bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrodeposition of Tungsten from Molten KF–KCl–WO3 and CsF–CsCl–WO3
Authors: Nohira Toshiyuki , Meng Xianduo , Ide Tatsuya , Norikawa Yutaro , Yasuda Kouji 
Published: December 2020

Introduction

Tungsten metal is known for its robustness, especially high melting and boiling points and hardness. However, its hardness and brittleness make it difficult to work. Thus, electrodeposition of flat and dense tungsten films is worth investigating. There are a number of reports on the electrodepositon of tungsten from high temperature molten salts such as fluorides [1], chlorides [2], oxides [3], etc. It is known that dense and coherent tungsten deposits are more easily obtained from molten fluorides compared to molten chlorides. One drawback of typical fluoride melts like LiF–NaF–KF is difficulty in removing the adhered molten salts by water washing because LiF and NaF have limited solubility to water [4]. Although good tungsten deposits can be electrodeposited from molten oxides [3], the operation temperature tends to be very high, typically over 1123 K.
From this background, we proposed new electrolyte baths, molten KF–KCl [5,6] and CsF–CsCl. Since all the components salts of KF, KCl, CsF and CsCl have large solubility to water [4], solidified salts on deposited films can be easily removed by water washing.

Results & Discussion

First, electrodeposition of tungsten was investigated in eutectic KF–KCl melt to which WO3 was added at 923 K. Cyclic voltammograms at copper and gold electrodes indicated the deposition of tungsten metal at more negative potential than 1.55 V vs. K+/K. The effects of electrolysis conditions on the morphology of deposits were studied by changing the cathodic current density from 12.5 to100 mA cm−2. As shown in Fig.1(a), a dense tungsten film with a thickness of approximately 20 µm was obtained on a copper substrate electrode at 12.5 mA cm−2 for 120 min. From the Raman spectra of molten KF–KCl and molten KF–KCl–WO3 at 923 K, the coordination structure of W(VI) complex ion was indicated to be fac-[WO3F3]3−.
Secondly, eutectic CsF–CsCl melt was used to lower the operation temperature. After adding 2.0 mol% of WO3, the electrodeposition was investigated using copper and gold electrodes at 823–923K. As shown in Fig.1(b), a flat and dense tungsten film was obtained by galvanostatic electrolysis at 12.5 mA cm−2 for 120 min at 873 K.

Acknowledgement

This study is supported by Sumitomo Electric Industries, Ltd. The present address of Kouji Yasuda is Graduate School of Engineering, Kyoto University.

References

[1] S. Senderoff, G. Mellors, Science, 153, 1475 (1966).
[2] M. Masuda, H. Takenishi, A. Katagiri, J. Electrochem. Soc., 148, C59 (2001).
[3] K. Koyama, M. Morishita, T. Umezu, Electrochemistry, 67, 667 (1999).
[4] D. R. Lide (Ed.), CRC Handbook of Chemistry and Physics, 88th Edition, Chap.4, p.43-101, CRC Press, Boca Raton (2007).
[5] K. Maeda, K. Yasuda, T. Nohira, R. Hagiwara, T. Homma, J. Electrochem. Soc., 162, D444 (2015).
[6] T. Nohira, Molten Salts, 62, 3 (2019).

Figure 1
Electrochemical Reduction of Tungsten Oxide in Molten Chlorides
Authors: Skryptun Igor N , Bosenko Olga V 
Published: December 2020

