bluuebunny/crossref_metadata_2025 huggingface dataset:
Fourteen-Membered Macrocyclic Fe Complexes for Oxygen Reduction Catalysis
Authors: Nabae Yuta , Moriya Makoto , Takahama Ryo , Kamoi Kazuki , Ohyama Junya , Kawashima Shin , Kojima Ryoichi , Okada Mariko , Hayakawa Teruaki
Published: December 2020

For the broad application of polymer electrolyte fuel cells (PEFCs), the development of nonprecious-metal (NPM) catalysts for oxygen reduction is extremely important. To date, many NPM catalysts have been synthesized by pyrolyzing Fe-, N-, and C-containing precursors; however, they suffer from low density and uncertain chemical structure of their active sites. To date, pyrolyzed Fe/N/C catalysts have been regarded as more active than typical macrocyclic MN4 complexes such as Fe porphyrin. The exact reason for this difference in catalytic activity has remained obscure because of the indistinct chemical structure of the active sites on the pyrolyzed catalyst. However, the recent significant progress in the direct microscopic observation of atomically dispersed Fe sites has prompted researchers to embed FeN4 sites in graphene sheets. Interestingly, these Fe centers are considered to be surrounded by a 14-membered ring consisting of C and N atoms, unlike the case of typical macrocyclic MN4 complexes that have 16-membered rings (e.g., porphyrin and phthalocyanine). This has inspired our research group to focus on the ORR catalytic activity of 14-membered macrocyclic Fe complexes. This study reports a novel 14-membered macrocyclic Fe complex. This 14-membered macrocycle possesses strong Fe–N bonds with an average bond distance of 1.90 Å, as evidenced by single-crystal X-ray diffraction (XRD), which are markedly shorter than those in porphyrin (2.0 Å). This complex demonstrates high electrocatalytic activity for oxygen reduction in both acidic and basic media.

Figure 1
Electrosynthesis of H2O2 over Cobalt-N-Doped Ordered Mesoporous Carbon Materials (Co-N-OMC)
Authors: Rawah Basil , Li Wenzhen
Published: December 2020

Electrochemical generation of hydrogen peroxide (H2O2) via two-electron oxygen reduction is a promising alternative to the conventional industrial anthraquinone process. The current challenges include discovering a sample and cost-effective electrocatalysts with high activity, selectivity, and stability. Herein, we reported a straightforward preparation of cobalt-N-doped ordered mesoporous carbon (Co-N-OMC) using dry-state low energy ball milling, followed by controlled pyrolysis. This fast, solvent-free, and scalable method used inexpensive materials containing cobalt acetate as the metal precursor, mesoporous SiO2 (KIT6) with a high surface area as the template for controlling the mesoporous structure; and imidazole as carbon and nitrogen sources, allowing simultaneous carbon matrix formation and nitrogen incorporation. Moreover, the Co-N-OMC electrocatalytic performance was compared with various materials, including N-OMC, Co-OMC, OMC, and non-mesoporous carbon, to separately examine each component's role, embedded Co, N dopant, and mesoporous morphology on the catalyst behavior. The optimal Co-N-OMC catalyst displayed an excellent electrocatalytic activity with H2O2 selectivity above 95% in an acid medium at very positive potentials. Furthermore, batch H2O2 electrolysis measurements confirmed the high H2O2 faradaic selectivity over 90% and H2O2 production of 555 mmol g-1 for a 60 min test. Finally, laboratory-scale H2O2 production was demonstrated in a flow electrolytic reactor with a Co−N−OMC cathode layer. The H2O2 electrolysis in flow cell configuration exhibitedabout a five-time-increase in H2O2 production ~ 2900 mmol g-1 for 60 min test with H2O2 faradaic selectivity above 90%. Such a considerable improvement in H2O2 production and selectivity is probably due to cobalt particles' coexistence with nitrogen dopants supported on a mesoporous structure. The optimal loading of cobalt might facilitate the two-electron pathway towards H2O2 generation.In addition, nitrogen dopants and the mesoporous structure may have lowered the ORR overpotential and improved mass transport in the catalyst layer, respectively.
Shape Effect of Zinc Nanostructures on Electrochemical CO2 Reduction
Authors: Xiao Jing , Gao Minrui , Luo Jing-Li
Published: December 2020

To mitigate CO2 emissions and enable the conversion of CO2 to carbon-neutral fuels, the research on electrochemical reduction of CO2 (CO2RR) is gaining momentum. As an earth-abundant material, Zn is a promising electrocatalyst for highly active and selective reduction for the reduction of CO2 to CO. However, the shape effect of the Zn-based electrocatalysts on CO2RR has not been well understood. Herein, we synthesized hexagonal Zn nanoplates and systematically explored its shape-dependent catalytic activity for CO2RR, so as to achieve a better understanding of the relationship between the morphology and the catalytic activity of non-noble metal catalysts. Compared with the similarly-sized Zn nanoparticles, the H-Zn-NPs exhibit remarkably enhanced current density, together with an improved CO Faradaic efficiency of over 85% in a wide potential window. Theoretical results reveal that the unique hexagonal Zn nanostructure offers an increased number of catalytically active sites which are active for CO2RR to CO.
Droplet Based Microfluidic Electrochemical Detection of Uric Acid, Ascorbic Acid and Dopamine
Authors: Sangam Srikanth , Jaligam Murali Mohan , Javed Arshad , Dubey Satish Kumar , Goel Sanket
Published: December 2020

