bluuebunny/crossref_metadata_2025_split huggingface dataset:
Achieving High Performance with High Oxygen Permeability Ionomer (HOPI) in Heavy Duty Fuel Cell MEAs
Authors: Macauley Natalia , Strasser Derek James , Coletti Kathryn , Ding Shuo , Tong Emily , Zhang Bingzhang , Liang Jiashun , Wu Gang 
Published: August 2024

Heavy-duty PEM fuel cells are expected to last 25,000-30,000 hours in the field. Therefore, materials, components, and interfaces used in these systems must be highly resistant to severe mechanical and chemical stress. Novel, highly active stable Pt and ordered PtCo intermetallic nanoparticles with well-controlled particle size and composition have been synthesized on a highly efficient PGM-free single metal active site rich carbon, to maximize their synergistic effects for enhanced performance and durability. Integrating these catalysts integrated with high O2 permeability ionomer (HOPI) in membrane electrode assemblies (MEAs) improved their fuel cell performance and durability, allowing the MEAs to achieve >1.2 A/cm2 at 0.7 V after 150k square wave accelerated stress test (AST) cycles, with a performance loss < 40 mV after 150K AST cycles.
In a PEM fuel cell, the catalyst ink formulation and mixing processes control catalyst layer coating quality, electrode morphology, and the resulting fuel cell performance and durability. Catalyst ink properties are a result of complex solvent-catalyst-ionomer interactions that depend on the mixing method employed. Here, we compare the performance and durability of electrodes made from ball milled inks for Mayer rod coating before and after the catalyst scale up. Ink rheology and catalyst particle size are used to correlate ink properties to electrode morphology and structure and ensure consistency from batch to batch, and from small lab scale to subsequent scale-up. We evaluate and discuss the challenges that arise when coating the more viscous inks on decals, where the HOPI creates many bubbles in the ink. We also present the challenges of hot-pressing inks that contain HOPI, and how employing a Nafion overspray made with different solvents (isopropanol vs. ethanol) can improve hot-pressing. We investigate the how ionomer to carbon ratio affects hot pressing with HOPI and crack formation in the electrode via scanning electron microscopy (SEM).
This work provides a comprehensive understanding of interactions between Pt, PtCo, carbon, ionomer, membrane, and GDLs and their impact on electrode structure, fuel cell performance and durability, as well as considerations for scale up to a R2R fabrication process. The attained information will be used to improve fuel cell electrode design, fabrication and scale-up.
Acknowledgement: The project is financially supported by the Department of Energy’s Fuel Cell Technology Office under the Grant DE-FOA-0002360 (Phase I) and DE-SC0021671 (Phase II).

Figure 1
Manganese Oxide Gas Diffusion Electrode Conditioning and Electrochemical Doping for Reversible Oxygen Reduction/Evolution Reactions
Authors: Pei Yu , Wu Wen Yu , Wilkinson David P. , Gyenge Elod L. 
Published: August 2024

Developing durable and active bifunctional gas diffusion electrodes for reversible oxygen reduction/evolution (ORR/OER) reaction catalysis is crucial yet challenging in the development of numerous electrochemical energy conversion systems, including regenerative fuel cells and rechargeable metal-air batteries. This research is focused on developing manganese oxide-based gas diffusion electrodes for reversible oxygen electrodes.
Core-porous shell Mn/Mn3O4 (abbreviated as MnOx) nanoparticles (QSI) demonstrated increased ORR/OER activities compared to γ-MnO2 (EMD) and b-MnO2.[1] The unique behaviour of core-shell MnOx is attributed to the charge transfer between the low-valent Mn core and the high-valent Mn3O4 shell, thereby regenerating Mn(III) active sites through comproportionation.[1]
The stability of transition-metal-based reversible oxygen electrodes remains a challenge. As shown in Figure 1, the deterioration of Mn/Mn3O4 during ORR and OER cycling can be attributed to three aspects: Mn active sites oxidation (Figure 1a), less active MnOx phase formation (Figure 1b), and material loss (carbon corrosion and dissolved MnO4
- formation) (Figure 1c).[2] As a result, the QSI MnOx electrode transformed from pristine to inactive status within 15 galvanostatic ORR/OER cycles. To improve the stability of the electrode, a set of in-situ electrochemical conditioning and electric field-driven metallic cation incorporation into MnOx GDE was investigated. Among the explored metal cations, the Ni2+ incorporation showed the most significant improvement in terms of activity and cyclic stability. The Ni-MnOx GDE demonstrated excellent stability for over 120 galvanostatic cycles at ±10 mA cm-2 in O2-saturated KOH without losing OER activity, surpassing the Pt/C-IrO2 benchmark.[3]
These findings position the MnOx electrodes as promising and sustainable alternatives to precious metal-based electrodes for ORR/OER catalysis and provide valuable insights into designing reversible oxygen electrodes for energy conversion and storage in alkaline systems, contributing to a green future.
[1] Pei, Y., Wilkinson, D. P., & Gyenge, E. L. Insights into the electrochemical behavior of manganese oxides as catalysts for the oxygen reduction and evolution reactions: monometallic core‐shell Mn/Mn3O4. Small, 2023, 19, 2204585.
[2] Pei, Y., Wilkinson, D. P., & Gyenge, E. L. Gas Diffusion Electrode Design and Conditioning with Manganese (III/IV) Oxide Catalyst for Reversible Oxygen Reduction/Evolution Reactions. ACS Energy & Fuels (2023), 37, 23, 19278–19291.
[3] Pei, Y., Wu, W. Y., Wilkinson, D. P., & Gyenge, E. L. High-Performance Reversible Oxygen Reduction/Evolution Gas Diffusion Electrodes with Multivalent Cation Doped Core-Shell Mn/Mn3O4 Catalysts. ChemElectroChem, in press.

