bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Switchable Electron Transfer Reactivity in Phthalocyanine Sc3n@C80 Supramolecular Ensembles
Authors: Trukhina Olga , Torres Tomas , Bottari Giovanni , Guldi Dirk M. , Echegoyen Luis , Rudolf Marc , Akasaka Takeshi , Almeida Veronica , Muñoz Nicolas
Published: February 2020

Phthalocyanines (Pcs) are planar, two-dimensional aromatic pophyrinoids which possess outstanding structural, optical and electrical properties as well as stability that render them perfect building blocks for the incorporation into multifunctional materials. Similarly, Ih
-Sc3N@C80 fullerene – the most abundant member of the fullerenes family after C60 and C70 – in addition to have excellent electron-accepting properties, provides conditions for an extra stabilization of charge-separated states due to the presence of the internal Sc3N species. This makes Ih
-Sc3N@C80 an ideal molecular partner for photo- and electroactive molecular systems such as Pcs.

Although several reports have appeared on the preparation of covalent Sc3N@Ih-C80 ensembles, there is no use of Ih
-Sc3N@C80 for the preparation of non-covalent assemblies. In this context, plenty of supramolecular systems arranged via coordination interactions have been successfully demonstrated for Pc-C60 supramolecular dimers and trimers. Low accessability of non-covalent supramolecular systems with Ih
-Sc3N@C80 is mainly caused by the more sophisticated synthesis and purification of the corresponding fullerene derivatives.

Herein, we report a novel example of donor-acceptor Pc/Ih
-Sc3N@C80 supramolecular dimers assembled via metal-ligand coordination interactions between Zn(II)Pcs and pyridil-substituted Ih
-Sc3N@C80  or C60 fullerene. Photophysical (ground- and excited state) and electrochemical studies on these ensembles showed that depending on the electron-donor or electron-acceptor character of the ZnPcs, a switchable electron transfer reactivity occurs in the case of the Ih
-Sc3N@C80 supramolecular systems, revealing the ability for this endohedral metallofullerene to behave either as electron donor or electron acceptor unit.
Cancer Hyperthermia Studies: On the Aqueous Structure and Radiofrequency-Induced Heating Properties of a Water-Soluble [60]Fullerene
Authors: Mackeyev Yuri , Muto Atsushi , Cheney Matthew , Serda Rita , Curley Steven A. , Wilson Lon J.
Published: February 2020

The symmetrical, malonodiserinolamide hexa-substituted [60]fullerene, C60-ser, is a key water-soluble C60 derivative of interest for the treatment of cancer by radiofrequency(RF)-induced hyperthermia due to its biocompatibility, neutral charge, lipophilicity, and ability to cross restrictive biological membranes. In aqueous solution C60-ser, which is surrounded by 24 hydroxyl groups, maintains relatively stable layers of closely-bound water molecules (hydration sphere), forms highly dynamic aggregates, sized between 100-400 nm in diameter, which exist in equilibrium with individual, hydrated C60-ser molecules. Our recent observations indicate that these dynamic C60-ser aggregates are built up of a single layer of C60-ser molecules, with water locked inside a hollow core structure. Using a thermal imaging camera, aqueous C60-ser solutions have been shown to produce heat when irradiated with an 13.56 MHz RF field (900W) in a concentration-dependent manner with a heating rate of up to 1.0 °C/sec at 10 mg/ml. This result establishes that C60-ser is a neutrally-charged, key [60]fullerene-based nanoparticle, that might be used for the treatment of cancer by RFH-induced hyperthermia.

We acknowledge Kanzius Foundation and Welch Foundation Grant C-0627 for financial support.

Figure 1
(Invited) Temperature, Magnetic Field, and Dimensionality Effects on the Raman Spectra of TaSe2
Authors: Hight Walker Angela R. , Simpson Jeffrey R , Chowdhury Sugata
Published: February 2020

In bulk form, TaSe2 exhibits transitions between commensurate and incommensurate charge-density wave (CDW) phases, and is attracting interest for advanced device applications.  In order to explore the evolution of the groundstate CDW phase with layer number, mechanical exfoliation of bulk crystals provides few- to single-layer flakes.  In the present work, we extend our opto-thermal Raman measurements1 on MoS2 to include other TMDs, specifically TaSe2 in both 1T and 2H crystallographic phases.  A novel, magneto-Raman microscope system affords measurement of low-frequency (down to 10 cm-1) vibrational modes as a function of: temperature (100 K to 400 K), magnetic field (0 T to 9T) and laser excitation. The dependence of the observed Raman-active phonons on temperature and magnetic field will be discussed and compared with earlier results on MoS2. Specifically, we observe the appearance of low-frequency, zone-folded modes in the CDW state, which soften with temperature similar to the higher frequency, in-plane E2g mode. Additionally, we compare the measured magneto-Raman results to calculations using ab initio, density functional theory.

1ACS Nano 2014 8, 986
Electrochemical Property of Platinum Supported on Thiol-Attached Reduced Graphene Oxide Composite Electrode for Fuel Cells
Authors: Kim Seok , Kwon Sung Sang , Woo Joo Hyeong , Jung Yongju
Published: February 2020

The direct methanol fuel cells (DMFCs) have been received much attention as promising energy converters in the portable application because of high energy density, low operating temperature, low fuel price and low pollutant emission. However, although there are many advantage of DMFC, commercialization of DMFCs is difficult due to poor methanol oxidation kinetics, nondurable Pt-based catalysts, expansive price and poison of Pt by formation of CO-like intermediates [1]. To overcome these problems, many studies have progressed with numerous scientists. One of the methods is to modify supports like carbon material.