Droplet based microfluidic devices offer numerous advantages, such as lesser sample volume, rapid analysis rate, and lower contamination issues. Moreover, out of several detection methods in microfluidic devices, electrochemical based sensing is superior owing to the well-established attributes such as specificity, lower limit of detection, rapid detection and the process possibility in a microfluidic environment. Although electrochemical sensing has been widely harnessed with continuous flow-based microfluidic devices, opportunities are still lying with droplet based microfluidic devices. Hence, the aforementioned unique features of Droplet based microfluidic devices are still untapped. The fusion of electrochemical detection with droplet based microfluidic devices is one way to realize smart Lab on chip devices. Performing electrochemical detections in specially designed and fabricated droplet-based microfluidic devices, with microchannels including electrodes, enable to conduct biochemical assays in a high throughput manner. In this work, a three-electrode system is printed on a glass substrate with conductive carbon paste using inkjet printing technology. One of the electrodes is modified with silver paste to use as a reference electrode. A microfluidic channel is fabricated using low-cost and clean-room free direct laser writing technology; and soft lithography technique is used for preparing PDMS mould. The mould is then bonded to a glass substrate with microelectrodes with a width of 300 µm and uniform spacing of 300 µm using plasma activation. Monodisperse and equidistant droplets are generated in the microfluidic device using oil as the continuous phase and analyte as the dispersed phase. The efficacy of the microfluidic device for electrochemical detection was measured using Cyclic Voltammetry technique for analytes such as Uric acid, Ascorbic acid and Dopamine. Flow rates of the dispersed phase are varied from 25 µl/min to 100 µl/min while maintaining the constant continuous phase to attain droplets of different sizes. The effect of droplet size carrying the analyte on electrochemical detection was investigated. The influence of varied scan rates (20 mV/sec to 100 mV/sec) on the detection of analytes was also studied. The selection of an appropriate scan rate for different flow rates was investigated and was set accordingly to the droplet generation frequency. In addition, the change in cyclic voltammetry with the response to the variation of concentration of the analyte was also explored. The steps of the proposed process are illustrated in Figure 1.

Figure 1
Development of a Novel Evaluation System of Tip Growth for Antifungal Compounds with the Use of Candida Albicans
Authors: Koyama Naho , Iida Yasuhiro
Published: December 2020

Mycosis is an infection to human caused by fungi, such as mold and yeast. Among mycosis, deep mycosis which infects organs and tissues, has become a particularly serious problem. To treat those deep mycosis, chemotherapy with antifungal agents is used. However, the types of antifungals are few and the treatment options are limited. Since fungi and humans have similar cell structures, existing antifungal agents have also been reported to have side effects on humans. Furthermore, the emergence of resistant fungi has become a problem due to the long-term use of the drug.

From those problems, development of an antifungal agent having a new mechanism of action is required.

Therefore, our laboratory focused on tip growth, a growth method specific to fungi. Tip growth elongates the cell by repeating the decomposition and synthesis of the cell wall (β-1,3-D-Glucan). It has been reported that the cell wall-degrading enzyme β-1,3-D-Glucanase (BGL2) involved in this tip growth is vesicular transported from the inside of the cell to the growth point. We consider that targeting vesicle transport during tip growth will provide selective toxicity to fungi. The purpose of this study is to develop novel antifungal agents targeting vesicle transport during fungal tip growth. An evaluation system for visualizing vesicle transport was constructed by fusing green fluorescent protein GFP downstream of BGL2 to be transported to the growth point by expression of the protein in Saccharomyces cerevisiae (the results of the localization were shown in Fig.1).

Using this evaluation system, vesicle transport inhibitory activity was screened for 100 kind herbal medicine extract. As a result, vesicle transport inhibitory activity was observed in 8 types.

In addition, we attempted to construct a similar evaluation system using Candida albicans and aimed to evaluate fungi that form hyphae that cause actual mycosis.

Fig.1 Confocal laser scanning microscope image of an evaluation system for antifungal compounds using S. cerevisiae.

(a) Localization of BGL2-EmGFP to growth point.

(b) Localization of BGL2-EmGFP to the division site.

(C) Intracellular distribution of BGL2-EmGFP treated with vesicle transport inhibitor.

Figure 1
Selective Oxygen Reduction to Hydrogen Peroxide on Transition Metal Single Atom Coordination
Authors: Jiang Kun
Published: December 2020

Molecular O2 can be electrochemically reduced to H2O via a 4e– pathway, or H2O2 with 2e– transferred in aqueous solutions. The former pathway is preferred in fuel cell applications to maximize the energy conversion efficiencies, and the latter one represents a green synthetic method for H2O2.

Here, through a flexible control of ORR pathways on different transition metal single atom coordination in carbon nanotube (CNT) support (M-CNT, M = Fe, Pd, Co, and Mn), we discovered Fe-CNT as the state-of-the-art H2O2 generation catalyst, with an early onset of 0.822 V versus reversible hydrogen electrode in 0.1 M KOH to deliver a 0.1 mA cm-2 H2O2 current, and a high H2O2 selectivity of above 95% in both alkaline and neutral pH. A wide range tuning of 2e–/4e– ORR pathways was achieved via different transition metal centers or neighboring metalloid coordination. By the synergistic investigation of operando spectroelectrochemistry and density functional theory calculations, Fe-C-O motifs, in a sharp contrast to the well-known Fe-C-N for 4e– ORR, are identified to be responsible for the selective H2O2 pathway. This high-performance iron single atom catalyst demonstrated an effective water disinfection as a representative application of electrochemical synthesis of H2O2.
Magnetic Chemistry and Its Possible Applications in Analytical Spectroscopy and Related Fields
Authors: Burns Matthew
Published: December 2020

Developments in chemistry have stemmed from applying principles from other fields that develops into a field itself. Magnetism applied to chemistry - Magnetic chemistry is one of them. Taking electrochemistry that uses an electric field/current inducing a reaction that doesn’t occur in natural conditions; magnetic chemistry uses a magnetic field inducing conditions and possibly reactions.