Figure 1
(Invited) Chemical Kinetic Method for Active-Site Quantification in Fe-N-C Catalysts and Correlation with Molecular Probe and Spectroscopic Site-Counting Methods
Authors: Bates Jason S. , Martinez Jesse J. , Hall Melissa N. , Al-Omari Abdulhadi A. , Murphy Eamonn , Zeng Yachao , Luo Fang , Primbs Mathias , Menga Davide , Bibent Nicolas , Sougrati Moulay Tahar , Wagner Friedrich E. , Atanassov Plamen , Wu Gang , Strasser Peter , Fellinger Tim-Patrick , Jaouen Frederic , Root Thatcher W. , Stahl Shannon S. 
Published: August 2024

Heterogeneous catalysts consisting of iron cations incorporated into nitrogen-doped carbon (“Fe-N-C”) have received extensive attention as leading alternatives to Pt for the electrochemical oxygen reduction reaction (ORR). Fe-N-C catalysts host mononuclear nitrogen-ligated active centers, FeNx, that frequently coexist with agglomerated Fe species. Although FeNx are the dominant active centers for ORR and other electrocatalytic reactions, the relative accuracies of methods to quantify them are still debated. Here, we develop a kinetic probe-reaction approach to quantify FeNx centers and compare it with spectroscopic and molecular probe methods.
Model Fe-N-C catalysts were synthesized to contain mononuclear FeNx species at low loadings (0.1–0.4 wt% bulk Fe) on solvent-accessible surfaces using a postsynthetic metalation approach and their Fe speciation was confirmed by low-temperature 57Fe Mössbauer spectroscopy. The initial rate of oxidation of a water-soluble hydroquinone molecule (per gcatalyst) catalyzed by these model materials correlates linearly with their density of FeNx centers, reflecting their intrinsic turnover frequency (TOF) for this reaction. This TOF, in turn, enables the estimation of the active-site density on any other Fe-N-C catalyst through a simple rate measurement. Kinetically determined FeNx site densities are measured on a suite of fourteen Fe-N-C catalysts with diverse synthetic origins and Fe speciation (0.3–8.4 wt% bulk Fe) and are compared with those estimated by low-temperature 57Fe Mössbauer spectroscopy, CO pulse chemisorption, and electrochemical stripping of NO derived from NO2
−. Kinetic quantifications of FeNx centers correlate well with those obtained from the CO pulse chemisorption method and Mössbauer spectroscopy. The broad survey of Fe-N-C materials also reveals the presence of outliers and challenges associated with each site quantification method. The kinetic method developed here does not require pretreatments that may alter active-site distributions nor specialized equipment beyond reaction vessels and standard analytical instrumentation, offering an attractive complementary approach.

