A segmented cell and PCB approach was used to demonstrate an advanced technique for measuring and understanding the electrochemical behavior of PEM water electrolyzers. By employing a semi-empirical model, discrete modes of overpotential and their spatial distributions were identified in an operating cell. Distributed area-specific resistance (DASR) measurements indicate that local dehydration of the polymer electrolyte membrane is the primary driver of increased polarization, behaving similarly to mass transport-limited currents at low flow rates due to ineffective gas-phase bubble removal. To improve quantification, the overall ohmic overpotential is divided into background (eta Ohm,b) and mass transport-coupled (eta Ohm,mt) components. Two types of anode diffusion media, a baseline PTL and a thin foil liquid/gas diffusion layer (LGDL), were examined. The results show significant variations in eta Ohm,b and also highlight that ineffective bubble removal leads to pronounced local dehydration. The effect of cell temperature on various overpotentials was also examined. Negligible differences in diffusion overpotential were observed when comparing PEWE performance using the PTL and LGDL, despite major differences in two-phase fluid transport within each diffusion media. This underscores the critical role of the catalyst layer's micro-porous structure in diffusion processes. The study highlights the complex nature and intricacies of mass transport limitations within PEWEs, providing critical insights for improving system efficiency and advancing sustainable hydrogen production. High resolution distributed measurements for both current density and area specific resistance have been presented.Analyzing the data with a semi-empirical zero-dimensional model helps to identify local overpotentials at both the global and local scale.Bubble accumulation and effective water transport is seen to affect diffusion as well as ohmic contributions to overpotentials .Overpotentials show significant spatial variations in their distribution.

Metal oxide is being researched as a potential replacement for the graphite anode in lithium-ion batteries. This material offers several advantages as an alternative anode for advanced rechargeable batteries, including higher theoretical capacity, superior discharge potential, affordability, natural availability, and safety characteristics [1]. Furthermore, when formed as nanoparticles, increased surface area enhances electrode activity and facilitates faster ion transport, which improves lithium mobility in lithium-ion batteries. However, the stability of the nanoparticles is considered a significant challenge. In this work, we present the synthesis conditions and characterization of stable spinel manganese oxide nanoparticles with various sizes and morphologies and high crystallinity [2]. We demonstrate that it is possible to control the size and shape of these nanocrystals under specific conditions by using the polyol process [3]. These nanomaterials were tested in half-cell configurations using lithium metal as the counter and reference electrodes. Figure 1 (a) presents the TEM images of Mn₃O₄ nanocrystals, which exhibit uniform particle sizes in the range of approximately 7–10 nm. A nanocomposite anode was fabricated by combining these Mn₃O₄ nanoparticles with graphite. Figure 1 (b) displays the first formation cycle of the composite anode, demonstrating enhanced specific capacity relative to conventional graphite which has specific capacity of 350 mAh/g, indicative of improved electrochemical performance. In this study, we are developing composite anode materials with varying weight percentages of metal oxides and different sizes and morphologies to enhance capacity, rate capability, and stability. References: He, S. Wu, N. Zhao, C. Shi, E. Liu, and J. Li, Carbon-encapsulated Fe 3 O 4 nanoparticles as a high-rate lithium ion battery anode material, ACS Nano, 2013, 7, 4459–4469. Rhadfi, J.-Y. Piquemal, L. Sicard, F. Herbst, E. Briot, M. Benedetti, and A. Atlamsani, Polyol-made Mn 3 O 4 nanocrystals as efficient Fenton-like catalysts, Appl. Catal. A, 2010, 386, 132–139. Rhadfi, L. Sicard, F. Testard, O. Taché, A. Atlamsani, E. Anxolabéhère-Mallart, Le Y. Du, L. Binet, and J.-Y. Piquemal, A comprehensive study of the mechanism of formation of polyol-made hausmannite nanoparticles: from molecular species to solid precipitation J. Phys. Chem. C, 2012, 116, 5516. Figure 1

In this study, tin (Sn) nanoparticles are demonstrated to effectively catalyze the reduction of CO2 to formate in an alkaline medium. Catalytically active Sn-based nanoparticles, supported on carbon black (Sn/C) and highly conductive graphene nanosheets (Sn/GN), present a promising approach to mitigating atmospheric CO2 emissions when integrated with capture technologies. Cyclic voltammetry and electrochemical impedance spectroscopy (EIS) were employed to evaluate the prepared catalysts in CO2-saturated 0.5 M KHCO3 using a three-electrode rotating disk electrode (RDE) configuration. The results revealed a significantly lower charge-transfer resistance for graphene-supported tin compared to carbon black-supported tin. The CO2 reduction to formate was further demonstrated in a full electrochemical cell setup resembling the architecture of a low-temperature polymer electrolyte fuel cell (PEFC) operating in an alkaline medium with an anion exchange membrane (AEM). Performance tests were conducted with both triple-serpentine and parallel flow field architectures, showing flow rate-dependent behavior. Additionally, an ex-situ RDE technique was utilized to detect and quantify formate production during CO2 reduction in the full-cell configuration. This work highlights the importance of catalyst support materials and flow field design in optimizing CO2 electroreduction systems.