Among many carbon materials such as carbon black, carbon nanotubes, graphene and carbon fiber, the graphene have unique properties which are planar structure, high surface area and outstanding mechanical and chemical properties [2, 3]. However, the Pt-graphene used in fuel cell has low electrocatalytic activity because of weak interaction between the graphene used as support and Pt particles. Recently, to overcome the low electrocatalytic activity, many efforts for modification of RGO surface have been devoted. It has been studied by considering conducting polymer, and surfactant dispersant and substitution materials of functional groups [4,5]. The key point for maximizing elelctrocatalytic acticity is dipersion, particle size and chemical composition of Pt particles.

In this study, we present Platinum (Pt) supported thiol-attached reduced graphene oxide (RGO-S). The functional groups of GO were substituted for thiol (SH), which result from strong nucleophilic substitution reaction. The sulfur (S) that has high affinity to metal combines with Pt by strong covalent bond. In conclusion, The RGO-S-Pt composite was synthesized and showed that the RGO-S-Pt composite was better than RGO-Pt composite in terms of electrocatalytic activity. Also, the electrocatalytic activity was different according to the various weight ratios of thiol. Especially, the RGO-S-Pt composite that has weight ratio of one (GO) to five (SH) presented the highest performance in terms of electrocatalytic acticity.

Acknowledgments

This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning, Korea (Grant No.: NRF-2011-0009007).

 

References

[1] Y. Zhao, L. Zhan, J. Tian, S. Nie, Z. Ning, Electrochim. Acta, 56 (2011) 1967

[2] J.Y. Park, S. Kim, J. Electrochem. Soc., 161(4) (2014) F518.

[3] C. Song, S. Kim, J. Electrochem. Soc., 162(10) (2015) F1181.

[4] J. Debgupta and V. K. Pillai, Nanoscale, 5 (2013) 3615

[5]  Q. L. Zhang, T. Q. Xu, J. Wei, J. R. Chen, A. J. Wang and J. J. Feng, Electrochim. Acta, 112 (2013) 127
Graphene Oxide Nanocomposites for Supercapacitor Electrodes
Authors: Pawar Pranav Bhagwan , Saxena Sumit , Suman Siddhartha , Shukla Shobha
Published: February 2020

High density energy storage is one of the current demands for sustaining renewable energy systems. This requires high charging and discharging rate, large power density and stability for prolong time of service. Several materials have been explored however none of them satisfy most or all of these requirements. Graphene oxide and Poly Vinyl Alcohol based nanocomposites have recently gained attention due to high mechanical stability. We have explored the use of Graphene Oxide – Poly Vinyl Alcohol nanocomposite as electrode material for supercapacitor applications. The oxygen containing groups in Graphene oxide enables the composite to store pseudo charge making it attractive for supercapacitor applications. Nanocomposite were synthesized by mixing poly vinyl alcohol and graphene oxide in solution phase. Electrochemical characterization shows that the Graphene Oxide – Poly Vinyl Alcohol has high specific capacitance and long life cycle, further they are ecofriendly, economical and hence potential candidates to be used as electrodes in supercapacitors.
(Invited) Graphene and Graphene-Analogue Aerogels: Synthesis and Applications
Authors: Worsley Marcus A.
Published: February 2020

Aerogels are porous solids used in a wide range of applications including sorbents, filtration, insulation, hydrogen storage, catalysis, batteries, and supercapacitors. Their unique properties are related to their high internal surface, low-density, and small pore/particle size.  Two-dimensional (2D) nanomaterials, such as boron nitride and graphene, also exhibit a range of distinct optical, electronic, and mechanical properties, but are typically limited to thin films and coatings.  Assembling 2D nanomaterials into monolithic aerogels expands their application space to include technologies and manufacturing processes that require a macroscopic 3D form factor.  Furthermore, placing the novel intrinsic properties of 2D materials in a low-density, high surface area architecture has the potential to unlock exciting new properties and features only displayed in the aerogel system.  Here, we present synthesis schemes for aerogels made from several different 2D materials, (e.g. boron nitride, graphene, dichalcogenides, etc.), including hybrid aerogels, combining two or more layered materials. Applications of these novel aerogels in applications including sorbents, sensing, energy storage, and catalysis will be covered.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
(Invited) Conjugated Polymer Nanostructures for Li-Battery
Authors: Zhang Qichun
Published: February 2020

In this presentation, I will talk about the prepareation, characterization and self-assembly of organic conjugated polymers and find their applications in Li-batteries.
Synthesis of Bimetallic Platinum-Iron Nanoparticles As Robust and Low-Cost Counter Electrode Materials for Dye-Sensitized Solar Cells
Authors: Omelianovych Oleksii , Larina Liudmila L. , Dao Van-Duong , Choi Ho-Suk
Published: February 2020

In this study, we report the synthesis of bimetallic FePt nanoparticles (NPs) on FTO substrate and their application as efficient counter electrodes (CEs) in dye-sensitized solar cells (DSCs). To overcome disadvantages related with conventional method, the synthesis of alloy NPs is carried out by dry plasma reduction. Bimetallic FePt NPs were synthesized on the FTO surface with the volume ratios of precursors as follows: 1:9, 2.5:7.5, 5:5, 7:3, 9:1. The CEs were denoted as Fe0Pt1, Fe0.1Pt0.9, Fe0.25Pt0.75, Fe0.5Pt0.5, Fe0.7Pt0.3 and Fe0.9Pt0.1. The highest efficiency was 8.93% for Fe0.25 Pt0.75 CE, which is higher than that of device employing Pt NPs CE. The results are contributed by high electrical conductivity and excellent catalytic activity of FePt alloy CEs. The obtained results suggest that the tailoring of electronic structure of Fe x Pt1-x (1 ≥ x ≥ 0) alloy can be used for enhancing the catalytic activity of CE, and in turn for construction of high-efficiency DSCs.
Development of Tin-Rich Methylammonium Halide Perovskites for Carbon-Based Solar Cells Free of Hole-Transport Materials
Authors: Tsai Cheng-Min , Diau Eric Wei-Guang
Published: February 2020

