bluuebunny/crossref_metadata_2025 huggingface dataset:
The Role of Li Salt in Highly Concentrated Electrolyte of Lithium Sulfur Batteries
Authors: Noh Hyungjun , Kim Hee-Tak
Published: February 2020

Recently, the properties of electrolyte have been reported as powerful parameter affecting the behavior of Li ion battery. Among them, Li salt has been regarded as important parameter that can influence not only the battery performance but also Li metal stabilization. In the same line with this view, highly concentrated salt has been attracted because of its various unusual functionalities such as high electrochemical stability for advanced lithium ion battery. However, even though highly concentrated electrolyte has many advantages for advanced Li ion batteries, it cannot be applied in Li-S batteries due to the limited solubility of sulfur related species.

In this paper, we applied different two types of salt in highly concentrated electrolyte for Li-S batteries. The combination of salt with electro-donating property changed the Li2S deposition chemistry and increased equilibrium concentration of polysulfides in electrolyte as well as Li metal stabilization. This unique effect of salt was clearly demonstrated using ex-situ analysis including Uv-vis, Raman spectroscopy with combination of computational simulation. This finding offers understanding about peculiar solvation structure under highly concentrated electrolyte and novel strategy for modulating electrochemical reduction mechanism in highly concentrated Li-S batteries
A Study on Overcoming the Inert Capacity of Polymer Sulfide Electrode with Conducting Materials
Authors: Park Jinkyu , Kim Seokwoo , Jin Dahee , Oh Jeonghun , Yoon Byeolhee , Choi Junyoung , Jo Hearin , Lee Yong Min , Ryou Myung-Hyun
Published: February 2020

Demand and use of electric vehicles (EVs) is rapidly increasing due to environmental pollution problems. However, electric vehicles have a big disadvantage of short mileage. In order to overcome these disadvantages, a large amount of batteries were mounted on the automobile to increase the amount of absolute energy. However, such a solution does not increase the fuel efficiency so much as the weight of the automobile increases. Therefore, a battery using a high energy density active material should be applied to lower the weight of the battery and increase the energy density. Recently, Li-S batteries among high-energy density next generation secondary batteries have a high capacity of 1675 mAh / g, and are being studied because of their advantages of being cheap and environmentally friendly. However, due to polysulfide elution, shuttle phenomenon and low conductivity, there is a problem of capacity reduction and cycle performance deterioration.

Recently, much research has been conducted to solve the problem of inhibiting the dissolution of polysulfide. Among previous works, there have been studies to synthesize polymeric active materials by adding organic sulfur additive to molten sulfur. The synthesized active materials inhibited the elution of the polysulfide and confirmed the improvement of cycle performance.

In this study, the polysulfide elution and shuttle phenomenon inhibited by using the active materials used in the above - mentioned studies and the electrochemical characteristics of the electrodes prepared by using two conductive materials separately were analyzed.
Nanoporous Carbon Coated Sb Anode for High Performance K-Ion Batteries
Authors: Verma Rakesh , Ki Hyeong-Seo , Park Chan-Jin
Published: February 2020

Potassium-ion batteries (PIBs) can be regarded as one of the most emerging energy storage devices alternative to current Li-ion batteries (LIBs), due to their resourceful, environment-friendly, and economic merits. For anode in PIBs, the recent researches have mainly focused on carbonaceous materials due to their high electric conductivity and low cost. Nevertheless, the capacities of carbonaceous materials are not satisfactory and cannot meet the growing demand for higher energy density batteries, which have seriously hindered their practical application. Recently, the alloy type materials such as Sn, Sb, Ge, and P have attracted much attention due to their superior capacity. Among various alloy type materials, Sb is a potential anode material for PIBs with a high theoretical capacity of 660 mA h g-1. However, a large volumetric change of ~400% during the alloying/dealloying processes may cause the fracture of active material and loss of electrical contact, leading to rapid capacity fading. To address this issue, numerous strategies have been proposed to mitigate the stress induced by volume change and enhance the electrochemical performance of Sb-based electrodes. An efficient and simple strategy is to synthesize carbon coated porous morphology and structure in nanoscale.

