Wettability based separation of ionomer-containing ultrafine particles for PEM water electrolyzer recycling

Membraneless Electrolyzers for Low-Cost Hydrogen Production in a Renewable Energy Future

In this paper, fabrication and testing of a miniaturized microcantilever-based particulate matter detector with integrated electrostatic on-chip ultrafine particle (UFP) separation and collection are presented. Mass added to the sensor causes a resonance frequency shift. To attract naturally charged particles, the cantilever is equipped with a collection electrode. In addition, a µ-channel is integrated, to improve the particle collection efficiency and to enable a size/mass-related particle separation. For electrical read-out, piezo-resistive struts are attached to the cantilever sidewalls near its clamping. This design offers high miniaturization potential, since no integration of transducing electronics on the cantilever beam is needed. The sensors are fabricated using Si bulk material and standard micromachining technology; the cantilevers have a thickness of 3 ± 0.5 µm, a width of 3.1 ± 0.3 µm, 5.9 ± 0.4 µm or 10.5 ± 0.4 µm and a length of 118.7 ± 0.8 µm, 168.8 ± 0.8 µm or 171.2 ± 1 µm, respectively. To this end, a front-side release process using cryogenic inductive-coupled plasma reactive ion etching was developed, which does not require additional sidewall passivation steps. Testing of the resonator function by operating the sensor inside a scanning electron microscope and reference measurements inside a temperature-controlled test chamber using synthetic carbon UFPs (~160 nm average mass concentration distribution) and a fast mobility particle sizer as a reference instrument were carried out. Here, the ability to detect low UFP mass concentrations in the range <10 µg m−3 could be shown with a limit of detection of ~1 µg m−3 and a collection time of ~10 min. In addition, a voltage dependence of the collection efficiency was found at constant UFP-concentration conditions, which is an indication of size-selective UFP collection.

Chemical dispersion has been commonly used to mitigate the negative effects of ultrafine particles in iron ore concentration processes. However, mechanical solutions such as ultrasound are proving to be more effective and without harmful side effects. This study compared the performance of different dispersants and ultrasound as pretreatments for reverse cationic flotation of goethite-rich slime tailings through sedimentation, dispersion, and flotation tests, along with particle size analysis. Additionally, large-scale molecular dynamics simulations were used for the first time to investigate the effects of ultrasonic shockwaves on mineral particle interactions. The results showed that ultrasonication is a superior pretreatment, enhancing particle dispersion and separation performance, cleaning mineral surfaces, and improving flotation results. Ultrasound achieved an increase in metallurgical recovery of around 9% while using only a dispersant reagent did not reach 5%. Simulations demonstrated the known effects of ultrasound, such as extreme temperature, bubble cavitation, and particle detachment, revealing the crucial microscopic mechanisms involved in particle separation by sonic waves. This study bridges experimental data with computational simulations, offering a comprehensive understanding of ultrasonication's effects on particle separation, paving the way for more efficient and sustainable processing technologies.

