bluuebunny/crossref_metadata_2025 huggingface dataset:
Breaking through the State-of-the-Art Frontier in Oxygen Electrocatalysis: Geometry Adaptive Catalysts (GACs)
Authors: Cepitis Ritums , Ivanistsev Vladislav , Kongi Nadezda
Published: August 2024

The grand challenge in oxygen electrocatalysis lies in overcoming scaling relations. The theoretical activity volcano positions the ideal catalyst at the apex. However, the OH–OOH scaling relation determines a linear path on the volcano surface that limits the activity. The current state-of-the-art (SOTA) in modeling confirms this scaling relation, at the same time it hinders the experimental development of novel oxygen reduction reaction (ORR) catalysts, impeding progress in sustainable energy solutions. To address this challenge, we propose to use the geometry effect and introduce the concept of Geometry Adaptive Catalysts (GACs).[1]

The geometry effect, based on preliminary research, involves changing catalytic activity by adjusting the adsorption energy of intermediates through the control of catalyst geometry. Our goal is to break through the SOTA frontier for ORR by synthesizing GACs and supporting our efforts with theoretical and computational modeling of the geometric effect. In this work we aimed to utilize the geometry effect by synthesizing GACs with various controlled structures, including specific intersite distances, and variable curvature. This enables precise control of catalyst geometry, allowing manipulation of catalytic activity and overcoming scaling relations. Key geometric parameters, namely inter-site distance, curvature, and specific stabilizations of ORR intermediates, are explored to test our hypothesis: Controlling catalyst geometry adjusts the ORR mechanism and adsorption energies of intermediates, enabling the switching, pushing, and even bypassing of scaling relations.

This approach holds promise for substantial improvements in environmental sustainability and human life quality, with broad applicability to various electrocatalytic reactions beyond ORR.

References

[1] R. Cepitis, V. Ivaništšev, J. Rossmeisl, N. Kongi, Geometry-adaptive catalysts for elevating towards the ideal oxygen electrocatalysis, (2023) preprint. DOI: 10.26434/chemrxiv-2023-g63m2-v2

[2] R. Cepitis, N. Kongi, J. Rossmeisl, V. Ivanistsev, Surface curvature effect on Dual-Atom site oxygen electrocatalysis. (2023) ACS Energy Letters, 8, 1330-1335. DOI: 10.1021/acsenergylett.3c00068
(Invited) Efficient Ternary Nicuw Hydrogen Oxidation Catalysts for Anion Exchange Membrane Fuel Cells
Authors: Liu Guimei , Shao Minhua
Published: August 2024

Anion exchange membrane fuel cells (AEMFCs) offer prospective approaches to replace proton exchange membrane fuel cells via cost-effective catalysts and membranes. While significant progress has been made in efficient nonnoble electrocatalysts for oxygen reduction reaction in alkaline media, the hydrogen oxidation reaction (HOR) in the alkaline condition still relies on high platinum loadings to compensate for its sluggish kinetics. Therefore, developing efficient non-noble metal electrocatalysts with Pt-like HOR performances in alkaline electrolytes is highly desired but a great challenge.

The hydrogen binding energy (HBE) has been identified as the primary descriptor for the HOR. Additionally, an unfavorable hydroxide binding energy (OHBE) is considered the rate-determining step in the Volmer reaction to generate water. Therefore, an ideal catalyst for HOR should achieve a balance between HBE and OHBE. However, despite being a promising non-noble metal, nickel exhibits excessively high HBE and lacks active sites for hydroxide adsorption, which hinders its further application in the real fuel cell.

In this work, NiW was successfully deposited onto Cu to form a ternary Ni-Cu-W alloy catalyst by a chemical reduction method. Through XPS spectra, we found the charge transfer from Ni to W to give Ni a higher valence state, contributing to a weakened hydrogen binding energy. Electrochemical measurements observed Ni-Cu-W exhibit an kinetic activity with 117.9 mA/mgNi at η= 50 mV, which is the highest among the reported platinum group metal-free catalysts. Ni-Cu-W alloy showcased robust stability, with no activity degradation during an accelerated long-term durability test between a low overpotential (-0.1 ~ 0.1 V, vs RHE) with 10,000 cyclic voltammetry scans and only a 5.7% activity loss at η= 50 mV when applying more larger overpotential (-0.1 ~ 0.2 V) with the same cycles. When assembled with this catalyst as anode and Pt/C as cathode, it delivered a peak power density of 289 mW/cm2. Both experimental and theoretical studies were conducted to gain insights into the catalyst's enhanced performance. Our findings revealed that the incorporation of Cu into the catalyst significantly weakened the adsorption of hydrogen species, while simultaneously lowering the energy barrier required for the absorption of hydroxide ions. These key observations might shed light on the underlying mechanisms responsible for the catalyst's improved activity and stability.
Machine Learning Accelerated Identification of Bifunctional Active Sites in Metal-Organic Framework Derived Metal Oxide Heterostructures for High-Performance Zinc-Air Batteries
Authors: CHOI Jong Hui , Kim Dong Won , Chun Hoje , Kang Jeung Ku
Published: August 2024