In the present study, we have successfully prepared a Nano porous Sb/C composite through a simple carbothermal reduction method. Fig.1 represents the XRD pattern and morphology of the synthesized nanoporous Sb/C composite. Further, the electrochemical performance of nanoporous Sb/C electrode was studied for the application as an anode material for PIBs. The nanoporous Sb/C electrode exhibited excellent electrochemical characteristics in terms of high specific capacity, excellent cyclability, and good rate capability. The superior performance of Sb/C electrode is attributed to the original high capacity of Sb active materials as well as the mitigation of stress and the improvement of electrical conductivity inside electrode by employing carbon coating. The effect of the alloying/dealloying process on the crystal structure of Sb/C was examined by the ex-situ XRD patterns recorded in various stages of discharge and charge. We consider that this work can provide a guideline to open up new research opportunities in the development of PIBs.

Figure 1
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
Cathode Materials for Rechargeable Aluminum Metal Batteries: Molecular-Level Insights, Challenges, & Opportunities
Authors: Messinger Robert J. , Jadhav Ankur , Xu Jeffrey
Published: February 2020

Rechargeable aluminum batteries are an emerging energy storage technology with great potential due to the high capacity, global abundance, low cost, and inherent safety of aluminum metal. However, few cathode materials have been demonstrated that exhibit high energy density and cycle life, in part due to the challenges associated with the high charge density of trivalent aluminum cations and the highly reactive nature of the chloroaluminate-containing ionic liquids commonly used as electrolytes. Here, investigations of selected intercalation and conversion cathodes for rechargeable aluminum metal batteries will be presented, including crystalline transition metal compounds, graphite, and sulfur-containing materials. Molecular-scale understanding of their charge storage mechanisms will be discussed, revealed by a combination of electrochemical methods, solid-state magic-angle-spinning (MAS) NMR spectroscopy, in situ diffraction methods, and electron microscopy. Intrinsic challenges—and opportunities—associated with intercalation and conversion cathode materials will be discussed. Overall, the results yield insights into possible rational design strategies for developing next-generation cathode materials for rechargeable aluminum metal batteries with improved energy densities, rate capabilities, and cycle lifetimes.
(Invited) Full Spectrum White LEDs of Any Color Temperature with Color Rendering Index Higher Than 90 Using a Single Broad-Band Phosphor
Authors: Dutta Partha S. , Liotta Kathryn M
Published: February 2020

A new phosphor alloy Ca1+xSr1-xGa2S3F2: Ce3+, Eu2+ with x = 0.04 exhibits a full spectrum emission in the entire visible wavelength range from 420 to 700 nm when excited by a LED chip with 400 nm emission. By simply depositing varying thicknesses (amount) of this phosphor powder on a 400 nm excitation LED source, white LEDs with correlated color temperatures (CCT) between 1700 K and 20,000 K and (x,y) chromaticity coordinates lying on the Planckian locus of the CIE chromaticity diagram has been demonstrated. To the best of our knowledge, this is the first report on the demonstration of a single full spectrum phosphor based white LEDs exhibiting the entire gamut of white light color temperature with CRI exceeding 90. Specifically CRI greater than 95 is reported for the CCT range of 2200 K – 8500 K.
(Invited) Impact of ECS Journal Focus Issues and Article Types on LDM Visibility and Recognition
Authors: Hess Dennis W.
Published: February 2020

Authors and readers of articles expect that ECS journals publish and disseminate content to specialized and more general communities within their technical domain. The technical domain is determined by the specific ECS Division and is manifested in the Topical Interest Area within which the article is published. This presentation will describe the various article types published by ECS journals along with reasons for their existence. The impact that article types such as focus issues can have and are having on the visibility and recognition of ECS and of Divisions like LDM, will be discussed.
(Invited) Data-Mining, a New Sr2LiAlO4:Eu2+/Ce3+ Phosphor for Solid-State Lighting Applications
Authors: Im Won Bin , Kim Yoon Hwa , Kim Ha Jun , Wang Zhenbin , Ha Jungmin , McKittrick Joanna , Ong Shyue Ping
Published: February 2020

There is a critical need for new earth-abundant phosphors to enable next-generation, highly efficient solid-state lighting. Here, we report the discovery of Sr2LiAlO4, the first known Sr-Li-Al-O quaternary crystal, via a carefully-targeted data-driven structure prediction and screening effort using density functional theory calculations. Sr2LiAlO4 is predicted and experimentally confirmed to be a thermodynamically and thermally stable phosphor host that can be excited with near-UV/blue sources. The Eu2+ and Ce3+-activated Sr2LiAlO4 phosphors exhibit broad emissions at lmax
~ 512 nm (green-yellow) and lmax
~ 434 nm (blue), respectively, with excellent thermal quenching resistance of > 88% intensity at 150°C. A prototype phosphor-converted white LED utilizing Sr2LiAlO4-based phosphors yields an excellent color rendering index exceeding 90. Sr2LiAlO4 therefore exhibits great potential for industrial applications in low-cost, high-color-quality WLEDs.