Three areas are discussed; principles involved, results from using a magnetic field on hydrocarbon fuels, and possible implements in analytical spectroscopy. Starting on how Faraday’s Induction Law is used in altering compound properties. Then, discussing paramagnetism/diamagnetism of atoms/compounds emphasizing diamagnetic compounds, then on intermolecular forces emphasizing on cohesive forces and pseudo structures formed (“clustering”) then discussing quantum principles - emphasizing electron coupling interactions focusing on angular momenta, spin-orbit interaction, and Zeeman Effect.

Then, showing results of how applying a magnetic field alters hydrocarbon fuels properties. Explaining how it reduces the “clustering” of molecules, surface tension, viscosity, pollution and increasing volatility and efficiency. Then explaining how an applied field affects the molecules emphasizing on how increasing field strength increases affects and mentioning on how it actually enhances infrared and UV-Vis spectra.

Then discussing how the results can be applied to analytical spectroscopy. The increased volatility can improve atomization/nebulization for ICP and GC, thus more target compounds analyzed with less waste reducing need for derivatizing agents. Spectra enhancement for spectra signals that are very weak in infrared and UV-Vis spectroscopy. Reducing mobile phase surface tension/viscosity thus conditions (flow rate, etc.) better adjusted for HPLC. Then showing how a NMR field can be used to do this.

Concluding, magnetic chemistry can be utilized to change properties/conditions of compounds and possibly induce reactions. By discussing underlying principles involved; Induction Law, paramagnetism, diamagnetism, intermolecular forces, and quantum principles, explaining how it occurs and results on applying a magnetic field to hydrocarbon fuels which has possible uses in analytical spectroscopy.
Degradation Processes in Pt Single Atom and Pt Nanoparticulated Electroatalysts
Authors: Speck Florian Dominik , Paul Michael T. Y. , Mayrhofer Karl J. J. , Zepeda Francisco Ruiz , Gatalo Matija , Hodnik Nejc , Choi Changhyuck , Cherevko Serhiy
Published: December 2020

Single atom catalysts (SACs) have quickly emerged as a new class of catalytic materials. When confronted with classical carbon supported nanoparticulated (NP) catalysts (Pt/C), SACs are often claimed to have superior electrocatalytic properties, e.g. stability. SACs possess the highest possible mass specific activity as compared to conventional NP catalysts. Therefore, the use of SACs is especially attractive for applications where noble metal catalysts are required. The enhanced mass activity can aid in reducing the metal loading, and thus the cost of these systems. On the other hand, however, decrease in noble metals loading may lead to stability issues, which are relatively unexplored till now.

In this study, the stability of high sulphur containing carbon supported Pt SACs is investigated using different accelerated stress protocols (ASTs). The amount of dissolved Pt and S is directly measured with on-line inductively coupled plasma mass spectrometry (on-line ICPMS). The morphological, compositional and chemical changes of the catalyst is also monitored by identical location transmission electron microscopy (IL-TEM) and X-ray photoelectron and absorption spectroscopies (XPS and XAS) before and after the ASTs. For the sake of comparison, traditional NP Pt/C catalyst is studied too. The results indicate that the main degradation processes in SACs and nanoparticulated Pt/C are different. For SACs, dissolution of S is identified as the main cause of degradation. It is concluded that, in case catalysts with improved anodic stability are desired, more robust ligands must be used.
Utilizing Hydrogen Underpotential Deposition for Carbon Monoxide Reduction to Formaldehyde
Authors: Yao Libo , Pan Yanbo , Shen Xiaochen , Wu Dezhen , Bentalib Abdulaziz , Peng Zhenmeng
Published: December 2020

Formaldehyde is an essential building block for hundreds of chemicals and a promising liquid organic hydrogen carrier (LOHC), yet its indirect energy-intensive synthesis process prohibits it from playing more significant role. Here we report a direct CO reduction to formaldehyde (CORTF) process that hybridizes thermal and electro-catalysis and utilizes hydrogen underpotential deposition property to overcome thermodynamic barrier and scaling relationship restriction. Using molybdenum phosphide as catalyst, formaldehyde can be produced with nearly 100% Faradaic efficiency in aqueous KOH solution, with its formation rate being one order of magnitude higher compared with state-of-the-art thermal catalysis approach. Simultaneous tuning of current density and reaction temperature leads to more selective and productive formaldehyde synthesis, confirming the effectiveness of “hybrid” approach. DFT calculations reveal that desorption of *H2CO intermediate likely serves as rate-limiting step, and the participation of H2O turns the reaction into thermodynamically favorable. Furthermore, a full-cell reaction set-up was demonstrated with CO hydrogenation to HCHO being achieved without any energy input, which shows the spontaneous potential of the reaction. Our study shows the advantage of hybridizing thermal and electro-catalysis in realizing thermodynamics and scaling relation confined reaction, which could serve as a new strategy in future reaction design.
Various Effects of Alkali Metal Ions on H2O2 Reduction Reactions at Pt Electrodes
Authors: Mukouyama Yoshiharu , Okada Haruki
Published: December 2020

The hydrogen peroxide reduction reaction (HPRR) has attracted much attention because it is involved in the oxygen reduction reaction which is an important cathode reaction in several fuel cell systems. Pt has an excellent electrocatalytic activity toward the HPRR. Thus, the HPRR at Pt electrodes has been widely studied including effects of electrolyte components and additives on it.

