bluuebunny/crossref_metadata_2025 huggingface dataset:
2D Layered Material Interface Confined Dynamically in-Situ Generated Ni(OH)2 Triggers Ultrafast Oxygen Evolution
Authors: Ibrahim Kassa Belay
Published: September 2023

Basic insights into the structural evolution of oxygen electrocatalysts under operating conditions are of substantial importance for designing water oxidation catalysts. Recently, the development of potent oxygen evolution reaction (OER) electrocatalysts has trigger researcher’s attention. Conversely, the design of active and stable catalyst under alkaline media is a substantial issues and challenges of the area due to the poor cyclability of catalysts and the sluggish water dissociation kinetics. Our work reports the design and synthesis of a two-dimensional (2D) SnS2 confined in-situ generated Ni(OH)2 nanoparticle electrocatalyst, which accelerates water oxidation and exhibits long term durability in alkaline solutions, leading to significant improvement in OER performance. A two-step method was used to synthesize the electrocatalyst, starting with the lithium intercalation of exfoliated SnS2 nanosheets followed by Ni2+ exchange in alkaline media to form SnS2 intercalated with Ni(OH)2 nanoparticles (denoted Ni-Ex-SnS2), which was fully characterized by in-situ X-ray absorption spectroscopy for two cycles. Electrochemical tests indicated that the electrocatalyst exhibits superior OER activity and excellent stability, with an onset overpotential and Tafel slope as low as 17 mV and 42 mV dec−1, respectively, which are among the best values reported in alkaline media. Furthermore, density functional theory calculations show that the co-joint roles of Ni(OH)2 nanoparticles and SnS2 nanosheets result in the excellent activity of the Ni-Ex-SnS2 electrocatalyst, and the good stability is attributed to the confinement of the in-situ generated Ni(OH)2 nanoparticles. The combination of electrochemical measurement, operando X-ray absorption spectroscopy and density functional theory (DFT) calculations revealed that the in-situ generated and confined Ni(OH)2 as the critical active species via the principle of nano-confinment and in-situ generations. This work proposes the plausible catalytic reaction pathway and mechanism.
(Cu3-x Nix)Co2-Layered Double Hydroxide Nanosheets for Enhanced Electrocatalytic Activity Towards Overall Water Splitting
Authors: Kansal Sakshi , Anshu Satvik , Ravindran Rahul , Priya Surbhi , Chandra Amreesh
Published: September 2023

The exploration of transition metal based electrocatalyst for overall water splitting is becoming important as hydrogen becomes integral part of energy landscape. Recently, a new class of compounds i.e. layered double-hydroxides (LDHs), also known as anionic clays, are have shown tremendous promise for use as electrocatalyst. The lamellar morphology of LDHs accommodates higher active sites, that contributes to the facile electron transfer and thus attracts a great deal of interest in catalysis application. Moreover, the high catalytic activity of LDHs are also linked to their facile anion exchange, specific electronic structures, and versatile chemical compositions.

Herein, we have developed a series of ternary layered double hydroxide (LDH) using pH-adjusted co-precipitation method with varying ratio of Cu, Ni and Co, which are used as an electrocatalyst for overall water splitting. (CuxNi1)Co1-LDHs (x = 0.5 1, 1.5, and 2 ) were systematically characterized using XRD, XPS, SEM, FTIR, TEM and BET techniques. The synergistic contributions from the electrocatalytically active metals and lamellar morphology of LDHs promotes water dissociation, facilitates faster release of H2-O2 gas bubbles, ameliorate electrolyte ion diffusion and improves electron transfer rate. It is further observed that the (CuxNi1)Co1-LDHs showed excellent electrocatalytic activity for both hydrogen evolution (HER) and oxygen evolution reaction (OER) with an overpotential of 147 and 218 mV for HER and OER, respectively at 10 mA cm-2. Tafel slope was found to be lowest for (Cu1Ni1)Co1-LDH. Further, the durability of the materials was also analysed by performing chronoamperometry for over 12 h. The overall water electrolytic cell using (Cu1Ni1)Co1-LDH as both electrodes can reach 50 mA cm−2 at 1.9V with outstanding durability.
(Digital Presentation) The Effects of Sulfur-Oxygen Ratio at the Heterogeneous Interface on Oxygen Evolution Reaction Performance of Ni3S2@Ni3Fe Catalysts for Alkaline Water Electrolysis
Authors: Bi Songhu , Geng Zhen , Jin Liming , Liu M , Xue Mingzhe , Zhang Cunman
Published: September 2023

Alkaline water electrolysis is the important pathway for the green hydrogen generation, where oxygen evolution reaction (OER) kinetics is limited due to the sluggish proton-coupled electron transfer in the four-electron reaction. It’s very important for the design of high-performance OER catalysts in order to improve its kinetics performance. Here, porous heterogeneous Ni3S2@Ni3Fe catalysts are prepared on nickel mesh (NM) by the electrodeposition process. Oxygen atoms are introduced into Ni3S2 by the vulcanization processes, and different S-O atom ratios are adjusted by varying vulcanization temperature. The influence of S-O ratio at heterogeneous interface on OER performance of Ni3S2@Ni3Fe is systematacially investigated. The results indicate that high S-O ratio improves the OER performance of Ni3S2-xOx@Ni3Fe, which is attributed to H2O adsorption ability enhancement on Ni3Fe surface due to the formation of unique heterogeneous electronic structure by density function theory (DFT) calculation analysis. The prepared NM/Ni3S2-xOx@Ni3Fe (vulcanization temperature at 300
oC) electrode exhibits the improved OER performance in 30 wt% KOH solutions at high current density up to 1000 mA cm-2. It provides the guidance for the design of high-performance Ni3S2-based heterogeneous catalysts by introducing oxygen atom and increasing the sulfur-oxygen ratio.