Aluminum-air batteries (AABs) have been attracting increasing attention due to their high specific energy, relatively low cost, and scalability [1]. Moreover, high-performance AABs could enable critical applications such as electric vehicles including aerial travel and military applications [2]. Alleviating limitations in AABs must address multiple processes. Among them, adopting a zero-gap cell design – commonly used in proton exchange membrane (PEM) fuel cells and electrolyzers – may allow for significantly higher power densities, which are essential for high energy and power applications. Developing a zero-gap cell structure to improve battery performance requires thorough investigation of the principal components, i.e., electrodes, diffusion media, membranes/separators, electrolytes, and cell architecture. Especially for high-power applications, commercialization of AABs requires a thorough understanding of optimal cell conditions and architecture [3]. In this study, we investigated the effects of varying aluminum purities and oxidant quality on AAB performance. In our novel cell architecture, we demonstrate enhanced battery performance, achieving high power densities exceeding 1 W cm⁻² — an outcome not previously reported in the literature, to the best of our knowledge. Overall, this research provides valuable insights into the advancement of high-power AABs and their potential in critical applications. References Rani, B., et al., Aluminum–air batteries: current advances and promises with future directions. RSC Advances, 2024. 14 (25): p. 17628-17663. Dilshad, M., et al., Next-Generation Aluminum-Air Batteries: Integrating New Materials and Technologies for Superior Performance. ACS Applied Energy Materials, 2025. 8 (6): p. 3248-3275. Gaele, M. F. and T. M. Di Palma, Polymer Electrolytes for Al-Air Batteries: Current State and Future Perspectives. Energy & Fuels, 2022. 36 (21): p. 12875-12895. Figure 1

Development of high voltage lithium-ion batteries (LIBs) is the most significant to electrifying the aircraft (eVTOL), electric vehicles, and large-scale high-power energy storage systems compared to present LIBs, which are voltage-limited at 4.2 V [1–3]. Spinel LiMn1.5Ni0.5O4 cathode is a promising candidate to supply Li+ ions at high voltage (> 4.2 V) for LIBs [4]. Even though several significant approaches have been devoted in the literature [5-7], commercialization of spinel LiMn1.5Ni0.5O4 cathode is very challenging and requires advanced research studies to attain long-term cycle stability and high-rate performance. Researchers at the University of Tennessee have developed a primary nanoparticle LiMn1.5Ni0.5O4 cathode with surface coating and networking architecture, capable of cycle durable, high-rate performance for high-voltage LIBs, by precursor structural advancement. Batteries with this cathode delivered discharge capacity of 100 mAh g–1 for the 12th cycle and 86 mAh g–1 for the 1000th cycle with minimized capacity fade at 20 C discharge rate [8]. To support the commercialization of UTK-LiMn1.5Ni0.5O4 cathode, electrochemical and thermal stability studies are performed for segregated primary nanoparticles with surface coating-networking architecture, as described in Figure 1. After stabilization of charge and discharge cycles at 1 C, we demonstrate 24 h rest at 100% state of charge (SOC), i.e. 4.9 V, which exhibited no significant changes in the voltage profiles and capacity performance, as shown in Figure 1a. Cyling studies continued with 24 h rest at fully-charged state (4.9 V) repeated for 1 to 30 cycles (Figure 1b) and extended the rest time for 168 h (1 week rest). From the observed voltage profiles and the charge- discharge capacity performance associated with 24 h/ 168 h rest, it is realized that the segregated primary nanoparticle LiMn1.5Ni0.5O4 cathode with surface coating and networking architecture are stable in presence of electrolyte containing 98% of 1M LiPF6 in EC+DEC (1:1 vol%) and 2% of FEC additive. To examine the thermal safety aspects of primary nanoparticles, in situ multimode calorimetry analyses [9] were carried out for the segregated primary nanoparticle LiMn1.5Ni0.5O4 cathode. The MMC results of the cathode at 100% SOC shows no exothermic peak or heat energy release as temperature ramped from RT to 300 °C; this observation confirms that the cathode material is thermally stable in presence of electrolyte (Figure 1c). The in situ MMC analysis of Li-ion full-cell (graphite vs. LiMn1.5Ni0.5O4 cathode, CR2032) at charge state was performed by increasing temperature, as given in Figure 1d. After SEI decomposition at 110 °C, suddenly the cell voltage dropped to 0 V, exhibiting a lower exothermic peak with less released heat energy at 235 °C during thermal runaway event. From the results of electrochemical and thermal stability studies, it is confirmed that segregated primary nanoparticle LiMn1.5Ni0.5O4 cathode with surface coating and networking architecture is robust towards commercialization for high-voltage Li-ion batteries include eVTOL aircraft, EVs, grid energy storage applications. Acknowledgements Research was sponsored by the DEVCOM Army Research Laboratory (ARL) and was accomplished under Cooperative Agreement Number W911NF2220007. The author Manikandan Palanisamy thanks the Department of Mechanical and Aerospace Engineering, University of Tennessee for financial support. References 1. X. G. Yang, T. Liu, S. Ge, E. Rountree and C. Y. Wang, Joule, 2021, 5, 1644–1659. 2. P. Manikandan, P. Periasamy and R. Jagannathan, J. Mater. Chem. A, 2013, 1, 15397–15405. 3. M. Palanisamy, M. H. Parekh, and V. G. Pol, Adv. Funct. Mater., 2020, 30, 2003668 (1–14). 4. Yu. Xingwen, Yu. Wiley A, A. Manthiram, Small methods, 2021, 5, 2001196. 5. S. Li, G. Ma, B. Guo, Z. Yang, X. Fan, Z. Chen and W. Zhang, Ind. Eng. Chem. Res., 2016, 55, 9352–9361. 6. F. Zou, Z. Cui, H. C. Nallan, J. G. Ekerdt and A. Manthiram, ACS Appl. Energy Mater., 2021, 4, 13297–13306. 7. Z. Zhu, D. Zhang, H. Yan, W. Li and Qilu, J. Mater. Chem. A, 2013, 1, 5492–5496. 8. M. Palanisamy and M. M. Mench, Adv. Energy Mater., 2025, 2404368 (1–16). 9. M. Palanisamy, K. W. Lin, C. T. Lo, and V. G. Pol, ACS Appl. Mater. Interfaces, 2022, 14, 28310−28320. Figure 1