The demand for electrochemical energy storage (ESS) systems and their market size has drastically increased in many applications ranging from portable devices through electric vehicles to large-scale grid systems over the past decades. Yet, a more advanced ESS is required due to the safety issues and limited energy density of currently commercialized lithium-ion batteries (LIBs) for wide and matured applications. As a solution to this challenge, zinc-air batteries (ZABs) have gained tremendous attention due to their high energy density, low cost, environmental friendliness, and much lower fire risk characteristics. ZABs utilize oxygen from the atmosphere at their cathode during discharge, where the atmospheric oxygen is reduced to hydroxide via an oxygen reduction reaction (ORR). On the other hand, hydroxide is released as oxygen via oxygen evolution reaction (OER) during charge. The fact that oxygen is drawn directly from the air enables high gravimetric and volumetric energy densities of ZABs compared to those of commercial LIBs. However, the sluggish kinetics of the four-electron transfer steps in ORR and the mass transport of oxygen in OER remain major challenges for the practical application of ZABs. Meanwhile, precious metal-based catalysts such as Pt/C and RuO2 are known to have good catalytic activity towards ORR and OER. However, the integration of different catalysts into the same cathode is very difficult. Additionally, the high cost and natural scarcity of novel metals limit their usage for practical applications.

We synthesized a bifunctional CoO/Mn3O4 heterostructure (CMH) OER/ORR electrocatalyst which was derived from metal-organic framework (MOF) for excellent activities in ZABs. The CMH cathode exhibited high ORR and OER performances, as demonstrated by the higher ORR current density than that of the Pt/C catalyst as well as the low OER overpotential exceeding those of the RuO2 catalyst. Remarkably, atomic structures of the CMH were elucidated using global optimization of genetic algorithm integrated with the machine learning force field. By adopting first-principles electronic structure calculations, we further revealed the charge transfer and active sites for both reactions in the identified heterojunction. Furthermore, assembling CMH cathode and Zn metal anode into a ZAB full-cell configuration achieves a ~5.5-fold higher energy density of 879 Wh kg-1 exceeding those of commercial lithium-ion batteries (LIBs), a high-discharge outstanding power density that is 1.39 times higher than novel metal catalysts, and robust cycle stability with negligible voltage decay which is far superior to that of benchmark Pt/C+RuO2 electrocatalysts.
Functionalization of Organic Redox Mediators to Mitigate Crossover in Chemically Regenerative Redox Fuel Cells
Authors: Bacabe Rémi , Jones Deborah J. , Rozière Jacques , Donzel Nicolas , Dupont Marc , Lecoeur Frederic , Cavaliere Sara , Niebel Claude , Blanchard Pierre-Yves
Published: August 2024

Chemically regenerative redox fuel cells are promising alternatives to conventional PEMFCs as stationary energy conversion devices since they avoid platinum-based catalyst at the cathode for the oxygen reduction reaction thanks to the chemical oxidation of the mediators in an external tank[1]. The requirements for the mediator are a high standard redox potential (0.6 V vs. SHE), high diffusion coefficient and fast electron transfer kinetic to reach high power density. Furthermore, the mediator must be stable in acidic medium (pH<1) and at the operating temperature of the system (40 to 80°C). The durability of the system will depend on the physico-chemical properties as well as on the chemical reactivity with oxygen in order to regenerate the reduced redox mediator. Loss of performance over time can be attributed to the crossover of the solubilized species from the cathode to the anode side and to the chemical instability over redox reaction. Crossover phenomena are commonly observed in aqueous organic redox flow battery using (2,2,6,6-Tetramethylpiperidin-1-yl)oxyl (TEMPO) as reactive species[2].

In this study, several mediators based on TEMPO with different PEG chain length are synthesized and characterized. The goal of the functionalization is to mitigate the crossover rate of the mediator through the membrane. Fuel cell tests were performed giving access to performance and power decrease over time. For a deeper understanding of the origin of performance losses, an ex situ electrochemical setup was developed to assess the impact of functionalization toward crossover.

[1] Singh R, Shah AA, Potter A, Clarkson B, Creeth A, Downs C, et al. Performance and analysis of a novel polymer electrolyte membrane fuel cell using a solution based redox mediator. J Power Sources 2012;201:159–63. https://doi.org/10.1016/j.jpowsour.2011.10.078.

[2] Small LJ, Pratt HD, Anderson TM. Crossover in Membranes for Aqueous Soluble Organic Redox Flow Batteries. J Electrochem Soc 2019;166:A2536–42. https://doi.org/10.1149/2.0681912jes.

Figure 1
Investigating the Impact of Air Pollutants on Fuel Cell Performance and Durability: Experimental and Modeling Approaches
Authors: Abd El Kader Ahmad , Marchand Marielle , Affonso Nóbrega Pedro Henrique , Beauger Christian
Published: August 2024

Fuel cells hold immense promise as efficient and sustainable power sources for transportation and stationary applications. However, their operation can be severely impacted by air pollutants, particularly sulfur dioxide (SO2) and nitrogen oxides (NOx). These pollutants can adsorb onto the platinum catalyst, leading to a decrease in fuel cell performance and durability.

In this study, we investigate the impact of SO2 and NO2 on PEM fuel cell performance and durability. The contamination tests were carried out at a constant current density of 0.5 A.cm−2, and they consisted of four steps: a pre-poisoning step to evaluate initial performance (15-16 h), poisoning step (50 h), self-recovery in a pure air stream (20-21 h) and a driven CV-induced recovery. Electrochemical characterizations were carried out at the end of each step (Polarization curve, Electrochemical Impedance Spectroscopy, Cyclic Voltammetry and H2 Crossover). Our initial investigation involved contaminating a single fuel cell with a low concentration of 0.1 ppm of sulfur dioxide (SO2). Remarkably, this resulted in a 1.1% decrease in cell voltage. Building on this foundation, our ongoing research aims to delve deeper into the impact of individual pollutant concentrations (SO2 and NO2) and their combined effects, considering varying temperatures and current densities to simulate real-world conditions.

