bluuebunny/crossref_metadata_2025 huggingface dataset:
Prospects in the Design of Porous Vs. Rib/Channel Flow Fields for Polymer Electrolyte Membrane Fuel Cells
Authors: Garcia-Salaberri Pablo A. , Perego Andrea , Zenyuk Iryna V.
Published: December 2024

Porous flow fields show promising characteristics to promote oxygen transport and improve performance of next-generation polymer electrolyte membrane fuel cells (PEMFCs) [1]. In this work, combined experimental and numerical work is conducted to examine the pros and cons of porous flow fields compared to conventional rib/channel flow fields (see Figure 1). The experimental performance data of a cathode porous flow field integrated into PEMFC is used to validate the numerical model, which is then used to perform a comprehensive parametric study involving both operational and constructive parameters [2]. The results show that the main advantages of the porous flow fields are: (i) the improvement of oxygen transport, (ii) the decrease of water saturation in the cathode MEA, reducing water flooding, and (iii) the increase of the distribution homogeneity (e.g., current density and temperature) in the in-plane direction [3,4]. In contrast, the main disadvantages are: (iv) the potential effect of electrical contact resistances between porous surfaces, and (v) the decrease of the water removal drag force in the cathode channel [5]. These issues can be mitigated with thinly manufactured foams and/or increasing the assembly compression ratio. In addition, hybrid porous flow fields incorporating a rib/channel pattern with fine pore-size porous ribs can be used to improve the contact between surfaces and increase the cathode gas flow velocity.

[1] G. Zhang et al., Porous Flow Field for Next-Generation Proton Exchange Membrane Fuel Cells: Materials, Characterization, Design, and Challenges, Chem. Rev. 123 (2023) 989-1039.

[2] P.A. García-Salaberri, I.V. Zenyuk, Boosting the Performance of Polymer Electrolyte Membrane Fuel Cells with Porous Flow Fields: Pros and Cons, Energy, In preparation.

[3] J.E. Park, Achieving breakthrough performance caused by optimized metal foam flow field in fuel cells, International Journal of Hydrogen Energy 44 (2019) 22074-22084.

[4] Y. Wu et al., Multi-length scale characterization of compression on metal foam flow-field based fuel cells using X-ray computed tomography and neutron radiography, Energy Conversion and Management 230 (2021) 113785.

[5] Y. Wu et al., Characterization of water management in metal foam flow-field based polymer electrolyte fuel cells using in-operando neutron radiography, International Journal of Hydrogen Energy 45 (2020) 2195-2205.

This work was supported by project PORHYDRO1 TED2021-131620B-C21/AEI European Union NextGenerationEU/PRTR, of the Ministry of Science and Innovation of Spain, Spanish Research Council.

Figure 1. Schematic of the combined experimental and numerical methodology used to examine the pros and cons of porous vs. rib/channel flow fields.

Figure 1
Influence of the Clamping Force and the Formation of Liquid Water Along the Channel on the Local Diffusion Processes in PEMFCs
Authors: Fischer Yannick , Oppek Philipp , Chuang Po-Ya Abel , Weber Andre
Published: December 2024

The success of PEMFCs in heavy duty applications depends on achieving high power densities while maintaining exceptional durability. Under high current density operating conditions, the transport of oxygen from the gas channel via the GDL and MPL to the active Pt-particles in the catalyst layer becomes performance limiting. In the different layers, oxygen transport takes place via various transport processes, such as Knudsen, molecular and ionomer diffusion. Gas transport in a fuel cell is influenced to varying degrees by the operating conditions, geometry of the flow channel, and the properties of the porous media. Porosity and tortuosity of the diffusion media depend on the local clamping force and the amount of liquid water present. In a large-active-area cell, the clamping force and liquid water as well as oxygen concentration, pressure and temperature can vary significantly between the inlets and the exits, which results in a spatially varying oxygen transport resistance and local performance along the channel. To enable targeted optimization of the operating strategy and component design for high current density operation, a comprehensive understand of the local diffusion processes and their dependencies is essential.

In our study, limiting current measurement is used as a diagnostic tool in combination with a segmented cell to determine the local oxygen transport resistance [1, 2]. In the measurement setup, the clamping force is manually set for each segment and recorded continuously throughout the experiment. By systematically varying the operating conditions (p, RH, T), clamping force and cathode gas composition (N2/He), we aim to deconvolute each transport mechanism and the allocation of the transport resistance to each individual layer. The local operating conditions, such as pressure and temperature, are simulated using empirical models based on local measurement data. The combined results allow us to obtain the local oxygen transport resistance as a function of local operating conditions and the clamping force along the flow channel.

In this study, the distribution of different gas diffusion processes and their impact on fuel cell performance along the channel are presented. In particular, the effect of the clamping force and the formation of liquid water along the channel on local porosity and tortuosity in the GDL are discussed. Furthermore, our results demonstrate how the overall performance of the cell can be optimized by adjusting the clamping force distribution along the flow channel.