Figure 1
(Digital Presentation) An Efficient and Stable of Low-Pt Catalysts for Full Water Splitting in Acidic
Authors: Zhang Jingjing , Li Bing , Zhang Cunman
Published: September 2023

Designing efficient platinum-based catalysts is of great interest for the lowering of Pt dosage and the enhance of catalytic activity on the full water splitting. However, it is still challenging to develop low-Pt catalysts with evenly distributed, proper sized particles on supports. Here, Metal-Organic Frameworks (MOF) derivatives were used as supports to prepare ultra-low platinum catalysts of uniform particle size. MOF derived transition metal heteroatom-doped carbon is a promising support for precious metal nanoparticles of electrocatalytic activity, because it provides abundant anchor points that enhance their adhesion, transition metals on the MOF skeleton can effectively prevent further growth of platinum particles, more importantly, through the proof-metal electron interaction, improve their intrinsic catalytic activity to achieve high activity and stable hydrogen evolution reaction. We will characterize the characteristics of the catalyst from several aspects, such as morphology, pore size and composition. Finally, we will verify the catalytic ability, rate ability and stability of low platinum catalyst with MOF derivatives support, through a comprehensive characterization of the catalyst HER and OER performance.
Experimental Aging and Lifetime Prediction in Grid Applications for Large-Format Commercial Li-Ion Batteries
Authors: Gasper Paul , Saxon Aron , Shi Ying , Smith Kandler , Thakkar Foram
Published: September 2023

Due to the growth of electric vehicle and stationary energy storage markets, the production and use of lithium-ion batteries has grown exponentially in recent years. For many of these applications, large-format lithium-ion batteries are being utilized, as large cells have less inactive material relative to their energy capacity and require fewer electrical connections to assemble into packs. The economics of these battery systems is highly dependent on cell lifetime, requiring accelerated aging tests to characterize cell degradation. However, testing of large-format lithium-ion batteries is time consuming and requires high current channels and large testing chambers, so not many reports on the lifetime of commercial, large-format lithium-ion batteries exist. Here, accelerated aging test data from four commercial large-format lithium-ion batteries is reported. These batteries span both NMC-Gr and LFP-Gr cell chemistries, are from a variety of manufacturers, have pouch and prismatic formats, and show a range of cell designs with varying power capabilities.

Accelerated aging test results are analyzed to examine both cell performance, in terms of efficiency and thermal response under load, as well as cell lifetime. Cell thermal response is characterized by measuring temperature during cycle aging, which is used to calculate a normalized thermal resistance value that may help estimate both cell cooling needs or to help extrapolate aging test results to different thermal environments. Cell lifetime is evaluated qualitatively, considering the average calendar and cycle life across a range of conditions, as well as quantitatively, using statistical modeling and machine-learning methods to identify predictive aging models from the accelerated aging data. These predictive aging models are then used to investigate cell sensitivities to stressors, such as cycling temperature, voltage window, and C-rate, as well as to predict cell lifetime in various stationary storage applications.

Results from this work show that cell lifetime and sensitivity to aging conditions varies substantially across the cell types, necessitating testing for each specific cell to make quantitative lifetime predictions. That being said, all commercial cells tested here are predicted to reach at least 10-year lifetimes for stationary storage applications. Based on the aging test results and modeling, some cells are expected to be relatively insensitive to temperature and use-case, making them suited for simple use cases with little or no thermal management and simple controls, while the lifetime of other cells could be extended to 20+ years if operated with thermal management and degradation-aware controls.

Figure 1
(Invited) Electrocatalytic Ammonia Splitting for Hydrogen Generation
Authors: Hamann Thomas
Published: September 2023

Much of the global effort toward producing solar fuels has involved splitting water to obtain molecular hydrogen. Unfortunately, hydrogen gas has a relatively low energy-per-volume, and extreme cryogenic temperature and pressure is needed to bring hydrogen to a condensed state. An interesting choice for a hydrogen storage medium that circumvents these setbacks is ammonia. Synthesis of ammonia (largely via the Haber-Bosch process) is already the second-largest chemical industrial process in the world, and as a result the infrastructure for ammonia storage and transport already exists. In the first part of this talk, I will introduce a new method of storing liquid ammonia at room temperature and atmospheric pressure by combing it with certain ammonium salts to form binary solutions. Preliminary electrochemical investigations of this interesting solvent system will be introduced, including electrolysis to generate hydrogen and nitrogen. The ammonia oxidation overpotential ultimately limits the efficiency of ammonia electrolysis. The second part of this talk will discuss electrocatalytic measurements of homogeneous electrocatalysts, including the transition metal complex, [Ru(tpy)(dmabpy)NH3]2+ (tpy = 2,2′:6′,2′′-terpyridine, dmabpy = 4,4'-dimethylamino-2,2'-bipyridine), in non-aqueous solvent systems with the aim of lowering the overpotential. Recent results at uncovering the mechanism of ammonia oxidation with this ruthenium catalyst will be presented and used to model and interpret the cyclic voltammetric response of electrocatalysis.
(Invited) Stimuli-Responsive Metal-Organic Frameworks
Authors: Thaggard Grace , Park Kyoung Chul , Shustova Natalia
Published: September 2023

