction efficiency at temperatures below 200oC by providing the electrolyser products – hydrogen and ammonia [1]. The reason behind this innovation lies in recognising DEF as a viable electrolyte, offering both safety and a promise of performance increase due to splitting of urea instead of water. Beyond the contribution to NOx reduction, this approach aligns with the broader societal and political imperatives of integrating cleaner energy solutions within the automotive sector. However, the development of a functional urea electrolyser involves certain complexities. The key considerations are the material stability under operating conditions, anode catalyst dissolution in DEF, mass transport limitations, and the reduction of relatively high cathode overpotentials. A notable aspect of our research involves addressing these challenges in scenarios both with and without potassium hydroxide alongside DEF, requiring a nuanced understanding of the electrochemical processes involved. Additionally, weight, packaging, and system integration play an important role in the development of an onboard urea electrolyser.This study systematically explores these challenges to devise a comprehensive understanding of the underlying electrochemical processes involved as well as the integration and operation strategy. The research methodology adopts single cell tests for which activation and measurement protocols have been established to achieve representative and comparable performance curve recordings and electrochemical impedance spectroscopy (EIS) data. Additionally, to various operating conditions of the electrolyte, the cell components screening adds to a considerable effort of this study. We explore the influence on the materials and design of the bipolar plates (BP) and porous transport layers (PTL); electrode performance and durability as well as the membrane selection. Within this study we consider anion exchange membranes (AEM) and bipolar membranes (BPM) for the performance comparison. Adopting both catalyst-coated membrane (CCM) and catalyst-coated substrate (CCS) approaches enables for examination of electrode preparation techniques and their influence on performance of the electrolysis cell. The initial results are promising, especially when employing 1 M KOH in the DEF electrolyte at 70oC, reaching 0.85 A cm-1 at 2 V. The respective performance curve is presented in Figure 1., together with a diagram of the electrolyser system integration into an existing Diesel exhaust line.This research represents a practical stride towards realising the denitrification of transportation sector especially in city cycle driving when the exhaust gases temperature is too low for the state-of-the-art SCR systems. By addressing identified challenges and optimising key parameters, our study lays a robust foundation for the scalable implementation of a functional urea electrolyser for transport applications and a basic understanding of the electrochemical processes behind the performance and stability of such a system.Figure 1.Depicts a recorded polarisation curve of a single cell using an anion exchange membrane (AEM) and nickel catalyst anode fed DEF and 1 M KOH as an electrolyte at 70oC. Below, the suggested integration of the electrolyser into latest generation Diesel exhaust aftertreatment system. It includes diesel oxidation catalyst (DOC), selective Diesel particulate filter (sDPF), hydrogen supported denitrification catalyst ‘H2-deNOx’ and finally a selective catalytic reduction (SCR) step.Reference: Esser, E., Kureti, S., Heckemüller, L., Todt, A. et al., "Low-Temperature NOx Reduction by H2 in Diesel Engine Exhaust," SAE Int. J. Adv. & Curr. Prac. in Mobility 4(5):1828-1845, 2022, https://doi.org/10.4271/2022-01-0538. Figure 1

Multiphase Modeling of Enhanced Bubble Evacuation in Alkaline Water Electrolysis Cells Based on Laterally-Graded 3-D Electrodes