References:

M. A. Rahman, M. Sarker, F. Mojica, P.-Y.A. Chuang, Electrochimica Acta 320 (2019), 134601

T. V. Reshetenko, J. St-Pierre, J. Electrochem. Soc. 161 (2014), 10, F1089-F1089
Nondestructive Nano-Imaging and Nano-Spectroscopy of Buried Battery Interfaces: Advancing in Situ and Operando Infrared Characterization Schemes for Basic Energy Storage Science
Authors: Larson Jonathan M. , He Xin , Bechtel Hans A. , Kostecki Robert
Published: December 2024

A critical component to the advancement and realization of beyond Li-ion electrical energy storage technologies is the careful study and characterization of the electrochemically active interfaces that govern the function and performance of such devices. Ideally, characterization of interfaces, and the interphases that grow therein, would be done in an inherently non-destructive way, while within its undisturbed native environment, and with nanoscale resolution over microscale areas (to resolve the kinds, and distribution, of the interphase building blocks). The practical realization of this, though, is extremely challenging because these interfaces and interphases are buried, highly reactive, nano-thin, and structurally and chemically heterogenous.

In this talk, we’ll discuss a brief history of an emerging and evolving infrared near-field methodology aimed at overcoming as many of these challenges as possible, to study electrochemical energy storage materials and interfaces in their native environment, non-destructively, and with nanoscale resolution. This is accomplished by employing a combination of precisely engineered and electrochemically controlled graphene/electrolyte interfaces, and diffraction-limit-breaking near-field optical probes capable of chemical imaging and vibrational spectroscopy at the nanoscale. We will present works published on graphene/liquid-electrolyte interfaces,1 and anode-free-based Li/polymer-electrolyte interfaces.2 We will show that in the former case, operando potential step voltammetry + nano-FTIR is capable of sensing concentration changes in the electric double layer.1 Furthermore, in the latter case, where we will spend most our time, in situ multimodal nano-FTIR, ATR-FTIR, infrared nano-imaging, and atomic force microscopy reveal nanoscale structural and chemical heterogeneities intrinsic to the solid polymer electrolyte initiate a cascade of additional interfacial nanoscale heterogeneities during Li plating and stripping, including Li-ion conductivity, electrolyte decomposition, and interphase formation.2

1.) Y.-H. Lu,* J.M. Larson,* A. Baskin, X. Zhao, P. Ashby, D. Prendergast, H. Bechtel, R. Kostecki, and M. Salmeron, Nano Lett
19, 5388-5393 (2019).

2.) X. He*, J. M. Larson*, H. A. Bechtel, and R. Kostecki, Nat Commun, 13, 1398 (2022).

(*: Denotes Equal Contribution)

Figure 1
Automating Energy Storage System Studies at the Advanced Photon Source: A Case Study of 11-BM
Authors: Wang Yang , Lapidus Saul
Published: December 2024

Traditionally, energy storage system characterization involves labor-intensive processes, from sample preparation to data acquisition and analysis. However, the integration of automation technologies streamlines this workflow, enhancing efficiency and throughput while minimizing human intervention. The 11-BM beamline, equipped with high-resolution X-ray diffraction capabilities, serves as a versatile platform for investigating the structural and chemical properties of materials crucial for energy storage applications.

The key components of the automated workflow deployed at 11-BM, including robotic sample handling systems, real-time data acquisition algorithms, and advanced machine learning techniques for rapid data analysis. By interfacing with sophisticated automation system involving robotics like UR5e and KX2, researchers can remotely design experiments, execute protocols, and retrieve results with minimal manual intervention, thereby accelerating the pace of research and innovation in energy storage technology.
Machine Learning Enabled Operando Optical Microscopy for Determination of Lithium Transport in Battery Electrodes
Authors: Kerner Nadine , Joshi Yug , Mead Monica , Eich Sebastian , Talei Roham , Schmitz Guido
Published: December 2024

Diffusion coefficients of electrode materials are often determined using galvanostatic (GITT) or potentiostatic intermittent titration technique (PITT), electrochemical impedance spectroscopy (EIS) or cyclic voltammetry (CV). However, these methods require special care, as each of their formal derivations use quite restrictive assumptions. As an alternative, a machine learning model is presented to extend a previously proposed optical method of studying lithium transport by operando microscopy. The herein reported model enables the measurement of concentration-dependent diffusion coefficients in a wide solubility range. For this purpose, a python code is developed that determines concentration profiles from RGB images using support vector regression (SVR), a flexible machine learning tool. To evaluate the diffusion coefficient, an inverse Boltzmann-Matano concept is applied. Representing the diffusion coefficient with generalized Redlich-Kister polynomials, concentration profiles are predicted and fit to the measured data. The method is demonstrated here on the example of delithiation of LiMn2O4, but it can, in-principle, be extended to any other battery material showing significant optical response on lithiation, which most of them do.
Neutron Imaging to Study Electrolyte Dynamics in Lithium-Ion Batteries
Authors: Antony Isabel Christine , Young Robert Scott , Coke Kofi , Ziesche Ralf F. , Kockelmann Winfried , Jervis Rhodri , Howard Chris Anthony , Rettie Alex , Rau Christoph , Jones Martin-Owen , Shearing Paul Robert
Published: December 2024