Development of stimuli-responsive materials is crucial for the next advancements in the technology and energy sectors. For instance, reversible tuning photophysical profiles of materials or modulation of energy transfer processes are key aspects for the development of next generation of logic gates, spatially- and temporally-resolved sensors, and on-demand drug delivery systems. Our recent efforts have focused on employment of metal-organic frameworks (MOFs) as a versatile platform for the material development, which contain photochromic moieties, allowing for tailoring MOF electronic and photophysical properties. In our work, confinement-imposed photophysics was probed for a variety of photoresponsive moieties including a not-well studied class of hydrazone-based photoswitches integrated into topologically distinct porous scaffolds. The performed studies involved a comprehensive analysis of photophysics-structure correlation performed for the first time in two-dimensional and three-dimensional porous frameworks using steady-state and time-resolved photoluminescence spectroscopy. This presentation will delineate our findings on a series of different frameworks with coordinatively immobilized photochromic molecules. Specifically, we will discuss static and dynamic tuning of photophysical and electronic properties through metal incorporation, guest encapsulation, and photoresponsive linker embedment. Our findings were employed to develop the first example of the field-effect transistor built upon photochromic MOFs foreshadowing framework implementation in the practical realm.
(Invited) Exploring Metal Organic Frameworks Intrinsic Photocatalytic Materials
Authors: Nyakuchena James , Huang Jier
Published: September 2023

Porous crystalline materials such as metal organic frameworks (MOFs) represent a novel class of materials for catalysis due to their inherent porous nature, exceptional thermal and chemical stability, structural flexibility. While many photocatalytic systems based on these materials have been developed in the past decade, a significant gap exists in our understanding of the correlation of photophysical and photocatalytic properties of MOFs with their structure, which hinders accurate prediction and informed design. We aim to address this challenge using an interdisciplinary approach that combines innovative material design and synthesis, fundamental mechanistic studies, theoretical prediction, and photocatalytic performance evaluation. In this talk, I will discuss our recent progress in developing porous crystalline materials as intrinsic light harvesting materials and heterogenous catalysts for solar fuel generation.
In-Situ Measurement of Charge Transfer at Cocatalyst/Semiconductor Interfaces in BiVO4 Particle Photocatalyst
Authors: Shen Meikun , Kaufman Aaron James , Boettcher Shannon W.
Published: September 2023

Semiconductor photocatalyst particles are known to transform solar energy to useful chemicals such as H2 or methanol. However, the efficiency of semiconductor photocatalysts often suffers from the quick charge carrier recombination. However, there is no real physical reasons for semiconductors to display this low performance. Multiple strategies have been proposed and applied to modify the semiconductor particles and enhance their solar-to-hydrogen efficiencies. It is often assumed that in semiconductor particles with well-defined crystal facets, the photogenerated charge carriers undergo facet-dependent separation. Thus, a common strategy is to deposit a HER electrocatalyst on ‘electron-selective’ facets and an OER electrocatalyst on ‘hole-selective’ facets. Although this strategy have showed plausible results in previous literatures, a precise understanding of how charge-carrier-selective contacts between the deposited electrocatalyst and semiconductor particles emerge and how the semiconductor photocatalysts are rationally designed is still missing.

In this work, we used both ex-situ and in-situ conducting AFM experiments and a new ionomer/catalyst–semiconductor test structures to characterize the charge transfer between semiconductor and deposited electrocatalysts at individual nanoparticle scale. We showed that the presence of the water/electrolyte interface is critical to induce hole selectivity between the CoOx OER cocatalyst and the BiVO4 semiconductor light absorber. We demonstrated that the negative surface charge on the semiconductor is central to induce hole selectivity. The work also demonstrates a facile strategy to control local pH and introduce water using thin-film ionomers for conductive AFM measurements. These new insights can be broadly applied to the rational design of semiconductor photocatalysts for overall water-splitting systems to control charge-carrier selectivity and improve their performance.
Observation of Electronic and Structural Interaction between Small Polaron and Host Material Using Femtosecond XUV Reflection Spectroscopy
Authors: Liu Hanzhe , Cushing Scott
Published: September 2023

Small polaron formation in transition metal oxides is believed to be a reaction bottleneck in many solar energy conversion applications. While polaron formation has been previously confirmed, the microscopic interaction between a small polaron and its host material is largely unexplored. Here, using femtosecond XUV reflection spectroscopy, we report the evidence of electronic and structural interaction between the small polaron and its host material in CuFeO2, a photoelectrode material for CO2 reduction. Initial small polaron formation is observed as a spectral blue shift occurring within the first 100 fs. After polaron formation, we observe an increased coherent oscillation signal around the polaron sites, which is attributed to polaron-induced optical phonons. This observation suggests that the polaron-associated local lattice distortion can launch optical phonons in neighboring unit cells. In addition to structural coupling, the electronic states in the host materials can also be modified during polaron formation. As an example, we report an increase of Fe oxidation states after photoexcitation. The population of these highly oxidized Fe atoms strongly correlates with polaron dynamics, suggesting that polaron can alter its surrounding electronic states in host materials.
(Invited) True Particle-Size Dependence of Photocatalytic Activity of Octahedral-Shaped Anatase Titania
Authors: Ohtani Bunsho , Takashima Mai
Published: September 2023