Figure 1
(Invited) Synthesis of Persistent Luminescent Nanophosphors for Point-of-Care Diagnostics
Authors: Finley Erin , Brgoch Jakoah
Published: February 2020

Point-of-care diagnostics have grown in demand as a reliable resource for bioanalytical technologies due to their ease of use and inexpensive manufacturing. To improve these technologies, researchers are expanding beyond traditional gold or latex nanoparticles and fluors, which are used alternative optical reporters, by developing a new class of reporters based on persistent luminescent inorganic nanophosphors. The appeal of nanophosphors is that their signature long luminescent lifetimes, which in some cases exceed 10 hours, limit the need for complex optical hardware. Additionally, these materials have the advantage of being environmentally benign while also exhibiting low cytotoxicity. However, the synthesis of persistent luminescent phosphors traditionally employ high temperature solid state methods, which tends to generate large particles and agglomerates (>15 μm). Most point-of-care diagnostic formats, such as immonochromographic lateral flow assays (LFAs), necessitate particle sizes that are submicron; therefore, alternative soft chemical synthetic routes that are conducive to forming significantly smaller particles are required. Unfortunately, many of the reported routes lead to impure products, as is the case with monoclinic SrAl2O4:Eu2+,Dy3+ where the presence of the hexagonal phase polymorph and Sr4Al14O25:Eu2+,Dy3+ are common. Consequently, the need to employ synthesis routes to limit these phase formations, while reducing particle size is essential. Here, two soft chemical routes, a reverse-micelle combined with microwave assisted heating and a sol-gel method are investigated to establish new alternative synthesis routes addressing these concerns. It can be shown that both methods produce phase pure products that maintain the necessary optical properties while also reducing the particle size of the persistent luminescent phosphors allowing application in a working LFA.
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.
Utilizing Ionic Liquids to Generate Sustainable Technologies
Authors: Di Bona Kristin R
Published: February 2020

This talk will serve as an introduction to Wyonics, a company exploring the role that ionic liquids can play in the generation of high-value technologies. Wyonics is utilizing the ability of ionic liquids to dissolve biopolymers to make useful materials for a wide range of high-value applications, including medical devices and drug delivery systems. As an example, we will describe the development of a Cu-biopolymer intrauterine device, designed to better control Cu2+ release as compared to existing intrauterine devices. Simple, sustainable processes were designed to reduce the cost of producing these medical devices while increasing their safety, biocompatibility, and global accessibility. Validation of this research strategy will lead to future developments in the field of nanoparticle-biopolymer drug delivery systems. We will also include an overview of the breadth of technologies (i.e., energy, resource recovery) actively being pursued by Wyonics and the role that ionic liquids will play in global sustainability.
Cellulose, Cellobiose, and Glucose Cause Similar Decreases to Molar Conductivity, Drastically Different Increases to Dynamic Viscosity of 1-Ethyl-3-Methylimidazoilum Acetate Based Solvents
Authors: Fahey Patrick J. , Durkin David P. , Fox Eric T. , Gobet Mallory , Greenbaum Steven , De Long Hugh C. , Trulove Paul C.
Published: February 2020

The effect of dissolved cellulose, cellobiose, and glucose on ion conductivity, density, and viscosity were evaluated for 1-ethyl-3-methylimidazolium acetate (EMIAc) and 1:1-mole-ratio mixtures of EMIAc with acetonitrile (1:1 EMIAc:AN) and water (1:1 EMIAc:H2O). Test solutions were made with these three solvent types by dissolving 0.1, 0.5, 1.0, and 3.0 wt.-% of either cotton, microcrystalline cellulose (MCC), cellobiose, or glucose. Each solute caused slight decreases in ion conductivity at higher solute contents, decreasing to factors only as low as 0.7 of their corresponding solvent-type’s conductivity. The solutes’ effects upon viscosity differed: Cellulose solutes caused massive increases in viscosity upon reaching higher solute contents, where the solvents’ viscosities increased to factors between 10 and 20 at 3.0 wt.-% MCC and to factors between 40 and 140 at 1.0 wt.-% cotton. This difference in impact on viscosity between MCC and cotton is possibly due to cotton’s higher degree of polymerization. Meanwhile cellobiose and glucose only increased viscosity to factors as high as 1.1 and 1.3, respectively, upon reaching 3.0 wt.-% solute contents. The large increases in viscosity and corresponding small decreases in conductivity make the solutions of 3.0 wt.-% MCC and 0.5 and 1.0 wt.-% cotton appear superionic.
(Invited) The Effect of an Ultrathin ALD Overlayer on the Performance of Photocatalytic CO2 Reduction By TiO2
Authors: Feng Xuhui , Pan Fuping , Li Ying
Published: February 2020

