bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Continuum Mathematical Modeling of Water Electrolysis: A Tutorial
Authors: Dizon Arthur , Liu Jiangjin , Weber Adam Z.
Published: July 2022

Widespread use of hydrogen energy is contingent on the development of reliable and economical sources of hydrogen. Electrolysis from renewably-derived low-carbon electricity is a potentially viable method of hydrogen generation. Prime among the electrolysis technologies are those utilizing ion-conducting polymers (ionomers) including proton-exchange-membrane water electrolyzer (PEMWE). However, these technologies need to exhibit increased efficiency, performance, and durability to become commercially viable. Like most electrochemical devices, PEMWEs involve multiple components (e.g., catalyst, ionomer, transport layers, membrane, plates) and multiple phases, with phenomena occurring across different time and length scales. Furthermore, it is difficult to experimentally probe many of the species and phenomena during operation. Thus, mathematical modeling at the continuum level has been an invaluable aid in exploring, understanding, and optimizing PEMWE cell and components. This is especially true in the highly coupled and complex physics and chemistries that occur with the membrane-electrode assembly (MEA). The physics in a typical volume-averaged non-isothermal model include multiphase transport in porous media, concentrated-solution theory, Ohm’s Law, and Butler-Volmer kinetics, and ion, gas, and water transport in the ionomer.

In this talk, different modeling approaches, governing equations, and constitutive relationships will be described, including the benefits and limits of modeling. While focus will be on continuum equations and macroscale effects, detailed submodels and approaches for scaling to full cells and specific components, respectively, will be introduced. For example, as shown in Figure 1, one can perform an applied voltage breakdown and describe the different mechanisms resulting in the necessary applied overpotentials, which is useful in identifying opportunities for improving cell performance by quantifying the potential losses associated with a specific mechanism. In the talk, the generation of such analysis will be discussed including various approaches. Also shown in Figure 1 is how modeling can be used to elucidate safety concerns and identify issues to be resolved, in this case, nonlinear hydrogen crossover. Finally, future directions for multiscale modeling and multi-model coupling will be discussed.

Figure 1
In Search of the Most Active FeN4 and FeN5 Based Catalyst for Theoxygen Evolution and Reduction Reactions
Authors: Tasca Federico
Published: July 2022

The oxygen evolution and reduction (OER and ORR) are fundamental chemical reactions in industrial processes as well as in living systems, being O2, the final electron (e-) acceptor of many reactions. Since then its importance in the fuel cell technology where energy would be stored in the form of H2 to be oxidized in conjunction with the reduction of the cheap and abundant O2. However, the OER and the ORR are complicated reactions because of the high Gibbs free energy (ΔG) associated to the O double bond and because of the transfer of up to 4 electrons and 4 protons. For its nature, those reactions proceeds through the consequent formation of more than one intermediate accounting for the so-called “scaling correlations”. The complexity of the reactions determines the slow kinetics and the difficulties into finding an adequate catalyst for it to proceed without energy losses. In this study we tested various Fe phthalocyanines (FeN4) adsorbed on carbon nanotubes in the absence and in the presence of pyridine axial ligands to form penta-coordinated catalysts (FeN5). The composites were analyzed spectroscopically, and electrochemically characterized at pH 13 and pH 1. Computational analysis simulate the reactions on the Fe metal center. Based on the activity of the catalyst for the reactions and on the calculated binding energies volcano-correlations and activity indexes are drawn.
(Digital Presentation) Time-Resolved Operando XAS of FexNi100-XOy Electrocatalysts for the Oxygen Evolution Reaction Reveals Temporal Shift in Ni K-Edge during Ni2+/3+ Redox Reaction
Authors: Greenlee Lauren F , Chen Jingyi , Acharya Prashant , Manso Ryan , Bare Simon R. , Hoffman Adam S. , Kekedy-Nagy Laszlo
Published: July 2022

FexNi100-xOy electrocatalysts have become a focus for alkaline water electrolysis and the oxidative half reaction of oxygen evolution. Under alkaline conditions, the oxygen evolution reaction (OER) can be promoted by non-precious metal oxide and hydroxide electrocatalysts. In particular, electrocatalyst compositions from first row late transition metals such as iron, nickel, manganese, and cobalt have emerged as some of the most active catalysts for the OER, and the role of iron has been identified as key within multi-metallic compositions. In our research, we have focused specifically on the iron-nickel bimetallic composition and have developed synthesis methods to be able to control the bimetallic composition, surface chemistry, and three-dimensional morphology of a suite of FexNi100-xOy nanoparticle electrocatalysts. With this subset of highly-active FexNi100-xOy nanoparticle electrocatalysts, we have recently been focused on operando x-ray absorption spectroscopy (XAS) studies to understand how the chemistry of the iron and nickel species within these nanocatalysts changes as a result of exposure to the electrochemical environment. This talk will focus on a set of operando data obtained with a quick scan detector at beamline 9-3 at SSRL, where we were able to capture temporal, dynamic changes to the nickel chemistry as a function of applied voltage in the Faradaic region of the OER. Specifically, we have captured the change in the Ni K-edge that occurs as a result of the voltage stepping through the Ni redox reaction, where the Ni species in our electrocatalyst oxidizes from a 2+ to a 3+/4+ oxidation state. This redox reaction is associated with a phase transition from Ni(OH)2 to NiOOH. Our measurements were able to obtain 90 s scans during a 15 min time period of measurement, where we find that the Ni redox reaction and phase transition occurs during the first 10 minutes of measurement. Modeling of the extended x-ray absorption fine structure (EXAFS) region suggests that both Ni – O and Ni – M (M = metal) scattering path atomic pairs undergo a compression in distance. Further, the time scale of the phase transition suggests that the Ni redox reaction is mass transport limited. In this talk, I will discuss these results and present our analysis of the time-resolved x-ray absorption spectroscopy data.
Catalytically-Active Phases and Reaction Mechanism of Ni-Based and Co-Based Layered Double Hydroxides for the Oxygen Evolution Reaction
Authors: Zeng Zhenhua , Zhu Jing , Dionigi Fabio , Li Wei-Xue , Strasser Peter , Greeley Jeffrey
Published: July 2022