Water electrolyzers and fuel cells can be used to create a closed loop system for space exploration. Electrolyzers allow for reliable self-sustainable generation of hydrogen and oxygen for energy storage, followed by conversion into electrical energy in a fuel cell. A first-order safety concern for water electrolyzer operation is hydrogen crossover. Transport of hydrogen to the oxygen rich anode in proton exchange membrane (PEM) water electrolyzers poses safety concerns when the hydrogen concentration in the anode flow field approaches the hydrogen lower flammability limit (LFL). Hydrogen storage efficiency relies on high hydrogen pressure, leading to pressure-driven hydrogen crossover. Mitigation of hydrogen crossover through research and development of a platinum metal recombination layer has been demonstrated in high performing, durable PEMWEs.1-4 Ouimet4 explored the use of a novel dual recombination layer configuration to mitigate PEM water electrolyzer hydrogen crossover. In addition, the current state of the art for PEM fuel cells and water electrolyzers rely on perfluoro-sulfonated acid (PSFA) based membranes. There are significant challenges facing the use of PSFA-based membranes; namely, environmental contamination and performance limitations. The use of a hydrocarbon membrane allows for the development of a PSFA-free system that shows higher efficiency and durability. Investigation of hydrocarbon membranes pave way for developing a PEM water electrolyzer that will demonstrate improved gas permeability resistance, mechanical strength, and thermal stability.5-8 There is a need for both hydrogen crossover mitigation strategies and durability testing with hydrocarbon membranes.The research outlined in this work is focused on the development of PSFA-free PEM water electrolyzers with low hydrogen crossover. In this work, the dual recombination layer configuration will be incorporated into a hydrocarbon membrane for PEM water electrolysis. Polarization, electrochemical impedance spectroscopy, electrochemical equivalent circuits, distribution of relaxation times, and materials characterization will be used to investigate the cell performance and durability. References G. Mirshekari, R. Ouimet, Z. Zeng, H. Yu, S. Bliznakov, L. Bonville, A. Niedzwiecki, C. Capuano, K. Ayers, and R. Maric, “High-performance and cost-effective membrane electrode assemblies for advanced proton exchange membrane water electrolyzers: Long-term durability assessment,” international journal of hydrogen energy, vol. 46, no. 2, pp. 1526–1539, 2021.Z. Zeng, R. Ouimet, L. Bonville, A. Niedzwiecki, C. Capuano, K. Ayers, A. P. Soleymani, J. Jankovic, H. Yu, G. Mirshekari, et al., “Degradation mechanisms in advanced meas for pem water electrolyzers fabricated by reactive spray deposition technology,” Journal of The Electrochemical Society, vol. 169, no. 5, p. 054536, 2022.A. Martin, D. Abbas, P. Trinke, T. Böhm, M. Bierling, B. Bensmann, S. Thiele, and R. Hanke-Rauschenbach, “Communication—proving the importance of ptinterlayer position in pemwe membranes for the effective reduction of the anodic hydrogen content,” Journal of The Electrochemical Society, vol. 168, no. 9, p. 094509, 2021.R. J. Ouimet, “Catalyst development by a novel fabrication process for energy applications,” University of Connecticut Doctoral Dissertation, 2021.P. Trinke, P. Haug, J. Brauns, B. Bensmann, R. Hanke-Rauschenbach, and T. Turek, “Hydrogen crossover in pem and alkaline water electrolysis: mechanisms, direct comparison and mitigation strategies,” Journal of The Electrochemical Society, vol. 165, no. 7, p. F502, 2018.P. Trinke, B. Bensmann, and R. Hanke-Rauschenbach, “Current density effect on hydrogen permeation in pem water electrolyzers,” International Journal of Hydrogen Energy, vol. 42, no. 21, pp. 14355–14366, 2017.H. Q. Nguyen and B. Shabani, “Proton exchange membrane fuel cells heat recovery opportunities for combined heating/cooling and power applications,” Energy Conversion and Management, vol. 204, p. 112328, 2020.C. Klose, T. Saatkamp, A. Münchinger, L. Bohn, G. Titvinidze, M. Breitwieser, K. D. Kreuer, and S. Vierrath, “All-hydrocarbon mea for pem water electrolysis combining low hydrogen crossover and high efficiency,” Advanced Energy Materials, vol. 10, no. 14, p. 1903995, 2020.

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.

Hydrogen, as a clean energy carrier, is of great potential to be an alternative fuel in the future. Proton exchange membrane (PEM) water electrolysis is hailed as the most desired technology for high purity hydrogen production and self-consistent with volatility of renewable energies, has ignited much attention in the past decades based on the high current density, greater energy efficiency, small mass-volume characteristic, easy handling and maintenance. To date, substantial efforts have been devoted to the development of advanced electrocatalysts to improve electrolytic efficiency and reduce the cost of PEM electrolyser. In this review, we firstly compare the alkaline water electrolysis (AWE), solid oxide electrolysis (SOE), and PEM water electrolysis and highlight the advantages of PEM water electrolysis. Furthermore, we summarize the recent progress in PEM water electrolysis including hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrocatalysts in the acidic electrolyte. We also introduce other PEM cell components (including membrane electrode assembly, current collector, and bipolar plate). Finally, the current challenges and an outlook for the future development of PEM water electrolysis technology for application in future hydrogen production are provided.

Mathematical modeling of an integrated photovoltaic-assisted PEM water electrolyzer system for hydrogen production

The high cost of noble metals is one of the key factors hindering the large‐scale application of proton exchange membrane (PEM) water electrolyzer for hydrogen production. Recently, single‐atom catalysts (SACs) with a potential of maximum atom utilization efficiency enable lowering the metal amount as much as possible; unfortunately, their durability remains a challenge under PEM water electrolyzer working conditions. Herein, a highly‐stable alloyed Pt SAC is demonstrated through a plasma‐assisted alloying strategy and applies to a PEM water electrolyzer. In this catalyst, single Pt atoms are firmly anchored onto a Ru support via a robust metal–metal bonding strength, as evidenced by these complementary characterizations. This SAC is used in a PEM water electrolyzer system to achieve a cell voltage as low as 1.8 V at 1000 mA cm−2. Impressively, it can operate over 1000 h without obvious decay, and the catalyst is present in the form of individual Pt atoms. To the knowledge, this will be the first SAC attempt at a cell level toward long‐term PEM. This work paves the way for designing durable SACs employed in the actual working condition in the PEM water electrolyzer.