To mitigate the challenges posed by anthropogenic climate interference, substantial efforts are imperative in order to limit the rise in global average temperature. One major declaration made by the international community through various climate agreements [1,2] calls for an elimination of greenhouse gas emissions, necessitating a shift from fossil fuels to sustainable renewable energy sources. Hydrogen and hydrogen-based fuels emerge as promising candidates to decarbonize a wide range of sectors – including transport, industry and chemical manufacture – due to hydrogen’s remarkable flexibility and storage capacity. At present, water electrolysis conducted by renewable electricity is considered as the most sustainable technology to produce green hydrogen.Among the various approaches for water electrolysis, two commercially available methods stand out: alkaline and proton exchange membrane (PEM) [3]. Alkaline water electrolysis (AWE) has the advantage of presenting the lowest cost per kilowatt of electricity but yields lower hydrogen production rates. In contrast, PEM electrolysis achieves superior performance, thanks to the use of costly and scarce electrocatalytic materials like Ir and Pt. Considering the unique strengths of each system, it is appealing to try to integrate the best of these two technologies, yielding high production rates per electrode area while benefiting from more cost-effective electrode materials.To this end, recent experimental work in our group has focused on the conception and analysis of flow-engineered 3-D electrodes into a novel laterally-graded cell configuration to allow alkaline water electrolysis to become PEM-like [4,5]. More specifically, 3-D electrodes such as foams were integrated into a zero-gap cell using a bi-layer configuration in which a fine foam (450 µm pore size) working as a catalytic electrode is put in contact with a coarser foam (3000 µm pore size) acting as a porous transport layer (PTL). Because of the high production rate in the 450 µm foam, a high forced upstream electrolyte flow is used to favour bubble removal and hence decrease the Ohmic resistance of the system. Thanks to the use of a bi-layer configuration in flow-through upstream flow mode, the many bubbles generated near the diaphragm were believed to be evacuated laterally towards the coarser foam, keeping the catalytic surface of the finer foam active throughout the process. The enhanced performance of this PEM-like system was confirmed experimentally and current densities of 2 A/cm2 were observed at cell voltages lower than 2 V (for 2 x 2 x 0.56 cm3 electrodes).The aim of this work is to use Computational Fluid Dynamics (CFD) simulations in order to assess flow behaviour into the bi-layer and validate the assumptions that were made based on the experimental results. First of all, a single-phase model (i.e. considering only the electrolyte) was used to solve the incompressible Navier-Stokes equations in OpenFOAM. The objective is to shift towards multiphase simulations by considering a simple mixture model to account for the presence of gas bubbles. The driftFluxFoam solver will be used to solve the general mixture model equations, in which velocity, density and viscosity are weight-averaged based on gas fraction and on the properties of both phases. This work also highlights two ways of incorporating porous media in the numerical simulations. The first way, called explicit, is based on the exact geometry of the foams, obtained thanks to high-resolution micro-CT (computed tomography) scanned data, but is extremely costly from a numerical point of view. The other method, called implicit, uses the Darcy-Forchheimer approximation to spatially average porosity over a given domain, which is less representative of the exact foam structure but generally allows to get first useful insights of the flow behaviour in porous media.An example of a laterally graded bi-layer configuration and some initial multiphase results are shown in Figure 1. The velocity vectors and the lateral velocity profile confirm that hydrogen bubbles can indeed be expected to be evacuated from the fine catalytic 450 µm into the coarser 3000 µm PTL foam. The main objective of our modeling approach is to demonstrate the relation between the observed electrochemical performance enhancement with multiphase mass transport phenomena occurring inside the 3-D electrodes in order to show the intrinsic interest of using such laterally graded bi-layer approach in all future alkaline water electrolysers. Figure 1

Doping of Porous Transport Layers to Optimize Electrical Contact Behaviour in PEM Water Electrolysis Cells

A high overall efficiency is crucial for large-scale polymer electrolyte membrane water electrolysers. Due to the harsh environment at the anode, a titanium oxide layer with high electrical resistivity passivates porous transport layers (PTL). A common used way to overcome this problem is noble metal coating (e.g. with platinum, gold or iridium). [1] For the very first time, we present a new and inexpensive way of maintaining the high conductivity of PTLs by doping the titanium surface that faces the catalyst layer. Sun et al. [2] modelled the conductivity of doped titanium oxide for different elements. With respect to their results and Koech et al. [3] we chose tin, niobium, antimony and yttrium as dopants. The implantation was carried out at the Ion Beam Center of the HZDR in Dresden, Germany. All doped PTLs displayed a lower cell voltage than the undoped reference as visible in figure 1a). While tin improves in the range of 2-3 % at a current density of 2A/cm², the other dopants best results reach values of over 4 % with niobium achieving the best performance with 4.4 % improvement (see figure 1b) for comparison). Figure 1c) shows the high frequency resistance (HFR) originating from impedance measurements. The observable improvement of up to 11.4% at 2A/cm² proves the fact that the advantage corresponds to a better contact resistance due to a lower resistance of the doped titanium oxide layer. The improvement in percent presents figure 1d).The measurement results show that doping can have a great impact on the contact resistance of titanium PTLs. These results open a new opportunity in the manipulation of porous transport layers for enhanced contact behaviour, where no experimental publications exist yet. Especially in comparison to noble metal coatings like iridium, doping has an enormous cost advantage when using non noble metals with the potential of lowering the overall electrolyser system costs while increasing its efficiency.[1] Liu, C., Shviro, M., Gago, A. S., Zaccarine, S. F., Bender, G., Gazdzicki, P., Morawietz, T., Biswas, I., Rasinski, M., Everwand, A., Schierholz, R., Pfeilsticker, J., Müller, M., Lopes, P. P., Eichel, R.-A., Pivovar, B., Pylypenko, S., Friedrich, K. A., Lehnert, W., Carmo, M., Exploring the Interface of Skin-Layered Titanium Fibers for Electrochemical Water Splitting. Adv. Energy Mater. 2021, 11, 2002926. https://doi.org/10.1002/aenm.202002926[2] Hu Sun, Zhu-tian Xu, Di Zhang. First-principles calculations to investigate doping effects on electrical conductivity and interfacial contact resistance of TiO2, Applied Surface Science, Volume 614, 2023, 156202, ISSN 0169-4332, https://doi.org/10.1016/j.apsusc.2022.156202.[3] Koech, R.K.; Ichwani, R.; Oyewole, D.; Kigozi, M.; Amune, D.; Sanni, D.M.; Adeniji, S.; Oyewole, K.; Bello, A.; Ntsoenzok, E.; et al. Tin Oxide Modified Titanium Dioxide as Electron Transport Layer in Formamidinium-Rich Perovskite Solar Cells. Energies 2021, 14, 7870. https://doi.org/10.3390/en14237870 Figure 1