Electrochemical water splitting using renewable energy is a key route to generate green H2 fuel. In this process, however, O2 generation at the anode through the oxygen evolution reaction (OER) is inherently slower by over four orders of magnitude than H2 generation at the cathode. Thus, improving OER efficiency has been a majority effort in electrolysis. Ni-based and Co-based layered double hydroxides (LDHs) are among the most active and studied catalysts for the oxygen evolution reaction (OER) in alkaline electrolytes. Because it happens under extremely oxidative aqueous conditions, however, in-situ crystal structures of the OER active phase are still largely unknown, significantly hindering the establishment of structure-property relationships.

In this talk, we provide the first direct atomic-scale evidence that, under applied anodic potentials, NiFe and CoFe LDHs oxidize from as-prepared α-phases to activated γ-phases. The OER-active γ-phases are characterized by about 8% contraction of the lattice spacing and switching of the intercalated ions from carbonate to potassium. The calculated surface phase diagrams indicate that surface O sites are saturated with H by forming bridge OH, and coordinatively unsaturated metal sites are poisoned by OH adsorption under OER conditions. These structures, and the associated reaction free energies, suggest that the OER proceeds via a Mars van Krevelen mechanism, starting with the oxidation of bridge OH at the reaction centers with dual metal sites, i.e., M1-OH-M2.

Our study suggests that the compound-dependent activity originates from the dual-metal site feature of the reaction centers. While this feature does not influence the OH-OOH scaling relationship, it leads to diverse OH-O scaling relationships, including those with near-zero slopes and negative slopes. Breaking OH-OOH scaling relationships were frequently discussed in the literature, as it determines the minimum overpotential. However, our study showed that, to approach the minimum overpotential dictated by a specific OH-OOH scaling relationship, the key is to break the OH-O scaling relationship. A possible route is to form binary metal oxyhydroxides with dual metal sites at the reaction centers or introduce a third element into NiFe LDH or CoFe LDH.

References:

Dionigi, Z. Zeng, I. Sinev, T. Merzdorf, S. Deshpande, M. B. Lopez, S. Kunze, I. Zegkinoglou, H. Sarodnik, D. Fan, A. Bergmann, J. Drnec, J. F. d. Araujo, M. Gliech, D. Teschner, J. Zhu, W.-X. Li, J. Greeley, B. R. Cuenya, P. Strasser, Nature Communications
2020, 11, 2522.

Dionigi, J. Zhu, Z. Zeng, T. Merzdorf, H. Sarodnik, M. Gliech, L. Pan, W.-X. Li, J. Greeley, P. Strasser, Angew. Chem., Int. Ed.
2021, 60, 14446-14457.
Mixed Metal Phthalocyanine-Modified Carbon Nanotubes for Bifunctional Oxygen Reduction and Evolution Reaction
Authors: Kumar Yogesh , Kibena-Põldsepp Elo , Kozlova Jekaterina , Rähn Mihkel , Treshchalov Alexey , Kikas Arvo , Kisand Vambola , Aruväli Jaan , Tamm Aile , Douglin John C. , Folkman Scott J. , Gelmetti Ilario , Garcés Pineda Felipe , Galan-Mascaros Jose Ramon , Dekel Dario R , Tammeveski Kaido
Published: July 2022

In this ever-expanding world, researchers are focused on changing how we consume energy. Progress has been made over time, but the devices such as low-temperature polymer electrolyte fuel cells and metal-air batteries that can replace the conventional fossil fuel engines still use noble metal catalysts,1 which hinders the mass production and long-term usage of the devices. Transition metal macrocyclic (MN4-type) catalysts are good alternatives for the noble metal catalysts due to their low-price and promising electrocatalytic activity.2 Thus, the aim of this study was to develop the bifunctional ORR/OER electrocatalysts using mixed transition metal phthalocyanine-modified multi-walled carbon nanotubes (MWCNT) by simple pyrolysis method.3

Among the prepared bifunctional catalysts, FeCoN-MWCNT showed the superior electrocatalytic ORR activity in alkaline media with half-wave potential of 0.86 V vs RHE and FeNiN-MWCNT catalyst exhibited the exceptional OER activity with E
j=10 mA cm–2
of 1.58 V (see Fig. 1a, b). Physical characterization of the prepared catalysts was investigated with (scanning) electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy. Further, catalysts were tested in anion-exchange membrane fuel cells (AEMFCs) as cathode material and very good peak power density of 692 mW cm–2 was obtained for FeCoN-MWCNT (see Fig. 1c). FeNiN-MWCNT was tested in anion-exchange membrane electrolyzer (AEMEL) and showed comparable results with state-of-the-art RuO2 catalysts (Fig. 1d). Altogether, this study unveils the insight into potential ways of preparing the bifunctional ORR/OER electrocatalysts with transition metal macrocyclic-based compounds.

References

S. Hussain, H. Erikson, N. Kongi, A. Sarapuu, J. Solla-Gullón, G. Maia, A. M. Kannan, N. Alonso-Vante, K. Tammeveski, Int. J. Hydrogen Energy, 45, 31775-31797 (2020).