Simultaneously, a comprehensive model is being developed using Simscape in Matlab. The model accounts for the pollutants either as single-component gases or as a mixture. For single-component gas adsorption, the Langmuir Isotherm model is employed. To capture the competitive adsorption of SO2 and NO2 on platinum in gas mixtures, we are testing the Modified Competitive Langmuir Isotherm Model. The model will further be calibrated and validated using the experimental results.

This combined experimental and modeling approach will provide a comprehensive understanding of the impact of air pollutants on fuel cell performance and durability. The insights gained from this study can inform the development of mitigation strategies and enhance the robustness of fuel cells in real-world applications as well as the sizing of a filter.

Figure 1
(Invited) PGM Catalysts on Atomic-Metal-Rich Carbon for Heavy-Duty Fuel Cell Catalysts: Performance and Durability Enhancement
Authors: Zeng Yachao , Yu Haoran , Liang Jiashun , Zhang Bingzhang , Cullen David A. , Macauley Natalia , Wu Gang
Published: August 2024

Proton exchange membrane fuel cells (PEMFCs) are a promising zero-emission power source for heavy-duty vehicles (HDVs). However, long-term durability of up to 25,000 h is challenging because current carbon support, catalyst, membrane, and ionomer developed for traditional light-duty vehicles cannot meet the stringent requirement. Therefore, understanding catalyst degradation mechanisms under the HDV condition is crucial for rationally designing highly active and durable platinum group metal (PGM) catalysts for high-performance membrane electrode assemblies (MEAs). Herein, we report a PGM catalyst consisting of platinum nanoparticles with a high content (40 wt %) on atomic-metal-site (e.g., MnN4)-rich carbon support. MEAs with the Pt (40 wt %)/Mn–N–C cathode catalyst achieved significantly enhanced performance and durability, generating 1.41 A cm–2 at 0.7 V under HDV conditions (0.25 mgPt cm–2 and 250 kPaabs pressure) and retaining 1.20 A cm–2 after an extended and accelerated stress test up to 150,000 voltage cycles. Electron microscopy studies indicate that most fine Pt nanoparticles are retained on or/and in the carbon support covered with the ionomer throughout the catalyst layer at the end of life. During the long-term stability test, the observed electrochemical active surface area reduction and performance loss primarily result from Pt depletion in the catalyst layer due to Pt dissolution and redeposition at the interface of the cathode and membrane. The first-principle density functional theory calculations further reveal a support entrapment effect of the Mn–N–C, in which the MnN4 site can specifically adsorb the Pt atom and further retard the Pt dissolution and migration, therefore enhancing long-term MEA durability.
Gaseous Nitric Oxide As Probe Molecule for Fe-N-C ORR Electrocatalysts
Authors: Wang Xiaoping , Ferrandon Magali S. , Kowalski Peter , Park Jaehyung , Kropf A. Jeremy , Zhang Hanguang , Zelenay Piotr , Zeng Yachao , Wu Gang , Myers Deborah J.
Published: August 2024

Iron nitrogen carbon (Fe-N-C) electrocatalysts remain the most promising platinum group metal-free (PGM-free) catalysts for the oxygen reduction reaction (ORR) in polymer electrolyte fuel cells (PEFCs). Although significant progress has been made in recent years in improving both the ORR activity and stability of the Fe-N-C catalysts, further enhancement in the catalyst durability while maintaining the activity is imperative for the practical applications. One of the major factors that hinders the further enhancement of the catalysts is the lack of clear understanding of the nature of the active sites and density of the active sites in the Fe-N-C catalysts due to the complexity of the Fe-N-C catalysts’ composition and structure. Gaseous nitric oxide was proven to be a suitable probe molecule that can bond to Fe and impede the ORR of the Fe-N-C catalysts. In recent years, we have studied the effects of gas-phase adsorption and desorption of nitric oxide on the redox features and ORR activity on Fe-N-C catalysts synthesized by different methods. We have used various characterization tools to quantify the amount of nitric oxide adsorbed and to identify the adsorption sites and geometry, including electrochemical stripping, temperature programmed desorption, and in situ X-ray techniques. The corresponding results obtained will be summarized in this talk. The implication of these results on the nature of the ORR active sites of the Fe-N-C catalysts will be discussed.

Acknowledgements

This work was supported by the U.S. Department of Energy (DOE), Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office (HFTO) under the auspices of the Electrocatalysis Consortium (ElectroCat 2.0). This work utilized the resources of the Advanced Photon Source, a U.S. DOE Office of Science user facility operated by Argonne National Laboratory for DOE Office. This work was partially authored by Argonne, a U.S. Department of Energy (DOE) Office of Science laboratory operated for DOE by UChicago Argonne, LLC under contract no. DE-AC02-06CH11357.
(Invited) Next Generation Designer Carbon Supports for Durable Polymer Electrolyte Fuel Cell Cathode Catalysts
Authors: Atanassov Plamen , Wang Hanson , Ferro Giovanni , Chen Celine H. , Roiron Camille , Zenyuk Iryna
Published: August 2024

The implementation of polymer electrolyte membrane fuel cells (PEMFC) in medium- and heavy-duty vehicles is a promising strategy to eliminate greenhouse gas emissions as the only byproduct is water. However, the durability of PEMFC catalysts, especially for the kinetically sluggish oxygen reduction reaction (ORR) that occurs at the cathode, remains a significant obstacle. Current state-of-the-art electrocatalysts are comprised of platinum-based nanoparticles anchored on high surface area carbon black supports (Pt/C). While these catalysts meet the U.S. Department of Energy’s near-term activity benchmarks [2], they suffer heavily from degradation mechanisms that can lead to catastrophic failure of PEMFCs. Hence, carbon support materials that promote durability are crucial to further development of ORR catalysts. Here, we report on the physical and electrochemical characterization of next-generation commercial FCX carbon supports that aim to mitigate these degradation mechanisms.