Figure 1
Investigation and Characterization of Interfacial Transport Phenomena in the Catalyst Layer Using Rheo-Impedance Measurement
Authors: Mora Joy Marie , Chuang Po-Ya Abel 
Published: August 2024

Electrodes or catalyst layers (CLs) are the heart of fuel cell and electrolyzer cell devices. They are mainly heterogeneous porous electrodes composed of catalyst particles, ion-conducting polymer material, and void spaces that make up the triple-phase boundary (TPB). It is important to tailor the CL’s microstructure such that there are abundant TPBs where reactions take place to maximize catalyst utilization and improve cell performance. However, this is a critical challenge due to lack of fundamental understanding of the interfacial transport within the CL. Understanding how catalyst ink parameters affect ink properties and how ink components interact, and ultimately, their relationship with CL microstructure formation and cell performance, are essential to designing electrodes. Electrode morphology is important and is controlled by the ionomer/catalyst interactions formed in precursor inks that evolve during mixing and electrode fabrication.
In this study, we probe interactions in catalyst inks with different formulations (ionomer-to-carbon ratio and IPA/water) using a new experimental method to unravel the complexities of ionomer/catalyst particle interactions. The new experimental method is a combination of rheological and electrical impedance spectroscopy measurements (rheo-EIS) that takes advantage of the dynamic nature of catalyst ink and the fact that the rheological and electrical behaviors of the ink are coupled to the microstructure of the material. Using rheo-EIS tool, in combination with zeta (ζ) potential and dynamic light scattering (DLS) measurements, we were able to systematically study how the level of agglomeration of the inks and microstructures evolve with respect to different I/C ratios, solvent formulation, and external shear forces. Results from the three-phase rebuilt test designed to simulate the ink coating condition with single-frequency EIS measurement give information on how the ionomer/catalyst particle interactions form and recover during the coating process. In addition, the full frequency range EIS measurements provide complementary data of the ionic and electrical resistance of the ink before and after high shear applications. Furthermore, the observations of the effect of I/C and IPA/water ratios from this study provide insights on how to better engineer suitable catalyst inks and how to control specific CL microstructure without the need for time-consuming optimization and empirical studies.
Passivation of Lead-Acid Batteries Lead Negative Electrodes by PbSO4 Crystals: Analysis from Modeling Cyclic Voltammetry Responses
Authors: Effat Mohammed , Knehr Kevin , Ferels Crystal , Chaudhari Nikhil , Papa Lopes Pietro Papa , Fister Tim 
Published: August 2024

Lead-acid batteries (LABs) play a pivotal role in the energy storage sector with applications spanning from starting-ignition-lightning batteries to grid energy storage. Passivation of lead negative electrodes by PbSO4 crystals is a one fundamental mechanism limiting the performance of LAB. In this regard, we developed an electrochemical mathematical model that simulates the nucleation and growth dynamics of PbSO4 crystals on a flat lead electrode, responsible for its passivation. The model considers the electrochemical dissolution of Pb2+ from lead electrode and the ternary transport of lead, bisulfate, and hydrogen ions in H2SO4 electrolyte. We have validated the model with a rich dataset of cyclic voltammetry (CV) responses collected at several scan rates and several concentrations of H2SO4. The model shows remarkable qualitative and quantitative agreement with the experimental data including the onset potential, center, height, and width of the CV peaks, discharge capacity, and particle size. The model is used to give insights on how different physical and operational parameters can influence the electrochemical response of lead negative electrodes.
Keywords: lead-acid battery, nucleation and growth, passivation, cyclic voltammetry
Hydrogen Fuel Cells Vs Lithium-Ion Batteries in Electric Vehicles
Authors: Abghoui Younes 
Published: August 2024

I will compare two prominent energy storage technologies—Hydrogen Fuel Cells (HFCs) and Lithium-Ion Batteries (LIBs)—with a focus on their application in electric vehicles (EVs). As the demand for sustainable transportation solutions intensifies, we look into the technological advancements, challenges, and sustainability perspectives associated with these two key players in the electrification of the automotive industry. I will showcase the performance metrics of HFCs and LIBs, including energy density, efficiency, rechargeability, and environmental impact. By considering the latest developments in both technologies, this offers insights into their respective strengths and limitations, shedding light on their suitability for different use cases within the EV ecosystem.Furthermore, I will discuss the infrastructural requirements and economic implications associated with the adoption of HFCs and LIBs in electric vehicles. It critically evaluates the current state of both technologies and anticipates future trends that may shape their role in sustainable transportation. This submission aims to contribute to the ongoing discourse surrounding alternative energy storage solutions for EVs, providing a balanced analysis that can inform policymakers, researchers, and industry professionals engaged in the pursuit of environmentally friendly and efficient mobility solutions.
I also will show some results on cathode exploration for the hydrogen evolution reaction on some novel materials towards the end which would be interesting for further investigation towards commercialisation.
2D Porous Frameworks for Sustainable Energy Storage Applications
Authors: Yu Minghao 
Published: August 2024