Methylammonium halide perovskite solar cells have received a tremendous amount of attention in recent years due to their skyrocketing efficiency improvement starting from 4% to 20% within six years. However, the employment of metal electrode, expensive hole-transporting materials (HTM), and particularly, environmentally hazardous material of lead presents a barrier to successful commercialization. In this study, we report on preparation and characterization of perovskite material with PbI2 partially replaced by SnI2 or SnCl2. Moreover, the performances of mixed perovskite solar cells are based on a HTM-free carbon electrode configuration. Noticeably, the case of employing SnCl2, CH3NH3SnyPb(1−y)I3-xClx, which shows completely different energy level trend to CH3NH3SnyPb(1−y)I3 and better photovoltaic performance when more SnCl2 component in the devices and stability of devices are 70 times more than SnI2 one. Moreover, the device has the highest powder conversion efficiency (PCE) of 2.15% (CH3NH3Sn0.75Pb0.25I3-xClx), which shows broad light absorption region up to 1000 nm and highest current density of 15.66 mA cm-2. In order to further improving device performance, a 20 mol% SnF2 additive was introduced into CH3NH3Sn0.75Pb0.25I3-xClx, after that current density can be improved to 23 mA cm-2, V
OCis 0.35V, FF is 0.52 and PCE will beyond 4.0% with a small effect of hysteresis and excellent long-term stability over 1000 h (storing at glove box).

Figure 1
(Invited) Efficient Electrocatalysis of Oxygen Reduction with Metallo-Corroles
Authors: Elbaz Lior , Levi Naomi , Mahammed Atif , Gross Zeev
Published: February 2020

The most active non-precious metal catalysts (NPMCs) for oxygen reduction (ORR) to date are the pyrolyzed catalysts, inspired from Heme-like complexes. These are usually composed of iron and/or cobalt coordinated by nitrogens, claimed to resemble the structure of porphyrins and phthalocynines, on the surface of a carbon support. Unfortunately, the exact structure of the catalytic sites remains a mystery and the solution for this conundrum seems be almost impossible. The advantages of using such catalysts are: (1) their high activity and (2) low price, which is derived from the cost of their precursors. The disadvantages are: (1) low durability compared to precious metal catalysts, and (2) their unknown structure, which limits their further improvement in order to obtain both the activity and durability benchmarks needed to become good alternatives for precious metals.

One of the most promising options to resolve these issues is to find non-pyrolyzed molecular non-precious metal catalysts for ORR that could be tuned to match the necessary requirements. Recently, Metallo-corroles, a relatively new family of molecular catalysts was reported to have very good potential as non-precious metal catalysts for ORR. The electro-reduction of oxygen was investigated, using a series of first row transition metal β-pyrrole-brominated 5,10,15-tris(pentafluorophenyl)-corroles [M(tpfcBr8), M=Mn, Fe, Co, Ni and Cu] as catalysts in alkaline solutions. The kinetics of the oxygen reduction reaction (ORR) on these catalysts was evaluated using the rotating disk electrode method in a solution of 0.1M KOH. These corroles were adsorbed on a high surface area carbon powder (BP2000) prior to electrochemical measurements, to create a unique composite material. The comparison between the corroles with different metal centers showed a favorable catalytic performance of the ORR in the case of Fe and Co Corroles. The mechanism by which these corroles catalyze the ORR was studied by the rotating ring disk electrode (RRDE) technique, showing that in the case of alkaline solutions, there is a favorable 4 electron transfer mechanism. When comparing the performance of these catalysts in alkaline solutions, to their performance in acidic media, it was clear that the former was substantially higher, both in the onset potentials of the ORR and in the overall kinetic parameters.
(Invited) Metal Ion Induced Cyclization of Phenoxybilinones to 5-Oxaporphyrin Metal Complexes
Authors: Mizutani Tadashi
Published: February 2020

Linear tetrapyrroles attracted interest of chemists and biochemists, due to the interesting optical properties, and

biological importance both in photosynthesis and photoreceptor. In particular, the dynamic structural changes

of linear tetrapyrroles such as cis-trans isomerization and coordination to various metal ions are unique

features of this class of compounds. We found that 19-phenoxybilinones undergoes cyclization upon reaction with

metal ions to yield 5-oxaporphyrin metal complexes. In this paper, we summarizes the scope and limitation of

this metal-induced cyclization of 19-phenoxybilinones, and report optical properties of the metal complexes of

5-oxaporphyrin.
(Invited) Catalytic and Biocatalytic Iron Porphyrin Carbene Formation: Effects of Binding Mode, Carbene Substituent, Porphyrin Substituent, and Protein Axial Ligand
Authors: Khade Rahul , Zhang Yong
Published: February 2020