The direct electrochemical reduction of titanium oxide to titanium metal in molten CaCl2 salt has been proven by the FFC Cambridge process. [1] Subsequently, the process has been applied to a number of refractory metals. However, there are limitations to the FFC Cambridge process. For example, the current efficiency of the process is quite low, 10-40%, to achieve sufficiently low oxygen content, 0.3%, in the final titanium product. [2] This could be due to a number of reasons, such as the increasing concentration of O2- ions in the melt as the reduction process proceeds. The metal oxide electrode has an inherent pore structure and sponge-type substrate electrodes can be used with a range of pore sizes, which has the advantage of high surface area and access of the melt to the oxide. However, when the metal oxide is reduced, oxide ions accumulation in the pores can significantly change the potential needed for the reduction, as shown in the Littlewood [3] predominance diagram. It can also result in the formation of other unwanted metal phases, such as those that include the salt’s metal, as it reacts with the oxide ions. Oxide ion build up close to the electrode surface can ultimately bring the reduction process to a halt, leaving the inner parts of the metal oxide unreduced.
1. Chen, G.Z., D.J. Fray, and T.W. Farthing, Direct
electrochemical reduction of titanium dioxide to
titanium in molten calcium chloride. Nature,
2000. 407(6802): p. 361-364.
2. Schwandt, C., D.T.L. Alexander, and D.J. Fray,
The electro-deoxidation of porous titanium
dioxide precursors in molten calcium chloride
under cathodic potential control. Electrochimica
Acta, 2009. 54(14): p. 3819-3829.
3. Littlewood, R., Diagrammatic Representation of
the Thermodynamics of Metal‐Fused Chloride
Systems. Journal of the Electrochemical Society,
1962. 109(6): p. 525.
In Situ Neutron Scattering to Elucidate the Mechanism of Rapid Lithium Ion-Conducting Garnet Synthesis Using Nanoparticles
Authors: Sacci Robert , Malkowski Thomas , Chen Xi Chelsea , Kirkham Melanie J. , McAuliffe Rebecca D , Armstrong Beth L , Veith Gabriel M. , Daemen Luke L 
Published: December 2020

Consumer safety is a market force that is impeding high energy-dense lithium metal batteries from entering the marketplace. As such, research and development into solid electrolytes (SE) have yielded several promising candidates for solid-state batteries. However, each class of SEs comes with particular problems that either increase processing cost, or decrease performance relative to current liquid electrolytes, or both. For example, Lipon and other similar lithium silicates and phosphates are stable against high voltage cathodes (>4.5 V) and lithium metal; however, their conductivity is poor, leading to low power density. Lithium phosphorus sulfides (LPS) have the opposite problem, high conductivity, and instability. Ceramic phases such as Li7La3Zr2O12 (LLZO) have attractive advantages to both classes of materials, inherently high Li conductivity and chemical robustness. However, these advantages come with a cost: complicated processing in terms of high-temperature synthesis and interface control. Concerning the first perceived processing problem, temperatures used for the solid-state synthesis of LLZO are 1000 °C or greater. These temperatures not only adds to the manufacturing costs, but it also promotes lithium evaporation, which then requires the addition of 5-20% excess lithium precursor; costs increase further. Because Li loss leads to a Li concentration gradient resulting in a mixed-phase product, single-phase cubic LLZO synthesis requires manual separation or multiple grinds and calcines. Therefore, we need a new method for LLZO synthesis, and to do that, we need to understand the reaction pathway.
This work demonstrates a method to improve the reaction kinetics and purity of LLZO through the use of nanoparticles of a known intermediate to improve the reaction kinetics and purity of LLZO. We will show in situ neutron scattering results that suggest the formation of La2Zr2O7 during typical LLZO occurs right before LLZO. This fact led to a strategy for reducing both synthesis time and temperature. We describe an efficient synthesis pathway for Al-doped LLZO using La3Zr2O
x
nanoparticles with nitrate precursors. The reaction is completed within one hour and produces a porous network of LLZO.
This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Division of Materials Science and Engineering. This research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory.
Engineering of Fermi Level by Construction of Hybrid Systems
Authors: Bienkowski Krzysztof , Solarska Renata Anna 
Published: December 2020

Hybrid heterostrures provide a versatile and largely enhanced systems in comparison to their single components. However, construction of effective visible-light responding and stable hybrid heterojunction based photoelectrodes remains a challenge due to stricte requirements regarding band alignment in such constructions. Therefore implementation of a conductive mid-layer of reduced graphene oxide (RGO) might be a crucial factor in band structure engineering. Herein we demonstrate the formation of an outperforming hybrid heterojunction photocatalyst containing diversified synthetic approaches RGO and thus allowing to engineer the Fermi level position within the working architecture.
Shifting the position of the Fermi level makes possible to increase the size of the depletion layer and PEC efficiency of the entire system increases.
Enabling Real-Time Detection of Electrochemical Desorptionphenomena with Sub-Monolayer Sensitivity
Authors: Cavalca Filippo , Trimarco Daniel 
Published: December 2020