Katsounaros and Mayrhofer have reported that alkali metal cations such as Li+, Na+, and K+ inhibit the HPRR in basic media [1]. The hydrated alkali metal cations and chemisorbed OH species on Pt, denoted as M+(H2O)
x
and OHads respectively, non-covalently stabilize each other, leading to the formation of quasi-specifically adsorbed hydrated metal ion clusters that blocks electrochemical reactions. The inhibition becomes stronger as the strength of the non-covalent interaction increases (K+ < Na+ < Li+), and consequently the rest potential decreases in this order, as reproduced in Figure 1a.

We have recently found that the HPRR in strongly acidic media is also affected by the alkali metal ions. As shown in Figure 1b, the HPRR is inhibited at U < 0.7 V in the presence of the ions. This indicates that the alkali metal ions inhibit the transport of electroactive species, namely, H+ and H2O2, toward the electrode surface. The HPRR current becomes smaller (in absolute value) in the following order: Li+ < Na+ < K+, that is, the inhibition becomes stronger in the reverse order of the strength of the non-covalent interaction. In this work, to explain this inhibition, we study the HPRR by electrochemical impedance method.

Interestingly, the metal ions induce a significance increase in the local pH at the electrode surface (pHs) during the HPRR when the concentration of H2O2 is relatively high, that is, when the HPRR consumes a large amount of H+ [2]. For instance, the pHs becomes strongly basic when 0.01 M H2SO4 + 0.05 M H2O2 + 0.05 M M2SO4 (where M stands for Li, Na, and K) is used as the electrolyte solution. We thus think that the non-covalent interaction can be induced during the HPRR even in the acidic media. Note that the pHs remains acidic in the case of Figure 1b because of the lower concentration of H2O2. In this work, we summarize the above-mentioned effects of the alkali metal ions on the HPRR.

REFERENCES

[1] I. Katsounaros and K. J. J. Mayrhofer, Chem. Commun., 48, 6660-6662 (2012).

[2] Y. Mukouyama, H. Kawasaki, D. Hara, Y. Yamada, S. Nakanishi, J. Electrochem. Soc.,
164 (2017) H675.

FIGURE CAPTION

Figure 1. The current (I) – potential (E) curves for a Pt-plate electrode in basic and acidic solutions measured under potential controlled conditions at a scan rate of 0.01 Vs-1. The basic solutions are 0.05 M alkali hydroxide (denoted as MOH) + 0.01 M H2O2, and the acidic ones are 0.05 M H2SO4 + 0.01 M H2O2 with or without 0.05 M alkali sulfate (denoted as M2SO4).

Figure 1
Accelerated Modeling of Lithium Diffusion in Solid State Electrolytes Using Artificial Neural Networks
Authors: Kumar Rao Karun , Yao Yan , Grabow Lars Christian
Published: December 2020

There is great interest in solid state lithium electrolytes to replace the flammable organic electrolyte for an all solid state battery. Previous efforts trying to understand the structure-function relationships resulting in high ionic conductivity materials have mainly relied on ab initio molecular dynamics. Such simulations, however, are computationally demanding and cannot be reasonably applied to large systems containing more than a few hundred atoms. Herein, we investigate using artificial neural networks (ANN) to accelerate the calculation of high accuracy atomic forces and energies used during molecular dynamics (MD) simulations (Figure 1A), to eliminate the need for costly ab initio force and energy evaluation methods, such as density functional theory (DFT). After carefully training a robust ANN for four and five element systems, we obtain nearly identical lithium ion diffusivities for Li10GeP2S12 (LGPS) when benchmarking the ANN-MD results with DFT-MD. We find that the ANN generated potentials scale linearly with atomic system size, compared to cubically in DFT (Figure 1B). To demonstrate the power of the outlined ANN-MD approach we apply it to a doped LGPS system to calculate the effect of concentrations of chlorine on the lithium diffusivity at a resolution that would be unrealistic to model with DFT-MD. We find that there is an optimal chlorine doping concentration which is a result of competing electronic effects of the effective dielectric constant and effective ionic radius of chlorine. Such effects could not be adequately studied with classical potentials. We find that ANN-MD simulations can provide the framework to study systems that require a large number of atoms more efficiently while maintaining high accuracy.