Iron porphyrin carbenes (IPCs) are important intermediates involved in various chemical reactions catalyzed by iron porphyrins and engineered heme proteins, as well as in the metabolism of various xenobiotics by cytochrome P450. However, there are no prior theoretical reports to help understand their formation mechanisms and identify key information governing the binding mode, formation feasibility, and stability/reactivity. A systematic quantum chemical study was performed to investigate the effects of carbene substituent, porphyrin substituent, and axial ligand on IPC formation pathways. Results not only are consistent with available experimental data, but also provide a number of unprecedented insights into electronic, steric, and hydrogen bonding effects of various structural factors on IPC formation mechanisms. These results shall facilitate research of IPC and related systems for sustainable chemical catalysis and biocatalysis.
(Invited) Growth, Structure, and Optoelectronic Properties of Crystalline Binary Porphyrins
Authors: Mazur Ursula , Hipps K W , Borders Brian , VanZijll Marshall
Published: February 2020

Multidimensional self-assembled crystalline nanostructures were synthesized from ionic porphyrin tectons. Porphyrins are an important class of organic semiconductors that structurally and functionally resemble naturally occurring photosynthetic and enzymatic chromophores and thus are extensively being studied as building blocks for molecular optoelectronics. 1D (rods) and 3D (hyperbranched sheave-like) porphyrin nanocrystals were examined by scanning probe microscopy, TEM, and diffraction methods. A model for predicting the crystal size distribution of 1D system was developed based on mass balance and included terms for nucleation, growth, and Ostwald (OR) ripening. The formation of 3D sheaf-like structures is the result of crystal splitting followed by the long term growth of individual nanoribbons. Integration constants and activation energies for the 1D and 3D porphyrin systems were obtained. A photoconductivity study of the 1D nanorods and a model for electron transport through the nanostructures will be presented. The mechanical properties of these ionic porphyrin assemblies are comparable to those of covalently bonded polymeric systems making them excellent candidates for flexible optoelectronic devices.
Solid State Rechargeable Li-Ion Batteries Prepared at Room Temperature over Flexible Organic Substrates: Performance and Limitations
Authors: El Gabaly Farid , Ware Nicholas , Fuller Elliot James , Talin Albert Alec
Published: February 2020

Solid-state Li-ion batteries (SS-LIBs) have been widely demonstrated and represent a safer, more stable alternative to wet batteries in several applications. Specifically, thin-film SS-LIBs allow integration with microelectronics and, in general, can be prepared over a wide range of substrates and shapes such as flexible metal sheets or coaxially deposited on wires. One of the best performing chemistries for thin-film SS-LIBs, based on its energy density, long-term stability and very-low self-discharge, has a LiCoO2 cathode, LiPON solid electrolyte, and Si anode. Preparation of the efficient 'high-temperature' LiCoO2 phase typically requires substrate annealing during deposition (300-500 C) and post-annealing of the sputter-deposited films (500-800 C in oxygen) to increase crystallinity. The process is incompatible with most flexible polymer substrates and other inexpensive organic materials that cannot be heated much beyond room temperature.

Here we demonstrate solid-state thin-film Li-ion batteries based on LiCoO2/LiPON/Si chemistry over a variety of flexible organic substrates using an all-room temperature preparation. The batteries show good overall performance and have a long cycle life. We compare several metrics of performance with state-of-the-art annealed LiCoO2 batteries on silicon substrates. Finally, we explore the cases when room temperature batteries show a larger initial capacity than high-temperature LiCoO2 SS-LIBs.

Figure 1
A Novel Sulfur Cathode Architecture for High Capacity and Durable Li-S Battery
Authors: Dharmasena Ruchira , Sumanasekera Gamini U , Jasinski Jacek B , Thapa Arjun , Sunkara Mahendra Kumar
Published: February 2020

Li-S battery technology has the potential for low cost and high capacity (up to 1470 mAh/g) battery technology for electric and stationary applications[1]. However, polysulfide creation and their dissolution in electrolytes and lack of conductivity makes it difficult to formulate sulfur cathode for Li-S battery [2-4]. Majority of the efforts to-date involved either coatings or impermeable membranes and electrolyte additives. Herein, we report the use of a mesoporous layer for Sulfur cathodes to suppress polysulfide dissolution and capacity decay in Li-S batteries.

 The electrode fabricated with the meso-porous coating exhibited high and stable gravimetric discharge capacity of ~ 750 mAh/g over 100 cycles. Sulfur is supported on carbonized polyacrylonitrile (PAN) to improve the electrical conductivity in the electrode. The other part of the electrode is designed in a simple way to withstand the expansion and contraction in order to obtain higher and stable gravimetric capacity with improved cyclability. Cyclic voltammetry and impedance spectroscopy is used to understand various processes during Li alloying and de-alloying reactions within sulfur cathode. Results are compared between electrodes with and without the meso-porous coating. The fabrication procedure for our sulfur cathode is simple and scalable in terms of commercial scale manufacturing.

REFERENCES

1. Bruce, P.G., et al., Li-O2 and Li-S batteries with high energy storage. Nat Mater, 2012. 11(1): p. 19-29.

2. Singhal, R., et al., A free-standing carbon nanofiber interlayer for high-performance lithium–sulfur batteries. J. Mater. Chem. A, 2015. 3(8): p. 4530-4538.

3. Ma, X.Z., et al., S–TiO2 composite cathode materials for lithium/sulfur batteries. Journal of Electroanalytical Chemistry, 2015. 736: p. 127-131.

4. Manthiram, A., et al., Rechargeable lithium-sulfur batteries. Chem Rev, 2014. 114(23): p. 11751-87.
Lithium Sulfide Nanocrystals Synthesized By an Energy-Efficient Process for Advanced Rechargeable Batteries
Authors: Li Xuemin , Ban Chunmei , Wolden Colin , Yang Yongan
Published: February 2020

Lithium-sulfur (Li-S) batteries are among the most promising next generation batteries to realize in the near future to meet the demands of electric vehicles and grid storage.  However, the direct use of lithium anode and sulfur cathode confronts safety concerns due to the dendrite growth of lithium metal.  An alternative is to use lithium sulfide (Li2S) nanomaterials.  However, the commercially available Li2S exists only as micro-powders, due to the high temperature processes used in the industrial synthesis.