Across many scientific and industrial fields, it is a challenge to analyze chemical reaction products with high sensitivity and fast time-response. This is especially true in systems related to electrochemical energy conversion and storage, such as batteries and fuel cells, where accurate monitoring of fast and transient reaction phenomena often reveals key insights.
Here, we present a unique analysis instrument using a microchip-based inlet system to couple a mass spectrometer directly to any liquid test environment, aqueous or non-aqueous, and exhibits a sensitivity 3-4 orders of magnitude than conventional differential electrochemical mass spectrometry (DEMS).1–3 The instrument allows to measure the evolution of volatile products and consumption of reactants at electrode surfaces. Due to its extraordinary sensitivity, the system can measure all the individual volatile molecules desorbing from an electrode surface during a single electrochemical turnover. Product formation can be measured from total Faradaic currents of 1 mA all the way down to 1 nA, corresponding to approximately 10 ppm of a monolayer desorbing from the electrode surface in 1s. These features enable time-resolved, fully quantitative measurements of transient phenomena during electrochemistry, providing fundamental insight in the electrochemical reaction mechanisms. Furthermore, an accurately calibrated on-chip gas system allows rapid gas switching between different gases, both inert and reactive. Due to the near-instantaneous equilibration between gas and electrolyte, the transient response of electrodes to rapid gas exposure changes can be measured.
The capabilities of this analysis system are showcased by various examples, including electrochemical water-splitting at low overpotential and low-surface area CO-stripping. In situ quantification of hydrogen and oxygen evolution is shown at Faradaic currents on the order of 1 nA. In comparison, conventional techniques can only detect down to about 10 μA of continuous product formation. Finally, the electrochemical stripping of < 1 % of a CO monolayer at standard potential scan-rates of 50 mV/s is shown (Fig. 1).
Figure 1. H2 evolution and CO stripping experiments using a polycrystalline Pt electrode in 1M HClO4.

Trimarco, D. B. et al. Enabling real-time detection of electrochemical desorption phenomena with sub-monolayer sensitivity. Electrochim. Acta
268, 520–530 (2018).

Roy, C. et al. Impact of nanoparticle size and lattice oxygen on water oxidation on NiFeOxHy. Nat. Catal.
1, 820–829 (2018).

Winiwarter, A. et al. Towards an atomistic understanding of electrocatalytic partial hydrocarbon oxidation: propene on palladium. Energy Environ. Sci. (2019) doi:10.1039/C8EE03426E.

Figure 1
Revealing Solvent Effects on Ion Insertion within Battery Primary Particles Using Operando Scanning Transmission X-Ray Microscopy
Authors: Chung Jinkyu , Koo Bonho , Kim Juwon , Seo Sungjae , Lee Danwon , Han Jeongwoo , Jo Sugeun , Kim Namdong , Shin Hyunjoon , Yu Young-Sang , Shapiro David , Lim Jongwoo 
Published: December 2020

LiFePO4 (LFP), the attractive commercial cathode materials, exhibits the phase separation between lithium-poor and lithium-rich phase within individual particles due to the wide miscibility gap. The boundaries between such phases develop large stress, lead to cracks within individual particles, and decay the cycle life. There have been lots of interest in investigating the origin of lithium heterogeneity and manipulating the phase boundaries within the particles during cycling. Previously, we revealed that insertion kinetics is dependent on the local lithium composition from which the hysteresis of lithium spatiodynamics originate. [ref.1] In addition, uniformity of ion insertion kinetics at electrolyte-electrode interface governs lithium heterogeneity and spatiodynamics in ether-based organic electrolyte. [ref.1] However, it remains still unclear how the chemical interaction of lithium ions, electrolyte molecules, and solid electrode controls nanoscale ion insertion kinetics. By developing operando scanning transmission x-ray microscopy (STXM) platform which maps lithium composition within individual LFP particles at 50 nm resolution during cycling, we investigated the interfacial lithium transport in various electrolytes: water, carbonates, and ethers. We synthesized LFP particles with platelet morphology and [010] crystallographic axis, which is fast ion diffusion direction, lied parallel to the monochromatic X-ray allowing to visualize lithium transport in the particles. Herein, we discover that aqueous electrolyte greatly accelerates lithium insertion kinetics, completely redirecting lithium heterogenesity and spatiodynamics compared with organic-based electrolyte. Aqueous environment kinetics show higher exchange current density (~700 mAm-2) than organic EC/DMC (~200 mAm-2) and also higher surface diffusion rate which account for the higher degree of intraparticle phase separation within the particles. By extracting kinetics parameters from our result, we experimentally demonstrate that heterogeneity and spatiodynamics in the single particle kinetics is determined by the strong interaction between the electrolyte molecules and the surface of electrode particles.
Ref. 1 J. Lim et al. Science (2016) 353 p566