Understanding the intricate dynamics within lithium-ion batteries (LIBs) is paramount for optimising their performance and longevity. Notably, the long-term performance of LIBs is affected by a multitude of degradation mechanisms, including the loss of mobile Li-ions, degradation of active electrode materials and impedance increase. This impedance increase is closely linked to the depletion of electrolyte within the cell, which plays a critical role in facilitating the transport of Li-ions between the cathode and anode. One main factor contributing to the electrolyte consumption is the formation of the solid electrolyte interphase (SEI). The initial cycles of a LIB, known as the formation cycles, experience the highest amount of SEI formation, which contributes to a 10% reduction in capacity, accompanied by a substantial loss of electrolyte. Here we employ operando neutron radiography and in-situ neutron tomography during the formation cycles to unravel the nuanced interplay between particle morphology (single crystal NMC811 vs polycrystalline NMC811), charge-discharge rates (C-rate), and electrolyte movement within LIBs. Neutron imaging is a non-destructive technique that leverages the high neutron attenuation of hydrogen to visualise the electrolyte movement and consumption during the formation cycles of batteries. By observing changes in the density of hydrogen over the volume of the cell, we uncover how varying particle shapes and C-rates influence the electrolyte distribution and consumption.
Optical and X-Ray Absorption Interrogation of Selenium-Based Redox in Carbon Nanofoam Supported SxSey Cathodes
Authors: Carter Rachel Elizabeth , DeBlock Ryan H. , Lefler Matthew , Neale Zachary Garbe , Love Corey T. , Sassin Megan B. , Rolison Debra R. , Long Jeffrey W.
Published: December 2024

Sulfur-based batteries have emerged as a leading contender for next-generation energy storage owing to their high redox capacity and the global availability of elemental sulfur. Yet the electronically insulating nature of sulfur limits the applicability of this battery chemistry. Redox kinetics are enhanced by coating sulfur onto a conductive, porous carbon scaffold1 and atomically mixing with selenium.2 Electrochemical discharge of S/Se blends exhibit additional voltage plateaus compared to a pure S cathode and in-situ optical microscopy identifies a more direct reaction pathway with less active material dissolution.3 Lab scale in-operando X-ray absorption spectroscopy reveals shifts in the Se K-edge correlated with features in electrochemical charge-discharge profiles, providing critical insights on the redox mechanism in nanocomposites of sulfur and selenium.

1. Neale, Z.G.; Lefler, M.J.; Long, J.W.; Rolison, D.R.; Sassin, M.B.; Carter, R.; Freestanding Carbon Nanofoam Papers with Tunable Porosity as Lithium-Sulfur Battery Cathodes. Nanoscale,
2023, 15, 16924-16932.

2. Deblock, R.H.; Lefler, M..J.; Neale, Z.G.; Love, C.T.; Long, J.W.; Carter, R.; Optical and X-ray Absorption Interrogation of Selenium-based Re-dox in Li-SxSey batteries, Energy Advances, 2024, 2024, 3, 424-429.

3. Carter, R.; NewRingeisen, A.; Reed, D.; Atkinson, R.W.; Mukherjee, P.P.; Love, C.T.; Optical Microscopy Reveals the Ambient Sodium Sulfur Discharge Mechanism, ACS Sustainable Chem. Eng.
2021, 9, 1, 92–100.
Correlating the Battery Performance and the Texture of Electrodeposited Lithium Metal in Zero-Excess Solid-State Lithium Metal Batteries
Authors: Li Zhuo , Fan Austin , Hatzell Kelsey
Published: December 2024

Zero-excess solid state lithium metal batteries are considered the next-generation battery system recognized for their high volumetric energy density and improved safety. However, the non-uniform plating behavior of lithium metal against the current collector leads to poor coulombic efficiency and lithium dendrite formation [1]. Thus, it is essential to understand and quantify the plating behaviors to optimize the system. The texture, or crystallographic orientation, of lithium metal can be used to evaluate the morphology of lithium metal within batteries [2]. In liquid batteries, a strong {110} texture has been correlated with a denser and dendrite-free morphology [2], which can lead to a better coulombic efficiency [3]. However, it is currently not understood how the crystallographic orientation is affected by the presence of hydrostatic stress which is common in zero-excess solid-state batteries. The lack of knowledge is in part because accessing buried solid-solid interfaces is challenging and even more challenging when considering the volatile nature of lithium metal. In this study, we addressed the challenge by adopting synchrotron-based X-ray pole figure measurements [4]. Both synchrotron-based and lab-based X-ray pole figure measurements were utilized to reveal the texture evolution of lithium metal understand various conditions such as hydrostatic stress and temperature. By combining texture measurement with electrochemistry, we deconvoluted the impact of accumulated capacity, temperature, and current density on the quality of plated lithium metal. Understanding the impact of these factors will enable better control of operating conditions to achieve a more uniform and dendrite free lithium deposition, thereby ensuring longer-lasting and more stable zero-excess solid-state lithium metal batteries.

References:

[1] Christian Heubner, Sebastian Maletti, Henry Auer, Juliane Hüttl, Karsten Voigt, Oliver Lohrberg, Kristian Nikolowski, Mareike Partsch, and Alexander Michaelis. From Lithium-Metal toward Anode-Free Solid-State Batteries: Current Developments, Issues, and Challenges. Adv. Func. Mater. 2021, 31(51), 2106608.

[2] Shi, Feifei, Allen Pei, Arturas Vailionis, Jin Xie, Bofei Liu, Jie Zhao, Yongji Gong, and Yi Cui. "Strong texturing of lithium metal in batteries." Proceedings of the National Academy of Sciences 114, no. 46 (2017): 12138.