We synthesized Pt/C electrocatalysts by decorating FCX carbons with spherical Pt nanoparticles approximately 2-3 nanometers in diameter. The surface and pore structure of the supports were extensively probed to determine their effects on anchoring of Pt nanoparticles and ultimately catalytic activity. After physical and electrochemical characterization of the catalysts, structure-to-property relationships were established, leading to a schematic for an “ideal” Pt/C electrocatalyst as shown in Figure 1. The hierarchical pore structure is crucial for mass transport, and Pt nanoparticles are housed on the edges of stable graphitic carbon domains. Lastly, a promising alternative to the traditional Pt/C synthesis pathway is shown. As degradation is more pronounced on the catalyst’s exterior surfaces, this novel electrocatalyst contains Pt nanoparticles inside the support’s mesopores to mitigate the loss of electrochemically active surface area [3]. The insights gained from this work can be applied to optimizing carbon support morphology and chemistry for durable and highly active ORR electrocatalysts.

[1] M. Rezaei Talarposhti, T. Asset, S. T. Garcia, Y. Chen, S. Herrera, S. Dai, E. J. Peterson, K. Artyushkova, I. Zenyuk, P. Atanassov, ChemPhysChem, 21 (2020) 1331-1339.

[2] D.A. Cullen, K.C. Neyerlin, R.K. Ahluwalia, R. Mukundan, K.L. More, R.L Borup, A.Z. Weber, D.J. Myers, A. Kusoglu, Nature Energy, 6 (2021) 462–474.

[3] G.S. Harzer, A. Orfanidi, H. El-Sayed, P. Madkikar, H.A. Gasteiger, J. Electrochem. Soc. 165 (2018) F770-F779.

Figure 1
MOF-Supported Intermetallic Pt-Ni Electrocatalyst for the Oxygen Reduction Reaction
Authors: Ustuner Gozde , Zhao Xueru , Zhang Bingzhang , Wu Gang , Sasaki Kotaro , Mahajan Devinder
Published: August 2024

The catalyst support materials demonstrate great influence on the performance and durability of oxygen reduction reaction (ORR) electrocatalysts. Metal organic frameworks (MOFs) have been the focus of many Pt alloyed catalyst supports due to their large surface areas and well-defined pore structures. MOF-based carbon supports and a special class of MOFs that have a zeolite-type structure, and Zeolitic imidazolate frameworks (ZIFs) offer high ORR activity and enhanced stability of Pt-alloyed catalysts due to their porous structure, large surface area, and good electrical conductivity. In this study, we used two different MOF-based supports, Mn-NC and ZIF-67 derived Co-NC, to synthesize a nitrogen (N)-doped intermetallic PtNi catalyst. The synthesized material exhibits enhanced ORR activity and stability in an acidic electrolyte that is superior to commercial Pt/C catalyst. The rotating disk electrode (RDE) measurements of the PtNi/Co-NC catalyst demonstrated that the mass activity (MA) and specific activity (SA) are 0.9 A mgPt
-1 and 1.8 mA cm-2, respectively at 0.9 V. The synthesized PtNi/Mn-NC catalyst demonstrated 1.4 A mgPt
-1 and 2.1 mA cm-2 at 0.9 V, which are higher than those achieved with the commercial Pt/C. The MEA performance of the MOF-based PtNi catalysts will also be discussed. The mechanism of the enhanced performance of the catalysts is being formulated, based on in situ X-ray absorption spectroscopy (XAS) analysis. This work provides a promising approach to improve the activity and stability of binary and ternary Pt-based electrocatalysts for ORR by the use of MOF-based supports.
Unsuspected Organometallic Fibers Used As Potential Separators for Supercapacitors Device
Authors: Maaliki Carine , Flamme Benjamin , Ah-Lung Guillaume , Nnandi Shyamapada , Mouchaham Georges , Thibonnet Jérôme , Montigny Bénédicte
Published: August 2024

Since the last decade, the interest of organic frameworks for electrochemical application the been more studied.1 In general, very few works have been found in the literature. We can mainly mention the use of these derivatives in the presence of inorganic materials both to form solid electrolytes or to protect electrodes. For example, 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (H4DOTA) has been used to functionalize PVA to coat the surface of the negative electrode in order to suppress its degradation.2 This resulted in the improvement of the electrochemical properties of the LMNO/graphite cell. Recently, Kim et al. reported the addition of 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane to a carbonate-based electrolyte intended to stabilize the Li metal-electrolyte interface by improving the solid electrolyte interphase.3 More recently, Liu et al. reported a novel carbonyl network polymer NP4 used as a cathode material for organic lithium batteries.4 Very few examples of fully organic frameworks used as separators have been reported.