Figure 1
Copper Sulfide Derived Nanoparticles Supported on Carbon for the Electrochemical Reduction of Carbon Dioxide
Authors: Tapia Rosales Marisol , van Oversteeg Christina H.M. , Helfferich Kristiaan H. , Ghiasi Kabiri Mahnaz , Ngene Peter , de Mello Donegá Celso , de Jongh Petra E. 
Published: December 2020

The electrocatalytic reduction of CO2 (CO2RR) and H+ (or H2O) into chemicals and fuels is attracting attention as a way to address current energy and environmental issues. One of the main focus in this field is the development and understanding of electrocatalysts that can promote the electrochemical CO2 reduction efficiently, and with high selectivity for the desired product. Copper electrodes are extensively studied and stand out because of their unique ability to produce a range of different products including hydrocarbons and oxygenates, which is ascribed to their intermediate binding strength for the CO intermediate. The use of oxide-derived Cu electrodes has arisen, because it promotes CO and COOH formation at low overpotentials, even though the electrodes are operating at potentials where the CuO should be reduced to metallic copper. Inspired by this, some recent studies have also shown that the use of sulfur-containing Cu or sulfide-derived Cu increases the selectivity towards formates, ethanol, propanol, or ethylene at intermediate overpotentials. The origin of these effects is still under debate, but it is often attributed to a change in the binding energy of the intermediates such as *OCHO, *COOH, and CO due to the formation of specific Cu surface structures or the presence of sub-surface sulfur or oxygen in the Cu or mixed phases.
In this work, we investigated the phase stability and catalytic performance of carbon-supported sulfide (CuS and Cu2S) derived Cu nanoparticles in the electrochemical reduction of CO2 in aqueous media. The CuS@C and Cu2S@C nanoparticles were prepared via a novel, liquid phase sulfidation method, in which carbon-supported CuO (CuO@C) nanoparticles were converted to either CuS@C (25±13 nm) or Cu2S@C (17±1 nm) as shown in Figure 1a. The stability of the supported nanoparticles was investigated using cyclic voltammetry, where reduction peaks were observed in the first cathodic scans of both CuS@C and Cu2S@C (figure 1c). The reduction was monitored operando under CO2 reduction conditions using in-situ X-ray absorption spectroscopy (XAS). The in-situ XAS spectra showed that at a potential of -0.9V vs. the reversible hydrogen electrode (RHE), both CuS@C and Cu2S@C are reduced to metallic Cu@C. Finally, the products formed by the CuS@C and Cu2S@C-derived catalysts were compared to those of CuO@C-derived catalyst. At current densities of -1.5mA/cm2, the CuS@C- and Cu2S@C-derived catalysts show increased production of formate (figure 1d), while CO production is suppressed, in comparison to the CuO@C catalyst. Cu-sulfide derived catalyst showed differences in formate production, indicating the initial Cu-sulfide phase influences the product selectivity.

Figure 1
Octahedral SnO2 Single Crystals for Selective CO2 Electroreduction
Authors: Liu Hai , Kuang Siyu , Ma Xinbin , Zhang Sheng 
Published: December 2020

CO2 electrochemical reduction is one of the effective ways to close the global anthropogenic carbon cycle. However, CO2 reduction is a sluggish process involving multi-electrons and multi-protons transfer and needs to compete with hydrogen evolution reaction (HER)1. According to the pioneering studies by Hori et al., metal catalysts can be classified into four categories in terms of main products, where formic acid/formate as an ideal hydrogen storage carrier is an attractive product. Indeed, a recent technoeconomic analysis shows that the 2e- products (formate and CO) are more desirable. The p-block transition metals (such as In, Sn, Pb, Tl, Bi) have been found to be able to selectively convert CO2 to formate. In particular, tin-based catalysts have been intensively investigated owing to its inexpensive price and low toxicity.
Our previous work has explored the size effect of SnO2 nanoparticles and carbon support effect on the catalytic activity for CO2 electroreduction2. Kanan’s group has also investigated bulk tin oxide layer for the CO2 electroreduction3. Unfortunately, all the aforementioned tin catalysts display volcano-type formate selectivity against potential plots, since too positive or too negative potentials favor competitive hydrogen evolution reaction, which limits their applications in practical CO2 electrolyzers.
Herein, we have synthesized octahedral SnO2 single crystals exposed with facets denoted (332) and (111). Interestingly, those high-energy facets exhibit remarkably high CO2 catalytic activity and high formate selectivity of over 80% within a ~500 mV potential window. Density function theory (DFT) calculations and In situ Raman spectroscopic studies demonstrate that the strong adsorption energies for *OCHO species and weak binding strength to HCOOH* favor formate production in a broad potential range. We believe this work will advance the development of practical CO2 electrolyzers.
Reference
1 Zhang, S.; Fan, Q.; Xia, R.; Meyer, T. J. Acc. Chem. Res. 2020, 53 (1), 255-264.
2 Zhang, S.; Kang, P.; Meyer, T. J. J. Am. Chem. Soc. 2014, 136 (5), 1734-1737.
3 Chen, Y.; Kanan, M. W. J. Am. Chem. Soc. 2012, 134 (4), 1986-1989.
Sulfonated Phthalocyanine Redox Flow Cell for High-Performance Electrochemical Water Desalination
Authors: Pan Yanbo , Yao Libo , Wu Dezhen , Bentalib Abdulaziz , Li Jialu , Peng Zhenmeng 
Published: December 2020