Proton exchange membrane (PEM) water electrolysis has emerged as a pivotal technology for sustainable hydrogen production, offering a clean and efficient pathway to generate hydrogen from water using renewable energy sources. Novel Pt/C catalysts fabricated via fluidized bed reactor atomic layer deposition (FBR-ALD) present promising advancements for PEM water electrolyzer cathode catalyst layers. The process enables a uniform and controllable deposition of Pt nanoparticles onto carbon support materials, enhancing catalytic activity and stability [1]. The resulting catalysts demonstrate improved electrochemical performance in PEM water electrolysis, attributed to optimized Pt dispersion and enhanced catalytic sites [2]. This study explores the synthesis and further processing of these catalysts into catalyst inks and subsequently cathode catalyst layers for water electrolysis, leveraging the precise control and scalability offered by FBR-ALD to minimize the Pt loading while maintaining high catalytic activity and performance. Detailed layer characterization techniques, including atomic force microscopy (AFM) and electrochemical analyses, elucidate the structural and electrochemical properties of the Pt/C catalysts. Insights gained from this research contribute to a decrease in expensive platinum group metal employment and the scalable development of efficient, cost-effective, and durable catalyst materials for hydrogen production through PEM water electrolysis.[1] F. Grillo, H. Van Bui, J. A. Moulijn, M. T. Kreutzer, and J. R. van Ommen, “Understanding and Controlling the Aggregative Growth of Platinum Nanoparticles in Atomic Layer Deposition: An Avenue to Size Selection,” J. Phys. Chem. Lett., vol. 8, no. 5, 2017. doi: 10.1021/acs.jpclett.6b02978.[2] W.-J. Lee, S. Bera, H.-C. Shin, W.-P. Hong, S.-J. Oh, Z. Wan, S.-H. Kwon, Uniform and Size-Controlled Synthesis of Pt Nanoparticle Catalyst by Fluidized Bed Reactor Atomic Layer Deposition for PEMFCs. Adv. Mater. Interfaces 2019, 6, 1901210. doi: 10.1002/admi.201901210

As global efforts toward carbon neutrality accelerate, developing low-cost hydrogen production from renewable energy sources has become a key priority. Proton Exchange Membrane (PEM) water electrolysis is a promising technology for large-scale, high-performance hydrogen production, and further advancements are essential to meet ambitious cost targets. To support strategic research and development, a technology roadmap has been established by the New Energy and Industrial Technology Development Organization (NEDO), Japan’s national R&D agency, to quantitatively assess the contributions of individual component innovations to the reduction of the Levelized Cost of Hydrogen (LCOH). As part of this effort, insights from this study’s simulation analysis have contributed to the development of this roadmap, helping to identify key cost reduction strategies and technological priorities.This study conducts a sensitivity analysis by employing a simulation model that integrates a degradation model to represent the performance degradation behavior of the water electrolysis system, along with real-world renewable energy data and electricity market prices from regions suitable for hydrogen production. The degradation model remains in an early stage of development, and challenges persist in fully capturing the complex mechanisms of performance degradation. Further investigation is required to enhance the understanding and modeling of degradation phenomena. Nevertheless, the model was developed based on publicly available data from published studies[1,2], which ensures its relevance and provides a foundation for future improvements.The results demonstrate that improving system durability and enabling high-current-density operation are critical to lowering LCOH, particularly under resource-constrained conditions with limited iridium usage. Reducing electricity costs is also essential for further LCOH reduction. While I–V performance improvements alone provide limited cost benefits, they become highly effective when combined with other technological advances. These findings provide quantitative insights to guide future R&D toward achieving the ambitious target LCOH of 18 JPY/Nm³, equivalent to approximately 30 JPY/Nm³ when including international transport costs. However, it should be noted that the simulated LCOH values are inherently dependent on the assumed conditions, including electricity pricing and system cost assumptions. Sensitivity to these factors should be carefully considered in the interpretation of results. Nevertheless, the cost reduction effects of the proposed technological advancements are broadly applicable, reinforcing the significance of establishing clear development targets to drive further innovation in PEM water electrolysis technology.AcknowledgmentsThe authors would like to express their gratitude to ENEOS Corporation for providing valuable data used in this study. We are also grateful to Mizuho Research ＆ Technologies, Ltd. for their contributions to defining the study’s assumptions and leading the establishment of target values. Furthermore, we would like to thank all members of the NEDO Water Electrolysis Roadmap Review Committee and Working Group for their insightful feedback and constructive comments.