This study investigates the path-dependent degradation in polymer electrolyte fuel cells (PEFCs) using two accelerated stress test (AST) protocols derived from the U.S. Department of Energy (DOE) guidelines. The first protocol, PtfCC AST, involved 15,000 cycles of square-wave voltage cycling (0.6-0.95 V vs. reversible hydrogen electrode, RHE) followed by 2500 cycles of triangular-wave voltage cycling (1.0-1.5 V vs. RHE). The second protocol, CCfPt AST reversed the order of execution of triangular-and square-wave cycling. Multimodal characterization techniques, including spatially resolved current distribution and post-mortem micro-X-ray diffraction (micro-XRD) platinum particle size mapping, revealed significant differences in degradation patterns. Different polarization performance (spatially distributed and averaged), electrochemically-active surface area (ECSA) loss, morphological changes, and Pt particle size maps of the active area at the end-of-life (EOL) for the same cumulative stress cycles indicate path dependency of degradation in PEFCs for the two tested protocols and the set of materials. The findings from this study highlight the complex interplay of degradation mechanisms, which are crucial for improving PEFC durability and predictive health monitoring in real-world applications with irregular cycling patterns.

In recent years, many researchers have focused on developing platinum-free catalysts for the oxygen reduction reaction (ORR) [1] due to the high cost and limited availability of platinum. Transition metal oxides present a promising alternative to this precious metal and are being explored for their potential in ORR catalysis 2], particularly in alkaline electrolytes. These oxides can serve as substitutes for platinum-based catalysts, especially in applications in metal-air batteries, including aluminum-air batteries. Moreover, catalysts at the nanometer scale demonstrate enhanced catalytic activity owing to their high surface area. Research indicates that both the size and shape of these nanocatalysts significantly influence their catalytic performance. In this work, we present the synthesis conditions and characterization of manganese oxide nanoparticles (Mn3O4, also known as hausmannite) with various sizes and morphologies.[3][4] these nanocatalysts were subsequently tested for electrochemical activity at room temperature and atmospheric pressure in an O2-saturated 0.1 M KOH solution. We demonstrate that the size and shape of these nanoparticles influence their catalytic activity towards ORR. References [1] Chandran, P., Ghosh, A. & Ramaprabhu, S. High-performance Platinum-free oxygen reduction reaction and hydrogen oxidation reaction catalyst in polymer electrolyte membrane fuel cell. Sci Rep 8, 3591 (2018) [2]Goswami, C., Hazarika, K. K. & Bharali, P. Transition metal oxide nanocatalysts for oxygen reduction reaction. Mater. Sci. Energy Technol. 1, 117–128 (2018). [3]T. Rhadfi, J.-Y. Piquemal, L. Sicard, F. Herbst, E. Briot, M. Benedetti, A. Atlamsani, Polyol-made Mn3O4 nanocrystals as efficient Fenton-like catalysts, Appl. Catal. A 386 (1) (2010) 132–139. [4] Rhadfi, T.; Sicard, L.; Testard, F.; Taché, O.; Atlamsani, A.; Anxolabéhère-Mallart, E.; Le Du, Y.; Binet, L.; Piquemal, J.-Y. J. Phys. Chem. C 2012, 116, 5516

To develop cost-effective and high-performing polymer electrolyte water electrolyzers (PEWEs) for gigawatt-scale applications, researchers have focused on reducing precious metal catalyst loadings and optimizing porous transport layers. However, the performance of PEWEs is also affected by system architecture. Mass transport losses are dependent on localized architecture and material interactions. In-situ measurements, such as current density distribution maps have demonstrated advantages in understanding the intricate characteristics and influence of two-phase flow within PEWEs. This study proposes the parameter of effective water transport number (EWTN) as a quantitative tool to investigate such current density distribution (CDD) measurements for PEWEs. Results show that higher flow-rates have EWTN values of 0.95 and above, indicating no mass transport limitations; while lower flow-rates with large gradients CDD have EWTN values between 0.6-0.8, indicating mass transport limited conditions. The new analysis also identified a correlation between mass transport losses due to bubble accumulation, membrane hydration, and ohmic overpotentials. To address these limitations, an unitized pin-type LGDL/flow-field design was developed, which effectively prevents local gas phase accumulation, resulting in improved mass transport characteristics. The results of this work show reduced flow-rate sensitivity with the pin-type architecture and ∼13% increased performance at 0.24 ml / min / cm 2 .