Here, attempts to prepare octahedral-shaped anatase titanium(IV) oxide (titania) particles (OAPs) of uniform bulk structure (anatase with negligible non-crystalline components), surface structure (only exposing {101} facets) and particle size are reported as the first and sole example of a "pure" metal-oxide powder. The OAP samples were prepared by sonication-hydrothermal (HT) reaction of potassium-titanate nanowires through the process modified from the previous report [1]. Characterization of the samples by Rietveld analysis of XRD patterns (including non-crystalline phases using an internal standard) [2], reversed double-beam photoacoustic spectroscopy (RDB-PAS; a method measuring energy-resolved distribution of electron traps mainly located on the surface of metal-oxide and the other semiconducting samples) [3,4] and SEM observations revealed the homogeneousness of crystalline bulk, surface and particle size, respectively, to indicate the samples "pure". By controlling the preparation conditions, several OAP samples with different average size ranging of ca. 60–260 nm keeping the purity of the OAP shape. Roughly speaking, the particle-size distribution of those samples was the size of ca. 80% particles in the range of +20% of the average. Photocatalytic activities of those samples in (a) methanol dehydrogenation with in-situ deposited platinum to yield hydrogen, (b) oxidative decomposition of acetic acid under aerobic conditions to yield carbon dioxide and (c) oxygen evolution from deaerated aqueous silver sulfate were examined under ultraviolet-light (> 290 nm) irradiation to find that there seemed no particle-size dependence for the systems (a) hydrogen evolution and (b) carbon-dioxide evolution, while the activity in system (c) to liberate oxygen was almost linearly increased with the particle size [5]. These particle-size dependences of photocatalytic activity seem strange but could be "true" considering the purity of those samples, i.e., almost pure bulk crystal component exposing only anatase{101} facets. The previously reported particle-size dependence might be incorrectly derived due to the unknown effects by the other structural parameters.

[1] Molecules
19, 19573 (2014). [2] Catal. Today
313, 218 (2018). [3] Chem. Commun.
52, 12096 (2016). [4] Electrochim. Acta
264, 83 (2018). [5] To be submitted.
(Invited) Computationally Guided Design of Sustainable Chemistry for Low-Cost Battery Technologies
Authors: Narayanan Badri
Published: September 2023

The ever-growing demand for storing electrical energy generated from intermittent source of renewable energy (e.g., sun, wind etc.) has necessitated development of new low-cost, safe, and sustainable battery systems that go beyond the conventional Li-ion technology. In this context, electrochemistry based on aluminum and iron – third and fourth most abundant elements on earth, respectively – offer the most promise. Unfortunately, long-standing issues with electrolyte design, cyclability, dendrite proliferation, and parasitic side-reactions has precluded deployment of rechargeable Al- or Fe- batteries. Most of the daunting issues stalling progress stem from dearth of atomic-scale understanding of solvation chemistry, ion-transport, chemical reactions, and material evolution in the bulk electrolyte, as well as electrode/electrolyte interfaces. In this talk, I will demonstrate how a synergistic integration of first-principles calculations, ab initio/classical reactive molecular dynamics simulations, electrochemical experiments, and spectroscopic measurements can pave the path towards advancing such understanding; and accelerate design of low-cost battery technologies. Specifically, I will showcase two recent successes of this approach, which led to (a) design of low-cost, fire-resistant inorganic molten-salt electrolytes containing AlnCl3n+1
– species, which allow fast de-solvation of Al3+ ions and prevent dendrite formation – both central for fast-charging Al-chalcogen batteries (200 C) with high cycle life, and (b) demonstration of a novel bi-directional Fe(OH)2/FeOOH redox chemistry facilitated by sulfate intercalation in Fe(OH)2, which drastically impairs parasitic hydrogen evolution, and Fe3O4 formation – consequently, enhancing capacity and cycle life of alkaline batteries. I will discuss these results in the context of accelerating design of new sustainable high-performance battery technologies for grid-storage.
Molecular Structures and Electrochemical Activity of Oversaturated Electrolytes
Authors: Li Yuanchao , Abbey Joshua , Singh Nirala , Nguyen Trung Van
Published: September 2023

In applications ranging from biochemistry to electrochemistry, the solvation structures and agglomeration forms of ions are a focus of basic scientific study. Prior research has found that the concentration level and preparation conditions of these ionic electrolytes can affect the hydrated structure (e.g., tetrahedral or octahedral) and aggregate framework (e.g., intermolecular connection like ion cluster or network, or intramolecular connection like dissociation or undissociation).1–3 Our recent studies on vanadium (IV) sulfate (VOSO4), a transition metal salt used in redox flow batteries, show that in addition to the electrochemically active ions that can readily convert to V2+, V3+, and V5+ oxidation state, inactive molecules with different solvation structures and agglomerates also form in the electrolyte, and some of the inactive molecules can be converted to active ions while others cannot. The order of the preparation, such as dissolving the metal salt in water first and then adding the acid or vice versa, seems to have an impact on the ratio of the active ions and inactive molecules in the electrolyte. Furthermore, the closer the vanadium salt concentration is to its solubility limit, the higher the fraction of the inactive non-convertible molecule is. Finally, the inactive molecules in these electrolytes can be converted to active molecules by heating the electrolyte to a higher temperature (e.g., >50oC) and then cooling it down to room temperature. Similar electrochemical behavior was also observed in oversaturated FeCl3 solution, indicating that the coexistence of electrochemically active and inactive species above the solubility may be common for transition metal salt solutions.