Therefore, our investigation to develop new supramolecular metal-based objects via a self-assembly process of molecular bricks will be presented. The work on cyclen derivatives allows to obtain metal complexes very stable able to pack in a well oriented dimension. Cyclen derivatives, in the presence of metal salts such as copper or zinc chlorides and polar solvents such as aliphatic alcohols, have a strong affinity for metals and spontaneously assemble in some conditions.5

In terms of applications, these self-assembled "organometallic" fibers represent an original and relatively easy to access substrate for fabricating 1D organic objects. Moreover, taking advantage of the properties and potentialities of these materials, we format an adequate shape to handle it as a potential separator for application in Energy Storage Systems (ESS).

After a presentation of their synthesis and their formatting as potential separators for supercapacitors, preliminary electrochemical studies will be discussed.

1. J. Mater.Chem. A
2016,
4, 16812; ACS Energy let.,
2022,
7, 885.

2. ACS Appl. Energy Mater.,
2021, 4, 128.

3. ACS Appl. Matter. Interface,
2022, 14, 35645.

4. J. Electoanalytical. Chem.
2023, 117251.

5. Chem. Commun.
2010, 46, 1464.

Figure 1
Modulation of the Intrinsic Radical Scavenging Properties of CeO2 Nanoparticles
Authors: Lee Doohwan , Hong Seung Hee , Yu Eunyoung
Published: August 2024

Cerium dioxide (CeO2) has been extensively investigated as a scavenger of reactive oxygen radicals, particularly in the context of polymer electrolyte membrane fuel cells. This study focuses on elucidating the impact of exposed crystal facets of CeO2 nanoparticles on their radical scavenging activities. The manipulation of crystal shapes, including rod, cube, and octahedral forms, allows for controlled variation of the exposed crystal facets of CeO2 NPs. Characterization of the resulting CeO2 NPs is conducted using XRD, Raman spectroscopy, XPS, BET, and Fenton’s reaction. The research reveals that the intrinsic radical scavenging activity of CeO2 NPs can be effectively modulated by controlling their exposed crystal facets.
In-situ X-ray Fluorescence Analysis of In-plane Cerium-ion Distribution Under Humidity Gradients in Proton Exchange Membrane
Authors: Morita Kaoruko , Takezawa Aika , Kitano Naoki , Kuwaki Akira , Kato Akihiko , Yamaguchi Satoshi , Shinozaki Kazuma , Orikasa Yuki
Published: August 2024

For the wide application of polymer electrolyte fuel cells, durability of more than 50,000 hours is necessary. Chemical degradation of the perfluorosulfonic acid (PFSA) membrane electrolyte is one of the degradation factors. Hydrogen peroxide generated from crossover gas reacts with impurities, and the resulting radicals break the chemical bonds in the electrolyte membrane. To quench the radicals, cerium ions are added to the membrane electrode assembly (MEA) as a radical quencher. However, cerium ions are known to move in the in-plane direction due to the humidity gradient during fuel cell operation. In areas where cerium ions are depleted, the chemical bonds of the PFSA are attacked by radicals. Therefore, it is necessary to understand the in-plane transport phenomena of cerium ions under fuel cell operating conditionsand incorporate into the development of MEAs. In this study, we developed an operando measurement cell that can track the change of cerium ion distribution over time by X-ray fluorescence spectroscopy (XRF) using high energy X-rays under fuel cell operation while controlling the in-plane humidity gradient. The in-plane transport of cerium ions, driven by the humidity and concentration gradients, was analyzed.

Two gas inlets were connected to an end plate with an X-ray transmission window to control two humidity environments on the left and right sides with in-plane direction of MEA. For MEA, Pt/C catalyst layer was coated on PFSA membranes in which a part of sulfonic acids were exchanged with cerium ions. GDL without cerium was used. Operando XRF measurements were performed at beamline BL37XU on SPring-8. The incident energy was 60 keV X-rays, and Ce-Kα fluorescence X-rays were counted. The beam size was 0.5×0.5 mm2. The cell temperature was 60°C, the different relative humidity (RH) in the in-plane direction was set to 90% and 50% using N2 gas, then the RH of the whole MEA was set to 95% to measure the relaxation behavior of cerium.

Fig. 1 shows the Ce intensity variation at the vertical center of the MEA under the condition of humidity difference with in-plane direction. The x-axis corresponds to the horizontal position of the MEA, with RH 90% on the left side and RH 50% on the right side. The y-axis corresponds to the time under the humidity gradient. The darker blue indicates weaker intensity of the Ce-Kα fluorescence X-ray and the white indicates stronger Ce intensity. This suggests that cerium ions move from the high humidity side to the low humidity side with the humidity gradient as the driving force. The time scale for this movement of a few millimeters was shown to be about tens of minutes.

Acknowledgments

The authors would like to thank M. Toida (Toyota Motor Corporation) for providing samples and for in-depth discussions.