A. Sarapuu, E. Kibena-Põldsepp, M. Borghei, K. Tammeveski, J. Mater. Chem. A, 6, 776–804 (2018).

Y. Kumar, E. Kibena-Põldsepp, J. Kozlova, M. Rähn, A. Treshchalov A. Kikas, V. Kisand, J. Aruväli, A. Tamm, J. C. Douglin, S. J. Folkman, I. Gelmetti, F. A. Garcés-Pineda, J. R. Galán-Mascarós, D. R. Dekel, K. Tammeveski, ACS Appl. Mater. Interfaces, 13, 41507–41516 (2021).

Figure 1
(Digital Presentation) Synergistic Effect of Cobalt and Nitrogen on the Spent Coffee Grounds Derived Carbon As an Efficient Catalyst for Alkaline Hydrogen Evolution
Authors: Sukhbaatar Bayaraa , Yoon Sanghwa , Yoo Bongyoung
Published: July 2022

Due to global electricity demand and ecological issues, eco-friendly and sustainable energy resource is becoming a hot topic in energy production and future economic development. On this point, efficient catalytic materials for electrochemical hydrogen evolution reaction (HER) are crucial in the research area. HER in alkaline medium has several advantages, including its lower vapor pressure, which helps produce pure hydrogen gas and provides better stability than acidic medium to metal contents by reducing catalyst’s corrosion. Primarily, carbon-based electrocatalytic materials such as hetero-atomic-doped carbon, transition metal-doped carbon, and co-doped carbon show off an effective HER performance. Because it has a large surface area, good chemical stability, it is inexpensive and earth-abundant.

Additionally, spent coffee grounds (SCG) contain a high amount of carbohydrates, melanoidins, and lipids that are given a possibility to be suitable carbon precursors for carbon catalyst synthesis. Moreover, SCG is becoming an environmental issue that produces many tons of waste worldwide each year due to the proliferation of global coffee consumption.

Here, we present cobalt nanoparticles embedded on nitrogen (N)-doped carbon catalyst, synthesized from SCG. Initially, SCG-derived nanoporous carbon was obtained by pyrolysis under high temperatures with KOH and urea. After that, carbon materials were functionalized with cobalt and nitrogen with the simple method.

Cobalt-embedded N-doped carbon catalyst has a high surface area and highly distributed nano-sized pores. Polarization measurement, Tafel plot, electrochemical impedance spectroscopy, chronopotentiometry, and cyclovoltammetry have tested the electrochemical performance. Even though the catalyst contained a negligible amount of cobalt (0.56 at. %), HER catalytic activity in alkaline medium has better resulted than non-functionalized carbon catalysts and was comparable to higher activity benchmark electrocatalysts such as RuO2 and 20% Pt/C. Also, experimental results demonstrate that excellent long-term stability for the alkaline hydrogen evolution. So, synergistic effects of cobalt nanoparticles content and N-doping on the SCG-derived carbon were indicated for efficient catalyst in the alkaline hydrogen evolution application.
Tailoring Binding Abilities By Incorporating Oxophilic Transition Metals on 3D Nanostructured Ni Arrays for Accelerated Alkaline Hydrogen Evolution Reaction
Authors: Kim Jaerim , Jung Hyeonjung , Jung Sang-Mun , Lee Noho , Kim Yong-Tae , Han Jeong Woo , Kim Jong Kyu
Published: July 2022

Developing efficient and inexpensive electrocatalysts for the hydrogen evolution reaction (HER) in alkaline water electrolysis plays a key role for renewable hydrogen energy technology. The slow reaction kinetics of HER in alkaline solutions, however, has hampered advances in high-performance hydrogen production. Herein, we investigated the trends in HER activity with respect to the binding energies of Ni-based thin film catalysts by incorporating a series of oxophilic transition metal atoms. It was found that the doping of oxophilic atoms enables the modulation of binding abilities of hydrogen and hydroxyl ions on the Ni surfaces, leading to the first establishment of a volcano relation between OH-binding energies and alkaline HER activities. In particular, Cr-incorporated Ni catalyst shows optimized OH-binding as well as H-binding energies for facilitating water dissociation and improving HER activity in alkaline media. Further enhancement of catalytic performance was achieved by introducing an array of three-dimensional (3D) Ni nanohelixes (NHs) that provide abundant surface active sites and effective channels for charge transfer and mass transport. The Cr dopants incorporated into the Ni NHs accelerate the dissociative adsorption process of water, resulting in remarkably enhanced catalytic activities in alkaline medium. Our approach can provide a rational design strategy and experimental methodology toward efficient bimetallic electrocatalysts for alkaline HER using earth-abundant elements.
High-Performance Fiber-Shaped Zn Microbattery Based on Dendrite-Free Anode and Ultraconductive Cathode
Authors: Zhai Shengli , Li Zhi
Published: July 2022

Rechargeable Zn-ion microbatteries emerge as a promising power solution due to their remarkable safety, high capacity, low cost, simple manufacturing, and environmental friendliness. Their fiber-shaped counterparts are particularly attractive due to their lightweight, tiny volume, and mechanical flexibility. However, it is still fundamentally challenging to construct high-performance fiber-shaped Zn-ion microbatteries (FZMB) because of the dendrite growth at the anode, the poor electrical conductivity of current cathode materials, the lack of suitable fiber substrates (high electrical conductivity and strong interaction with cathode materials).