To produce solar fuels from CO2 photoreduction with water, TiO2 is most frequently studied as it is inexpensive, earth-abundant, and chemically stable. But the darwbacks of using TiO2 include low light absorption in the visible range, low CO2 adsorption capability, and fast charge recombination. We have developed many strategies to improve the catalytic performance of TiO2 through surface engineering, and one recent approach is to coat an ultrathin overlayer of metal oxide (e.g. Al2O3 or MgO) on TiO2 photocatalyst though atomic layer deposition (ALD). In one experiment, we found coating an ultrathin Al2O3 on TiO2 nanorods with 5 ALD cycles led to significant improvement, mainly because of the surface passivation by ALD overlayer and resultant reduced surface recombination. In another experiment, we found coating an ultrathin MgO overlyaer on porous TiO2 with 5 cycles of ALD layers led to even more significant enhancement in CO2 photoreduction. The changes of surface properties in correlation with the ALD coating layer thickness as well as the photocatalytic performances were investigated.
Three-Dimensional Hierarchical Copper Nanostructures As Advanced Electrocatalysts for CO2 Reduction
Authors: Wang Chao
Published: February 2020

Cu-based nanomaterials have received increasing interests for electrocatalytic applications in the CO2 reduction reaction. It is however challenging to design nanostructured Cu electrodes to improve both the chemical kinetics and molecular transport under the reaction conditions. Here we report on a new type of three-dimensional, hierarchical Cu nanostructures as advanced electrocatalysts for CO2 reduction. Driven by thermal oxidation, CuO nanowires and/or porous structures are grown on commercial Cu foams with three-dimensional (3D) frameworks. An electrochemical method is used to reduce CuO to Cu with the structural features largely preserved. The derived hierarchical Cu nanostructures are demonstrated to be highly active and selective for CO2 reduction, achieving >80% Faradaic efficiency and ~3 times of enhancement in terms of CO2 conversion rate as compared to the Cu nanowires grown on planar electrodes. Our work highlights the great potential of 3D Cu nanostructures for improving the energy efficiency and power performance of CO2 electrolysis.
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.
(Invited) Synthesis of Ultrastable Hairy Perovskite and Plasmonic Core/Shell Nanoparticles for Perovskite Solar Cells
Authors: Lin Zhiqun
Published: February 2020

We develop a viable strategy to create uniform ultrastable perovskite/metal oxide core/shell nanoparticles with good control over the dimension by capitalizing on amphiphilic star-like triblock copolymers as templates. The diameter of the perovskite core and the thickness of the metal oxide shell can be independently and precisely regulated by tailoring the molecular weights (i.e., the lengths) of the inner and intermediate blocks of star-like triblock copolymers, respectively. The successful synthesis of perovskite/metal oxide core/shell nanoparticles is confirmed by a suite of characterizations. Moreover, metal/metal oxide core/shell nanoparticles are also synthesized using amphiphilic star-like triblock copolymer templates. The resulting perovskite/metal oxide nanoparticles exhibit the remarkable compositional, thermal, moisture stabilities. These perovskite/metal oxide and metal/metal oxide nanoparticles are then used in perovskite solar cells, with which improved device performance is observed.
Novel Visible-Light-Driven Photocatalysts for Efficient Hydrogen Generation: Hybrid Composites of Ti-Based MOF and Low-Dimensional Nanoparticles
Authors: Kim Tae Woo , Sohail Muhammad , Kim Hyunuk
Published: February 2020