Figure 1
Introducing Platinum Cryoaerogel As a Low Loading Cathode Catalyst in PEM Water Electrolysis
Authors: Stein Lukas , Moß Christopher , Ismael Mohammed , Trinke Patrick , Bensmann Boris , Hanke-Rauschenbach Richard , Borg Hadir , Zhao Zhijun , Dorfs Dirk , Bigall Nadja
Published: August 2024

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

[1] Müller, D., Zámbó, D., Dorfs, D., Bigall, N. C., Cryoaerogels and Cryohydrogels as Efficient Electrocatalysts. Small 2021, 17, 2007908. https://doi.org/10.1002/smll.202007908

Figure 1
Operando Spectroscopic Studies of Solid Oxide Fuel Cell Operation Using Dimethyl Ether as an Alternative Fuel
Authors: Maza William A , Steinhurst Daniel , Kidwell David , Owrutsky Jeffrey
Published: August 2024

Dimethyl ether (DME) is an oxygen-containing fuel that is an attractive alternative to the reforming of light alkanes like CH4. Its higher volumetric exergy compared to CH4 yields comparable power densities to other fuels while decreasing its potential for performance degradation that results from coking. We have characterized an SOFC operating at 800 °C on DME using a suite of operando optical and ex post facto methods. Based on exhaust gas infrared spectroscopy, DME decomposes to CH4, C2H2, H2O, CO2, and CO. Electrochemical analysis indicates that under dry DME the maximum power output of an anode supported button cell Ni-YSZ SOFC is only 10% lower than under CH4 (where H content was matched in the fuel stream). FTIR analysis of the anode exhaust gas indicates an electrochemical response under galvanostatic conditions resulting in the consumption of both CH4 and C2H2 to form CO, CO2, and H2O. Operando near-infrared thermal imaging reveal more cooling at the anode surface with DME than CH4 resulting from increased endothermic cracking of CH4. Additional contributions to the cooling are possible from reforming reactions.
Regulated Interfacial Proton and Water Activity Enhances Mn2+/MnO2 Platform Voltage and Energy Efficiency
Authors: Xue Xinzhe , Liu Zhen , Eisenberg Sam , Ren Qiu , Lin Dun , Coester Emma , Zhang Heng , Zhang Jin , Wang Xiao , Li Yat
Published: August 2024

Aqueous zinc battery (AZB) is one of the most promising energy storage systems for large-scale applications due to its high safety, low cost, and environmental friendliness. To match the high capacity of zinc metal (~820 mAh g-1), various cathode materials, such as oxides, open structure analogues, chalcogens, and halogens, have been explored for AZBs. Among them, manganese dioxide (MnO2) has been considered to be one of the most attractive candidates due to its high capacity (~308 mAh g-1 for one-electron transfer) and adequate redox potential (~0.70 V vs. SHE). Recently, the MnO2 dissolution/deposition charge storage mechanism has been demonstrated to further increase the voltage and capacity of Mn-based AZBs. The dissolution/deposition (Mn2+/MnO2) is a two-electron transfer process, which doubles the theoretical capacity of MnO2 cathode to ~616 mAh g-1 and considerably increases the redox potential (~1.229 V vs. SHE). The charge storage via the dissolution/deposition mechanism pushes the aqueous-based energy density even higher, to over 1000 Wh kg-1.

However, this charge storage mechanism involves liquid-solid transition, as well as the thermodynamics and kinetics of this reaction are highly dependent on the acidity and interfacial environment. Yet, the opposite effect of interfacial H+ on the dissolution/deposition processes and the role of interfacial H2O are rarely discussed. Here we introduce tetrafluoroborate anion (BF4
-) into the sulfate-based electrolyte to regulate the interfacial H+ and H2O activity. First, BF4
- hydrolysis increases the electrolyte’s acidity, promoting MnO2 dissolution. Second, BF4
- forms an H-bond network with interfacial H2O that assists H+ diffusion while retaining sufficient H2O supply to facilitate MnO2 deposition. As a result, the cathode-free Zn//MnO2 electrolytic cell achieves a high plateau of ~1.92 V and energy efficiency of ~84.23 % in the BF4
- containing electrolyte. Significantly, the cell delivers 1000 cycles at 1 C with ~100 % Coulombic efficiency and a high energy efficiency retention of 93.65 %. Our findings disclose a new strategy to promote Mn2+/MnO2 platform voltage and energy efficiency for future large-scale energy storage systems.
Thermal Modeling of Li-Ion Cylindrical Cells at Scale
Authors: Sare Hadarou , Dong Dongmei
Published: August 2024

The electric vehicle industry has created a demand for batteries with higher power densities. The current design choice for low-weight lithium-ion battery packs for electric vehicles is to create stacks arranged in parallel or series configurations to match the power demands. The individual cells are separated and placed in a cooling duct to pull heat away from the longitudinal surface convective. The amount of cooling is dependent on the internal temperature of batteries core. The current design of the cylindrical cell is to roll the cathode, anode, and separators into a jelly roll together and attach a tab to the cathode and anode at opposite corners of the sheet. The tabs connect to the positive and negative terminals of the cell to draw current away from the cell. The tabs may act as an agent for drawing heat away from the center of the battery. Currently, commonly used cylindrical cells have a form factor of 18650, 21700, or 26650. The thermal, geometrical, and electrical properties of 18650 and 21700 cylindrical cells are studied and it is found that the 21700 cells showed additional degradation and stronger heating. Recently, companies like Tesla have produced cylindrical cells with a 4680-form factor, which is a decent way to increase the ratio of active material vs. inactive material in a cylindrical cell. However, large diameter thick cylindrical cells suffer from thermal issues. Even large format pouch cells suffer through heat trapped within the stack.