Mitigating the Corrosion of Anodized 304 and 316 Stainless Steel with GOx/PEDOT Coating for Bioelectrochemical Saline Water Applications

Steels are the most used alloys worldwide as they have superior mechanical properties, such as ductility and elasticity. Stainless steel (SS) is used far and wide from infrastructure, households, vehicles, surgical equipment, and medical implants, to electrochemical applications such as supercapacitors, fuel cells, lithium-ion batteries, aqueous rechargeable batteries, and bioelectrochemical systems (BES)1 such as microbial fuel cells (MFCs)2 and microbial electrolysis cells (MECs)3. Even though oxidized stainless steel is a very effective electrode material for BES, it has a high risk of corrosion due to the removal of the protective Cr-based passive oxide layer4.Hereby, this research aims to investigate the corrosion behavior of anodized stainless steel (SS) 304 and 316 mesh in saline water for potential use in BES with high salinity and try to mitigate that corrosion behavior using biocompatible materials. The tested electrodes include SS304 and SS316 mesh before and after anodization (anodized SS, AN-SS), in comparison to AN-SS coated with double layers of graphene oxide (GOx) and poly(3,4-ethylenedioxythiophene) (PEDOT). SS 304 and 316 were anodized using selective leaching protocol to enhance the removal of the bioincompatible and insulating Cr-based layer. The removal of that layer makes SS more susceptible to dissolution and hence further protection is needed. Both GOx and PEDOT were selected to enhance the surface conductivity, biocompatibility, and corrosion resistance. GOx was synthesized using the electro-exfoliation of a graphite sheet at a constant voltage of 10.0 V in terephthalic acid + NaOH solution, followed by centrifuging at 3000 rpm to remove the large particles.5 After several cycles of washing, the freeze-dried GOx was mixed with Nafion for ink preparation, which was used to coat the An-SS using the spray coating method. The coated electrode was further covered with a PEDOT layer, using the chronpotentiometry electropolymerization method (2 mA/cm2, for 10, 30, or 60 min). Several characterization techniques such as SEM, EDX, XPS, FT-IT, Raman spectroscopy, XRD, and TEM, were used to characterize the physical and chemical structure of the coating materials and the the fabricated electrodes. The corrosion behavior was evaluated using potentiodynamic and potentiostatic methods. Based on the anodic polarization results, the corrosion, passivation, and breakdown (due to dissolution) regions were identified. In this presentation, the corrosion behavior (Ecorr, Icorr, breakdown potential, etc) of the studied electrodes will be correlated with their chemical and physical structures. References K.-B. Pu, J.-R. Bai, Q.-Y. Chen, and Y.-H. Wang, in Novel Catalyst Materials for Bioelectrochemical Systems: Fundamentals and Applications, ACS Symposium Series., vol. 1342, p. 165–184, American Chemical Society (2020) https://doi.org/10.1021/bk-2020-1342.ch008.A. A. Abbas, H. H. Farrag, E. El-Sawy, and N. K. Allam, Journal of Cleaner Production, 285, 124816 (2021).Y. Zhang, M. D. Merrill, and B. E. Logan, International Journal of Hydrogen Energy, 35, 12020–12028 (2010).P. Ledezma, B. C. Donose, S. Freguia, and J. Keller, Electrochimica Acta, 158, 356–360 (2015).H. S. Wang et al., Green Chem., 20, 1306–1315 (2018).