Two-dimensional (2D) porous frameworks have garnered significant research interest as a new generation of multifunctional materials. Examples of such frameworks include 2D covalent organic frameworks and 2D conjugated metal-organic frameworks. These structures are characterized by their regular porosities, large specific surface areas, and exceptional chemical stability. Moreover, 2D porous frameworks exhibit distinct properties, such as designable topologies and well-defined redox-active sites, which have sparked increased exploration of these materials for electrochemical energy storage applications.[1] In this presentation, I will illustrate how 2D porous frameworks offer promising electrode alternatives for the next generation of energy storage devices. This will be demonstrated through examples including 2D polyarylimide covalent organic frameworks for multivalent metal batteries[2-3] and 2D conjugated metal-organic frameworks, which serve as appealing pseudocapacitive electrodes[4-5]. Besides, I will present our recent endeavors in exploring 2D crystalline polymers as effective interfacial coatings for batteries.[6-7] These coatings facilitate efficient interfacial ion transport and charge transfer, thus effectively enhancing the overall electrochemical reaction kinetics, reversibility, and durability.
References:
[1] M. Yu et al., J. Am. Chem. Soc. 2020, 142, 12903-12915.
[2] M. Yu et al., J. Am. Chem. Soc. 2020, 142, 19570-19578.
[3] M. Yu et al., J. Am. Chem. Soc. 2023, 145, 6247-6256.
[4] M. Yu et al., J. Am. Chem. Soc. 2021, 143, 10168-10176.
[5] M. Yu et al., Angew. Chem. Int. Ed. 2023, e202306091.
[6] M. Yu et al., Small 2022, 18, 2107971.
[7] M. Yu et al., Nat. Commun. 2023, 14, 760.
Coupling Microkinetics with Continuum Transport Models to Understand CO2R on Planar and Optimized Patterned Electrodes
Authors: Lin Tiras Y , Roy Thomas , Govindarajan Nitish , Guo Jack , Hahn Christopher , Varley Joel 
Published: August 2024

Electrochemical CO2 reduction has emerged as an attractive technique to sustainably produce valuable fuels and chemicals, while reducing CO2 emissions. In addition to the specific electrode material, the microenvironment local to the electrode interface – e.g., the electrolyte pH, CO2 concentration, buffer concentration – plays a significant role in determining the selectivity and activity of the electrolyzer. In this work, we demonstrate a multi-scale approach, where microkinetic simulations of Au are coupled to a two-dimensional continuum transport model in a flow reactor configuration. Specifically, concentrations and potentials solved for in the continuum model are fed into microkinetic models along the planar electrode surface, which return concentration fluxes that are used to update the continuum model. We find that local quantities at the electrode interface, such as the CO2 concentration and pH, vary not only with the applied potential and flow rate, but also with position on the electrode. We investigate two ways to increase CO2 availability at the interface: (1) increasing the applied flow rate, thus reducing the boundary layer thickness, and (2) introducing an inert defect in the middle of the electrode, allowing CO2 to partially replenish within the depletion boundary layer. Inspired by the effect of a single inert defect, we explore electrodes patterned with inert defects and multiple catalyst materials, i.e. a generalized tandem system. We show how the specific pattern of the electrode can be optimized in order to target a specific desired product. The different parts of the electrode have different goals that work together: converting CO2 to CO, converting CO to C2+ products, and allowing concentrations to replenish through the boundary layer. Overall, our aim is to demonstrate the need for multi-dimensional, multi-scale approaches to simulating CO2 reduction to elucidate the reaction environment near the electrode.
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL release number: LLNL-ABS-857537.
(Invited) Challenges and Opportunities in the Integration of CO2 Capture and Conversion
Authors: Kenis Paul J.A 
Published: August 2024