[3] Hu, Xitao, Yao Gao, Yongming Sun, Zhen Hou, Yufeng Luo, Danni Wang, Jiangpeng Wang, Biao Zhang, Zijian Zheng, and Quan Li. "Preserving the Li {110} Texture to Achieve Long Cycle Life in Li Metal Electrode at High Rates." Advanced Functional Materials 34, no. 11 (2024): 2307404.

[4] Wenk, H-R., and S. Grigull. "Synchrotron texture analysis with area detectors." Journal of applied crystallography 36, no. 4 (2003): 1040-1049.
Operando Bragg Coherent Diffraction Imaging of Commercial Polycrystalline and Single Crystal NMC811 Electrodes
Authors: Llewellyn Alice V. , Jervis Rhodri , Shearing Paul R
Published: December 2024

Commercial candidates for electric vehicle batteries include Ni-rich Li(Ni0.8Mn0.1Co0.1)O2 (NMC811) cathodes due to their high specific capacity (200 mAh/g) and reduced cobalt content, which has positive socio-economic repercussions. Despite all of the advantages, these materials suffer from a range of degradation modes, many of which are associated with the redox and crystallographic behavior at high states of charge and are thought to be the cause of rapid capacity fade. NMC811 suffers from anisotropic changes in the crystal structure during cycling, which induce strain and can then lead to issues such as particle crack formation. Gathering data at multiple length scales is imperative for understanding the discrete mechanisms at play. Bragg Coherent Diffraction Imaging (BCDI) is a key tool for obtaining data at the nano-scale by providing high spatial resolution images of individual particles. BCDI also affords the unique opportunity to resolve the strain of individual crystals at the picometer scale, producing data with the highest quantifiable imaging resolution of battery electrodes and allowing for the detection of evolving defect modes such as shearing and stacking faults in the crystals during cycling.

NMC811 typically employs the archetypal cathode particle morphology, consisting of a secondary particle agglomerate (~ 10 μm) made up of nanometer-sized primary particles. It is widely accepted that crack formation occurs at grain boundaries between primary particles. One mitigation method is to switch to a single crystal morphology, reducing the number of grain boundaries within particles and therefore improving overall performance. However, there is still a limited understanding of the subtle mechanistic differences between the two morphologies during cycling.

In this work, Operando BCDI was employed to study both polycrystalline and single crystal NMC811 electrodes in both pristine and aged states. Non-uniform distributions of inter- and intracrystal strain were observed for both polycrystalline and single crystal morphologies, even in the pristine state. Strain values an order of magnitude higher were observed for polycrystalline NMC811 compared to single crystal NMC811, likely a cause for the single crystal morphology’s superior performance. The nucleation of crystal splitting was also observed for a pristine single crystal during cycling, which could subsequently result in intergranular cracking. This feature is only resolvable with extremely high-resolution techniques such as BCDI. This work ultimately adds to the understanding of the central role of crystal-scale dynamics during cycling and the potential ramifications for a cell's electrochemical performance, leading to informed material design.
Exploring Ion Transport Dynamics in Liquid Electrolytes: Insights from in-Situ FTIR Imaging of Lithium Electrodes
Authors: Porter Jason Morgan , Dick Schuyler
Published: December 2024

While solid-state batteries have demonstrated potential in enhancing metal electrode stability, achieving the same stability in liquid electrolytes remains elusive. The instability of the SEI plays a pivotal role in the stability of metal electrodes in liquid electrolytes. Despite several promising strategies to stabilize metal electrodes in liquid electrolytes, the intricate relationship between the composition of the liquid electrolyte and the formation and stability of the SEI is still not fully understood.

This study delves into the constraints of ion transport in liquid electrolytes, specifically focusing on the process of lithium plating and stripping on metal electrodes. A customized short pathlength transmission flow cell, equipped with symmetric lithium electrodes, is employed to simultaneously image lithium deposition, capture electrochemical measurements, and perform in-situ Fourier Transform Infrared (FTIR) imaging. This methodology illuminates the complex relationship between electrolyte transport, local composition, and the morphology of lithium plating.

The research utilizes quantitative analysis of electrolyte components, Li+, PF6-, EC, and EMC, through spectral analysis with chemometric methods and machine learning. The composition of the local electrolyte, which undergoes significant changes under rapid charge conditions, impacts SEI composition, and by extension lithium plating morphology. In situ FTIR imaging, with a resolution of five microns, is used to evaluate the role of preferential diffusion and/or migration of solvent and ionic species. Synchronized optical imaging, with a superior resolution of one micron, providing visual images of lithium structures that are correlated with solvent and ion concentration distributions measured in the infrared. The findings establish a link between ion transport dynamics and the efficiency of lithium plating and stripping, which has far-reaching implications for the performance and safety of electrochemical systems.
Analytical Electron Microscopy Investigation of PEM Electrolyzer Degradation Mechanisms Under Different Durability Test Protocols
Authors: Yu Haoran , Padgett Elliot , Li Kui , Cullen David A. , Alia Shaun M , Komini Babu Siddharth , Mukundan Rangachary
Published: December 2024

Hydrogen as an energy carrier is a promising solution to reduce carbon emissions and fight climate change. The US Department of Energy (DOE) announced the Hydrogen Shot initiative to reach $1 per 1 kilogram of hydrogen in 1 decade (by 2031). Although millions of metric tons of hydrogen are produced each year by industry, cost-effective approaches such as steam methane reforming involve the release of carbon dioxide. Water electrolysis is one of the key technologies of producing hydrogen from renewable energy sources which has zero carbon emission, but significant and rapid innovations are required to reach the Hydrogen Shot cost target.