Figure 1
(Invited) Imaging Li Metal Transformations Garnet Solid Electrolyte Interfaces with Machine Learning
Authors: Hatzell Kelsey , Dixit Marm , Zaman Wahid , Mukherjee Partha P. , Verma Ankit , Kenesei Peter , Park Jun Sang , Almer Jon
Published: December 2020

Reversible lithium metal anodes that can achieve high rate capabilities are necessary for next generation energy storage systems. Recently, there has been renewed interest in using solid electrolyte separators with lithium metal anodes. Solid electrolyte can act as a barrier for unwanted physical and chemical decomposition that lead to unstable electrodeposition (e.g. dendrite and filament growth). However, numerous experimental investigations have revealed that the strength of the separator cannot mitigate unstable electrodeposition and electrically shorting. Instead, the formation and growth of filaments is tied to unique chemo-mechanical properties that exists at buried solid|solid interfaces. Herein, in situ tomography of Li|LLZO|Li cells is carried out to track morphological transformations in Li metal electrodes and buried solid|solid interfaces during stripping and plating processes. Optimized experimental parameters enable high resolution, high contrast reconstructions that enable lithium metal visualization. Quantitative analysis tools (machine learning, image processing) are developed that enable quantification of physical descriptors of lithium metal (spatial current density, porosity, spatial distribution of pores) during cycling. Hotspots in lithium metal are correlated with microstructural anisotropy in the solid electrolyte. Modeling studies show large heterogeneity in transport and mechanical properties of electrolyte at the electrode|electrolyte interfaces. Local domains showing lower effective properties (transport and mechanical) are identified to be regions where failure modes can initiate due to non-uniform stress and flux distributions.
Operando Gassing Studies of All-Solid-State Battery Cells
Authors: Teo Jun Hao , Strauss Florian , Janek Jürgen , Brezesinski Torsten
Published: December 2020

All-solid-state batteries (SSBs) are considered as next-generation energy storage technology with the possibility of higher energy and power densities as well as safety compared to conventional lithium-ion batteries [1]. SSBs with sulfidic solid electrolytes (SEs) as a component are thought to be the closest towards practical implementation [2] despite widely reported side reactions at the cathode active material (CAM)/SE interface. Advances in coating technology have helped suppress these detrimental reactions to a certain extent [3]. We demonstrate the use of differential electrochemical mass spectrometry (DEMS) on evaluating the stability of a protective surface coating [4]. Analysis of the gas evolved provides insights into possible reaction mechanisms at the CAM/SE interface. DEMS was also used to investigate the practical safety performance of sulfide-based SSBs with respect to possible harmful gas evolution such as H2S and SO2 [5].

Key Words: All-solid-state battery, differential electrochemical mass spectrometry, electrochemical energy storage

References

Janek, W. Zeier, Nat. Energy, 1 (2016) 16141.

J. Nam, D. Y. Oh, S. H. Jung, Y. S. Jung, J. Power Sources, 375 (2018) 93–101.

-Y. Kim, F. Strauss, T. Bartsch, J. H. Teo, T. Hatsukade, A. Mazilkin, J. Janek, P. Hartmann, T. Brezesinski, Chem. Mater., 31 (2019) 9664 – 9672.

Bartsch, F. Strauss, T. Hatsukade, A. Schiele, A-Y. Kim, P. Hartmann, J. Janek, T. Brezesinski, ACS Energy Lett., 3 (2018) 2539–2543.

Strauss, J. H. Teo, A. Schiele, T. Bartsch, T. Hatsukade, P. Hartmann, J. Janek, T. Brezesinski, ACS Appl. Mater. Interfaces, 12 (2020), 20462–20468.
(Invited) All-Solid-State Batteries Using Li7La3Zr2O12 Garnet Electrolyte Framework
Authors: Doeff Marca M , Yi Eongyu
Published: December 2020

All-solid-state batteries (ASSB) using LLZO (variants of Li7La3Zr2O12) garnet solid electrolyte with lithium metal anode potentially offer higher energy density and improved safety. Rational design of cell architecture as well as manufacturing scalability are key aspects to consider as the technology readiness level advances. A thick composite cathode layer attached to a thin solid electrolyte layer is desirable to obtain superior energy densities. Furthermore, the architecture within the composite cathode may be engineered to contain directional conduction paths of lithium ions or electrons for enhanced rate capabilities.

Here, we demonstrate a functioning bulk-type LLZO based all-solid-state battery with a practical form factor incorporating the above described design concepts. Freeze-tape-casting (FTC), a scalable and environmentally friendly ceramic processing method, is used to construct 3D porous LLZO scaffolds composed of vertical arrays of LLZO walls. The thin solid-electrolyte layer is fabricated by tape-casting (TC). By sintering the stacks of FTC and TC green tapes, porous/dense bilayers and porous/dense/porous trilayers of LLZO frameworks are obtained. An ASSB was constructed using a porous/dense bilayer by infiltrating LiNi0.6Mn0.2Co0.2O2 cathode powder and carbon black into the porous layer and adhering lithium metal foil to the dense side. We find it crucial to introduce a plastic crystal based soft solid electrolyte to the porous layer to electrochemically connect all cathode components, obviating the need for co-sintering to establish contact. The soft nature of the plastic crystal based solid-electrolyte may be able to accommodate the volume change of the cathode material as it cycles. In this device, which contained no liquid component, the initial discharge capacities were similar to those observed in a lithium ion battery configuration using the same cathode powder at C/10 rates.
Welcome Remarks - L01: Fundamentals and Applications of Physical and Analytical Electrochemistry, Electrocatalysis, and Photoelectrochemistry
Authors: Suroviec Alice
Published: December 2020

Welcome to L01: Fundamentals and Applications of Physical and Analytical Electrochemistry, Electrocatalysis, and Photoelectrochemistry! Take a moment to listen to welcome remarks from the lead organizer, Alice Suroviec.
Effect of Excess Na Contents in Precursor on the Property of Na2Zn2TeO6 Ceramic Solid Electrolyte
Authors: Inada Ryoji , Itaya Akihiro , Sakurai Yoji
Published: December 2020

P2-type layered sodium (Na) ion conducting oxide Na2M2TeO6 (M = Mg, Zn, etc.) have attracted much attention for the application to all-solid-state Na-based batteries with high safety and lower cost, because of the high ionic conductivity above 10-4 S/cm at room temperature range and excellent chemical and electrochemical stability [1, 2]. Generally, Na in precursor materials is easy to volatilize in high temperature processing, so that the excess Na in precursors must be added to compensate the Na loss and suppress the composition shift in final products and undesired secondary phase formation. In this work, we investigated the effect of excess Na contents in precursor on the property of Na2Zn2TeO6 (NZTO) solid electrolyte synthesized via a conventional solid state reaction method.