Oversaturated electrolyte solutions are unstable and have been of little interest because they have been deemed to have no applications. However, for applications where the oversaturation state is only needed within its duration of stability, they provide many benefits such as higher concentrations that could translate to higher current density or power output in power source applications and higher energy density in a long-duration energy storage applications. Our presentation will discuss the stabilities, electrochemical performances, and possible solvation structures of VOSO4 and FeCl3 solutions with different concentrations and preparation methods.

References

S. Kim, H. Kim, J.-H. Choi, and M. Cho, J Chem Phys, 141, 124510 (2014).

I. Persson, J Solution Chem, 47, 797–805 (2018).

D. L. Wertz and M. L. Steele, Inorg Chem, 19, 1652–1656 (1980).
Design and Characterization of Azobenzene Electrolytes for Aqueous Redox Flow Batteries
Authors: Singh Siddhant , Tami Jessica L. , Gruich Cameron , Oudeif Fairooz , Goldsmith Bryan R. , McNeil Anne Jennifer , Kwabi David G.
Published: September 2023

Aqueous redox-flow batteries (RFBs) containing organic redox electrolytes are a promising technology for grid-scale renewable energy storage. Most electrolytes currently under consideration for these RFBs contain charge-storing molecules that are drawn from a narrow collection of molecular scaffolds, and undergo rapid decomposition, which results in high rates of capacity fade. To inform efforts at developing more stable aqueous RFB electrolytes, it is critical that the kinetics of charge carrier decomposition and its relationship to capacity fade are well understood.

In this work, we explore a relatively new class of redox-active organic molecules known as azobenzenes as potential charge carriers in aqueous RFBs. The electrochemical properties and cycling performance of a range of substituted azobenzenes are characterized using cyclic voltammetry, chronoamperometry, and constant current-constant voltage cycling. Decomposition products are identified using UV-vis and proton nuclear magnetic spectroscopy, as well as mass spectrometry. We discern the influence of decomposition during flow cell cycling by combining in-line UV-vis spectroscopy with multivariate curve resolution, which allows us to quantify decomposition kinetics and estimate UV-vis spectra of intermediate species/decomposition products. These results are being used to drive de novo computational design of new azobenzene molecules that can eliminate or substantially mitigate the identified decomposition pathways.
A 3-Step Bimetallic Thermally Regenerative Ammonia Battery
Authors: Rochin Jose R. , Cross Nicholas R. , Sweeney Alana , Hall Derek M.
Published: September 2023

Large amounts of low-grade heat (T < 100 °C) are readily available from a wide range of sources, such as industrial facilities, geothermal wells, and solar thermal systems. The potential benefits of harvesting low-grade heat sources to produce power include reduced carbon footprints and increased system efficiencies of thermal power generation systems. Thermally regenerative ammonia batteries (TRABs) are one of the more promising technologies in the space, but like many other emerging technologies, they still lack the power density needed to be economically viable. Though bimetallic TRAB (B-TRAB) systems have increased TRAB power densities by using two dissimilar metals to dramatically increase cell potentials, they suffer from poor coulombic efficiencies due to their reliance on metallic copper in the presence of dissolved ammonia. A typical bimetallic TRAB uses four steps for its cycle operation: (1) high-voltage electrochemical discharge, (2) thermal ammonia separation, (3) low-voltage electrochemical charge, and (4) thermal ammonia separation. To address B-TRAB efficiency issues, we reduced the number of steps needed to complete a battery cycle to three by removing a thermal charging step and modified the electrolyte composition to favor the Cu(I, II) reaction at the positive electrode. Cycle tests with the new 3-step B-TRAB increased coulombic efficiency to 85%, nearly double the coulombic efficiency of the 4-step B-TRAB. Likewise, the new system had an average discharge power density of 15.55 mW cm-2, 25% larger than the 4-step B-TRAB, with a net energy density of 0.92 Wh L-1 at a current density of 10 mA cm-2. These modifications to the B-TRAB concept collectively increased multiple performance metrics, further increasing the favorability of TRABs as competitive low-grade waste heat harvesting devices.
Advances in Chelated Metal Electrolyte for Aqueous Flow Batteries
Authors: Marshak Michael P. , Reber David , Waters Scott E. , Davis Casey M , Thurston Jonathan R.
Published: September 2023

Flow battery electrolyte containing chelated metal ions can support high voltage, high power, and high efficiency battery cycling in pH-neutral conditions. In this talk the coordination behavior and flow battery performance of chelated metal ions including vanadium, chromium, iron, and cerium will be presented. Key to enabling this approach is the fundamental understanding of the coordination properties of the chelating agent to specific metal ions and oxidation states. Techno-economic analyses suggest that the performance advantages of chelation more than offsets the cost of the chelating agents. Finally, strategies towards high concentration (> 2 M) cycling of these electrolytes will be presented, and the implications of energy density on overall system footprint will be discussed.
Large Scalable High Ion Conductive and Selective Double Layer Membrane Achieved through Dual Ion Conducting Mechanisms
Authors: Ji Tongtai , Zhu Hongli
Published: September 2023