Thermo-Mechanical Properties and Benefits of Borosilicate Glass for SOEC Sealants

Boro-silicate glass materials have ideal properties for sealing oxidizing and reducing environments and electrically insulating solid oxide electrolysis cells (SOEC), while maintaining a glassy phase at high temperatures (750-900°C) to minimize chemo-mechanical degradation and gas permeability 1,2. Glass seals are typically applied as a slurry; hence, they are also expected to have non-wetting properties to prevent glass infiltration into the porous electrode structures during manufacturing 3. During the first startup, the initial temperature ramp serves to evaporate any binder in the slurry and to go through the glass transition phase, which cures the glass and increases hardness to improve resistance to creep. Typical glass materials operate in visco-plastic regimes (i.e., beyond the material’s glass transition temperature) and must be chemically stable while operating in steam-rich and oxygen-rich environments. To fully understand the performance of borosilicate glass seals, optimize the manufacturing, assembly, and maintenance of SOEC, we must be able to measure and analyze the glass material properties (i.e., glass transition temperature, coefficient of thermal expansion, modulus, creep, hardness) at the same operating conditions relevant for SOEC operation. In this work, we characterize the thermo-mechanical properties of borosilicate glass powder and sintered samples at various temperatures (ranging from ambient to 850°C), and at different aging conditions (i.e., atmosphere composition, temperature, and duration). The atmosphere composition is changed between air, steam-N2 mixtures, and H2-N2 mixtures to evaluate the chemical stability of borosilicate glass relating to the possible depletion of boron and silicon via the formation of boron hydroxide and silicon vapor when exposed to steam- and hydrogen-rich environments. The aging temperature and duration is varied to evaluate the crystallization kinetics, particle size growth, and its effect on mechanical properties. We employ a combination of Simultaneous Thermal Analysis - STA (i.e., combined Thermogravimetric Analysis - TGA, Differential Scanning Calorimetry - DSC, Fourier Transform Infrared - FT-IR spectroscopy, and Quadrupole Mass Spectroscopy - QMS), and nanoindentation as characterization techniques, while surface roughness is estimated with a 3D confocal optical microscope.Surface roughness varies between 0.83-1.38 𝜇m ± 1.1-1.76 𝜇m (Sa ± Sq). Both powder and solid samples are analyzed via STA with sequential temperature ramps (constant heating rate at 10 K/min in Ar atmosphere) up to 1500°C to estimate the effect of crystallization and particle size on the glass transition onset. For a sample aged at 850°C for 340 h, the first ramp shows typical DSC exothermic peaks (mW/mg) at around 800°C, with a midpoint glass transition occurring at 900°C. However, on the second ramps, peaks lower to around 500°C and the glass transition is estimated to be around 700°C. Subsequent tests consistently mirrored the trend of the second temperature ramp, showing minimal deviation and influence of crystallization and particle growth. Nanoindentation is performed between room temperature and 600°C to characterize both sintered glass samples “as-received” and aged at temperatures between 750-950°C for 340 h. Comparing a sample aged at 750°C with an “as-received” sample, the elastic moduli equally decreased from 100 GPa at room temperature to 40 GPa at 600°C, with comparable hardness values ranging from 10 GPa at room temperature to 0.5-0.9 GPa at 600°C, respectively. A.G. Sabato, G. Cempura, D. Montinaro, A. Chrysanthou, M. Salvo, E. Bernardo, M. Secco, F. Smeacetto, Journal of Power Sources, 328, 262-270 (2016)Dilshat U. Tulyaganov, Allu Amarnath Reddy, Vladislav V. Kharton, José M.F. Ferreira, Journal of Power Sources, 242, 486-502 (2013)S.-B. Sohn, S.-Y. Choi, G.-H. Kim, H.-S. Song, G.-D. Kim, Stable sealing glass for planar solid oxide fuel cell, J. Non. Cryst. Solids. 297 (2002) 103–112. doi:10.1016/S0022-3093(01)01042-0 Figure 1