bluuebunny/crossref_metadata_2025_split huggingface dataset:
High Mass-Loading Sulfur Cathodes with Microporous Activated Carbon and Their Performance Improvement
Authors: Matsui Yukiko , Uchida Satoshi , Ishikawa Masashi 
Published: February 2020

A sulfur (S) cathode has a high theoretical capacity (1,672 mAh g-1). However, a major problem is the behavior of Li polysulfide (Li2Sn) intermediates, which may dissolve into an electrolyte. If dissolution of Li2Sn occurs, this should lead to a rapid capacity decay. We have investigated microporous activated carbon as matrix stabilizing S and realized stable cycling performance.1-2 However, the S content (ca.30wt%) and S loading were reatively low, which remains to be improved. To enhance them, in this study we applied alkaline-activated carbon with a large pore volume and also a porous 3-D Al current collector. Using these materials together with our fluorinated electrolyte, we have successfully realized stable and high capacity of the S-based cathode.
Methods: activated carbon (AACR) used in this study was an alkaline-activated type. AACR-S composite (AACR-1) was prepared by mixing AACR and S at a weight ratio of AC:S = 47:53, and then applying heat treatment: 155°C for 5 h, then 300°C for 2 h. The AACR- 1 composite cathode was prepared by mixing the AACR-1 composite, acetylene black, and alginate binder at a respective weight ratio of 90:5:5 and loading the resulting slurry into a 3-D Al current collector, “celmet (Sumitomo Electric Industries)”. The electrolyte was 1.0 mol dm-3 LiTFSI/FEC:HFE(1:1)+VC [9+1] (by vol.). All the cell components were installed into a pouch cell with a Li anode. A typical charge-discharge cycling test was carried out at 167.2 mA g-1 (0.1 C) with cutoff voltages of 3.0 and 1.0 V at 25°C.
Major results and conclusion: we carried out the thermogravimetric analysis of elemental S and the AACR-1. The weight loss of AACR-1 corresponds to the S content: 53wt%. We also investigated the discharge capacities of AACR-1 and also SAC-2 (for comparison, we also tested steam-activated with the S content, 34wt%) cathodes during cycling. Their respective S mass loading into the 3-D collector was 6.9 and 5.4 mg cm-2. The AACR-1 system showed higher S weight-basis capacity in spite of its higher S content and mass loading. Furthermore, the present fluorinated electrolyte contributed to stable capacity retention: 946 mAh (g-S)-1 at the 100th cycle due to the resulting stable SEI at the cathode. We will report other results in an attempt to inhibit the initial irreversible capacities and to increase discharge capacities, focusing on the the effect of electrolyte conditions and charge-discharge conditions .
This work was supported by “Advanced Low Carbon Technology Research and Development Program, Specially Promoted Research for Innovative Next Generation Batteries (ALCA-SPRING)” from JST.
Unraveling the Electrochemical Energy Storage Mechanism of Vanadium Hexacyanoferrate-Based Metal-Organic Frameworks As a Cathode for Aqueous Rechargeable Batteries
Authors: Lee Ji-Hoon 
Published: February 2020

Considering the environmental pollution crisis caused by fossil fuel and the limited supply of those, developing alternative power stations is strongly urged. Accompanying the development of alternative power stations, the introduction of large-scale stationary energy storage systems (ESSs) connected with the electrical power grid is vital for enhanced accessibility of electricity and leveling-off the intermittent spikes in the generated power. To date, Li ion batteries (LIBs) have been successfully demonstrated as feasible power sources for portable devices. Nonetheless, the application of LIBs into ESSs faces obstacles due to the limited source and continuously increasing cost of raw lithium and high flammability and the high cost of the organic electrolytes. Consequently, aqueous rechargeable batteries (ARBs) with readily accessible electroactive guest ions of H3O+, Na+, or Mg2+, are the most suitable energy devices for ESSs.
Very recently, Prussian blue analogues (PBAs) holding an important category of metal-organic frameworks have been highlighted as a promising candidate of electrode materials to be used in rechargeable batteries due to their ideal crystal structure and desirable electrochemical characteristics. Typically, PBAs have a typical cubic structure constructed with two transition metal ions (or clusters) linked via cyanide (−CN−) groups. However, the specific capacity of most PBAs obtained with aqueous electrolytes is limited to less than ≈60 mA h g−1. It indicates that the optimal combination of transition metal ions is the most crucial factor in improving their electrochemical performances, because the performance of PBA is mostly governed by the electrochemical process of the metal ions upon insertion/extraction of guest ions. Herein, new kind of PBAs constituted with vanadium and iron ions (V/Fe PBAs) were fabricated using a simple co-precipitation method, and their electrochemical performance as well as related mechanisms of energy storage was investigated under aqueous electrolytes. The V/Fe PBAs provided an improved capacity of ~ 100 mAh-1 under a C-rate of ~ 0.55 C, taking advantage of the multiple-electron redox reactions of V and Fe ions. In addition, the mechanism of energy storage and the cycling behavior were elucidated by monitoring the ex-situ X-ray absorption near-edge spectra, microstructural changes, dissolution of the transition metal ions, and changes in the resistance of charge transfer and surface layer during cycling. V/Fe PBA is the most attractive candidate cathode material for ARBs because of their high cost efficiency, simple synthesis, and the promising electrochemical performance, which is sufficient to meet the requirements of ARBs for large-scale ESSs.