Polymer electrolyte water electrolyzers (PEWEs) are pivotal in the transition to a clean energy economy, promising green and efficient hydrogen production. Understanding the complexities of overpotentials within PEWEs is crucial for optimizing their performance and efficiency 1 . For PEWEs to attain the highest possible system efficiency, considering a specific material set and operating parameters, meticulous design is imperative. The goal is to achieve a high reaction rate that is not only optimal but also uniform across the entire active surface area of the electrodes. This uniformity should ideally be maintained with minimal sensitivity to variations in operating conditions. This study focuses on the contribution of different overpotential categories and reveals their spatial variations through in-situ analysis to understand and overcome the issues caused by non-uniformity in reaction. Employing a segmented cell and printed circuit board (PCB) approach 2 , current density distribution (CDD) and distributed area-specific resistance (DASR) measurements are obtained, enabling a detailed examination of the mass transport overpotentials (as shown in Figure 1). Typically, in the fuel cell community, modeling mass transport limitations is thought of as diffusion-limited transport 3 . In the anode porous transport layer (PTL), oxygen accumulation (i.e. product transport limitation) can cause membrane dry-out and an increase in ASR 4 . The experimental results elucidate the intricate relationship between ohmic and mass transport losses, emphasizing the deep coupling induced by the two-phase nature of the system. Figure 1 shows that, as mass transport limitation grows, the highest increase in overpotential comes from mass transport-coupled ohmic losses. Beyond conventional diffusion limited mass transport losses, bubble dynamics significantly impact local hydration and ASR, highlighting the need for a holistic approach in device optimization 5 . This research contributes to the understanding of PEWE dynamics, providing a basis for informed engineering decisions. By unraveling the intricate interdependencies between overpotentials, this work empowers the efficient utilization of expensive catalyst materials. Moreover, it offers insights into mitigating the challenges associated with bubble removal, accomplishing this with lower pumping requirements that scale non-linearly. These insights enrich both theoretical understanding and are paramount for enhancing system efficiency and economic viability of PEWEs, thereby advancing the prospect of sustainable hydrogen production. Reference N. Danilovic and I. Zenyuk, Electrochem. Soc. Interface , 30 (2021). F. H. Roenning, A. Roy, D. S. Aaron, and M. M. Mench, J. Power Sources , 542 , 231749 (2022) https://linkinghub.elsevier.com/retrieve/pii/S037877532200742X. A. Z. Weber et al., J. Electrochem. Soc. , 161 , F1254–F1299 (2014) https://iopscience.iop.org/article/10.1149/2.0751412jes. C. Immerz, B. Bensmann, P. Trinke, M. Suermann, and R. Hanke-Rauschenbach, J. Electrochem. Soc. , 165 , F1292–F1299 (2018). P. Satjaritanun et al., iScience , 23 , 101783 (2020) https://doi.org/10.1016/j.isci.2020.101783. Figure 1

The demand for electric vehicles (EV) and electric vertical take-off and landing (eVTOL) aircraft is growing exponentially. The lithium-ion battery (LIB) is commonly selected for such applications due to its promising relatively high energy and power density. However, range limitations, capacity fade, and durability of Li-ion systems limit EVs. These questions become even more vital when discussing aerospace applications of eVTOL, which have more stringent requirements for safety, power, and durability. Additionally, cell-to-cell-variations (CtCv) play a major role in pack performance. To address the current needs, this work employs a characterization method combining the techniques of electrochemical impedance spectroscopy (EIS) and distribution of relaxation times (DRT), allowing for better characterization of cell performance and degradation at relevant high C-rates. In this work, cells are cycled at high-rate discharge (10C and 25C) at various temperatures to mimic eVTOL applications, with characterization tests being performed at beginning of life and every 50 cycles for a total of 500 cycles. By applying DRT to the EIS data, the electrochemical processes inside the cell can be deconvoluted and examined [1-3]. Gaussian peaks are fit to the DRT distribution function, and the resistance of each process can be predicted, thereby monitoring changes in HFR, interfacial particle-particle interactions, SEI/CEI interphase layers, and charge transfer/intercalation kinetics at various states of charge (SOC) and cycle number. Furthermore, diffusion related processes can also be identified and estimated from DC current-interrupt/application methods. Degradation tests were performed to simulate various thermal boundary conditions faced by eVTOLs ranging from 20°C to -20°C. The results reveal that, at high discharge rates operating at room temperature, cells reached up to 90°C and signatures of degradation in the SEI layer are seen in the DRT data. Other cells cycled at 0°C show evidence of lithium plating due to the cold environment. Active cooling at 20°C showed the least degradation as identified from the various internal processes. This method of testing provides an approach to comprehensively analyze individual internal degradation modes of a Li-ion battery. References: [1] Wan, Ting Hei et al. “Influence of the Discretization Methods on the Distribution of Relaxation Times Deconvolution: Implementing Radial Basis Functions with DRTtools” Electrochimica Acta, Vol. 1842015, http://dx.doi.org/10.1016/j.electacta.2015.09.097 [2] Iurilli, Pietro et al. “Detection of Lithium-Ion Cells’ Degradation through Deconvolution of Electrochemical Impedance Spectroscopy with Distribution of Relaxation Time” Energy Technology, Vol. 10, 2022, https://doi.org/10.1002/ente.202200547 [3] Chen, Xiang et al. “Detection of lithium plating in lithium-ion batteries by distribution of relaxation times” Journal of Power Sources, Vol. 496. 2021. https://doi.org/10.1016/j.jpowsour.2021.229867 Figure 1