Here we focus on low temperature proton exchange membrane (PEM) electrolyzers which have demonstrated high efficiency and high capacity recently. Successful deployment of PEM electrolyzers requires reducing cost while simultaneously improving performance and lifetime. To evaluate and project electrolyzer performance and lifetime more effectively, accelerated stress test (AST) protocols are being developed. The primary goal of this work is the identification of key stressors of degradation and their related degradation mechanisms. Parameters of interest, such as upper and lower potential limit, dynamic vs constant load, temperature, start-up/shut-down procedures, etc., are varied in different AST protocols to elucidate their effect on membrane electrode assembly (MEA) degradation.

Electron microscopy offers an in-depth examination of the MEA after AST. In this presentation, we will discuss the following findings that shed light on the degradation mechanisms of electrolyzer MEAs. Firstly, the crystalline structure of the Ir oxide catalyst was compared before and after degradation, showing a structural change from amorphous Ir oxide to nano-sized crystallites. Then, through energy dispersive X-ray spectroscopy (EDS), a correlation is found between type of AST protocol, performance loss, and degree of Ir lost from the anode due to Ir dissolution and migration toward the membrane. We will also show the migration of Ir and Ti to the cathode forming Ir-coated Pt particles and Ti oxide, respectively, for long term tests. Lastly, we find that cathode degradation occurs if a start/stop protocol is employed where Pt particle coarsening and dissolution into the membrane can be observed. [1]

References

[1] Funding for this work was provided by U.S. Department of Energy Office of Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office through the H2NEW Consortium. Electron microscopy research conducted as part of a user project at the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory.
Quantifying H2 Crossover in PEM Water Electrolyzers Operating at High Differential Pressure
Authors: Gawas Ramchandra , Wang Guanzhi , Rudnicki Paul E. , Dizon Arthur , Kushner Douglas I. , Peng Xiong , Mukundan Rangachary
Published: December 2024

Large-scale deployment of proton exchange membrane water electrolyzers (PEMWEs) is crucial for producing clean and economically viable hydrogen to create hydrogen-based energy ecosystems that can replace existing carbon-intensive processes. Efficient operation of PEMWEs requires the use of thinner membranes to reduce ohmic losses as well as the differential pressure operation to increase the overall system efficiency. The high differential pressure operation of PEMWEs with thin membranes results in significant hydrogen crossover from cathode to anode. This crossover-H2 has considerable implications on PEMWE performance, durability, as well as operational safety.

In this work, we develop a method to accurately quantify hydrogen crossover rates in PEMWEs operating at high differential pressure. Our analysis shows that crossover-H2 is oxidized at the anode catalyst layer resulting in measurable hydrogen oxidation reaction (HOR) currents. We combine this HOR current measurement with online gas chromatography with thermal conductivity detector to determine H2 concentration in the anode outlet and also calculate H2 crossover rates at various operating current and differential pressures (up to 30 bar). Further, we use this methodology to evaluate the effect of porous transport layer (PTL) coatings (Pt, Ir, and Au) on the HOR current as well as the hydrogen crossover rate in PEMWEs.

Acknowledgment: This research is supported by the U.S. Department of Energy (DOE) Hydrogen and Fuel Cell Technologies Office (HFTO) through the Hydrogen from Next-generation Electrolyzers of Water (H2NEW) consortium.
Hierarchical Electrode Design for Highly Efficient and Stable Anion Exchange Membrane Water Electrolyzers
Authors: Yanagi Rito , Weber Adam Z. , Peng Xiong
Published: December 2024

Anion exchange membrane water electrolyzer (AEMWE) is a promising technology for green hydrogen production to reduce carbon emissions in industrial and heavy-duty transportation sectors. AEMWE has the advantage of using nonplatinum group metal oxides for the anode oxygen evolution reaction (OER) and therefore lower the capital expenditure comparing to proton exchange membrane water electrolyzers (PEMWE). However, the commercialization and deployment of AEMWE in large scale is still limited by its durability. Herein, we study how electrode structure and the cell operating conditions affect the cell stability and performance. Catalyst layer structures, including porosity and tortuosity, were investigated and correlated with cell performance for better understanding and designing AEMWE. Durability of different catalyst layers were investigated and correlated with catalyst layer structure and ionomer stability. Electrode fabrication methods were found to have significant impact on the catalyst layer structure and therefore catalyst utilization. With a doctor blading method to fabricate the catalyst layer, electrodes were scaled up from 5 cm-2 to >25cm-2 with negligible voltage loss. With these findings, cell performance was improved towards <1.8V at 2A cm-2 and durability of >500h was achieved at 2A cm-2 for a 25 cm-2 cell in 0.5M KOH.
Nickel–Iron Oxyhydroxide Catalyst-Integrated Unified Electrode for High-Performance and Durable Anion-Exchange Membrane Water Electrolysis
Authors: Park SungBin , Park Ji Eun , Sung Yung-Eun
Published: December 2024