We developed a simple and scalable process to fabricate dendrite-free fiber anodes by sputtering an ultrathin conductive carbon layer on rock-like Zn deposits around carbon fibers (CF) . The carbon layer plays a critical role in suppressing dendrites by uniformizing the surface electric field and provide additional surface and abundant nucleation sites. The obtained CF@Zn@C can stably run over 200h. Plus, we demonstrate a highly conductive and well-interacted fiber cathode, i.e., PEDOT: PSS@PANI core-sheath fiber, with a record high conductivity of 3676 S cm−1. The superior conductivity enables a fast electron transfer which is beneficial to high rate performance. Based on the same PEDOT: PSS platform, we have fabricated the next-generation FZMB by using citriate as electrolyte additives to suppress the dendrite formation. Compared to the carbon layer on the Zn anode, the use of additives in the electrolyte is much easier in production. .

Figure 1
(Invited, Digital Presentation) Zinc-Based Energy Storage System Deployments and Developments for Transition to a Clean Energy Future
Authors: Banerjee Sanjoy
Published: July 2022

Rechargeable zinc-based alkaline batteries are an attractive electrochemical energy storage option with zinc anode costs of $3/kWh at full (theoretical) 2 electron capacity. When paired with high-capacity, inexpensive cathodes like manganese dioxide, and accounting for incomplete utilization of the active materials capacities, inactive materials costs (like for current collectors etc.) and manufacturing costs, rechargeable zinc-manganese dioxide batteries costing about $20-30/kWh appear to be within reach. The challenges to meeting these cost targets, and the current status of such rechargeable zinc alkaline batteries will be discussed. The first generation of rechargeable zinc-manganese dioxide batteries are now being deployed in residential, commercial, and utility-scale energy storage applications. In some cases, the applications require several thousand cells to meet the power and capacity requirements. Even such large systems do not require battery management systems at the cell level, being remarkably resilient to overcharging, without flammability and thermal runaway issues, and passing UL 9540A certification requirements without any protective measures being necessary. However, operation of these early deployments, indicate that to optimize systems performance and durability, energy management systems to manage overall systems charge-discharge protocols, taking the specific cell electrochemical characteristics, are desirable. The lessons learned and desirable innovations in designing and managing such large assemblies of cells will also be discussed.
(Invited) Sustainability, Safety, Scalability, Rechargeability, and Manufacturability Courtesy of Architected Zinc Anodes
Authors: DeBlock Ryan H. , Hopkins Brandon J. , Ko Jesse S. , Parker Joseph F. , Chervin Christopher N. , Skeele Nathaniel L. , Long Jeffrey W. , Rolison Debra R.
Published: July 2022

Towards the goal of decarbonizing electrification, concerns remain over the sustainability of the requisite Li and Co, as well as the stringent transportation limits on the amount and operational state of Li allowed in airfreight. Rechargeable zinc-based batteries using aqueous electrolyte offer a compelling alternative to lithium-based batteries with the added benefit of a two-electron anode that augments the energy density, helping to compensate for lower cell voltage inherent to aqueous electrolytes. To solve the standing caveat with rechargeable zinc-based batteries — that they form separator-piercing dendrites — we built on our understanding of the importance of 3D co-continuous wiring of electrons, ion, and molecules in energy-storing nanoarchitectures. Sponge form factors fabricated by fusing ~50 µm zinc particles into a monolithic pore–solid architecture physically prevents formation of dendrites even at high charging current density [1,2]. Throughout the story of the NRL Zn sponge anode, each successive generation of the electrode has been fabricated with manufacturability as a foremost consideration, such that the current sponge formulation (Gen 5) is processed quickly, at scale, to sizes necessary for decarbonizing electrification. I will present the performance of these “big and strong” zinc sponges versus a variety of cathodes and the potential paths forward for the development and transition of this safer energy-storage technology.

[1] J.F. Parker, C.N. Chervin, E.S. Nelson, D.R. Rolison, J.W. Long, “Wiring zinc in three dimensions re-writes battery performance―Dendrite-free cycling.” Energy Environ. Sci., 7, 1117–1124 (2014).

[2] J.F. Parker, C.N. Chervin, I.R. Pala, M. Machler, M.F. Burz, J.W. Long, and D.R. Rolison, “Rechargeable nickel–3D zinc batteries: An energy-dense, safer alternative to lithium-ion.” Science, 356, 415–418 (2017).
The Influence of Electrochemical Treatment on Electrode Reactions for Vanadium Flow Batteries
Authors: Noack Jens , Roznyatovskaya Nataliya , Kunzendorf Jessica , Skyllas-Kazacos Maria , Menictas Chris , Tübke Jens
Published: July 2022

The motivation for this work was to obtain an overview of the electrochemical behaviour of vanadium reactions on electrochemically treated glassy carbon electrodes in order to be able to make reproducible statements about changes with the treatment. In addition, optimal conditions for the reactions should be found in order to create a basis for targeted pre-treatment of the electrodes and, if applicable, a possibility for in situ treatments. Furthermore, if possible, causes should be determined by the behavior. A glassy carbon electrode was first polished and then treated in 2 M H2SO4 at different potentials. In a separate measurement setup, linear sweep voltammograms were then recorded instead of cyclic voltammograms in order to change the electrode as little as possible and to calculate kinetic values from the obtained data. In addition, roughness values were determined at selected treatment potentials using confocal microscopy and the surface composition was analyzed using XPS. The reaction rates increased significantly in all reactions compared to polished electrodes and had an optimum treatment potential of approx. 1600 mV vs. Hg/Hg2SO4, although the oxidation reaction of V2+ and the reduction reactions of V3+ and VO2+ had opposite tendencies to oxidation of VO2+ and the reduction of VO2
+ in the area of low treatment potentials. In the former, the kinetics increased and in the latter, they decreased. No correlation was found to the roughness or size of the stretched surfaces, although these changed significantly as a result of the treatment. XPS measurements gave indications of a dependence on oxygen functional groups for the different reactions.