Polymer Electrolyte Water Electrolyzers (PEWEs) stand as promising energy storage solutions, leveraging variable renewable energy sources to produce hydrogen. Simulating the intricate two-phase fluid dynamics within these systems necessitates the use of complex numerical models since direct experimentation to capture these dynamics is difficult. Currently, most models adopt a macroscopic continuum approach. However, integrating various modeling scales, especially coupling two-phase flow interactions between channels and the porous media within such systems, remains challenging1. This works attempts to address the challenge by developing an advanced Allen-Cahn Navier-Stokes (AC-NS) coupled Lattice Boltzmann Method (LBM) model. Unlike traditional diffuse-interface LBM models based on the Shan-Chen model2, the AC-NS approach demonstrates enhanced stability and accuracy, with minimal parasitic velocities at fluid interfaces. By implementing Allen-Cahn formulation to minimize the free-surface energy of the fluid interfaces3,4, this work showcases the ease of coupling a phase-field (to capture both liquid and gas phase interactions) with the incompressible Navier-Stokes equations using a LBM framework. This highlights the model’s efficacy in predicting the flow dynamics for binary fluid systems with high density and viscosity ratios within porous media (as shown in Figure 1) at relatively low computational costs. Furthermore, such a model emphasizes the advantage of incorporating natural boundary conditions and using physical parameters such as surface tension and contact angles, tailored to fluid and geometric properties. Lastly, a methodology to integrate the pore-scale model with existing macroscopic continuum scale models will be presented. Such a framework is essential to accurately calculate the mass transport limitations within PEWEs and predict the performance of a PEWE5,6. Therefore, this work achieves a major step towards enhancing the predictive capabilities of numerical models in advancing the design and optimization of PEWE systems. References: B. Xu et al., Energy Rev., 3, 100073 (2024) https://doi.org/10.1016/j.enrev.2024.100073. X. Shan and H. Chen, Phys. Rev. E, 47, 1815–1819 (1993) https://link.aps.org/doi/10.1103/PhysRevE.47.1815. M. Geier, A. Fakhari, and T. Lee, Phys. Rev. E, 91, 063309 (2015) https://link.aps.org/doi/10.1103/PhysRevE.91.063309. E. Ezzatneshan and A. A. Khosroabadi, J. Appl. Fluid Mech., 15, 1771–1787 (2022) https://www.jafmonline.net/article_2102.html. B. Han, J. Mo, Z. Kang, and F. Y. Zhang, Electrochim. Acta, 188, 317–326 (2016). B. Han et al., Int. J. Hydrogen Energy, 42, 4478–4489 (2017). Figure 1

This study investigates the impact of liquid water distribution in a polymer electrolyte fuel cell (PEFC) on the spatially heterogeneous platinum (Pt) catalyst degradation. The membrane electrode assemblies (MEAs) are aged using accelerated stress tests (ASTs) in varied cathode gas environments (N2 and air) to instigate Pt catalyst degradation. The study employs high-resolution neutron imaging and synchrotron micro-X-ray diffraction (micro-XRD) to map liquid water distribution and Pt particle size, respectively. Neutron radiographs reveal liquid water accumulation primarily within the diffusion media, especially under flow field lands, due to thermal resistance differences between channels and lands. Aged MEAs exhibit increased water retention, likely due to increased hydrophilicity of the diffusion media with aging. Synchrotron micro-XRD maps unveil significant heterogeneity in Pt particle size distribution in the aged MEAs, correlated with preferential liquid water accumulation under flow field lands. This study highlights the critical role of flow field design and water distribution in catalyst degradation, underscoring the need for innovative strategies to enhance fuel cell durability and performance.

The U.S. Department of Energy (DOE) interim (2030) targets for polymer electrolyte fuel cells (PEFCs) in heavy duty vehicle applications call for reduced system cost (US $80/kW), increased peak efficiency (68%), and longer system lifetime (25,000 hrs) [1]. Designing high-performance, durable, low-temperature hydrogen fuel cells involves intricate trade-offs between cell-level geometries and materials, as well as considering system-level complexities and efficiencies. Optimal reactant gas management, particularly oxygen transport to the cathode, is a crucial part of the design process. Despite efforts to enhance convective mixing and reduce liquid water accumulation through novel flow distribution architectures, recent commercialization trends favor formed bipolar plates with a parallel/serpentine channel architecture. These plates with flow distribution channels prove to be the most cost-competitive for heavy-duty automotive applications. Porous and high-pressure-loss flow channel networks, while promising in performance under specific operating conditions, fall short in justifying the additional cost or parasitic power associated with implementation in commercial systems [2]. This study introduces a hybrid porous layer [3],[4] with organized convection pathways that significantly improves performance compared to conventional bipolar plates. Exceptional performance (see Figure 1) is demonstrated across diverse operating conditions (e.g. wet, cold conditions up to dry, hot). The results of this study offer the potential to achieve high performance with reduced weight, as well as manufacturing and assembly cost using this hybrid architecture. References: [1] D. A. Cullen, K. C. Neyerlin, R. K. Ahluwalia, R. Mukundan, K. L. More, R. L. Borup, A. Z. Weber, D. J. Myers, and A. Kusoglu, “New roads and challenges for fuel cells in heavy-duty transportation,” Nat Energy, vol. 6, pp. 462–474, 2021, doi: 10.1038/s41560-021-00775-z. [2] G. Zhang, Z. Qu, W. Q. Tao, X. Wang, L. Wu, S. Wu, X. Xie, C. Tongsh, W. Huo, Z. Bao, K. Jiao, and Y. Wang, “Porous Flow Field for Next-Generation Proton Exchange Membrane Fuel Cells: Materials, Characterization, Design, and Challenges,” Chemical Reviews, vol. 123, no. 3. American Chemical Society, pp. 989–1039, Feb. 08, 2023. doi: 10.1021/acs.chemrev.2c00539. [3] P. Sharma, J. Owejan, D. Aaron, and M. M. Mench, “Porous Carbon Fiber Flow Fields for Heavy-Duty Polymer Electrolyte Fuel Cell (PEFC) Applications,” ECS Meeting Abstracts, vol. MA2023-01, no. 38, p. 2255, Aug. 2023, doi: 10.1149/MA2023-01382255mtgabs. [4] J. P. Owejan and S. G. Goebel, “Performance evaluation of porous gas channel ribs in a polymer electrolyte fuel cell,” J Power Sources, vol. 494, May 2021, doi: 10.1016/j.jpowsour.2021.229740. Figure 1