Na2CO3, ZnO and Te2O3 were used as precursor materials and the excess Na contents were adjusted to 3, 7 and 10% over the stoichiometric composition. They were pulverized and mixed for 3 hours by planetary ball milling and then calcined at 850ºC for 6 hours in air using a SiC crucible. Calcined powders were ground again and then pelletized by cold isostatic pressing at 300 MPa. Finally, the pellets with different excess Na contents were sintered at 850ºC for 12 hours in air using a SiC crucible.

From XRD analysis, P2-type layered NZTO phase were mainly confirmed in all sintered samples, but only the sample with 3% excess Na in precursor contained small amount of secondary phases, which is attributed to the Na volatilization during high temperature processing. From SEM observation, it was confirmed that all sintered samples have porous structures. The relative densities were in the range from 80 to 83% and nearly independent of the excess Na contents.

Au film was formed on both the end surfaces of each sintered NZTO sample as an ion-blocking electrode and electrochemical impedance was measured at 27-202ºC to investigate the ionic conducting property. As results, the ionic conductivity of NZTO samples strongly depends on the excess Na contents in precursor. The sample with 3% excess Na showed the lowest total (grain + grain boudary) conductivity of 0.5 x 10-4 S/cm at room temperature, while the conductivity for the samples with 7 and 10% excess Na was well above 10-4 S/cm. In our experiment, 7% excess Na in precursor is the best and the highest total conductivity of 3.8 x 10-4 S/cm at room temperature and low activation energy of 0.27 eV were obtained. Since the relative density of our NZTO samples are not so high and the contribution of grain-boudary resistance is large at present, the total conductivity could be improved further by densification via optimizing sintering processing.

This work was partly supported by Iketani Science and Technology Foundation.

[1] Y. Li, et al., Chem. Eur. J. 24, 1057-1061 (2018).

[2] Y. Li, et al., ACS Appl. Mater. Interfaces 10, 15760−15766 (2018).

Figure 1
Noble Metal “Shell” Formation on the Surface of Acoustically-Levitated Solvent Droplets
Authors: Abbuhl Kyla , McCardle Harley , Davis James H. , Duranty Edward R.
Published: December 2020

In the past few years, more and more attention has been focused on processes occurring in small volumes such as microdroplets and thin films due to the increases in reaction rates and other phenomena recently reported in the literature. Our group has primarily investigated the thermodynamics of physical and chemical changes taking place in acoustically-levitated droplets ranging in volume from five to 10 microliters in size. Levitating a droplet using a standing acoustic wave allows for convenient study of reactions occurring within the droplet or any process reliant on the droplet’s surface using visualization techniques such as microphotography and infrared imaging. We have used this technique in the past to study the evaporation process of levitated solvent droplets, including those of ionic liquids, as well as the neutralization thermodynamics of strong acids and bases within a levitated droplet.

In this work we present the initial characterization of droplet “shells” formed on the surface of levitated solvent droplets which contain a noble metal salt and a small piece of transition metal wire. In these experiments silver nitrate or a gold (III) salt was dissolved in a levitated solvent droplet (either in deionized water, silver bis(trifluoromethanesulfonyl)imide ionic liquid, or a DMF/water solution) after which a small (~0.5cm) section of zinc or copper wire was dropped into the levitated drop. The resulting reduction of the noble metal salt to the noble metal solid was observed for each solvent/noble/transition metal combination using a DSLR camera equipped with a close-up lens. In many cases a dark precipitate formed on the surface of the wire, indicating the formation of metal solid much in the same fashion as the silver “tree” general chemistry experiment. However, in the case of the silver nitrate/DI water/copper and gold(III)/DI water/zinc combinations, a metallic solid ( shiny, silver-colored for silver nitrate and black for gold(III)) formed a shell at the droplet/air interface. More study of the shell structures is planned including examination using SEM. While specific applications of these structures is not immediately clear, we envision they may be of interest as high surface area catalysts.

Figure 1
Radiation-Driven Chemistry in Molten Salts
Authors: Wishart James F. , Iwamatsu Kazuhiro , Layne Bobby H.
Published: December 2020

A variety of molten salts are proposed as liquid fuels or coolants in a new fleet of molten salt nuclear reactors that would have operational and safety advantages over present reactor systems. The molten salt will be exposed to high radiation levels under these conditions, therefore understanding the chemical effects of radiolysis on the molten salt fuel or coolant is essential to reliable, efficient and sustainable reactor operation. This understanding begins with identifying the primary salt radiolysis products and characterizing their reactivities, in pure salt and also under conditions that represent loading with fuel (actinides), fission products and corrosion products. These reactions form subsequent products that determine the chemical evolution of the molten salt fuel over the duration of its lifetime in the reactor. To obtain predictive insight into this radiation-driven chemical evolution, we investigate these reactions by performing pulse radiolysis transient absorption spectroscopy at the BNL Laser-Electron Accelerator Facility using a high-temperature sample configuration. Examples will be given of how the composition of the molten salt determines the identities and reactivities of the primary radiolysis products, and we will follow their reactions with metal ions that are representative of the reactor fuel environment. This work was supported as part of the Molten Salts in Extreme Environments Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science.