One critical aspect in enhancing the performance and longevity of anion-exchange membrane water electrolyzers (AEMWE) is the oxygen evolution reaction (OER). In our study, we present a novel three-dimensional unified electrode architecture, where nickel and iron are integrated within a gas diffusion layer (GDL) in oxyhydroxide form, serving as the anode in AEMWE. Traditional electrodes in water electrolysis typically consist of separate catalyst and GDL layers, whereas our unified electrode combines these elements into a single layer. Compared to a conventional electrode utilizing IrO2, our unified electrode demonstrates superior catalytic activity and maintains stability for over 500 hours. Electrochemical analysis of the AEMWE employing the unified electrode reveals a performance of 3600 mA cm-2 at 1.9 V, surpassing many other AEMWE studies. Furthermore, our unified AEMWE exhibits excellent performance even at ultra-high current densities. Thus, the unified electrode design represents a promising advancement in enhancing AEMWE performance and reducing hydrogen production costs.
Compression of Porous Transport Layers Enhanced Bubble Transport in Polymer Electrolyte Membrane Water Electrolyzers
Authors: Zhu Lijun , Lee Jongmin , Ham Chaeyoung Tina , Chadwick Eric Alexander , Parmar Harsharaj Birendrasingh , Trtik Pavel , Bazylak Aimy
Published: December 2024

At high current densities, oxygen bubble formation limits the performance of polymer electrolyte membrane (PEM) water electrolyzers, particularly due to bubble accumulation at the porous transport layer (PTL)/catalyst layer (CL) interface. Efficient bubble removal from the PTL/CL interface is therefore crucial for PEM water electrolyzers1,2. Bubble transport at the PTL/CL interface is dominated by mechanical compression 3,4. However, it is still unclear how mechanical compression impacts bubble transport at the PTL/CL interface, due to difficulties in capturing the multiphase flow and differentiating liquid/gas in the pores of the titanium PTL. Thanks to its spatial resolution and high transmissivity for titanium, neutron imaging enables visualization of the bubble distribution in the PTL hence allowing for the identification of the role of compression in the bubble transport.

We conducted operando neutron imaging for PEM water electrolyzers and examined the relationship between compression ratio and electrochemical performance. Neutron imaging results showed that the through-plane bubble distributions became more homogeneous as compression increased. Additionally, pore network modelling simulations indicated that compression-induced catalyst coated membrane intrusion homogenized the bubble distribution in the PTL. We identified an optimal compression condition for enhanced interfacial bubble transport that can contribute to the next-generation material development to improve the efficiency of PEM water electrolyzers at high current densities with low mass transport losses.

References

J. K. Lee and A. Bazylak, Joule, 5, 19–21 (2021).

S. Yuan et al., Prog.
Energy Combust.
Sci., 96, 101075 (2023).

T. Schuler, T. J. Schmidt, and F. N. Büchi, J. Electrochem.
Soc., 166, F555–F565 (2019).

A. Martin et al., J. Electrochem. Soc., 169, 014502 (2022).
Electrospun Micro Porous Layer for Enhanced Proton Exchange Membrane Water Electrolysis
Authors: Diaz-Abad Sergio , Komini Babu Siddharth , Spendelow Jacob S.
Published: December 2024

Current porous transport layers (PTLs) utilized in proton exchange membrane water electrolyzers (PEMWEs), suffer from limited interfacial contact area with the catalyst layer which reduces the performance. Although high anode catalyst loadings can mitigate this issue, it contradicts the objective of reducing the loading of precious metals in PEMWEs to lower costs. The combination of poor in-plane conductivity of the anode catalyst and the poor interfacial contact results in increased contact resistance and reduced catalyst utilization which leads to accelerated catalyst degradation due to non-uniform exposure to the applied voltage or current in the catalyst. Micro-porous layers (MPLs) can alleviate the interfacial contact problem. MPLs provide with high surface areas and low pore size, facilitating enhanced contact with the catalyst layer and improving catalyst utilization. Furthermore, the hierarchical MPL morphology can aid in efficient oxygen removal and enhanced water transport to the anode catalyst layer.

In this study, titanium-based MPLs were fabricated via electrospinning employing a titanium precursor and a carrier polymer. Electrospun offers a superior control on the morphology of the resulting fibers. The electrospun fibers were subsequently calcined to yield TiO2 fibers, forming the MPL. The MPL was then integrated into a commercial felt based PTL substrate through hot-pressing and sintering to enhance the improved integration between the MPL and substrate. We will present the electrochemical performance evaluation including polarization curves, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry. Surface characterization of the MPL and catalyst layer surface was performed via scanning electron microscopy (SEM) and laser profilometry before and after electrolyzer testing.

Acknowledgement

This research is supported by the U.S. Department of Energy (DOE) Hydrogen and Fuel Cell Technologies Office through the Hydrogen from Next-generation Electrolyzers of Water (H2NEW) consortium. Program manager Dave Peterson and Mackenzie Hubert.
(Invited) Pathways Toward Efficient and Durable AEM Water Electrolyzers
Authors: Tricker Andrew , Ertugrul Tugrul , Lee Jason Keonhag , Lang Jack Todd , Zenyuk Iryna , Weber Adam Z. , Peng Xiong
Published: December 2024