Herein we report a thermodynamically favorable method by taking the advantage of hydrogen sulfide (H2S), a major industrial waste gas.  Considering the fact that H2S traditional abatement methods are energy intensive and cost ineffective due to the thermodynamic limitations and low values of the products sulfur and water, it is mutual beneficial to combine the alkali sulfide synthesis with the H2S abatement.  The synthetic reaction developed is spontaneous and irreversible at ambient temperature and pressure, proceeding to completion very rapidly.  

Specifically, lithium naphthalenide (Li-NAP) in dimethoxyethane (DME) was used to react with H2S, producing anhydrous Li2S nanocrystals, and 1,4-dihydronaphthalene, itself a value-added chemical that could be used as liquid fuel.  The phase purity, morphology, and homogeneity of the resulting Li2S nanopowder was confirmed by X-ray diffraction and scanning electron microscopy.  The synthesized Li2S nanoparticles (100 nm) were assembled into cathodes and their performance was compared to cathodes fabricated using commercial Li2S micropowders (1 - 5 µm).  Electrochemical analyses demonstrated that the synthesized Li2S nanoparticles were superior in terms of (dis)charge capacity, cycling stability, output voltage, and voltage efficiency.
Electrochemistry in the Next Generation of Rechargeable Batteries: Challenging the Maze with Multiscale Computational Modeling
Authors: Franco Alejandro A. , Yin Yinghui , Thangavel Vigneshwaran , Quiroga Matias , Morcrette Mathieu
Published: February 2020

The development of the next generation of rechargeable batteries and their consequent market penetration, require a rational guide for the optimization of the balance between the intrinsic capacity of the used storage materials, their statistical utilization in the composite electrodes and the macroscopic cell design.

Computational multiscale modeling emerges nowadays as a powerful tool for building such a rational guide through the in silico representation of complex processes involving electrochemistry and species transport in operando conditions [1-3].

In this contribution we discuss our most recent progresses on the development of a novel integrative multiscale modeling platform devoted to understand the impact of the electrodes mesostructure on the electrochemical response of rechargeable batteries. The platform is supported on a combination of deterministic (continuum) and stochastic (Kinetic Monte Carlo) models resolving detailed electrochemistry and reactants/charge transport [4-6]. It allows capturing, with three-dimensional resolution, the impact of properties such as active material particles percolation, pore size distributions and pores interconnectivity, on the discharge cell performance (Figure). The flexibility of the approach is illustrated here through the investigation of hierarchical carbons as positive host electrode material in lithium-sulfur [7] and lithium-O2 batteries.  In general, simulations reveal heterogeneities on the spatial location of electrochemical activity and nucleation centers with a strong dependence on the carbon mesostructural properties. Specific similarities and differencies between the two illustrated applications are discussed and possible ways for optimizing the electrodes performance are suggested.

[1] Physical Multiscale Modeling and Numerical Simulation of Electrochemical Devices for Energy Conversion and Storage: From Theory to Engineering to Practice. A.A. Franco, M.L. Doublet, W.G. Bessler (Eds.), Springer (2015).

[2]  A.A. Franco, RSC Advances, 3 (32) (2013) 13027.

[3] A.A. Franco (Ed.), Rechargeable Lithium Batteries: From Fundamentals to Applications, Woodhead/Elsevier Science (2015).

[4] G. Blanquer, Y. Yin, M.A. Quiroga, A.A. Franco, J. Electrochem. Soc., 163 (3) (2016) A329.

[5] K. H. Xue, E. McTurk, L. Johnson, P.G. Bruce,  A.A. Franco, J. Electrochem. Soc., 162 (4) (2015) A614.

[6] M. Quiroga, K.H. Xue, T.K. Nguyen, H. Huang, M. Tulodziecki, A.A. Franco, J. Electrochem. Soc., 161(8) (2014) E3302.

[7]  K.H. Xue, V. Thangavel, Y. Mammeri, M.A. Quiroga, C. Guery, P. Johansson, M. Morcrette, A.A. Franco, in preparation (2015).

Figure 1
Electrochemical Properties of Silicon Electrodes Having Polyimide Binders for Lithium-Ion Batteries
Authors: Song Danoh , Lee Seung Hyun , Kim Kyuman , Cho Inseong , Ryou Myung-Hyun , Park Won Ho , Lee Yong Min
Published: February 2020

A soluble polyimide (PI) for lithium-ion battery polymeric binder is newly synthesized by a two-step reaction. Two monomers, bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BCDA) and 4,4-oxydianiline (ODA), are reacted to form polyamic acid through ring opening, and followed by condensation reaction for PI. Although the molecular weight of PI is low around 10,945, the electrode slurry consisting of Si/carbon black/PI (6/2/2 by weight) in N-methyl- 2-pyrrolidone (NMP) shows proper viscosity for coating, and the physical state of cast and dried Si electrode is quite good enough to be adhered the current collector. As a control case, a Si electrode having the conventional polyvinylidene fluoride(PVdF) binder of a molecular weight of 350,000 is also prepared under the same condition, and then both are evaluated with 2032-type coin half cells. Although the initial Coulombic efficiency of PI binder is similar to that of PVdF binder, it delivers much higher discharge capacity (2167 mAh/g vs. 1740 mAh/g). In addition, its cycle life also outperforms than the PVdF binder. This enhancement is closely related to the better adhesion strength of Si electrode with PI binder (0.217 kN/m vs. 0.185 kN/m), which is confirmed by Surface And Interfacial Cutting Analysis System (SAICAS).