As the share of sustainable energy sources in the electricity supply rises, large-scale energy storage becomes increasingly important. All vanadium flow batteries, as one of the most promising large-scale energy storage methods, have reached the commercialization stage because of their unique feature of uncoupling power and energy, as well as the advantages of long life, high safety, and low cost. The ion-selective membrane is an essential part of flow batteries, which allows specific ions to pass through to maintain a neutral charge and prevents the crossover of active species to maintain the capacity. However, the high cost and low ion-selectivity of the commercialized ion-selective membranes (i.e., Nafion membranes) hindered the further promotion of the flow batteries. Herein, we developed a large scalable double-layer ion selectivity membrane with a unique bifunctional nanoporous boron nitride (PBN) ion selective layer and a low-cost porous polyetherimide (PEI) ion conductivity and support layer. PBN was synthesized by a large scalable template-free method, which was further decorated with Nafion resin. The nano-sized and tortuous pores of the PBN can effectively block the crossover of vanadium ions and provide excellent ion selectivity based on the pore size exclusion mechanism. Furthermore, the super-acidic sulfonic acid groups of Nafion decorated on the nanoporous structure of PBN provide high-speed proton transfer channels that increase proton conductivity through both Grotthuss and vehicle mechanisms. The low-cost porous PEI ion conductivity and support layer was prepared by the phase separation method. The well-aligned asymmetric finger-like porous structure of the PEI membrane provides excellent ion conductivity. The addition of a hydrophilic polymer additive, polyvinylpyrrolidone, further increased its ion conductivity. The PBN–PEI double layer membrane, prepared by a simple spray coating method, demonstrated an excellent ion selectivity (1.49×108 mS cm−3 min), which is almost 15 times higher than that of the pristine PEI membrane (6.71×106 mS cm−3 min) while maintaining high ion conductivity (64 mS cm−1). The PBN–PEI membrane achieved superior performance (97% of coulombic efficiency, 94% of voltage efficiency, and 91% of energy efficiency at 40 mA cm−2) than the Nafion 115 membrane in the all-vanadium flow battery with higher discharge capacity at all current densities and high stability with a lower capacity fading rate (0.17% per cycle vs. 0.74% per cycle at 100 mA cm−2). The PBN–PEI membrane also demonstrated a stable operation in the all-vanadium flow battery at a current density of 100 mA cm−2 over 700 cycles. The work presented the remarkable performance of the ultra-thin PBN bifunctional layer in terms of ion conductivity and selectivity; the combination with the low-cost high ion-conductive porous PEI membrane and a simple fabrication process demonstrated a great potential for commercialization of the PBN-PEI double-layer membrane.
A Membrane-Electrolyte System Approach to Understanding Ionic Conductivity and Crossover in Aqueous Organic and Metalorganic Flow Batteries
Authors: George Thomas Young , Thomas Isabelle C. , Haya Naphtal O. , Deneen John P. , Wang Cliffton , Aziz Michael J.
Published: September 2023

The ion exchange membrane is a critical component of most aqueous flow batteries, where it provides a transport medium for charge carrying ions while suppressing undesired crossover of redox active species. The all-vanadium redox flow battery (VRFB), the most developed flow battery chemistry to date, is also the system for which most studies of flow battery membranes have been done. These studies have shown that the concentration and composition of the acidic vanadium electrolytes influence water content in the membrane phase, and therefore influence the transport phenomena through the membrane pores. In the present work, we build on this understanding by evaluating the effects of iron(II/III) hexacyanide electrolyte concentration, pH, and cations on cation exchange membrane performance, to inform design of aqueous organic and metalorganic flow batteries (AORFBs).

The size and charge numbers of established redox active materials for AORFBs afford them lower crossover than metal ions like vanadyl or iron. However, many emerging AORFB chemistries with extreme stability use neutral or alkaline electrolytes where sodium or potassium, not protons, must carry ionic current through the membrane. In these flow batteries, the membrane resistance regularly contributes the most to polarization losses. The widely-used cation exchange membrane Nafion has a factor-of-ten reduction of conductivity in potassium form compared to when it is protonated in acidic environments. Ohmic resistance of the membrane is therefore a substantial limiting factor on practical current densities and power densities for battery operation.

In order to investigate the membrane-electrolyte system, we first describe simple methods for conductivity and electrolyte uptake measurements that can be used to screen a variety of membrane materials and electrolytes. We show the influence of pre-treatment, cation (sodium or potassium), supporting electrolyte, and iron hexacyanide concentration on Nafion conductivity and electrolyte uptake, and compare these results with a non-fluorinated Fumatech membrane (E-620). We also assess pre-treatment, concentration, and cation effects on ferricyanide permeability. Considering the membrane and contacting flow battery electrolyte as one system, our results emphasize that the total ion concentration of the electrolyte affects membrane water content, and there are conditions where additional supporting electrolyte can have a harmful effect on membrane conductivity. We also show that maximizing the concentration of iron hexacyanide by using mixed cation electrolytes results in increased membrane resistance, signifying that conductivity and volumetric capacity become a tradeoff.
A High-Power-Density Low-Temperature Heteropoly Acid Aqueous Redox Flow Battery
Authors: Ai Fei , Lu Yi-Chun
Published: September 2023

Aqueous redox flow batteries (ARFBs) are promising technology for safe and long-duration energy storage owing to their flexible architecture decoupling power and energy, which is the key to achieving massive utilization of intermittent renewable energies (solar and wind power)1. However, the high-power density at low temperatures is prohibited by the weak stability, sluggish kinetics, and limited solubility of active materials. These challenges not only preclude the commercialization of ARFBs in the high-power density market (e.g., electric automobile) but also make the renewable electric grid vulnerable to severe weather fluctuations.