Figure 1
Co/Co-Fe Nanoparticles/N-Doped Carbon Composite as Bifunctional Electrocatalyst for Rechargeable Metal-Air Batteries
Authors: Medina Danea , Andronescu Corina , Barwe Stefan , Bobrowski Tim , Masa Justus , Schuhmann Wolfgang 
Published: February 2020

In secondary metal-air batteries, it is indispensable to develop novel bifunctional catalysts for the low overpotential oxygen reduction/oxygen evolution reaction to allow on the one hand very high energy density combined with high capacity and low price.1,2 Therefore, the widespread use of rechargeable metal-air batteries strongly depends on the substitution of precious metal-based bifunctional electrocatalysts towards the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) with catalysts from high-abundant materials.3 This seems to be possible since the electrolyte in typical Ni- or Zn-metal air batteries is highly alkaline.
Here, we report a novel Co/Co-Fe nanoparticle/N-doped carbon composite (Co/CoxFey/NC) obtained by thermal treatment of a composite of Co-Fe layered double hydroxide (Co-Fe LDH) and polybenzoxaxine (pBO) under ammonia atmosphere. The latter undergoes thermal degradation to form a conductive nitrogen-doped carbon matrix encapsulating Co/Co-Fe nanoparticles thereby circumventing the use of any binder material to immobilize the catalyst particles on the electrode surface.4 Within this work, the influence of the temperature, duration of treatment and the nature of gas atmosphere employed during the thermal treatment, as well as the ratio Co-Fe LDH:pBO on the electrocatalytic activity performance were investigated, leading to identification of an optimal Co/CoxFey/NC catalyst exhibiting remarkable bifunctional activity towards ORR and OER in 0.1 M KOH with an overpotential difference between these two reaction as low as 0.76 V at -1 mA cm-2 for the ORR and at 10 mA cm-2 for the OER, respectively. Moreover, the stability of Co/CoxFey/NC catalyst was evaluated in an air-breathing set-up, alternating between the OER and the ORR at a current density of 10 mA cm-2 in 6 M KOH to simulate the charge discharge cycles in rechargeable metal-air batteries for a total of 120 charge-discharge cycles each lasting 10 minutes.
References:
[1] Y. Li, H. Dai, Chem. Soc. Rev. 43 (2014) 5257-5275.
[2] J. Fu, Z.P. Cano, M.G. Park, A. Yu, M. Fowler, Z. Chen, Adv. Mater. 29 (2017) 1-34.
[3] J. Masa, W. Xia, I. Sinev, A. Zhao, Z. Sun, S. Grützke, P. Weide, M. Muhler, W. Schuhmann, Angew. Chem. Int. Ed. 53 (2014) 8508-8512.
[4] C. Andronescu, S. Barwe, E. Ventosa, J. Masa, E. Vasile, B. Konkena, S. Möller, W. Schuhmann, Angew. Chem. Int. Ed. 56 (2017) 11258-11262.

Figure 1
The Role of the Supporting Electrolyte on the Covalent Modification of Carbon Surfaces with Organic Groups
Authors: Ramírez-Chan Daniel E , González Felipe J. 
Published: February 2020