Acknowledges

This work was supported by the Human Resource Training Program for Regional Innovation and Creativity through the Ministry of Education and National Research Foundation of Korea (NRF-2014H1C1A1066977) and the Energy Efficiency & Resources Core Technology Program of the Korea Institute of Energy Technology Evaluation and Planning(KETEP) granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea (No. 20142010102980).
Influence of Electrolyte Solvent Properties on Li-O2 Battery Discharge Product Morphology
Authors: Zakharchenko Tatiana Konstantinovna , Itkis Daniil Mikhailovich
Published: February 2020

Li-air batteries (LAB) can theoretically enable energy storage with 5-fold increased specific energy in comparison to that of Li-ion systems. A number of fundamental problems prevent LAB from being reversibly rechargeable however. Precipitation of the discharge products, e.g. lithium peroxide (Li2O2), inside a positive electrode is one of the key processes that control battery performance [1], thus detailed understanding of product deposition mechanisms is required to achieve deeper discharge and complete reversibility.

Product formation is a result of multistep chemical process ending up with crystallization. Depending on the discharge conditions and, especially, electrolyte solvent, different growth mechanisms occur giving rise to quite different morphologies. Recently, it has been reported that solvent’s donor number play a key role in lithium peroxide formation processes [2]. Here we test the proposed theory in a wider range of solvents, including DMA and sulfolane.

Carbon paper was used as an electrode material with controlled porosity. Solvent list included DMSO, MeCN, DMA, DME and sulfolane and was demonstrated to be relatively stable to ORR products and intermediates. Composition, structure and morphology of the discharge products formed during potentiostatic discharge were analysed.

It was shown that oxygen reduction in the presence of lithium ions in the electrolyte proceeds with the formation of plate-like particles Li2O2 that form a film or agglomerate complex morphology. The formation of Li2O2 crystalline plates proceeds via superoxide disproportionation in solution [3].  

[1] Christensen J, Albertus P, Sanchez-Carrera RS et al. A Critical Review of Li-Air Batteries// J. Electrochem. Soc. 2012, 159:R1.

[2] Johnson L, Li C, Liu Z et al. The role of LiO2 solubility in O2 reduction in aprotic solvents and its consequences for Li–O2batteries// Nature Chem. 2014, 6:1091–1099.

[3] T.K. Zakharchenko, A. Y. Kozmenkova, D.M. Itkis et al. Lithium peroxide crystal clusters as a natural growth feature of discharge product in Li-O2 cell// Beilstein J. Nanotechnol., 2013:4.
Enhanced Electrochemical Reversibility of Li-Rich Layered Li2MO3 Cathodes: Understanding Aliovalent Co3+ Substitution with Excess Lithium
Authors: Arunkumar Paulraj , Im Won Bin
Published: February 2020

Li-rich layered materials are the promising high capacity cathode with superior energy density for the next-generation Li-ion batteries. The existence of excess lithium in these cathodes resulted in the high discharge capacity (>250 mAh g-1) with excellent structural and electrochemical stability. However, several challenges that hinder their application are poor rate capability and electrochemical Li irreversibility due to O2 loss in the first charging cycle and undesired phase transformation during cycling.[1]

Extensive efforts has been made to improve the Li reversibility, employing aliovalent metal doping in the Li2
MO3 component due to an enhanced structural stability and improved electronic conductivity.[2, 3] In a step further, an intentional inclusion of excess lithium as a charge compensation in the aliovalent doped Li2
MO3 cathodes were least investigated.

Herein, we report Li2+x
Ru1-x
Co
x
O3 (x = 0, 0.1, 0.2, and 0.5) cathode with an enhanced electrochemical Li reversibility at high C rate. The structural and electrochemical properties were investigated by X-ray diffraction, solid-state NMR, X-ray photoelectron spectroscopy, galvanostatic cycling, and cyclic voltammetry to understand the enhancement in the Li reversibility and rate capability of the cathode. High-performance Li2.1Ru0.9Co0.1O3 cathode delivered an initial capacity of 250 mAh g−1 and enhanced Li+ extraction of 1.00 mol (78 % capacity retention) after 50 cycles at 1C compared to 0.48 mol of Li+ extraction in the pristine Li2RuO3. Low Co3+ content could realize an enhanced reversible Li+ extraction originating from the cation ordering, facile charge transfer, and improved reversible anion-redox chemistry. The origin of the enhanced Li reversibility on the structural and electrochemical properties of cathodes were investigated.

References

M.M. Thackeray, C.S. Johnson, J.T. Vaughey, N. Li, S.A. Hackney, J. Mater. Chem.,
15 (2005) 2257-2267.

M. Sathiya, K. Ramesha, G. Rousse, D. Foix, D. Gonbeau, A.S. Prakash, M.L. Doublet, K. Hemalatha, J.M. Tarascon, Chem. Mater.,
25 (2013) 1121-1131.

M. Sathiya, G. Rousse, K. Ramesha, C.P. Laisa, H. Vezin, M.T. Sougrati, M.L. Doublet, D. Foix, D. Gonbeau, W. Walker, A.S. Prakash, M. Ben Hassine, L. Dupont, J.M. Tarascon, Nat. Mater.,
12 (2013) 827-835.