Green hydrogen will play a key role in decarbonization efforts, especially for heavy industries.[1] Durable, efficient, and low-cost electrolyzers are critical to realize economical and green hydrogen production. Anion exchange membrane water electrolyzer (AEMWE) is an emerging technology that combines the benefits of low components cost of conventional alkaline electrolyzers and the high efficiency of proton-exchange membrane (PEM) electrolyzers.[2] Although promising, a significant hurdle to commercial deployment of AEMWEs is the durability under industrially relevant conditions. Here, we demonstrate how porous transport layers comprised of natively active materials (PTL electrodes) can be used to achieve efficient and durable AEMWEs.[3] Specifically, stainless-steel fiber PTLs were used as anodes, without the addition of a catalyst layer. When comparing the PTL electrode to traditional catalyst layers, electrolyzer cells with several commercial anion-exchange ionomers (AEI) were subjected to current cycling. This accelerated stress testing (AST) of the electrolyzer cells showed that no significant degradation in the PTL electrode, while cell using traditional catalyst layers exhibited a loss in performance and the complete degradation of the ionomer functional group. When assessing the industrial applicability, the active area of the electrolyzer was increased up to 50 cm2, which showed the same performance as the 5 cm2 cell. The durability of the electrolyzer was tested at 2 A cm-2 in 0.1 M KOH for 660 h. During this period, the cell exhibited a degradation rate of 5 µV h-1, which was comparable to typical PEM electrolyzers. The use of experiment and modeling was used to investigate the role of the structure of the PTL in influencing cell performance. The inclusion of a denser layer on the membrane side increased the utilization of the electrode by decreasing the bubble coverage on the fiber surfaces and increasing the effective electrolyte conductivity within the electrode. Finally, we demonstrate a facile etching method to modify the surface of the PTL fibers to increase the active surface area of the anode and achieve a cell current density of 2.3 A cm-2 at 1.8 V.

References:

[1] D. S. Mallapragada, Y. Dvorkin, M. A. Modestino, D. V Esposito, W. A. Smith, B.-M. Hodge, M. P. Harold, V. M. Donnelly, A. Nuz, C. Bloomquist, Joule
2023, 7, 23–41.

[2] L. Wan, Z. Xu, Q. Xu, M. Pang, D. Lin, J. Liu, B. Wang, Energy Environ Sci
2023, 16, 1384–1430.

[3] A. W. Tricker, T. Y. Ertugrul, J. K. Lee, J. R. Shin, W. Choi, D. I. Kushner, G. Wang, J. Lang, I. V Zenyuk, A. Z. Weber, X. Peng, Adv Energy Mater
2023, 2303629.
Liquid Alkaline Water Electrolysis: Are the Reports of Its Demise Premature?
Authors: Leonard Daniel , Maurya Sandip , Kang Sun Young
Published: December 2024

The future for hydrogen is bright. There is a widely recognized need to produce large quantities of emissions-free hydrogen to achieve the decarbonization goals expressed in national climate change ambitions. Electrolysis has attracted more attention as the most viable near-term process to meet that need. From the research community’s perspective, the course of electrolytic hydrogen production technology is expected to be led by proton exchange membrane (PEM) technologies. PEM will eventually be supplanted by anion exchange membrane (AEM) technologies, which are expected to maintain all of the PEM capabilities without the precious metal drawbacks. Liquid alkaline (LA) water electrolyzer systems will fall by the wayside as they are based on century-old technology and should not meet the high H2 production needs of the future.

The source of LA’s poor reputation is due to the materials used as catalysts. While low cost, they are mainly designed with simplicity and longevity in mind. Simply opening the door to the possibility of using Pt and Pt alloy catalysts as the hydrogen evolution electrodes can lead to increases in hydrogen production without substantially increasing the cost of the electrolyzer stack. We show that using a reasonable Pt loading of 0.3 mg/cm2 at the cathode and a standard Ni foam anode results in a ten-fold increase in hydrogen production. The cell remains stable without a quantifiable loss in performance after 250 h at a current density of 2 A/cm2 in 30 wt% KOH at 80 oC. This result exceeds the 2026 performance and durability targets for liquid alkaline electrolysis set by the U.S. Department of Energy (DOE). When the Ni foam anode modified by the electrodeposition of an NiFe layered double hydroxide (LDH), the performance is identical to the current PEM benchmark, FuGeMEA. The result is within 100 mV of DOE’s ultimate technical target for LA performance, 2.0 A/cm2 at 1.7 V. The degradation rate using the NiFe LDH anode system is too high at present (461 mV/kh rather than the 2.1 mV/kh target).

From a cost perspective the use of Pt at the cathode results in only a small increase at the system level, extrapolating from the International Renewable Energy Agency’s 2020 “Green hydrogen cost reduction” report. While the ultimate goal is to remove the need for precious metal catalysts entirely, in the near-term their adoption in liquid alkaline may speed the cost reductions necessary to meet the hydrogen cost goals. They are simply too promising to be ignored.

The authors would like to acknowledge the support of the DOE Hydrogen and Fuel Cell technology Office and the Hydrogen from Next-Generation Electrolyzers of Water (H2NEW) Consortium.
Optimization of Porous Transport Layers in PEM Electrolyzers Using Pore Network Modeling with Combinations of Fiber Size and Volumetric Fractions
Authors: Ghosh Amit , Uddin Aman
Published: December 2024