In this study, we describe a polyoxometalate-based active material with exceptionally fast redox kinetics and high electron solubility at low temperatures2. We optimize the charging process to achieve high electrochemical performance and will discuss factors that would influence solubility. We evaluate the kinetics of the polyoxometalate-based materials by rotating ring-disk electrodes measurement (RRDE) and adjust the electrolyte composition to increase the energy density and electrochemical stability of polyoxometalate-based electrolytes. We will discuss the full polyoxometalate-based ARFBs’ electrochemical performance, the influence of the supporting, and the possible degradation mechanism of the full cell (e.g., side reaction (hydrogen evolution, decomposition of the active materials) and crossover).

Acknowledgment:

The work is supported by a grant from the Research Grant Council (RGC) of the Hong Kong Special Administrative Region, China (project no. CUHK 14308622).

Reference:

(1) Yao, Y.; Lei, J.; Shi, Y.; Ai, F.; Lu, Y.-C. Assessment methods and performance metrics for redox flow batteries. Nature Energy
2021,
6 (6), 582.

(2) Ai, F.; Wang, Z.; Lai, N.-C.; Zou, Q.; Liang, Z.; Lu, Y.-C. Heteropoly acid negolytes for high-power-density aqueous redox flow batteries at low temperatures. Nature Energy
2022,
7 (5), 417.
Precipitation/Dissolution of Supersaturated V(III) Sulfate Electrolytes
Authors: Mouron Spencer , Cho Daniel , Li Yuanchao , Nguyen Trung Van
Published: September 2023

Redox flow batteries (RFBs)-based storage systems have the unique feature of separate power generating and energy storage units that can be individually sized. RFBs can be used for days-long energy storage, but because of the low solubility of most ions and molecules in both aqueous and non-aqueous solvents,[1,2] scaling these RFB systems for days-long applications requires significant storage volume and floor area.

Our team has been working on a new storage method that significantly increases the energy storage density while still maintaining the traditional flow battery design.[3] This method involves storing the reactants as both soluble ions and an undissolved solid form, only the liquid containing soluble ions is circulated through the batteries. To achieve this, a solid form of Vanadium salt must be precipitated within the storage tanks, necessitating a study on the precipitation and dissolution of various vanadium salts. Past work has been done by our group on the Vanadium (IV/V) solution,[4] we now focus on the Vanadium (II/III) solution. This presentation will discuss the production of Vanadium (III) sulfate salt electrolytes, and the precipitation rate of said salt at oversaturation.

References

[1] V. Singh, S. Kim, J. Kang, and H. R. Byon, Nano Res.,
12, 1988-2001 (2019).

[2] K. Gong, F. Xu, J. B. Grunewald, X. Ma, Y. Zhao, S. Gu, and Y. Yan, ACS Energy Lett.,
1, 89-93 (2016).

[3] Y. Li and T. V. Nguyen, Provisional US patent application number 62/941,064 filed 2019/11/27, International Application No. PCT/US20/61455 filed 2020/11/20 (WO2021108244A1).

[4] Y. Li and T. V. Nguyen, J. Electrochem. Soc., 169, 110509 (2022).
Low-Tortuous and Dense Electrode for High-Energy Lithium-Sulfur Batteries
Authors: Feng Shuo , Fu Yucheng , Shi Lili , Anderson Cassidy , Lu Dongping
Published: September 2023

Lithium-sulfur (Li-S) batteries feature a high theoretical capacity of 1675 mAh/g and hence is considered as a promising alternative to lithium-ion batteries. However, deployment of Li-S batteries has been hindered by the low practical energy and limited cycle life.1, 2 Reducing cathode porosity is essential to balancing the electrolyte distribution in Li-S cell, conserving more pore-filling electrolyte to extend cell cycle life.3-5 However, low-porosity electrodes built with nanosized sulfur/carbon (S/C) materials suffer from high tortuosity that significantly deteriorates electrode wetting and hence sulfur utilization. Enabling operation of high-loading sulfur electrodes under both low-porosity and lean-electrolyte conditions is still a challenge and is seldom discussed. In this study,6 we demonstrated a novel and facile strategy for constructing low-tortuosity through-pores across both vertical and planar directions of electrodes by casting large particles into single-particle-layer electrodes. Through multi-scale characterizations and simulations, correlations between material/electrode structures, electrolyte permeability, polysulfide migration, and sulfur reactions were elucidated. The high-loading and dense sulfur cathode fabricated by this method delivers a high specific capacity (>1000 mAh g-1) at a very low electrolyte/sulfur (E/S) ratio of 4 μL mg-1. This study provides a novel approach to reducing the tortuosity of dense sulfur electrodes by manipulating the porosity distribution, which would be also applicable to improving the rate capability of other high-energy electrodes. More details of the progress will be discussed at the meeting.

Reference.