Figure 1
Effect of Tungsten Oxide Structure on Enhancing the V(II)/(VIII) Reaction and Inhibiting H2 Evolution for All-Vanadium Redox Flow Battery
Authors: Al Najjar Taher , K. Allam Nageh , El Sawy Ehab
Published: July 2022

Renewable energy sources require high-efficiency storage systems to allow for its integration within the electrical grid and to supply that energy when needed. All-vanadium redox flow batteries (VRFBs) are very promising for this application because they can store high amounts of energy, are designed to work for long periods, and their solutions can be used indefinitely.1 VRFBs have various advantages when combined with renewable energy sources. The relatively high cost of VRFBs limits their widespread deployment. Enhancing the kinetics of the electrochemical reactions is needed to increase the power density and energy efficiency of the VRFB, and hence decrease the kWh cost of VRFBs. Different carbon materials are used as electrodes in VRFBs (carbon felt, paper and cloth), and each of these materials affects the performance of the battery differently either through sluggish kinetics or a high chance for parasitic reactions catalyzation.2 Modification of these electrodes by carbon-based3 or metal oxides2 nanomaterials can increase the power density of the battery and suppress the parasitic reactions. Some metal oxides like tungsten oxide4 can enhance vanadium reactions alone or when used as composites with nanocarbon materials.

This work aims at enhancing the VRFBs negative half-cell reaction (V2+/V3+) kinetics and inhibiting the hydrogen evolution parasitic reaction. Carbon cloth electrodes were modified, using different tungsten oxide nanostructures such as nanowires, nanoflakes, and nanospheres, and tested at different loadings. The results suggest that the change in tungsten oxide structure would lead to a change in the electrode overall performance as a result of changing the electrical conductivity, the wettability of the electrodes, the coverage of the carbon cloth, and the number and nature of the active sites available to catalyze the V2+/V3+ reaction, with the tungsten oxide nanowires showing to be the best electrode modifier.

References:

R. K. Sankaralingam, S. Seshadri, J. Sunarso, A. I. Bhatt, and A. Kapoor, Journal of Energy Storage, 41, 102857 (2021).

A. Wodaje Bayeh et al., Sustainable Energy & Fuels, 5, 1668–1707 (2021).

F. A. E. Diwany, B. A. Ali, E. N. E. Sawy, and N. K. Allam, Chem. Commun., 56, 7569–7572 (2020).

M. Faraji, R. Khalilzadeh Soltanahmadi, S. Seyfi, B. Mostafavi Bavani, and H. Mohammadzadeh Aydisheh, J Solid State Electrochem, 24, 2315–2324 (2020).
High-Capacity Bio-Inspired Redox Flow Batteries with Insoluble Redox Boosters
Authors: Gokoglan Barut Tugba Ceren , Pahari Shyam Kumar , Visayas Benjoe Rey B. , Aravamuthan Sundar Rajan , Mayes Maricris L. , Cappillino Patrick J. , Agar Ertan
Published: July 2022

Redox flow batteries (RFBs) are considered to be one of the key technologies for addressing the intermittency problem in renewable energy sources, due to their unique architecture that allows for unprecedented scalability and flexibility, and cost-effectiveness in long-duration storage [1]. Despite their promise, typical RFBs suffer from low energy density because of the limit imposed by the solubility of the redox active species in the electrolyte [2]. One promising approach to bypass the solubility limitation and drastically improve the energy density is the addition of insoluble charge storage materials into the electrolyte tanks. These redox active materials are reversibly oxidized/reduced in the tanks upon interaction with the redox active species dissolved in the electrolyte. Thus, the capacity is no longer dependent on the concentration of soluble species but rather the quantity of solids in the tanks [3-4]. This new concept is called redox-mediated flow battery (RMFB).

In this presentation, we demonstrate a high energy density RMFB using a highly stable bio-inspired active material (vanadium(IV/V)bis-hydroxyiminodiacetate (VBH)) and a suitable solid storage material. VBH, as a high-stability active material [5], provides an ideal scaffold to investigate the complex electrochemical processes that occur during RMFB operation, which remain virtually unexplored [6]. For the solid storage material, a Prussian Blue Analogue (PBA) is synthesized and coupled with VBH mediators. Symmetric cell cycling experiments are performed with and without the solid energy booster material to provide evidence that the addition of a compatible solid material greatly improves the energy density. Compatibility between the PBA and VBH is investigated using cyclic voltammetry (CV) experiments. Optimization of the critical parameters such as the amount of solid storage material, the operating current density, and the electrolyte flow rate is presented.

References:

[1] Z. Li, M. S. Pan, L. Su, P.-C. Tsai, A. F. Badel, J. M. Valle, S. L. Eiler, K. Xiang, F. R. Brushett, Y.-M. Chiang, Joule, 1, 306-327 (2017).

[2] S. K. Pahari, T. C. Gokoglan, B. R. B. Visayas, J. Woehl, J. A. Golen, R. Howland, M. L. Mayes, E. Agar, P. J. Cappillino, RSC Adv., 11, 5432-5443 (2021).

[3] R. Yan, Q. Wang, Adv. Mater., 30, 1802406 (2018)

[4] X. Wang, M. Zhou, F. Zhang, H. Zhang, Q. Wang, Curr. Opin. Electrochem.,
29, 100743 (2021).

[5] T. C. Gokoglan, S. K. Pahari, A. Hamel, R. Howland, P. J. Cappillino, E. Agar, J. Electrochem. Soc.,
166, A1745-A1751 (2019).