Highly efficient electrodes with facile fabrication, excellent performance, low cost, and high durability are of paramount significance for the development of gigawatt-scale proton exchange membrane electrolyzer cells (PEMECs).1-5 In this study, amorphous Ir0.8Ru0.2Ox (80% Ir, 20% Ru) catalysts with high intrinsic activity are first deposited on Ti sintered powder via a room temperature electrodeposition process, serving as high-performance anode electrodes in PEMECs. Different Ir loadings of 0.16, 0.24, 0.4, and 0.72 mg/cm2 were deposited and evaluated in PEMECs. As a result, low average cell voltages of 1.623 and 1.875 V are achieved at 2 and 6 A/cm2, respectively, achieving high cell efficiency of 91%-94% at 2 A/cm2, superior to the commercial CCM.1, 3, 6 Moreover, with an Ir loading of 0.4 mg/cm2, the Ir0.8Ru0.2Ox electrode shows a low-performance loss after a 900-h operation at an ultrahigh current density of 5 A/cm2, resulting in a low degradation rate of only about 39 uV/h in the last 200 h. The remarkable performance and durability of the Ir0.8Ru0.2Ox electrode are mainly due to the high intrinsic activity of Ir0.8Ru0.2Ox catalysts exposing abundant active sites, sufficient Ir3+ content, a well-controlled Ir and Ru ratio, efficient phase transformation, and excellent catalyst support. References Mo, Jingke, Zhenye Kang, Scott T. Retterer, David A. Cullen, Todd J. Toops, Johney B. Green Jr, Matthew M. Mench, and Feng-Yuan Zhang. "Discovery of True Electrochemical Reactions for Ultrahigh Catalyst Mass Activity in Water Splitting." Science Advances 2, no. 11 (2016): e1600690. Ding, Lei, Weitian Wang, Zhiqiang Xie, Douglas S. Aaron, Adam Paxson, Monjid Hamdan, Matthew M. Mench, and Feng-Yuan Zhang. "Efficient Integrated Electrode Enables High-Current Operation and Excellent Stability for Green Hydrogen Production." ACS Sustainable Chemistry & Engineering 11, no. 30 (2023): 11219-11228. Ding, Lei, Zhiqiang Xie, Shule Yu, Weitian Wang, Alexander Y. Terekhov, Brian K. Canfield, Christopher B. Capuano, Alex Keane, Kathy Ayers, David A. Cullen, Feng-Yuan Zhang. "Electrochemically Grown Ultrathin Platinum Nanosheet Electrodes with Ultralow Loadings for Energy-Saving and Industrial-Level Hydrogen Evolution" Nano-Micro Letters 15, 144 (2023). Ding, Lei, Weitian Wang, Zhiqiang Xie, Kui Li, Shule Yu, Christopher B. Capuano, Alex Keane, Kathy Ayers, and Feng-Yuan Zhang. "Highly Porous Iridium Thin Electrodes with Low Loading and Improved Reaction Kinetics for Hydrogen Generation in PEM Electrolyzer Cells." ACS Applied Materials & Interfaces (2023): 24284. Xie, Zhiqiang, Shule Yu, Xiaohan Ma, Kui Li, Lei Ding, Weitian Wang, David A. Cullen et al. "MoS2 Nanosheet Integrated Electrodes with Engineered 1T-2H Phases and Defects for Efficient Hydrogen Production in Practical PEM Electrolysis." Applied Catalysis B: Environmental 313 (2022): 121458. Xie, Zhiqiang, Lei Ding, Shule Yu, Weitian Wang, Christopher B. Capuano, Alex Keane, Kathy Ayers, David A. Cullen, Harry M. Meyer III, and Feng-Yuan Zhang. "Ionomer-free nanoporous iridium nanosheet electrodes with boosted performance and catalyst utilization for high-efficiency water electrolyzers." Applied Catalysis B: Environmental 341 (2024): 123298. Figure 1

High-entropy alloys (HEAs) are a class of metal alloys consisting of four or more molar equal or near-equal elements. HEA nanomaterials have garnered significant interest due to their wide range of applications, such as electrocatalysis, welding, and brazing. Their unique multi-principle high-entropy effect allows for the tailoring of the alloy composition to facilitate specific electrochemical reactions. This study focuses on the synthesis of high-purity HEA nanoparticles using the method of femtosecond laser ablation synthesis in liquid. The use of ultrashort energy pulses in femtosecond lasers enables uniform ablation of materials at significantly lower power levels compared to longer pulse or continuous pulse lasers. We investigate how various femtosecond laser parameters affect the morphology, phase, and other characteristics of the synthesized nanoparticles. An innovative aspect of our solution is its ability to rapidly generate multi-component nanoparticles with a high fidelity as the input multi-component target material at a significant yielding rate. Our research thus focuses on a novel synthesis of high-entropy alloying CuCoMn1.75NiFe0.25 nanoparticles. We explore the characterization and unique properties of the nanoparticles and consider their electrocatalytic applications, including high power density aluminum air batteries, as well as their efficacy in the oxygen reduction reaction (ORR). Additionally, we report a unique nanowire fabrication phenomenon achieved through nanojoining. The findings from this study shed light on the potential of femtosecond laser ablation synthesis in liquid (FLASiL) as a promising technique for producing high-purity HEA nanoparticles.