Since the thermal conductivity of the anode and cathode electrodes is often near 1 W/m-K, it becomes difficult for the heat to be extracted from the center of a large-diameter cylindrical cell without forming a considerable thermal gradient. PyBaMM, an open-source mathematical modeling software written in Python programming language, has the capability to simulate different electrochemical models such as the Doyle-Fuller-Newman (DFN), Single particle model (SPM), and SPMe, and varying chemistry. The software provides easy access to the cell parameters modification and graphical user interface capabilities. The PyBaMM framework also allows to simulation lumped, isothermal, and base thermal models which are electrochemically coupled. PyBaMM uses CasADi (computer algebra systems algorithmic differentiation). The thermal gradient and heat dynamics within a porous electrode are modeled using PoreSpy and openpnm, two open-source Python libraries used to design porous networks and model physical equations such as governing heat flow, concentration gradient, and movement of water/oil through porous shale media.

We have explored and combined heat dynamic models for Li-Ion cylindrical cells at both cell and electrode levels with reduced-order Doyle-Fuller-Newman electro-chemical model frameworks implemented in the PyBaMM python library. Radial temperature gradient at cell and electrode levels were both generated from simulations with a distributed parameter model as a function of electrolyte and separator thickness and thermodynamic properties.

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Exploring the Role of Redox-Shuttle Mediators in Lithium-Sulfur Batteries
Authors: Vailaya Ganesh , Holc Conrad , Townsend William , Kibler Alexander , Newton Graham , Walsh Darren , Johnson Lee
Published: August 2024

The lithium-ion battery (LIB) is widely acknowledged as the state-of-the-art battery technology today and is used in consumer electronics, stationary storage, and electrified transportation1,2. However, there is a drive towards developing technologies with higher energy densities. The lithium-sulfur battery is one of the most promising next-generation batteries for high-energy applications, due to its high theoretical gravimetric energy density of 2567 W h kg-1, low raw material costs, and reduced environmental impact3. Despite these potential advantages, lithium-sulfur batteries are still beset with difficulties, one of the most significant is the so-called “polysulfide shuttle effect.” Operation of the battery involves the conversion of sulfur to polysulfide species, which dissolve into the electrolyte and diffuse to the lithium metal electrode, leading to loss of active material. This results in poor cycle life, rapid capacity fading and low coulombic efficiencies4.

The use of dissolved, electrochemically active redox mediators could mitigate these effects by catalysing sulfur redox reactions during cell cycling. While it is generally agreed that the redox potential of the mediators is a key factor in their operation, no report to date has conclusively demonstrated how mediators of varying potentials can target specific sulfur redox reactions. Herein, we report a study of the mediators 9-fluorenone (9-FO), duroquinone (DQ), 2,6-di-tert-butyl-1,4-benzoquinone (TBBQ) and 1,5-bis(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)anthra-9,10-quinone (AQT) to understand their interactions with sulfur, lithium polysulfides, lithium sulfide and lithium metal5. We use liquid-chromatography mass spectrometry (LC-MS) to isolate various polysulfide chain lengths after reaction with mediators. It is observed that high potential redox mediators, such as TBBQ, are better able to drive Li2S oxidation to higher polysulfide chain lengths, and low potential redox mediators such as 9-FO push sulfur towards lower chain polysulfides. This offers a novel and effective approach to screening suitable redox-active molecules. Galvanostatic cycling is employed to relate these chemical interactions to enhanced cell performance. Developing a fundamental understanding of how redox mediators operate in a cell will aid in the molecular design of novel redox-active compounds.

[1] J. Vetter, P. et al: Ageing mechanisms in lithium-ion batteries, J. Power Sources, 2005, 147, 269–281.

[2] D. Castelvecchi: Electric cars: the battery challenge, Nature, 2021, 596, 336–339.

[3] P. G. Bruce et al: Li-O2 and Li-S batteries with high energy storage, Nat. Mater., 2012, 11, 19–29.

[4] S. Zhang et al: Recent advances in electrolytes for lithium-sulfur batteries, Adv. Energy Mater., 2015, 5, 1–28.

[5] Y. Tsao et al: Designing a quinone-based redox mediator to facilitate Li2S oxidation in Li-S batteries, Joule, 2019, 3, 872–884.
Lithium Superoxide in Li-O2 Batteries: Performance and Mechanisms
Authors: Park Moon Gyu , Wang Hau , Amine Rachid , Assary Rajeev S , Amine Khalil , Curtiss Larry A.
Published: August 2024

Lithium superoxide (LiO2) is generally regarded as an intermediate formed during the Li-O2 battery discharge and transformed into lithium peroxide (Li2O2). Indeed, its chemical/electrochemical stability is low, making it recognized as a temporary discharge product in Li-O2 battery chemistry. However, in 2016, utilizing an iridium (Ir)-based electrocatalyst, Curtiss and Amine et al. found that LiO2 can be epitaxially grown on the surface of Ir catalyst and can be stable under cycling conditions.1 In the study, a templating mechanism was suggested, where a good lattice matching of LiIr3 surfaces (formed on the Ir catalyst) with that of LiO2 facilitates LiO2 formation as a singular discharge product. Following studies showed some superior electrochemical properties of LiO2 in comparison to Li2O2, including lower charge overpotentials. Meanwhile, some other transition metal compounds have recently exhibited LiO2 formation, where the formation mechanism suggested may not be a templating method. In this case, there could be strong adsorption of LiO2 in specific structures, resulting in suppressed Li2O2 generation. Herein, we will present experimental and computational results on some new catalysts for LiO2 formation and discuss possible underlying mechanisms.

Acnowledgement

This work was primarily supported by the US Department of Energy under contract DE-AC02-06CH11357 from the Vehicle Technologies Office, Department of Energy, Office of Energy Efficiency and Renewable Energy.