Polymer Electrolyte Membrane (PEM) electrolyzers as a promising technology in addressing climate change challenges and facilitating the development of renewable energy sources at lower costs. They offer clean operation and scalability, making them a valuable tool for harnessing energy without leaving any carbon footprint. However, a key challenge to widespread PEM electrolyzer adoption is the cost of the porous transport layer (PTL). In this study, we address this challenge by utilizing stochastic modeling to develop 3D PTL models numerically. To optimize the structural and transport properties of the PTL, we explored a range of combinations for the radius (2, 3, 4, 5 µm) and volumetric fraction (20%, 40%, 60%, 80%, 100%) of small fibers dispersed within a matrix of large fibers (6 µm) (Figure 1). The structural properties (e.g., mean surface roughness, specific surface area) were analyzed numerically, whereas transport properties (e.g., thermal conductivity, electrical conductivity, and diffusivity) were analyzed via pore network modeling. Before further analysis, our model was validated against both experimental and numerical results from previous research works. In our study, we observed that increasing the volumetric fraction of small fibers, while decreasing their radius, led to reduced surface roughness and higher thermal and electrical conductivity. However, this came at the cost of increased tortuosity, which hindered the diffusion and permeability of the material. Conversely, PTLs with a higher volumetric fraction of large fibers exhibited the opposite trend.

By combining these insights, we developed customized multi-layer PTLs. These PTLs have a small fiber radius at the catalyst side and a large fiber radius at the flow-field side. This design leverages the advantages of both small and large fiber radii. Our customized multi-layer PTLs demonstrated improved gas removal, higher electrical conductivity, and better heat dissipation while maintaining good surface contact area and reduced roughness. To utilize the benefits of our modeled multi-layer PTL in an electrolyzer cell, the volumetric fractions of the fiber radius should be adjusted based on operating conditions. By tailoring the fiber characteristics and PTL geometries, we can develop optimized PTL models that can be scaled to real-time PEM electrolyzer setups for renewable energy generation, paving the way for a better future.

Figure 1
Accelerated Stress Tests Protocol Development for Industrial PEM Electrolyzer Stacks
Authors: Ruttala Devi varaprasad , Kulkarni Devashish , Ouimet Ryan J. , Bakovic Sergio P , He Yanghua , Fortiner Serafina , Soucie Hanna , Capuano Christopher B. , Carmo Marcelo , Ayers Kathy
Published: December 2024

The deployment of NEL’s next-gen PEM water electrolyzer stacks and systems is very much dependent on our ability to evaluate the degradation of individual components and thereby predict 50000 hr. operability of the stack. In addition, Nel Hydrogen is constantly working to unveil degradation mechanisms from our long run (< 100.000 hours) fielded stacks, so that we can make the developing of accelerated stress tests (ASTs) less challenging. Typically, performance losses in PEM electrolyzer stacks are the result of electrode, membrane, and/or PTL degradation during different operation strategies. Here we accelerated the performance losses of electrodes used in PEM water electrolyzer stacks using an in-house developed voltage cycling protocol. Membrane degradation was also accelerated through cation-doped catalyst coated membranes and is assessed through ex-situ monitoring of fluoride emission rates during the stack operation. We also leveraged a fielded Nel Hydrogen legacy PEM stack that ran for over 50000 hr. and other R&D stacks that ran for intermediate life span of 5000 hr. at steady state. A correlation of the degradation mechanism to different cell components observed from that of the AST protocols is then here reported.
Effect of Cations Contamination on Durability of Proton Exchange Membrane Water Electrolyzer
Authors: Rodriguez Mayra , Diaz-Abad Sergio , Spendelow Jacob S. , Komini Babu Siddharth
Published: December 2024

Cation contamination in proton exchange membrane water electrolyzers (PEMWE) presents a significant challenge for industrial applications impacting both performance and durability. Common sources of cation contamination include salts present in the feed water or those resulting from corrosion of components and balance of plant systems. The cations ion-exchange with the protons in Nafion® membrane, leading to a significant reduction in proton conductivity of the membrane.1 This decrease in conductivity directly affects the performance of electrolyzers resulting in increased energy consumption, and reduction in lifetime of the PEMWE, which places a significant economic and operational barrier on commercial hydrogen production.2 The cation can accelerate the degradation of the catalyst and the membrane. However, the effect of cation on the durability are not well understood.

In this work, the effects of cation contamination, originating from various sources, on the performance and durability were investigated. Specifically, we investigated cations that are present in feed water (Na+, K+, Mg2+) and metal cations (Fe2+, Ti+, Al3+, Cu2+) that are introduced as the result of corrosion of the PEMWE components. In this study, cations were introduced by soaking the catalyst coated membranes (CCMs) in a solution with a known concentration of cation. The effect of PEMWE performance as a function of the cation concentration was studied. Subsequently, accelerated stress tests (AST) were performed to evaluate how cation concentrations affect the degradation of the membrane and the catalyst.

Acknowledgement

This research is supported by the U.S. Department of Energy (DOE) Hydrogen and Fuel Cell Technologies Office through the Hydrogen from Next-generation Electrolyzers of Water (H2NEW) consortium. Program manager Dave Peterson and Mackenzie Hubert.

LA-UR-24-23217

References

(1) Li, N.; Araya, S. S.; Cui, X.; Kær, S. K. The effects of cationic impurities on the performance of proton exchange membrane water electrolyzer. Journal of Power Sources
2020, 473. DOI: 10.1016/j.jpowsour.2020.228617.

(2) Becker, H.; Murawski, J.; Shinde, D. V.; Stephens, I. E. L.; Hinds, G.; Smith, G. Impact of impurities on water electrolysis: a review. Sustainable Energy & Fuels
2023, 7 (7), 1565-1603. DOI: 10.1039/d2se01517j.