The state-of-the-art Li-ion battery has energy density plateauing at ~300 Wh/kg [1]. Replacing the graphite-based anode with Li metal is one promising pathway to increase energy density. However, a lithium metal anode is prone to non-uniform plating/striping that leads to capacity decay and dendrite formation. Solid-state batteries (SSBs) hold great promise for next-generation energy storage systems due to their potential to address safety concerns, provide energy density, and enable the use of high-energy electrode materials such as lithium (Li) metal. Additionally, SSBs exhibit greater mechanical stability and can limit dendritic growth [2]. Furthermore, solid electrolytes show much higher thermal stability, are non-toxic, and have high energy density. Among the various types of solid-state electrolytes, composite polymer electrolytes (CPEs) have emerged as a promising option owing to their excellent ionic conductivity, mechanical flexibility, and compatibility with Li metal electrodes. Polyethylene oxide (PEO) polymer electrolyte has very good interfacial contact between electrode and very flexible in nature [3]. But PEO by itself is unstable. A PEO composite with solid ceramic offers the potential for better stability with high conductivity as well as improved physical properties. Our research focuses on elucidating key parameters that affect the electrochemical behavior and stability of these systems, aiming to enhance their overall performance and longevity. One of the primary factors under investigation is the composition and morphology of the composite polymer electrolyte. We explored PEO polymer and LLZTO ceramic fillers to optimize the electrolyte's mechanical strength, Li-ion conductivity, and interfacial stability with Li metal electrodes [2]. Through systematic characterization techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), and impedance spectroscopy, we gain insights into the microstructure and ion transport properties of the CPE. The combination of PEO and Polyvinylidene fluoride (PVdF) polymer creates a remarkably robust and flexible polymer electrolyte, renowned for its exceptional mechanical and electrochemical stability. Figure 1 (a) shows the cycling profile of PEO/PVdF electrolyte at different C rates with LFP cathode and Li metal as anode. Compared to PEO membrane, the composite exhibits higher ohmic polarization. However, this composite polymer electrolyte demonstrates better stability and high-rate capability than a pure PEO membrane. At 1-C rate charging and discharging condition cell shows 99% columbic efficiency and good capacity retention. In Figure 1(b) and (c) show the SEM image of PVdF and PEO composite membrane respectively. Which shows PEO completely covers the PVdF network and helps better contact with solid electrode. Reference: Bapi Bera, Anirban Roy, Douglas Aaron, and Matthew M Mench, “Understanding the Transport Phenomena in Solid State Battery (SSB)”, Electrochemical Society Meeting Abstracts-241, 2022, 1, 45-45. Yanda Fu et al., “Surface Defects Reinforced Polymer-Ceramic Interfacial Anchoring for High-Rate Flexible Solid-State Batteries”, Adv. Funct. Mater. 2023, 33, 2210845. Sahore, Z. Du, X. C. Chen, W. B. Hawley, A. S. Westover, and N. J. Dudney, Practical considerations for testing polymer electrolytes for high-energy solid-state batteries, ACS Energy Lett. 2021, 6, 2240-2247. Figure 1

This study presents an in-depth analysis of heterogeneous aging patterns in membrane electrode assemblies (MEAs) subjected to diverse accelerated stress test (AST) conditions, simulating carbon corrosion (CC AST) and Pt particle size growth in fully humidified (Pt AST-Wet) and underhumidified (Pt AST-Dry) H2/N2 atmospheres. Multimodal characterization techniques are used to focus on heterogeneous aging patterns, primarily examining the variations in current distributions and Pt particle size maps. The findings reveal distinct characteristics of current distributions for all the AST cases, with substantial changes and strong current gradients in the CC AST case, indicative of severe performance degradation. Notably, despite significant differences in Pt particle size growth at the end-of-life (EOL), the Pt AST-Wet and Pt AST-Dry cases show minor changes in spatial current distributions. Moreover, a preferential growth of Pt particles under serpentine flow field bends in the Pt AST-Wet case is observed for the first time. This study provides crucial insights into the role of mass transport properties in shaping fuel cell performance, and highlights the need to consider factors beyond electrochemically-active surface area (ECSA) when assessing fuel cell durability. This study examines heterogeneous aging patterns in polymer electrolyte fuel cells under various stress test conditions, revealing distinct current distribution and catalyst growth changes. Despite differing Pt particle size growth, spatial current distributions show only minor variations in wet and dry Pt particle size growth tests. In contrast, the carbon corrosion test leads to substantial current gradients. image

Aluminum-air batteries (AAB) are regarded as one of the most promising beyond-lithium high-energy-density storage candidates. This paper introduces a three-dimensional (3D) Al 7075 anode enabled by femtosecond laser and friction-stir process which, along with a special double-face anode architecture provides world-class performance. Electrochemical characterizations prove that the corrosion resistance of the modified 3D Al 7075 FSP anode was enhanced, and electrochemically active surface area (ECSA) was increased compared with that of normal Al 7075 anode. Friction-stir processing reduced the mean grain size from 30 mu m to 3 mu m. The discharge performance of 3D Al 7075 FSP anode is shown to be quite stable, and the average values of energy density are significantly increased from 2256 mWh g-1 to 2941 mWh g-1 at 100 mA cm-2. In a double-face flowing Al-air battery system, the 3D Al 7075 FSP anode exhibited significantly better electrocatalytic performance (discharge voltage of 0.76 V at 400 mA cm-2, and power density of 337.8 mW cm-2) than that of a commercial Al 7075 anode.