[6] M. Moghaddam, S. Sepp, C. Wiberg, A. Bertei, A. Rucci. P. Peljo, Molecules, 26, 2111 (2021).
High Energy and Low-Cost Membrane-Free Chlorine Flow Battery
Authors: Hou Singyuk , Chen Long , Fan Xiulin , Wang Chunsheng
Published: July 2022

Grid-scale energy storage is essential for reliable electricity transmission and renewable energy integration. Redox flow batteries (RFB) provide affordable and scalable strategies for stationary energy storage. But most of the current RFB chemistries are based on expensive transition metal ions or synthetic organics. Here, we report a reversible Cl2/Cl- redox flow battery through electrolysis of aqueous NaCl electrolyte, the as-produced Cl2 is stored and extracted using carbon tetrachloride (CCl4) or mineral spirit flow. The immiscibility between the CCl4 and NaCl electrolyte enables a membrane-free design with energy efficiency of >91 % and energy density of 125.7 Wh/L. With the inherently low cost of active materials (~5 $/kWh) and highly reversible redox reaction of Cl2/Cl-, the chlorine flow battery leaves significant space to meet the stringent price and reliability target for stationary energy storage.

Figure 1
A Molten-Salt Battery for Seasonal Energy Storage
Authors: Li Minyuan Miller , Weller Jon Mark , Polikarpov Eugenia , Reed David , Sprenkle Vincent , Li Guosheng
Published: July 2022

Cost-competitive renewable energy sources, such as wind and solar energy, are more rapidly replacing fossil fuels for power generation. As their integration into the power grid increases, the inherent intermittency exposes a great challenge in maintaining the grid stability. Therefore, the development of low-cost energy storage technology suitable for large-scale manufacturing is essential for the further deployment of renewable energy. We noticed that renewable electricity production usually follows predictable seasonal trends. For example, the longer daylight in summers corresponds to more solar power generated. If any seasonal excess can be efficiently stored and redistributed in times of needs, a power grid based on 100% renewable energy is more feasible. Unfortunately, current rechargeable battery technologies have not been optimized for seasonal storage, as the self-discharge rate ranges from approximately 3–5% for lithium-ion batteries to almost 30% for nickel metal hydride batteries in the first month.

In this presentation, we will demonstrate the concept of a rechargeable molten-salt battery with earth-abundant elements and simple construction that preserve the stored energy for long periods of time. Due to its unique operating mechanism, this battery can discharge most of its stored capacity (> 90%) after a period of 1 to 8 weeks. This approach brings new possibilities to seasonal energy storage and helps the grid to overcome short supply during seasonal fluctuations.
Facile Synthesis of Span with Enhanced Sulfur Percentage and Higher Local Conductivity for Development of Stable Lithium-Sulfur Pouch Cells
Authors: Sarode Krishna Kumar , Kalra Vibha
Published: July 2022

Li-S batteries are regarded as the most promising energy storage systems due to their high energy density (2600 Wh/kg). But practical realization of the Li-S batteries is limited by low boiling ether electrolytes, polysulfide shuttling and insulating nature of sulfur. To address the above issues, chemically linked, confined sulfur - nitrogen containing conductive polymer composite has been developed as a novel composite cathode for Li-S batteries in carbonate electrolyte. But the polymer-sulfur composite limits the sulfur percentage reducing the achievable capacity typically to <600 mAh/g. In this work, we developed a facile synthesis methodology to tailor the sulfur percentage from 37% to up to 65%, resulting in a gravimetric capacity of 700 – 750 mAh/g per weight of the complete sulfur-polymer composite at 0.5C. Additionally, the composite is doped with metal dopants such as Mg, Co, Ni etc that improved the local conductivity, showed lower impedance, and enhanced the cycling performance compared to pristine sample. We made 25 cm2 pouch cells using the best cathode against Li-metal and carbonate electrolyte, which cycled stably for 200+ cycles with an areal capacity of >3mAh/cm2 and loading of -6 mg/cm2. This is unique as despite phenomenal coin cell level cycling shown in Li-S literature, most Li-S pouch cells typically fail in ~50 cycles.
(Digital Presentation) Studies on Dielectric and Electrical Properties of Glycerol Intact Polyvinylpyrrolidone: Ferrous Sulfate Based Less Toxic Dielectric Gel Polymer Electrolyte for the Application of Capacitor Energy Storage System
Authors: Pathak Jyotishman , Chaturvedi Harsh
Published: July 2022

The iron(ii) divalent ion conducting electrolyte matrix has prepared in different ratio of glycerol and polyvinylpyrrolidone (PVP) blend by impregnating ferrous sulfate crystals. The complexation of the polymer mixing transformed into gel format, the composition has been analyzed by the Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) characterization techniques. The amorphous nature of electrolyte to support the ion conduction has been revealed by XRD as well as the FTIR results confirmed the glycerol and PVP interaction feasibility with the ferrous sulfate mixing. Further overall electrical conduction and dielectric behaviors has been explored through Electrochemical impedance spectroscopy (EIS) within the frequency range of 1Hz to 1GHz, the complex permittivity analysis is employed in order to verify dynamic modes of ion conduction symptoms including short to long range ion hopping in polymer backbone segmental movement along with dielectric dissipation level. The studies provide us a feasible direction to utilize this new iron assisted dielectric matrix with eco friendly glycerol composition to be applicable for iron based capacitor-battery hybrid energy storage system.
How Electrochemical Impedance Spectroscopy Helps Drive Innovation in Fully Hydrocarbon, Reinforced Polymer Electrolyte Membranes
Authors: Adamski Mike , Lee Hsu-Feng , Britton Benjamin
Published: July 2022

The realm of hydrocarbon-based polymer electrolyte membranes (PEMs) has undergone substantial changes over the past decade. A new era has emerged, based upon strong, fundamental R&D emphasizing both improved performance across a wider range of operating conditions, and greater combined chemical-mechanical stability, when integrated into a state-of-the-art fuel cell. The groundwork has been laid for commercialization of highly promising, fluorine-free technologies which simultaneously outperform previous generation materials, and address weaknesses historically attributed to all hydrocarbon-based membranes. Hydrocarbons address critical issues with perfluorinated sulfonic acid (PFSA) materials. Reduced gas crossover allows longer component lifetimes, operational window for system pressures, and reduced hydrogen venting. Higher temperature tolerances allow system operation or excursions to ≥ 100 °C, which affords a myriad of potential benefits such as reduction in heat exchanger volume, improved system water management, and increased catalyst activity due to mitigated activation losses. Furthermore, higher operating temperatures go hand-in-hand with greater pollution tolerance, and hence reduced hydrogen purity requirements.