Magnetically modified electrocatalysts for oxygen evolution reaction in proton exchange membrane (PEM) water electrolyzers

Green hydrogen production is importance in the upcoming hydrogen economy era. Proton exchange membrane (PEM) water electrolysis is one of the most important technology to produce the green hydrogen that requires only water and extra electricity supplied from renewable energy. Large amount of hydrogen production and low production cost is most important for hydrogen economy and we need to find out how to decrease hydrogen production cost, which can be come true with high performance and high durability of the component of PEM water electrolysis. The hydrogen production rate is affected by performance of the HER electrode and production cost is affected by material cost and durability of electrode in the PEM water electrolysis. HER electrode is composed of an electrocatalyst (Pt/C) and proton conducting ionomer (PFSI), among them, proton conducting ionomer directly affects to the performance and durability of the electrode. So, designing of the electrode structures through ionomers is essential. In this study, for reduction of hydrogen production cost, highly dispersed ionomers were developed. Effect of dispersing solvents for ionomer on the performance and durability of catalyst layers was investigated. Developed ionomer dispersion shows higher performance and durability in the PEM water electrolysis, which result was made by the electrochemical characterization such as I-V polarization, voltage increasing rate during durability test, and so on as well as the microscopic characterization such as SEM and TEM were carried out to evaluate the effect of ionomer dispersions on the performance and durability of HER electrode in PEM water electrolysis. Acknowledgments This research was supported in part by the Hydrogen Energy Innovation Technology Development Program of the National Research Foundation (NRF) funded by the Ministry of Science, ICT ＆ Future Planning (NRF-2019M3E6A1063677) and by 2021 Green Convergence Professional Manpower Training Program of the Korea Environmental Industry and Technology Institute funded by the Ministry of Environment.

Proton exchange membrane (PEM) water electrolysis has become increasingly attractive due to the penetration of renewable energy (e.g, solar and wind). Hydrogen production from PEM water electrolysis is advantageous over other technologies due to its simple and clean nature. Membrane and electrode assemblies (MEAs) of PEM electrolyzers typically use iridium (Ir) as an anode catalyst and Pt as a cathode catalyst. Performance and durability of the MEAs play an essential role for the cost and viable commercialization of PEM water electrolysis. However, unlike the well-established MEA benchmarks of PEM fuel cells, the performance and durability of PEM electrolyzer MEAs have not been thoroughly studied. The objective of this work is to establish benchmark MEA performance and durability for PEM water electrolysis. For this purpose, a series of oxygen evolution reaction (OER) catalysts, which includes commercial Ir black and various Ir nanostructures, has been evaluated under test protocols established at Giner Inc. These approaches include high-voltage hold (>1.8 V), accelerated stress test (e.g., voltage cycling from 1.4 to 2.0 V), and constant low-current operations. The polarization curves of the MEAs will be obtained after each test. The morphology and structure of MEAs after durability tests will be characterized to correlate to their performance and durability. The established performance and durability may provide metrics and guidance to the community of PEM water electrolysis. Acknowledgement: The financial support is from the Department of Energy under the Contract Grant DE-SC0007471.

In order to adopt water electrolyzers as a main hydrogen production system, it is critical to develop inexpensive and earth-abundant catalysts. Currently, both half-reactions in water splitting depend heavily on noble metal catalysts. This review discusses the proton exchange membrane (PEM) water electrolysis (WE) and the progress in replacing the noble-metal catalysts with earth-abundant ones. The efforts within this field for the discovery of efficient and stable earth-abundant catalysts (EACs) have increased exponentially the last few years. The development of EACs for the oxygen evolution reaction (OER) in acidic media is particularly important, as the only stable and efficient catalysts until now are noble-metal oxides, such as IrOx and RuOx. On the hydrogen evolution reaction (HER) side, there is significant progress on EACs under acidic conditions, but there are very few reports of these EACs employed in full PEM WE cells. These two main issues are reviewed, and we conclude with prospects for innovation in EACs for the OER in acidic environments, as well as with a critical assessment of the few full PEM WE cells assembled with EACs.

Three-dimensional CFD simulation of proton exchange membrane water electrolyser: Performance assessment under different condition