Over the past 15 years or so, the electroreduction of CO2 for the synthesis of intermediates for the chemical industry as well as for the synthesis of small molecule fuels has become a very active area of research. Activities span the whole value chain from electro-catalyst synthesis and characterization, to electrode and cell design and optimization, as well as studies on techno-economic feasibility and life cycle assessment of envisioned overall processes. In the vast majority of these studies, >98% pure CO2 is being used as the feed. In reality, CO2 feeds captured from industrial flue gasses or even those captured from air may not be close to 100% in CO2.
This presentation will explore the integration of a nanomembrane-based CO2 capture method with different CO2 electrolysis approaches. The nano-membrane-based CO2 capture is based on work by Fujikawa and Selyanchyn (Polymer J.
2021, 53, 111), using polydimethylsiloxane-derived membranes that are preferentially permeable to CO2 over nitrogen. Multistage arrangement of modules comprised of arrays of membranes allows for efficient concentration of CO2 from air, from 420 ppm to tens of percent, using just vacuum pumps to drive the process. We explore the use of these concentrated CO2 streams that still contain nitrogen and some oxygen as the feed in subsequent CO2 electrolysis conversions to CO, to methane, or to other products, depending on catalyst choice. We study the effects of feed composition, catalyst chosen, and cell configuration on product speciation, conversion efficiency, etc.
(Invited) Atomically Dispersed Metal Electrocatalysts for CO2 to CO Conversion: From Single to Dual Metal Sites
Authors: Wu Gang 
Published: August 2024

Carbon-supported nitrogen-coordinated single-metal site catalysts (i.e., M−N−C, M: Fe, Co, or Ni) are active for the electrochemical CO2 reduction reaction (CO2RR) to CO.(1) We comprehensively engineered FeN4 and NiNx sites for electrochemical CO2 reduction to CO considering the particle sizes of the catalysts, metal content, and the M−N (M: Fe or Ni) bond structures.(2, 3)The unique M-N-C model allows us to elucidate each factor′s role exclusively regarding the promotion of CO2 reduction.(4)Optimal particle sizes and Fe content provide favorable external factors to improve mass activity. Structural changes of M−N bonds controlled by thermal activation temperatures can intrinsically enhance CO selectivity and kinetic activity. Notably, the NiN3 active sites with optimal local structures formed at higher temperatures (e.g., 1200 °C) are intrinsically more active and CO-selective than NiN4, providing a new opportunity to design a highly active catalyst via populating NiN3 sites with increased density. Further improving their intrinsic activity and selectivity by tuning their N−M bond structures and coordination is limited. We further expand the coordination environments of M−N−C catalysts by designing dual-metal active sites.(5)The Ni-Fe catalyst exhibited the most efficient CO2RR activity and promising stability compared to other combinations. Advanced structural characterization and theoretical prediction suggest that the most active N-coordinated dual-metal site configurations are 2N-bridged (Fe-Ni)N6, in which FeN4 and NiN4 moieties are shared with two N atoms. Two metals (i.e., Fe and Ni) in the dual-metal site likely generate a synergy to enable more optimal *COOH adsorption and *CO desorption than single-metal sites (FeN4 or NiN4) with improved intrinsic catalytic activity and selectivity.
References

Pan F, Zhang H, Liu K, Cullen D, More K, Wang M, et al. Unveiling Active Sites of CO2 Reduction on Nitrogen-Coordinated and Atomically Dispersed Iron and Cobalt Catalysts. ACS Catalysis. 2018;8(4):3116-22.

Li Y, Adli NM, Shan W, Wang M, Zachman MJ, Hwang S, et al. Atomically dispersed single Ni site catalysts for high-efficiency CO2 electroreduction at industrial-level current densities. Energy & Environmental Science. 2022;15(5):2108-19.

Mohd Adli N, Shan W, Hwang S, Samarakoon W, Karakalos S, Li Y, et al. Engineering Atomically Dispersed FeN4 Active Sites for CO2 Electroreduction. Angewandte Chemie International Edition. 2021;60(2):1022-32.

Li J, Zhang H, Samarakoon W, Shan W, Cullen DA, Karakalos S, et al. Thermally Driven Structure and Performance Evolution of Atomically Dispersed FeN4 Sites for Oxygen Reduction. Angewandte Chemie International Edition. 2019;58(52):18971-80.

Li Y, Shan W, Zachman MJ, Wang M, Hwang S, Tabassum H, et al. Atomically Dispersed Dual-Metal Site Catalysts for Enhanced CO2 Reduction: Mechanistic Insight into Active Site Structures. Angewandte Chemie International Edition. 2022;61(28):e202205632.