The award-winning hydrocarbon-based PEM, Pemion®, produced by Ionomr Innovations, is nested at the center of these exciting developments. Mechanically reinforced composite membranes are produced at scale utilizing advanced roll-to-roll manufacturing techniques, affording a hydrocarbon-based PEM that, for the first time, exhibits performance parallel to or greater than incumbent perfluorinated sulfonic acid (PFSA)-based PEMs. These developments, however, would not be possible without powerful characterization methods such as electrochemical impedance spectroscopy (EIS). Assessments of a membrane’s in-plane and through-plane proton conductivity are used to derive valuable insight to its constituents, the ion-conducting ionomer and chemically-inert mechanical reinforcement, as well as their interrelation. The anisotropic nature of the composite membranes is probed via comparison of in-plane and through-plane conductivity. The sensitivity of through-plane conductivity measurements to experimental parameters such as cell pressure are probed, and a new cell design is realized to reduce measurement error. These data help identify favorable and unfavorable material processing and manufacturing techniques, and their implications to in-situ fuel cell performance. The net consequence of these findings is establishing EIS as a core component of an iterative material design and production process for output of consistent, high-performance PEMs.
Effect of Catalyst Double Layer on Performance without Micro Porous Layer in Anode for High Temperature Polymer Electrolyte Membrane Fuel Cell
Authors: Pak Chanho , Jung Hyeon Seung , Kim Do-Hyung , Hyunsoo Chun
Published: July 2022

Catalyst double layer (CDL) structure on gas diffusion electrode (GDE) without microporous layer (MPL) is developed for the anode of high temperature polymer electrolyte membrane fuel cell (HT–PEMFC). Polytetrafluoroethylene and polyvinylidene fluoride is applied for the outer and inner layer as the hydrophobic binder for fabricating 3D electrode structure. The effect of Pt ratio in anode CDLs on the GDE performance was investigated by single cell test and electrochemical analysis using poly(benzimidazole) (PBI)–based membrane, with Pt loading under 0.3 mg/cm2 at ambient pressure air on 150℃. The results show that optimal CDL anodes present performance of 0.65V at 0.2A/cm2 and peak power density is 0.41W/cm2 at mass transfer region which is higher than conventional single layer anode with MPL. Furthermore, the 3D structure of the outer catalyst layer in anode read high catalyst utilization and preventing leakage of electrolyte with a short–term durability test shows good stability with PBI membrane.
Understanding the Effect of Blending Ethanol with Formic Acid on Pd Activity Towards Acidic Oxidation of Concentrated Formic Acid
Authors: Al Najjar Taher , Ahmed Nashaat , El Sawy Ehab
Published: July 2022

Direct liquid fuel cells are among the most promising energy conversion devices for sustainable energy applications, especially as portable energy sources. The two most effective fuels are methanol and formic acid (FA), and even though methanol has higher energy content, it is toxic, non-renewable, and has high fuel crossover. However, FA can be produced easily from biomass and it is non-toxic and has a higher open circuit potential among other factors1. Usually, FA can be oxidized through two pathways, a direct pathway that is most desirable and directly produces CO2
2. While the indirect pathway produces CO as an intermedia that can adsorb to the catalyst surface deactivating it (poisoning effect)3. Palladium is known to be the most active catalyst for FA oxidation in acidic media4 but it is also easily poisoned by CO accumulation on its surface. The increase in FA concentration to get higher energy density would make the indirect oxidation pathway more favorable lowering the efficiency of the fuel cell. To overcome this problem low molecular weight organic additives were suggested to be used in combination with FA to suppress this poisoning effect by competing with CO molecules for the adsorption sites on the catalyst surface.

In this work, the effect of using ethanol and FA blend fuels on the behavior of Pd/C towards FA oxidation was investigated. The preliminary cyclic voltammetry study showed promising results about ethanol's ability to inhabit the indirect FA oxidation pathway. However, the results obtained by the chronopotentiometry and by studying the first derivatives of the cyclic voltammetry data give more insightful results on the effect of ethanol in the fuel blend. It was found that ethanol will inhabit the indirect oxidation of FA up to specific concentration but it will also affect the direct oxidation after a giving time and that the applied potential will have an effect on the adsorption orientation of Ethanol molecules on the catalyst surface.

References

1) Sun, J.; Luo, X.; Cai, W.; Li, J.; Liu, Z.; Xiong, J.; Yang, Z. Ionic-Exchange Immobilization of Ultra-Low Loading Palladium on a RGO Electro-Catalyst for High Activity Formic Acid Oxidation. RSC Adv. 2018, 8 (33), 18619–18625.

2) Jiang, K.; Zhang, H.-X.; Zou, S.; Cai, W.-B. Electrocatalysis of Formic Acid on Palladium and Platinum Surfaces: From Fundamental Mechanisms to Fuel Cell Applications. Phys Chem Chem Phys 2014, 16 (38), 20360–20376.