Dörfler, S.; Althues, H.; Härtel, P.; Abendroth, T.; Schumm, B.; Kaskel, S., Challenges and Key Parameters of Lithium-Sulfur Batteries on Pouch Cell Level. Joule
2020,
4 (3), 539-554.

Xue, W.; Miao, L.; Qie, L.; Wang, C.; Li, S.; Wang, J.; Li, J., Gravimetric and volumetric energy densities of lithium-sulfur batteries. Current Opinion in Electrochemistry
2017,
6 (1), 92-99.

Lu, D.; Li, Q.; Liu, J.; Zheng, J.; Wang, Y.; Ferrara, S.; Xiao, J.; Zhang, J. G.; Liu, J., Enabling High-Energy-Density Cathode for Lithium-Sulfur Batteries. ACS Appl Mater Interfaces
2018,
10 (27), 23094-23102.

Kang, N.; Lin, Y.; Yang, L.; Lu, D.; Xiao, J.; Qi, Y.; Cai, M., Cathode porosity is a missing key parameter to optimize lithium-sulfur battery energy density. Nat Commun
2019,
10 (1), 4597.

Feng, S.; Liu, J.; Zhang, X.; Shi, L.; Anderson, C.; Lin, Y.; Song, M.-K.; Liu, J.; Xiao, J.; Lu, D., Rationalizing nitrogen-doped secondary carbon particles for practical lithium-sulfur batteries. Nano Energy
2022,
103.

Feng, S.; Singh, R. K.; Fu, Y.; Li, Z.; Wang, Y.; Bao, J.; Xu, Z.; Li, G.; Anderson, C.; Shi, L.; Lin, Y.; Khalifah, P. G.; Wang, W.; Liu, J.; Xiao, J.; Lu, D., Low-tortuous and dense single-particle-layer electrode for high-energy lithium-sulfur batteries. Energy & Environ. Sci.
2022.
Engineering Lung-Inspired Flow Field Geometries for Redox Flow Batteries with Stereolithography 3D Printing
Authors: Muñoz Perales Vanesa , van der Heijden Maxime , Garcia-Salaberri Pablo A. , Vera Marcos , Forner-Cuenca Antoni
Published: September 2023

Redox flow batteries are a promising electrochemical technology for low-cost, scalable and long-duration energy storage, but their energy market penetration is hampered by elevated costs1,2. One effective strategy is to increase the overall efficiency of the electrochemical stack. At the core of the electrochemical cells, the design of the flow fields—which distribute the electrolyte through the porous electrodes—determines, in combination with the electrode microstructure, the performance of the system3. To date, current designs are inspired on fuel cell technologies but have not been engineered for redox flow cells where single-phase reactive flows are sustained4.

In this work, we tailor lung-inspired flow field geometries for carbon paper electrodes using stereolithography 3D printing5,6. We propose two new lung-inspired geometries—with two and three channel levels—and compare them to a baseline interdigitated flow field. A two-step process based on stereolithography 3D printing followed by the application of a conductive coating is used to manufacture these complex flow field geometries. We employ a suite of electrochemical (i.e., polarization and electrochemical impedance spectroscopy) and fluid dynamic (pressure drop measurement) techniques together with numerical modelling to elucidate flow architecture-performance relationships. We find that lung-inspired structural patterns homogenize the electrolyte distribution into the electrode, accessing a larger electrode reaction area. These fractal geometries can outperform traditional interdigitated flow fields, providing a more favourable balance between low pressure drop and high electrochemical performance (Figure 1). In this talk, I aim to leverage lung-inspired flow field geometries as a promising prospect for engineering advanced flow cell architectures for emerging electrochemical devices.

References

1 E. Sánchez-Díez, J. Power Sources, 2021, 23.

2 L. F. Arenas, C. Ponce de León and F. C. Walsh, J. Energy Storage, 2017, 11, 119–153.

3 R. M. Darling and M. L. Perry, J. Electrochem. Soc., 2014, 161, A1381–A1387.

4 C. R. Dennison, E. Agar, B. Akuzum and E. C. Kumbur, J. Electrochem. Soc., 2016, 163, A5163–A5169.

5 J. Marschewski, L. Brenner, N. Ebejer, P. Ruch, B. Michel and D. Poulikakos, Energy Env. Sci, 2017, 10, 780–787.

6 M. P. Browne, E. Redondo and M. Pumera, Chem.
Rev., 2020, 120, 2783–2810.

Figure 1
A Strategy for Enhancing the Durability of Both Anode and Cathode Under Fuel Starvation Cycles
Authors: Ahn Chi-Yeong , Park SungBin , Lee SoYeon , Shim Hyungwon , Sung Yung-Eun
Published: September 2023

A polymer electrolyte fuel cell (PEFC) system is one of the power sources of mobility such as automobiles, ships, and railroads that are in the spotlight. Since PEFC can operate at low temperatures, one of its strengths is its fast response speed to the rapidly changing output of mobilities. However, various degadation conditions of the PEFC may be formed in various operating conditions of these mobilities. In particular, several studies have been conducted on the reverse voltage phenomenon of PEFC due to hydrogen starvation, and the introduction of reversal tolerant anode (RTA) has sought to improve durability under reverse voltage conditions. However, during the reverse voltage cycle, cathode degradation was also observed, and we sought to find the cause. Therefore, in this conference, we would like to identify the cause of the aforementioned phenomenon and present a strategy to improve the durability of the cathode.