A novel visible-light-driven photocatalyst, hybrid composites of MIL-125-NH2(Ti-MOF) and low-dimensional nanostructures(i.e, 0D CdS nanoparticles (NPs) and 2D ZnCr-LDH nanosheets(NSs)), has been developed for H2 generation from water under visible light irradiation. For synthesis, ZnCr-LDH and CdS nanoparticles are first prepared according to the previous studies. The hybrid composites was synthesized by growing Ti-MOF in a colloidal suspension of ZnCr-LDH NSs or CdS NPs under solvothermal reaction. The obtained hybrid composites were systematically characterized by various tools such as powder XRD, XAFS, FESEM, TEM/EDX, BET, UV-Vis, and so on. In case of hybrid composites of Ti-MOF/ZnCr-LDH NSs, according to powder XRD and FESEM, the crystallinity and morphology of Ti-MOF after the hybridization with ZnCr-LDH NSs became lower and irregular in comparison with pure Ti-MOF. This result implies that ZnCr-LDH NSs limit the crystal growth of Ti-MOF. The hybrid composites were performed photocatalytic test for H2 generation under visible light irradiation (λ≥420 nm). From the test, we found that the hybrid material has a photocatalytic performance for hydrogen generation much better than each component. More interestingly, in this work the highly efficient H2 production of the present hybrid material was achieved without a co-catalyst such as Pt. Through deep investigations using XPS, PL, and electrochemical analyses, we found that the improved photocatalytic activity results from the increase of the lifetime of the photoinduced electrons and holes by strong coupling of two components and their proper band alignment. In addition, hybridization of Ti-MOF with ZnCr-LDH NSs or CdS NPs improves a photo- and chemical stability compared to each component before hybridization. In this work, we will discuss in detail about synthesis procedure, structural formation, photocatalytic ability, and mechanism for the present hybrid composites.
Effective Light Scattering Building Block for Enhanced Photoelectrochemical Performances of Flexible Solar Cells
Authors: Cui Lingling , Zhang Xiao LI
Published: February 2020

Solar cells fabricated on flexible plastic substrates possess great potential towards commercialization standing on their light-weight, low-cost, low-tech fabrication, and flexibility to tolerant different outdoor/indoor application requirements. A lack of a suitable material with both effective light scattering and high surface adhesion properties that would allow the development of a mechanically stable light trapping top-coating layer through a low temperature process prevents today’s flexible plastic dye-sensitized solar cells (DSCs) to reach comparable high power conversion efficiency (PEC) towards commercialization. In the present work, submicron sized titania particles with intensive surface roughness were strategically synthesized using a combined sol-gel and thermolysis approach. When used as a light trapping layer in flexible DSCs, the ideal strong light scattering ability of such materials enabled dramatic enhancements on light harvesting and thus greatly contributed to the photocurrent performances. This led to a nearly 30% PEC enhancement when compared to the flexible DSCs using photoanodes made of nanoparticles with a similar film thickness.
Photoelectrochemical Oxidation of Methane at TiO2 nanotubes Arrays
Authors: Kadosh Yanir , Korin Eli , Bettlehiem Armand
Published: February 2020

Methane, the primary component in natural gas, has extensive utilities in the chemical industry and as an energy source. The depletion of petroleum reserves highly motivates the exploitation of natural gas as an important hydrocarbon feedstock with a small environmental footprint. However, this potential energy source is being wasted due to the lack of an efficient utilization process that will integrate natural gas in the existing energy infrastructure. Methane is mostly burned in order to use its heat for power generation. In order to utilize methane efficiently, it may be chemically converted for energy conversion. Unfortunately, methane’s molecular structure has neither a functional group, nor a polar distribution to facilitate chemical interactions, resulting in a low chemical reactivity. Its C-H bond has one of the highest bond energies among hydrocarbons (413kJ/mol).

An alternative approach to utilize this fuel more efficiently is by the use of fuel cell technology. This has been demonstrated for the electrochemical oxidation of methane in solid oxide fuel cells at high temperatures (650-1100℃).

The present research investigates the photoelectrochemical oxidation of methane at anodized Ti photoanodes. TiO2 semiconductor generates highly reactive holes upon illumination that can drive the oxidation reaction. In this type of activation, the exploitation of light energy may dramatically reduce the energy required for the oxidation reaction. TiO2 photoanodes with a nanotube arrays structure are prepared via anodization of Ti foils followed by annealing at 500℃. This structure, which was characterized by SEM, XRD and TEM, has an efficient exposure to light with high surface area for the photocatalytic reaction. When examined by linear sweep voltammetry, this photoanode exhibits an increase of ~15% in the saturation photocurrent density (~0.5mA/cm2 at +0.2V vs. Hg/HgO) in the presence of methane, as compared to that obtained in the presence of an inert gas (water oxidation).