3) Gunji, T.; Matsumoto, F. Electrocatalytic Activities towards the Electrochemical Oxidation of Formic Acid and Oxygen Reduction Reactions over Bimetallic, Trimetallic and Core–Shell-Structured Pd-Based Materials. Inorganics 2019, 7 (3), 36.

4) Gharib, A.; Arab, A. Improved Formic Acid Oxidation Using Electrodeposited Pd–Cd Electrocatalysts in Sulfuric Acid Solution. Int. J. Hydrog. Energy 2021, 46 (5), 3865–3875.
(Digital Presentation) Power-Generation and Mass-Transport Characteristics of Direct Formic Acid Fuel Cell Using Pore-Designed Anode Electrode
Authors: Miskan Madihah , Tsujiguchi Takuya , Kodama Akio , Osaka Yugo
Published: July 2022

Controlling of mass transport in the anode catalyst layer has become one of the major challenges in Direct Formic Acid Fuel Cells (DFAFCs) owing to the poor formic acid transport and crossover. This study is aim to introduce the microfiber-pores designed anode catalyst layers by mean to improve the mass transport limitation and eventually improving the performance of DFAFCs. Polystyrene fibers (PSFs) were fabricated with different diameter by electrospinning prior to control their length by ultrasonic homogenization. Different amount of PSF as a pore forming agent were then added to the catalyst ink before catalyst coated membrane (CCM) were made by spraying the catalyst ink on the membrane. The CCM were then soaked in ethyl acetate solution to remove the PSF in order to improve the porous structure of anode catalyst layer. Different diameter and amount of PSFs exhibited different pore properties of the catalyst layer and its effect on the mass transport and the performance of DFAFC were then investigated. From the results, the microfiber-pores designed anode catalyst layers showed better performance remarkably at the higher current density region as compared to the conventional anode catalyst layer. Moreover, it was also found that there were optimum diameter and amount of PSF used for the highest performance of DFAFC. This could be attributed to the existence of the microfiber-pores have provide larger active catalyst region which accelerate the fuel transport and the CO2 emission in anode catalyst layer. Thus, these results indicate that the introduction of the microfiber-pores on the anode catalyst layer is a promising approach in order to improve the mass transport resistance, leading to enhance the DFAFCs performance.
How to Impede Hydrogen Evolution on Carbon Based Materials?
Authors: Oates Rose Patricia , Murawski James , Hor Carys , Shen Xuyang , Weber Daniel J , Oezaslan Mehtap , Shaffer Milo S P , Stephens Ifan Erfyl Lester
Published: July 2022

Hydrogen is a highly attractive zero-emission energy sector. However, in many electrochemical systems, such as carbon dioxide reduction, batteries and supercapacitors hydrogen evolution reaction (HER) is an undesired competing reaction. It is therefore important to tailor these electrochemical systems in order to minimise hydrogen production. Carbon black materials are often added to the catalyst layers as they are low cost, abundant, inert, and have a high conductivity and surface area. This work has investigated HER activities for seven different commercial carbon materials to identify the required structural properties of carbon for minimizing the hydrogen evolution reaction.

Rotating disk electrode, X-ray diffraction, and nitrogen adsorption/ desorption were used to determine the electrochemical and physical characteristics of the carbon materials. An on-chip electrochemical mass spectrometer was used to further probe the gaseous products being produced at the electrode insitu; we established that the exact onset of the HER at -0.4 V vs RHE, as shown in Figure 1. Furthermore, we have correlated our electrochemical experiments to earlier characterization data on the same carbon materials, including: X-ray photoelectron spectroscopy, elemental analysis (e.g. Fe, H, S, C) using neutron activation analysis.1 Our results indicate that the most graphitic carbons with low amount of metal impurities are the best for inhibiting H2 evolution.

V Čolić, S. Yang, Z Révay, I E L Stephens & I Chorkendorff, Electrochim
Acta, 2018,
272, 192–202.

Figure 1
Fe-N-C PGM-Free ORR Catalysts: An Investigation of the Source of Observed Redox Peaks and Their Significance to Catalysis
Authors: LaRochelle Richard Lynne , Payakapan Napachat , Jia Qingying , Mukerjee Sanjeev
Published: July 2022

Iron-based platinum group metal free (PGM-free) carbonaceous catalysts of a type commonly called “Fe-N-C” have high activity metals in the oxidation reduction reaction (ORR) in acid electrolytes. However, the durability of Fe-N-C catalysts is typically low. One puzzling feature of Fe-N-C catalysts is that they often – but not always – exhibit redox peaks near the expected potential of Fe2+ à Fe3+ + e- (0.77 V vs. SHE). It has been observed that the absence of these peaks is correlated with improved catalytic performance. While the source of these peaks has not been identified rigorously as iron redox, it has been observed that the peaks appear in the presence of iron and do not appear in voltammograms of either N-C substrate alone or cobalt catalyst analogs (Co-N-C). Furthermore, the redox potential of these peaks shifts when the electrolyte is changed from sulfuric acid to perchloric acid, whereas the halfwave potential of the ORR does not change. What, then, is the source of these peaks? And does the redox event have significance to the catalytic mechanism? The study reported here investigates the effect of a series of acid electrolytes on the observed redox peaks, showing a progressive shift to lower potentials in perchloric, sulfuric, and phosphoric acids. Furthermore, these peaks are demonstrated to be absent in the case of N-C substrate alone. Addition of iron salts to the electrolytes results in the appearance of peaks in the voltammograms of N-C, with associated changes in the capacitance, indicating that the source of the peaks is surface-adsorbed iron salts. Therefore, the appearance of redox peaks is an indicator of the degradation of the catalyst and no change in the halfwave potential would be expected, as the adsorbed salts are not catalytically active.