A reliable clean water supply is now one important and challenging issue for the human society. With the facts that only 0.4% of the water on earth is readily drinkable and 98% of the water is saltwater, water desalination for clean water production has become a key strategic solution to satisfy the increasing global water demand. Over the years, different saltwater desalination technologies were researched and developed, including reverse osmosis membrane desalination (RO), electrodialysis (ED), capacitive desalination (CDI) and multi-effect distillation (MED). However, some inherent technical issues, like high operation cost, large capital cost and/or low desalination capacity, associate with these existing technologies that lead to a high clean water production cost and limit their applications. Thus, there is a need of new water desalination technology that can purify saltwater with low cost and high efficiency.
In this work we report a new water-soluble nickel phthalocyanine tetrasulfonic acid tetrasodium salt (NiPcTATS)-based redox flow desalination battery (RFDB) for safe, effective and efficient water-salt separation. The fabricated RFDB cell exhibited a high desalination rate at 3.4 gNaCl/(molNiPcTATS∙hr) even with a low 0.5 V cell voltage and required as low as 11.5 kJ/mol salt in energy consumption. The cell showed excellent reversibility and durability for long-term operation, benefiting from the fast-redox kinetics and chemical stability of the redox couple. With no consumption of the redox couple and energy recovery during the salination process, this new method provides a continuous desalination capability with unlimited salt removal capacity. We also demonstrated the use of simple solar panel for effectively driving the RFDB cell, proving it a promising and practical technology for clean water production in remote places like islands and ships.
The Gate Cut Process Window Discussion
Authors: Ji Shi-liang , Han Qiu-Hua , Zhang Hai-Yang 
Published: December 2020

The technology of FinFET has led to the continuity of device scaling and enabled the prolongation of Moore’s Law towards the 7 nm and beyond nodes. The gate cut last has been widely adopted since it can provide better SiP/SiGe growth environment, hence yielding the better electrical performance. However, This approach requires a higher level of defect control.
As we all know, the first task of gate cut is to completely cut off the gate, so that the metal gate that do not need to be connected can realize electrical separation. If good electrical insulation can not be achieved, there will induce a large leakage, so that the working voltage is increased. However, due to the miniaturization of the size, the distance between the end of the metal gate and the effective Fin is very short, which requires that the gate cutting can not only achieve electrical isolation through the size increase. The filling and patterning of the various materials of the metal gate must be considered. On the other hand, defect control is also critical for many special structures, such as gate ends formed by SaDP and gate cutting with special relationship to Fin.
This paper focuses on defect issues related to gate cutting in FinFET. It mainly includes: the first, some common defects related to gate cutting itself, such as the absence of cutting pattern caused by etch bias in dense and iso areas, the mutation of gate cutting pattern caused by stress introduction, and the gate bridge caused by tapered bottom profile, etc. The second, defect issues caused by gate cutting size affecting other manufacturing processes, such as residue generated by HKMG pattering, dummy poly gate residue, capping layer residue, single diffusion break induce metal gate bridge, etc. The third, defect issue of a structure that has a special relationship to the gate cut pattern, gate line end bridge, etc. In this article, we will discuss these typical defect issues in detail to gain a better understanding of the gate cut process. By understanding these defects, we can better control the metal gate cut process and maximize the process window.