Figure 1
Corrosion of Ceramic and Carbon-Based Materials in FLiNaK
Authors: Polovov Ilya B. , Abramov Aleksandr , Alimgulov Ruslan , Zolotarev Daniil A. , Gibadullina Alfiya F. , Trubcheninova Anastasiya I. , Volkovich Vladimir A. , Khotinov Vladislav A. , Zhilyakov Arkadiy Yu. , Belikov Sergey V.
Published: December 2020

Molten salt nuclear fast nuclear reactor (MSNFR) is one of the prospective design in frame of Generation IV concept. This technology is also required for reprocessing of spent nuclear fuel (SNF) in molten salts to extract valuable components. Recycling SNF consists of extraction uranium and plutonium with the disposal of minor actinides and fission products. These stages need the materials that retain their corrosion and mechanical properties for long time under the influence of high temperatures, radiation fields and contact with molten salts. Various steels and alloys were widely studied to assess their use under such extreme conditions. Alternative materials include ceramics, composite and carbon materials, which have high corrosion resistance in various media and can be used up to 1000 °C.

In the present work the corrosion and mechanical properties of nitride ceramics (Si3N4 and BN) and carbon-based materials (carbon-carbon composite material (C/C) and high-density carbon) were studied in a molten mixture of lithium, sodium, and potassium fluorides (FLiNaK) in the temperature range of 550–750 °C under inert atmosphere. Corrosion tests were performed under static conditions, and the duration of each test was 100 h to enable the comparison of the experimental data.

It was found that carbon-containing materials (C/C and high-density carbon) showed high corrosion resistance in the melt. C/C samples had lower corrosion rates (less than 0,1 mm/year in the entire temperature range), while the high-density carbon showed better mechanical properties. The main disadvantage of these materials is their impregnation by molten salt due to relative high porosity. However, C/C composite and high-density carbon are promising structural materials for salt media based on FLiNaK in the selected temperature range.

Tested nitride ceramics (BN, Si4N3) demonstrated relatively low corrosion resistance in fluoride systems compare to carbon-containing and metallic materials. The corrosion rates of these materials in FLiNaK exceeded the value of 1 mm/year. The plastic properties of nitride ceramics were also poor. Possible application of such materials for MSNFR and SNF reprocessing is under further investigation.
A Method of Producing Al–REE Master Alloys Using Exchange Reduction Reaction
Authors: Maksimtsev Konstantin V. , Mukhamadeev Andrey S. , Fofanov Grigoriy L. , Rebrin Oleg I. , Polovov Ilya B.
Published: December 2020

Modern aerospace engineering relies on Al-based alloys with enhanced high-temperature strength properties and oxidation resistance. These requirements can be fulfilled by modifying alloys’ structure employing rare earths metal doping. Direct addition of metallic rare earths to aluminium is complicated due to high chemical activity of molten rare-earth metals and significant vapor pressure of aluminium at elevated temperatures. To overcome these drawbacks, lanthanide-containing master alloys with relatively low REE content can be employed instead of pure scandium.

Currently there are three methods for preparing aluminium-based alloys containing rare earths, i.e. direct fusing, molten salt electrolysis and exchange or metallothermic reduction reactions. In the last case, Al–Gd and Al–Sc master alloy can be prepared by aluminothermic reduction of GdF3 or ScF3 in a molten binary NaF–KCl salt mixture at 800–1050 °С.

In the present work we suggest the modification of the above mentioned method for aluminium–cerium and aluminium–neodymium master alloy production with a lanthanide concentration of 1 to 7 wt. %. Based on thermodynamic calculations we proposed that the high-temperature exchange reaction between metallic aluminum and corresponding fluoride containing salt electrolyte should be carried out at temperatures from 740 to 780 ° C to provide the higher recovery of REE. The influence of the time of the exchange reaction and «aluminium–salt» ratio on the process to obtain ligatures of various compositions is analyzed. The yield higher than 85 % is achieved.

The microstructure of the alloys represents a metal matrix of aluminum in which intermetallic compounds of Ln3Al11 compositions are distributed In the case of an exchange reaction between aluminum and cerium fluoride, the formation of a new phase, presumably related to the Al4Ce intermetallic compound, is found.
Enhancing the Specific Heat Capacity of Molten Salts for Heat Transfer Applications Using Nanoparticles
Authors: Maltsev Dmitry , Halstenberg Philip , Dai Sheng
Published: December 2020