Figure 1
Structural and Morphological Tuning of LiCoPO4 materials Synthesized By Solvo-Thermal Methods for Li-Cell Applications
Authors: Brutti Sergio , Manzi Jessica , Di Lecce Daniele , Hassoun Jusef , Panero Stefania
Published: February 2020

Olivine-type lithium metal phosphates (LiMPO4) are promising cathode materials for lithium-ion batteries. LiFePO4 (LFP) is commonly used in commercial Li-ion cells but the Fe3+/Fe2+ couple can be usefully substituted with Mn3+/Mn2+, Co3+/Co2+ or Ni3+/Ni2+, in order to obtain higher redox potentials. In this communication we report a systematic analysis of the synthesis condition of LiCoPO4 (LCP) using a solvothermal route at low temperature, being the latter a valuable candidate to overcome the theoretical performances of LFP. In fact LCP shows higher working potential (4.8 V vs 3.6 V) compared to LFP and similar theoretical capacity (167 mAh g-1). Our goal is to show the effect of the synthesis condition of the ability of LCP to reversibly cycle lithium in electrochemical cells. LCP samples have been prepared through a solvo-thermal method in aqueous-non aqueous solvent blends. Different Co2+salts have been used to study the effect of the anion on the crystal growth as well as the effect of solution acidity, temperature and reaction time. Materials properties have been characterized by fast-Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopies. The correlation between structure/morphology and electrochemical performances has been investigated by galvanostatic charge-discharge cycles in lithium half cells with a EC:DMC LiPF6 electrolyte. Going beyond the stoichiometrically-pure LCP phase, we also investigated the effect of iron doping on LCP structural features and the corresponding electrochemical properties. The simultaneous effect of iron doping and post-synthesis high-temperature annealing boosts the electrochemical performances in Li cells. The optimized material has been assempled with an high capacity anode based on a Sn-C composite to demostrate the use of an LCP-based material in a complete Li-ion cell.
(Invited) Pattern and Emissivity Insensitive Dopant Activation and Silicide Contact Formation Annealing in a Hot Wall Rapid Thermal Annealing System
Authors: Yoo Woo Sik
Published: February 2020

Rapid thermal annealing (RTA) enabled shallow junction formation requires very short time annealing at high temperatures for low thermal budget. RTA is typically done by lamp-based radiant heating. Radiant power from lamp arrays is close-loop controlled to execute the temperature of the Si wafer as programmed. The increase of annealing temperature and the decrease of annealing time are generally required for more aggressive device scaling. However, the use of non-equilibrium radiant heat sources (photon energy from lamp arrays) makes the heating process sensitive to the optical properties of the Si wafers.

Local temperature non-uniformity during RTA is considered an important contributor for within-die process variations which cause significant problems for advanced complimentary metal-oxide-semiconductor (CMOS) device manufacturing. RTA-induced variations strongly depend on circuit layout patterns and optical properties of exposed materials on the surface of the Si wafers. This phenomenon is often referred to as “pattern effect” known from the early days of RTA introduction in the semiconductor industry.

In efforts to reduce the “pattern effect”, various approaches have been proposed and implemented in device manufacturing. Shielding device patterns from the radiant heat source is a common approach, having limited success. It is done by either placing a dummy wafer on the pattern side of the Si wafer or backside heating. One other common approach is to homogenize the optical properties of the pattern side of Si wafer by either adding an optical absorption layer or dummy patterns. A differential thermal energy control technique is also proposed for pattern effect suppression. Non-radiative heating techniques have been proposed and demonstrated effectiveness of this “pattern effect” suppression.    

In this paper, various silicide contact formations on implanted single crystalline Si in source/drain region and implanted poly-Si in gate region were studied over wide ranges of RTA temperature and time using a hot wall RTA system which uses mainly natural convection and conduction through ambient gas. Dopant profiles of the silicide and doped Si after silicidation in the hot wall RTA system were characterized. Proposed possible silicide formation and dopant diffusion mechanisms are discussed. Differences between radiant heating and non-radiant heating on the silicide formation and dopant profiles are compared. The pattern and emissivity insensitive dopant activation and silicide contact formation annealing results will be introduced and potential applications of the hot wall RTA technique in advanced CMOS devices will be proposed.
Fabrication of Graphene/Porous Silicon Nitride Material for Field-Effect Transistors
Authors: Ge Daohan , Qian Dongliang , Chen Guanggui , Zhang Liqiang , Ren Naifei
Published: February 2020

Graphene, a novel material, has attracted significant attention due to its distinctive band structure and fascinating physical properties. These unusual properties have caused the emergence of tantalizing potential applications, ranging from field effect transistors to chemical and biochemical sensors. Due to their low mass, high quality factor, and good optical properties, silicon nitride micromembrane resonators are widely used in force and mass sensing applications. However, for practical graphene devices, many problems need to be solved, such as morphology control, interfacial engineering between graphene and silicon nitride substrate.

       Here, we transfer graphene to the silicon nitride substrates with two different morphologies (holes and grooves). Monolayer graphene film can be prepared on the copper via chemical vapor deposition (CVD) process as previous reported method. Next step is transfering graphene to the substrate. The morphologies of graphene on the substrate were obtained by SEM (Fig. 1a,b). As shown , the graphene in the hole and groove is not suspended, but directly exposed to the substrate. The graphene’s Raman information in hole is achieved by the micro-Raman spectrometer (Fig. 1c), which shows good quality . Such hybrid Graphene/Porous Silicon Nitride structures can be used to fabricate field-effect transistors.