Covalent modification of carbon electrodes has been developed during the last 30 years with the implementation of different reduction or oxidation electrochemical strategies [1]. These methods have been of interest for many applications due to the physical and chemical stability of the grafted films. Among these methods, the direct and mediated oxidation of carboxylates allowed the attachment of organic groups like saturated [2] and unsaturated alkyl chains [3] and substituted benzylic [4] and phenylalkylic groups. When the grafted film bears moieties electrochemically actives, they can be characterised through their response in cyclic voltammetry experiments, however, the main features of the redox active groups are far from the ideal behaviour for adsorbed species [4]. Therefore, in this work is analysed the effect of the cation size of the supporting electrolyte used during the grafting by mediated oxidation of 4-nitrophenylbutyrate on the ideality of the redox process of the nitrobenzene group. It was found that the reversible reduction process of the adsorbed nitrophenyl groups is closer to an ideal behaviour when the size of the supporting electrolyte cation follows the next order: n-Hx4N+ > n-Bu4N+ > Et4N+ > Me4N+. This order reveals different levels of compactness of the grafted film and explain the behaviour of ferrocene as redox probe, whose apparent reversibility decreases in the same order of cation size.
References
[1] D. Bélanger, J. Pinson, Chem. Soc. Rev., 2011, 40, 3995
[2] P.D. Astudillo, A. Galano, F.J. González, J. Electroanal. Chem., 2007, 610, 137
[3] D.M. Hernández-Morales, F.J. González, Electrochem. Commun., 2014, 46, 48
[4] C.P. Andrieux, F. González, J.M. Savéant, 1997, 119, 4292
Accounting for Unsteady-State Behavior during Electrochemical Impedance Spectroscopy
Authors: Shrestha Sujan , Sholin Mark , Schiller Carl Albrecht , Fröba Steffen , Multerer Michael , Strunz Werner 
Published: February 2020

Electrochemical Impedance Spectroscopy (EIS) is one of the most effective methods to characterize an electrochemical system. Most of the common mathematical tools available for the correct interpretation of EIS data assumes a steady-state system. So, the system should have a constant voltage at a given current or vice versa during the duration of experiment. However, the system can deviate from a steady-state because of the perturbation applied during EIS measurement or because of the intrinsic chemistry of the system. For example, during charging or discharging of a battery at a constant current, voltage is drifting due to the changes in chemistry of the materials inside the battery. This drift in voltage can be significant especially during lower frequency scans that can lasts hours (<0.3 mHz). In such a case, extracting meaningful data from EIS can be challenging due to violation of the steady state condition.
Here we show a reliable method to correct for the drift that might occur during such a low frequency measurement. This method takes advantage of the fact that phase angles in many systems are not affected by such an unsteady state behavior. Therefore, drift-free impedance modulus data is reconstructed from the phase angle spectrum with the help of a Z-HIT algorithm that applies the logarithmic form of the Hilbert transform to systems exhibiting ‘two-pole’ behavior. From this drift-free EIS data, the severity of drift can be analyzed. In addition, a better-fitted equivalent circuit model can be simulated. Furthermore, this method removes inaccuracy during multi-sine excitation combined with other tools. Applicability of this method in characterizing different electrochemical devices such as batteries, fuel cells and supercapacitors is presented.
Keywords: EIS, Z-HIT, Battery, Supercapacitor, Fuel cells,
References:
[1] C. A. Schiller, F. Richter, E. Gülzow 3, N. Wagner; J. Phys. Chem. Chem. Phys. 3 (2001) 374
[2] W. Ehm, R. Kaus, C. A. Schiller, W. Strunz, New Trends in Electrochemical Impedance Spectroscopy and Electrochemical Noise Analysis, ed. F. Mansfeld, F. Huet, O. R. Mattos, Electrochemical Society Inc., Pennington, NJ, 2001, vol. 2000-24, 1
[3] C.-A. Schiller, R. Kaus; Bulgarian Chemical Communications, Volume 41, Number 2 (2009), pp. 192-198
Electric Conductivity of Li/Na Binary Molten Carbonate Coexisting with Nanoparttcles of CeO2:Sm3+
Authors: Mizuhata Minoru , Kubo Hiroshi , Maki Hideshi , Matsui Masaki 
Published: February 2020