Reference

1 Curtiss. L. and Amine. K. et al. A lithium–oxygen battery based on lithium superoxide. Nature 2016, 529, 377-382
(Digital Presentation) Innovative Cylindrical Cell Design for Sustainable Static Zinc-Bromine Battery Technology
Authors: Alghamdi Norah S. , Rana Masud , Luo Bin
Published: August 2024

Zinc-bromine flow batteries (ZBFBs) are suitable for large-scale stationary energy storage applications due to their scalability, flexibility, safety, and sustainability [1, 2]. However, the ZBFBs' efficiency is compromised by the heavy accessories and pumps involved in flowing electrolytes on the electrode surface [3]. Because of their heavy weight and other accessories, ZBFBs can only be used for large energy storage systems. Further research is required to expand the application fields of the small-scale static zinc-bromine battery, including portable applications. Therefore, we proposed an innovative cylindrical cell design for a static zinc-bromine battery with a non-flowing liquid electrolyte that offers substantial improvements over existing zinc-bromine flow battery technology. This design aims to enhance coulombic efficiency and energy density, particularly targeting portable applications such as electric vehicles and E-bikes. Our battery configuration involves electrodes (carbon felt and carbon sponge) separated by a microporous separator for ionic migration. The liquid electrolyte, comprising zinc bromide, zinc chloride, potassium chloride, and 1-ethyl-1-methyl pyrrolidinium bromide, facilitates the electrochemical reaction. The battery's electrochemical process involves the plating of zinc ions at the anode and the formation of a bromine complex at the cathode during charging, with reverse reactions during discharge. The entire proposed static battery configuration is made of recyclable Polytetrafluoroethylene (PTFE) polymer, ensuring environmental sustainability. The anode comprises highly conductive graphene-coated carbon felt, while the cathode employs a graphene-coated high-surface-area carbon fiber sponge. Here, we aim to provide more details on the manufacturing methods for the assembly, emphasizing slurry preparation, electrode modification, and electrolyte concentration to achieve enhanced battery performance. With 96 % coulombic efficiency and stable cyclability, the present technology outperforms the existing commercial zinc-bromine battery. Comparative analyses with conventional zinc-bromine flow batteries highlight the advantages of this static battery, including its compactness, reduced weight, and potential for higher energy density. This research represents a significant step towards developing static zinc-bromine batteries suitable for widespread use in portable applications, surpassing the limitations of current zinc-bromine battery technologies.

References:

Rana, M., et al., Scientific issues of zinc-bromine flow batteries and mitigation strategies. Exploration. n/a(n/a): p. 20220073.

Rajarathnam, G.P. and A.M. Vassallo, The Zinc/Bromine Flow Battery: Materials Challenges and Practical Solutions for Technology Advancement. 2016: Springer.

Alghamdi, N.S., et al., Zinc–Bromine Rechargeable Batteries: From Device Configuration, Electrochemistry, Material to Performance Evaluation. Nano-Micro Letters, 2023. 15(1): p. 209.
Efficient Ni-NC Gas Diffusion Electrodes for CO2 Electrolyzer with High Utilization Efficiencies and Single Pass Conversions Towards CO
Authors: Brueckner Sven , Ju Wen , Strasser Peter
Published: August 2024

The electrochemical CO2 reduction in membrane electrolyzer devices can become a key technology to close the anthropologic carbon cycle. For industrialisation of CO2 electrolyzers, however, performance shortcomings of today’s state-of-art electrolyzer designs and cathodes have to be addressed. Alkaline Membrane CO2 electrolyzers suffer from low utilization efficiency of CO2 due to an acid-base CO2 loss to carbonates, which limits the CO2 utilization efficiency and single pass conversion to 50% in AEM CO2-to-CO electrolyzer. Bipolar Membrane CO2 electrolyzers suffer from high cell voltage and lower Faradic efficiencies due to the acidic environment. All thoses designs suffer from layer flooding or salting events which limit the durability of the cells. New cell designs and new diagnostic tools are needed to predict, diagnose, and eliminate detrimental operating regimes of CO2 electrolyzers.

In this work, we report on NiNC catalyst-based cathode GDEs for CO2 reduction to CO in a zero-gap membrane electrolyzer cell. We compare AEM and BPM cell designs. We propose the carbon crossover coefficient, CCC, as a new diagnostic analysis tool to monitor and understand through- or in-plane mass transport limitations in AEM and BPM cells. We also demonstrate how N2 bleeds can be used as diagnostic tools to recognize salting inside the electrolyzer cell.

In our AEM studies, we show that sufficient CO2 access to the catalyst surface sites is important to achieve a high performance. Under near neutral conditions on the anode we report 85% FE towards CO at 300 mA cm-2 at 3.6 V with single pass conversion of 40% which is very close to the theoretical maximum. In addition, we can report high energy efficiency but only a utilization efficiency of around 50%.

In our BPM studies, we show that NiNC GDEs are active and stable cathodes in zero-gap membrane electrolyzer. Protons raise the utilization efficiency as the carbonate will decompose into CO2 and water. To handle the changed electro osmotic water drag we replaced the ionomer with PTFE and could achieve 82% FE and 69% single pass conversion at 500 mA cm-2 with close to 100% CO2 utilization efficiency towards CO.

We show that using a either an AEM or BPM electrolyzer design we can reach over 100h stable performance at 100 mA cm-2.

Figure caption: CO2 singel pass conversion and lambda comparison of AEM and BPM CO2 reduction electrolyzer cells.

Figure 1