Molten salts have physical properties that include thermal stability over a large temperature range, low vapor pressure at high temperature, and are nearly immune to radiological effects. Due to these favorable properties, molten salts are being considered as a promising candidate for next generation heat transfer fluids for use in generation IV nuclear reactors. One drawback of molten chloride salts thermo-physical properties is their low specific heat capacity (around 1.0–1.5 (J/(g×K)). It has been shown that addition of nanoparticles in molten salts leads to a large increasing in the specific heat capacity of these salts, once melted with the particles. The aim of this study is to investigate the effect that nanoparticles have on specific heat capacity of zinc potassium chloride solutions. The hollow carbon nanospheres (hCNS, outer diameter is 20–30 nm; wall thickness 7 nm) and zeolite nanoparticles (ZSM-5, size 10–30 nm) were chosen for this study. The colloidal solutions of ZnCl2–KCl (46 mol% KCl) eutectic melt (Tm.p. = 220 oC) with different amounts, 0.3 to 2 wt% of nanoparticles, were prepared by mechanical mixing of required amount of salt with nanoparticles at 350oC for at least 24 hours until stable colloidal solutions were formed. Specific heat capacity of the samples was measured using a differential scanning calorimeter (HDSC; PT1000, Linseis Inc.) under the argon atmosphere according to established literature procedures. Measurements were carried out between 250–350oC temperature region with 10oC/min temperature rate using platinum crucibles with platinum lids for containment. The obtained experimental results (fig. 1) demonstrate that specific heat capacity of ZnCl2–KCl eutectic melt increases with increasing amounts of both types of nanoparticles used to form the colloidal solution.

Figure 1
Kinetic and Thermodynamic Properties of Samarium Chlorides Dissolved in Alkali Chloride Melts Obtained by Electrochemical Transient Techniques
Authors: Kuznetsov Sergey , Stulov Yuri , Gaune-Escard Marcelle
Published: December 2020

Lanthanide elements, which are present in spent fuel from fast nuclear reactors can be converted into molten salts by anodic dissolution. The lanthanide elements are the most difficult fission products to separate from actinides due to their similar chemical properties. Thus a knowledge of the electrochemistry and thermodynamics of lanthanide compounds in molten salt systems is very useful for the understanding the recycling of spent nuclear fuel.

The electroreduction of SmCl3 in alkali chloride melts (NaCl-KCl, KCl, CsCl) was studied in the temperature range 973-1173 K by different electrochemical methods. The diffusion coefficients (D) for Sm(III) and Sm(II) were determined by linear sweep voltammetry, chronopotentiometry and chronoamperometry methods showing that D decreases with increase of samarium oxidation state, while the activation energy for diffusion increases. Decreasing values of D were also obtained when the cation in the second coordination sphere changed from Na to Cs. It was shown that such changes are due to the decreasing of counter polarizing effect of cations with increasing cationic radius.

The standard rate constants of charge transfer (k
s) for the Sm(III)/Sm(II) redox couple were calculated on the basis of cyclic voltammetry data using Nicholson’s equation. The following row of the standard rate constants of charge transfer has been experimentally determined: k
s (KCl) < k
s (CsCl) < k
s (NaCl-KCl). The nature of working electrode on the rate of charge transfer for the Sm(III)/Sm(II) redox couple was studied. It was found that the values of k
s determined at a molybdenum electrode were higher than those at a glassy carbon electrode.

The formal redox potentials E*

Sm(III)/Sm(II) were obtained in alkali chlorides melts from the linear sweep voltammetry data. From the values of the formal redox potentials were calculated the Gibbs energies and equilibrium constants for the reaction:

SmCl2(sol.) +1/2 Cl2(g.)
« SmCl3(sol.) (1)

It was determined the increasing of the formal entropy for the reaction (1) in transition from NaCl-KCl to CsCl melt that associated with a greater degree of ordering of the reaction products due to the complex formation.
Application of Phosphate Precipitation for Removing Strontium and Barium from Alkali Chloride Based Melts
Authors: Ivanov Alexander B. , Byzova Elizaveta D. , Volkovich Vladimir A. , Chukin Andrey V. , Griffiths Trevor R.
Published: December 2020

Alkali chloride based melts can be used as working electrolytes in prospective technologies of pyrochemical reprocessing of spent nuclear fuels. After extracting fissile materials the melts contain ions fission product elements having more negative electrode potentials than uranium and plutonium. These include rare earth, alkaline earth and alkali metals. One of possible methods for removing rare earths from alkali chloride based melts is phosphate precipitation. Alkaline earth metals also form sparingly phosphates and therefore phosphate precipitation can be potentially used for removing strontium and barium from molten electrolytes.

The present work was aimed at studying the reaction of solutions of strontium or barium chloride in alkali chloride based melts with sodium orthophosphate. The experiments were conducted in LiCl–KCl and NaCl–KCl–CsCl eutectic based melts at 550 oC, and in NaCl–KCl equimolar mixture at 750 oC.

To determine the conditions required for complete removal of strontium and barium, the initial phosphate-to-barium molar ratio in the melt was set at 0.5; 1; 2; 4; 6 and 8. Residual alkaline earth content in the melt was determined by chemical analysis. Precipitated strontium and barium phosphates were subjected to X-ray powder diffraction analysis.

Selecting a possible method of separating solid precipitate from molten salt requires information on size of particles forming the solid phase. Particle size was determined by laser diffraction and examples of particle size distribution curves for precipitates formed in LiCl–KCl–BaCl2 melts are shown in Fig. The precipitates consisted of particles ranging from 0.5 to 100 microns. Increasing the initial PO4
3– : Ba2+ molar ratio resulted in increasing particle size but even at the molar ratio of six over 50 % particles were less than 10 μm.

Fig. Particle size distribution curves for barium phosphate precipitated from LiCl–KCl eutectic based melts at 550 oC. Initial PO4
3– : Ba2+ mole ratio was 0.5 (line 1); 1.0 (2); 2.0 (3); 4.0 (4) and 6.0 (5).

Figure 1