Many studies on ion conduction in a composite electrolyte of ceria-based oxide doped with a rare earth elements such as CeO2:Sm3+, CeO2:Gd3+, etc. and molten carbonate have been carried out in order to decrese the operating temperature and make various ions act as conductive species. Ionic conduction of molten carbonates is influenced by the coexisting solid phase such as LiAlO2, Al2O3, ZnO and so on., and their specific surface area and melt content. For Li/Na carbonate melt/ CeO2:Sm3+ coexisting systems, a lowering of eutictic point and an increase of ionic conduction below the eutectic point were observed. In this study, nano-ordered ceria particles are used and the conductivity and thermal behavior of binary carbonate were measured in order to discussthe effect of the specific surface area of ceria particles.
Based on the report of Kim, Cassir et al., nano-ordered CeO2:Sm3+ particles were prepared. Citric acid and ethylene glycol were mixed with predetermined amounts of Ce(NO3)3 and Sm (NO3)3 aqueous solution, and heated for 12 hours with stirring at 343 K. The organic precursor was obtained by heating at 573 K for 12 hours. Furthermore, the precursor was heated at 383 K for 1 hour under an air atmosphere and calcied at 673 K for 4 hours to obtain Sm3+ doped CeO2 with Sm ratios of 10 and 20 mol% (SDC10 and SDC20). As the liquid (melt) phase, Li2CO3 and Na2CO3 were dehydrated in CO2 at 473 K for 48 hours, and the prepared eutectic (Li0.51Na0.49)2CO3 (LN) was used. Oxide and LN were mixed so as to obtain a predetermined liquid phase volume fraction to obtain CeO2- LN or SDCs -LN. The mixed sample was pressed at 60 MPa for 30 minutes and fired at eutectic temperature or higher to prepare pellets for AC impedance measurement in the temperature range of 623-773K in 25 Hz-1 MHz.
A temperature dependence of ionic conductivity in ceria/LN coexisting system is shown in Figure 1. At a liquid phase volume fraction of 25 vol% or more, a bending point due to eutectic melting of the molten salt was observed in the vicinity of 720 K. In the region below the inflection point, it was confirmed that the conductivity of the liquid phase volume fraction of 45 vol% was smaller than the value of 15 - 35 vol%, and as the liquid phase amount increased. This is because, as the liquid phase amount increases, the bulk molten salt crystallizes and suppresses ion conduction. At 15 vol%, there was no remarkable change in conductivity even before and after the inflection point, and there was no enthalpy change at 25 vol% or less. Results suggesting that the molten salt existing at the solid interface is in the molten state even below the transition point.

Figure 1
Electrochemical Properties of Uranium and Zirconium on Solid and Liquid Electrodes in 3LiCl–2KCl Based Melts
Authors: Maltsev Dmitry S. , Volkovich Vladimir A. , Raguzina Ekaterina V. , Strepetov Kirill E. , Kozlova Anastasiya A. , Soldatova Maria N. 
Published: February 2020

Spent nuclear fuel (SNF) reprocessing for fast neutron reactors can be organized by employing high temperature pyrochemical methods. Fused salts and liquid metals or alloys are the working media in the pyrochemical processes. Electrochemical deposition and electrochemical separation of uranium from fission products is an important stage of pyrochemical SNF reprocessing. Reliable data on electrochemical properties of uranium and fission product elements are required for development and optimization of the pyrochemical processes.
Uranium and zirconium have very close electrode potentials and separating uranium (fissile material) from zirconium (fission product) is an important and difficult to solve task in the pyrochemical reprocessing. This work devoted to studying electrochemical properties of zirconium and uranium employing cyclic voltammetry method in 3LiCl–2KCl eutectic based melts containing uranium and zirconium chlorides. Various types of electrodes were tested to determine uranium and zirconium deposition potentials aiming to finding the cathode material with the largest difference of uranium and zirconium potentials. Tungsten was used as a solid cathode, and liquid alloys based on Ga, Al, Zn, Sn and their mixtures were tried as low-melting liquid cathodes. Electrochemical measurements were made in temperature range of 450–800 0C. On the basis of the results of electrochemical measurements the possibility of separating uranium and zirconium employing liquid metal alloys was elucidated.
Acknowledgements: This work was supported by the Russian Science Foundation (project No 17–73–20156).
Electronic Absorption Spectra of Uranium(V) Species in Fused Alkali Chlorides
Authors: Volkovich Vladimir A. , Shatkovskyi Yaroslav A. , Aleksandrov Denis E. , Maltsev Dmitry S. 
Published: February 2020