With a recent emphasis on heavy-duty vehicle applications over light-duty, the performance targets for polymer electrolyte fuel cells (PEFCs) have become more demanding. For instance, achieving a net power output of 2.5 kW/g -PGM (1.07 A/cm 2 current density) at 0.7 V is required after a 25,000-hour equivalent accelerated stress test (AST) [1]. In recent studies with traditional land/channel architecture, it has been demonstrated that Pt particle size growth is non-uniform and greater under flow field lands compared to channels [2]–[5]. It is hypothesized that preferential water accumulation under the lands during ASTs is responsible for such heterogeneity. However, a direct link between water accumulation/storage and particle size growth has not yet been established. In this study, we utilized high-resolution neutron radiography at NEUTRA, PSI, Switzerland to systematically map and quantify through-plane water content; synchrotron micro-XRD measured spatial Pt particle size distributions in fully functional fuel cells compatible with neutron imaging. The membrane electrode assemblies (MEAs) were aged using the U.S. Department of Energy’s (DOE) square-wave AST (0.6 V to 0.95 V vs. reversible hydrogen electrode, RHE) in both air and nitrogen environments at the cathode [5]. Correlations between through-plane water distribution and Pt particle size distribution maps were established for both pristine and aged samples. Understanding the role of architecture is crucial for assessing degradation, particularly in conventional flow fields where channel-land bias influences thermal and mass transport, impacting liquid water distribution. This knowledge can inform the design and engineering of PEFC components to enhance durability and reduce overall costs for vehicle applications. References: [1] D. A. Cullen, K. C. Neyerlin, R. K. Ahluwalia, R. Mukundan, K. L. More, R. L. Borup, A. Z. Weber, D. J. Myers, and A. Kusoglu, “New roads and challenges for fuel cells in heavy-duty transportation,” Nat Energy , vol. 6, pp. 462–474, 2021, doi: 10.1038/s41560-021-00775-z. [2] L. Cheng, K. Khedekar, M. Rezaei Talarposhti, A. Perego, M. Metzger, S. Kuppan, S. Stewart, P. Atanassov, N. Tamura, N. Craig, I. V. Zenyuk, and C. M. Johnston, “Mapping of Heterogeneous Catalyst Degradation in Polymer Electrolyte Fuel Cells,” Adv Energy Mater , vol. 2000623, pp. 1–7, 2020, doi: 10.1002/aenm.202000623. [3] K. Khedekar, M. R. Talarposhti, M. M. Besli, S. Kuppan, A. Perego, Y. Chen, M. Metzger, S. Stewart, P. Atanassov, N. Tamura, N. Craig, L. Cheng, C. M. Johnston, and I. V Zenyuk, “Probing Heterogeneous Degradation of Catalyst in PEM Fuel Cells under Realistic Automotive Conditions with Multi-Modal Techniques,” Adv Energy Mater , vol. 11, no. 35, p. 2101794, 2021, doi: 10.1002/aenm.202101794. [4] P. Sharma, B. Bera, D. Aaron, M. M. Besli, S. Kuppan, L. Cheng, J. Braaten, N. Craig, S. Stewart, M. Metzger, C. Johnston, and M. M. Mench, “Spatially Resolved Heterogeneous Electrocatalyst Degradation in Polymer Electrolyte Fuel Cells Subjected to Accelerated Aging Conditions,” J Electrochem Soc , vol. 169, no. 11, p. 114506, Nov. 2022, doi: 10.1149/1945-7111/ac9ee5. [5] P. Sharma, L. Cheng, D. Aaron, S. Mehrazi, J. Braaten, N. Craig, C. Johnston, and M. M. Mench, “Unveiling Local Aging Patterns Following Accelerated Stress Testing of High-Performance Polymer Electrolyte Fuel Cells,” Small , no. 2306433, 2023, doi: 10.1002/smll.202306433.

Generating green hydrogen through proton exchange membraneelectrolyzercells (PEMECs) is promising to build future sustainable energy systems.Operating PEMECs at high current densities with high efficiency isa realistic strategy to reduce the capital costs of PEMECs and increasetheir sustainability. Herein, an Ir-integrated electrode was developedvia facile electrodeposition as an efficient anode for PEMECs, successfullyachieving high-current operation of up to 6 A/cm(2). Moreimportantly, the electrode shows excellent stability under an ultrahighcurrent density of 5 A/cm(2), showing almost no performanceloss after the stability test. Further studies indicate that a platinumprotection layer on Ti substrates plays a crucial role in superiorperformance and stability, which not only provides electrodes withimproved electrical conductivity resulting in improved catalyst activitybut also enhances the crack-free catalyst layer achieving catalysts'adhesion improvement to the substrate and prevents substrate oxidation.With platinum, the cell voltage can be improved by 33, 59, and 87mV at current densities of 2, 4, and 6 A/cm(2), respectively.Overall, considering efficient high-current operation capability,remarkable stability, and significantly simplified and low-cost fabricationprocess with easy scalability, the developed integrated electrodesare believed to have great potential in future sustainable energysystems. An efficient Ir-integratedelectrode was developed for PEMECs,achieving high-current operation and remarkable stability under 5A/cm(2) with almost no performance loss.