Figure 1
Characterization of GaN Device Interconnect Metallization Reliability
Authors: Kilgore Steve , Hill Darrell , Green Bruce
Published: February 2020

The gallium nitride (GaN) semiconductor market continues to rapidly expand because GaN device technology offers considerable performance advantages compared to gallium arsenide (GaAs) and silicon (Si) devices.  GaN has inherently higher breakdown field strength, charge density, and electron velocity at high voltage.  These material properties permit GaN devices to operate at higher bias voltages and higher current densities than GaAs and Si devices.  Commercial applications can utilize RF power amplifiers at higher frequencies (> 2 GHz) and higher power (> 400 W) in a single packaged GaN transistor.  However, this higher power density operation requires examination of the degradation and reliability of these GaN devices at elevated temperatures.  The evaporation deposited gold interconnect metallization of GaN HFET devices was stressed to evaluate its high temperature reliability.  Optimized test structures were designed to assess the electromigration wear-out in evaporated deposited Au films encapsulated with SiN passivation.  A current density of 1 MA/cm2 with oven stress temperatures in excess of 335 °C was applied to large quantities of Au interconnects.  The selected failure criteria of 50% resistance increase yielded Au lifetime distributions that followed typical log-normal electromigration failure statistics.  All log-normal sigma values were less than 0.6 which is an indication of a mono-modal failure mechanism.  The activation energy value was measured from multiple stress temperatures.  Physical characterization of the evaporated Au interconnect structures are discussed along with a comparison to electroplated Au interconnects.
Growth of Aluminum Doped SiC Single Crystal By PVT Method
Authors: Jung Eunjin , Kwon Yong Jin , Jeong Seong Min , Lee Myung Hyun , Choi Doojin , Kim Younghee
Published: February 2020

SiC has been well known as superior ceramic material with excellent thermal and electrical properties, high strength, good chemical resistance and high hardness. For these reasons, SiC is an ideal substrate for the fabrication of optoelectronic and power devices. N-type and p-type SiC wafers can be used for a variety of applications such as heat-resistant semiconductor device. So the doping level in the SiC crystal growth is an important element. N-type SiC wafer which can be doped by nitrogen or phosphorus and p-type by aluminium, boron, gallium or beryllium. In this study, SiC crystal growth was performed using SiC powder as the source material containing aluminum (120ppm) by PVT method. The PVT setup was inductively heated to temperature up to 2150°C (top of the crucible). Polymorphism of grown crystals were assessed using X-ray diffraction and Raman spectroscopy and the doping distribution of aluminum in SiC wafer was determined using hall measurement using the van der Pauw method and Raman spectroscopy. Absorption spectra of SiC crystals were measured by UV-VIS spectrophotometer.
(Invited) Gallium Oxide Based Materials and Devices
Authors: Jena Debdeep
Published: February 2020

The availability of high-quality bulk crystals of beta-gallium oxide (Ga2O3) has provided a shot-in-the-arm for extending electronic device technologies beyond the currently popular SiC and GaN.  Though for high-voltage electronics Ga2O3 has a much larger bandgap (~4.6 eV) than GaN, it is still smaller than AlN and diamond.  The thermal conductivity of Ga2O3 is also abysmally low compared to AlN and diamond. What then is the potential of Ga2O3 for electronic device technologies?  Though it is impossible to predict, I will present my opinions on what aspects of this new material can provide significant advantages over other material systems for electronic and photonic devices.  I will then provide expermental data and theory and modeling on the electronic, optical, and thermal properties of the Ga2O3 material system that has been investigated in my group.  I will also present a summary of our MBE-based epitaxial growth of Ga2O3 based materials, and device results.
Electrodeposition of Doped ZnO Layer Using Three Different Dopant (Properties and structure)
Authors: Saeed Mahfouz Ali
Published: February 2020

Zinc oxide (ZnO) is a conductive oxide, which serves as the n-type semiconductor. Furthermore, ZnO has other favorable properties including high electron mobility, stability, and good transparency.

We were introduced the new electrolyte composition (previous conferences), which is far more dilute than systems that had been previously described, and which yields much improved CIGS films.

In this work we introduce ZnO layer doped with either indium or gallium or Aluminum were electrodeposited potentiostatically at 75oC from aqueous solutions containing Zn(NO3)2 and either InCl3 or GaCl3 or Al(NO3)3. Undoped ZnO was used as substrate. The films were used for the preparation of PN-junctions based on electrodeposited CuGaInSe2 thin solid films. CIGS and CIGSS functional photovoltaic devices, based entirely on electroplating.  

Complete electrodeposited devices were generated and tested exhibiting efficiencies ranging from 2 to 6% with quantum efficiency exceeding 0.6. This is the first that such a comprehensive process had been described, leading the way to a potential fabrication of an entire device using an electrochemical route, enabling effective manufacturing integration and scaling.

The effects of mass transport on the deposit composition and its adhesion to the substrate are discussed. Sample polarization curves at different electrode rotation rates are provided for the three different doped ZnO layer (figure 1).

The final composition, oxides contents, crystallography and oxides effects on the deposit quality were determined using Energy-dispersive X-ray spectroscopy technique (EDS) and XRD (figure2). Profilometer was used to determine the deposit thickness. 

References

[1]  Hossain, F. Nishii, J. Takagi, S. Sugihara, T. Ohtomo, A. Fukumura, T. Koinuma, H. Ohno, H. Kawasaki, M.,  

       Physica E. 21 (2004) 911.

[2]  Rousset, J. Saucedo, E. Lincot, D. Chemistry of Materials 21 (2009) 534.978-

[3]  Chikoidze, E. Nolan, M. Modreanu, M. Sallet, V. Galtier, P. Thin Solid Films 518 (2008) 8146.              

[4]  Machado, G. Guerra, D. Leinen, J. Ramos-Barrado, R. Marotti, A.Dalchiele, Thin Solid Films 490 (2005) 124 –

      131.

Figure 1