Alkali chloride based melts can be used in pyrochemical reprocessing various types of spent nuclear fuels, especially those of fast neutron reactors. There is a possibility of refabricating uranium oxide or mixed uranium-plutonium oxide fuel by electrodeposition of UO2 or (U,Pu)O2 from chloride melts containing uranyl (or a mixture of uranyl and plutonyl) ions. At high temperatures uranyl chloro species undergo decomposition yielding UO2
+ ions and finally UO2. Increasing temperature and lowering partial pressure of chlorine in the atmosphere above the melt shifts the equilibrium towards the decomposition products. In fact, uranium(V) ions are often present in uranyl-containing melts and, if unaccounted for, result in increased current efficiency of UO2 electrodeposition process.
Electronic absorption spectroscopy allows a convenient method for detecting and measuring concentration of uranium(V) in uranyl-containing electrolytes. Absorption spectra of uranium(V) species in fused salts were reported over fifty years ago but still remain the least studied especially from the quantitative side concerning molar absorption (extinction) coefficient values. Uranium(V), f
1-electron configuration, absorbs in the visible region of the spectrum and the spectra have there two broad bands with the maxima around 620 and 775 nm not overlapping with the absorption of uranium(VI) ions, Fig. These bands correspond to two f–f transitions in UO2Cl4
3– complex ion, i.e., φ5u → 3π1u and φ5u → 3π3u. The aim of the present work was studying the effect of temperature and cationic melt composition on the absorption spectra of uranium(V) ions and determining molar absorption coefficients. The measurements were performed in individual alkali chlorides and their mixtures of various compositions including LiCl, CsCl, LiCl–KCl, LiCl–KCl–CsCl, NaCl–KCl, NaCl–CsCl. The temperature range varied from 350 to 850 oC depending on the melt. Uranium(V) ions were obtained in situ by reducing uranium(VI) ions with hydrogen. Uranium dioxide was also produced but no soluble uranium(IV) species in the melt were detected. After recording the spectrum a sample of the melt was taken and analyzed for the total uranium concentration and the mean uranium oxidation state which always was between five and six. From that, concentration of U(V) and V(VI) ions in the melt were calculated and U(V) extinction coefficients determined. The results obtained allow determination of U(V) concentration in technological electrolytes.
Acknowledgement. This work was supported by the Ministry of Education and Science of the Russian Federation (project No. 4.5062.2017/8.9).
Fig. Electronic absorption spectra of LiCl–KCl based melts containing U(VI) ions (line 1) and a mixture of U(VI) and U(V) ions at a 3 : 2 ratio (line 2). Total uranium concentration 0.038 mol/l, T = 550 oC.

Figure 1
Electrochemical Synthesis of Carbon Nanotubes in Carbonate Melts
Authors: Karatsukova Romina , Kushkhov Hasbi , Ligidova Marina , Marzhokhova Maryana 
Published: February 2020

The work is devoted to studies by the method of electrochemical synthesis of carbon nanostructure and nanotubes in carbonate melts.
The mechanism of electrochemical synthesis in carbonate melts is investigated by the cyclic voltammetry, galvanostatic electrolysis and scanning electronic microscopy.
The optimum conditions of electrochemical synthesis of carbon nanosized structures and nanotubes in ionic carbonate melts are presented in the work. The series of physical and chemical analyses are conducted. The composition of synthesis powder were established with X-Ray structural methods. Their results indicate the presence of carbon nanotubes and graphite in sample. The dispersive analysis of powders was showed that the particle size of the obtained sample lie in the micrometer range. The obtained sample was investigated of the morphology and composition by using scanning electron microscopy. The results confirm the presence of carbon nanotubes.
Numerical Modeling of Degradation in Photoelectrochemical Water Splitting Devices
Authors: Nandjou Fredy , Haussener Sophia 
Published: February 2020

One of the main challenges for advancing large-scale implementation of photoelectrochemical devices is performance loss, mainly due to photocorrosion [1]. Semiconductors with good photoabsorption behavior and interesting band alignments are inherently non-stable, and therefore photocorrode in few minutes to hours.
Usually, photocorrosion is interpreted on the basis of energy schemes, comparing the quasi-Fermi levels of charge carriers to the corrosion potentials of the photoelectrode [2]. However, the competition between the pure redox process of water splitting and photoelectrode dissolution/passivation can be highly influenced by kinetic parameters [3].
We use a physics-based model to study photocorrosion phenomenon in monolithic photoelectrochemical devices. The studied device is composed of different catalyst covered semiconductors, immersed in a liquid electrolyte. Acidic and alkaline conditions are tested. The catalyst layer is considered a nanoporous media, the solid phase being composed of a supporting structure and catalyst particles. Accurate thermodynamic and kinetic measurements on different semiconductor/catalyst/electrolyte combinations support our study. These measurements include rotating ring-disc measurements, cyclic voltammetry and chronoamperometry. The simulation results show how irradiation intensity, kinetic parameters, and mass transport in the two-phase flow can impact the stability of the photoelectrode/electrolyte interface.
[1] F. Nandjou and S. Haussener. Degradation in photoelectrochemical devices: Review with an illustrative case study. J. Phys. D: Appl. Phys. 50 (2017) 124002.
[2] Gerischer H, et al. Report EUR 9531 EN (1984), Commission of the European Communities.
[3] R. Memming. The Role of Energy Levels in Semiconductor
‐
Electrolyte Solar Cells. J. Electrochem. Soc. 125 (1978) 117.