bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Transistor Strain Measurement Using Electron Beam Techniques
Authors: Zuo Jian Min , Kim Honggyu , Zhang Jiong , Rouviere Jean-Ruc
Published: February 2020

Strain and the related stress in nanoelectronic devices play a critical role in semiconductor technologies. In general, strain arises from the lattice mismatch between dissimilar materials and thus strain is critical for the design and growth of epitaxial heterostructures in micro- and nano-electronics. In transistors, strained silicon channels provide a major boost to the performance of metal-oxide-semiconductor field-effect transistors (MOSFETs), e.g., the use of epitaxial strain of Si and Ge alloys in PMOS [1]. In the near term, the transistor technology is pushing towards the sub 10 nm technology node. At this length scale, resolving strain in the devices requires a resolution of sub nanometer with not only high resolution, also high accuracy and reliability. The use of novel architectures and alternative materials in the transistor technology also demands metrology capable of handling these structural and material changes.

High resolution strain measurement can be performed using high energy electrons either in reciprocal space using convergent beam electron diffraction (CBED), scanning electron nanodiffraction (SEND), nanobeam electron diffraction (NBED) [2], or scanning precession electron diffraction (SPED) or in real space through direct imaging using high resolution electron microscopy (HREM), scanning transmission electron microscopy (STEM) [3] or dark-field electron holography (DFEH)[4]. The resolution and strain measurement sensitivities range from Å to several nm and 10-3 to 10-4respectively. Recent developments in aberration corrected STEM especially have improved the spatial resolution to sub- Å and the precision of measuring atomic column positions to picometers [3].

This talk will review high resolution and high sensitivity electron beam techniques for strain characterization in nanodevices and device materials. Examples include planar and a finfet transistors and III-V heterostructures. For finfet transistors, we demonstrate that NBED provides an effective approach for strain mapping (See figure below) and some of challenges will also be highlighted. In III-V heterostructures, we will describe atomic resolution Z-contrast imaging based methods for high resolution interfacial strain analysis and its applications for the investigation of interfacial intermixing and atomic layer-by-layer strain profiles in InAs/GaSb and InAs/InAsSb superlattices, targeted for middle- and long-wavelength IR detection.

References

[1] J. Welser, J. Hoyt and J. Gibbons, Electron Device Letters, IEEE 15 (3), 100-102 (1994)

[2] Beche, A., et al., Ultramicroscopy,131, 10-23 ( 2013).

[3] J.-M. Zuo, A. B. Shah, H. Kim, Y. Meng, W. Gao and J.-L. Rouviére, Ultramicroscopy 136, 50-60 (2014).

[4] Cooper, D., et al., Applied Physics Letters, 96(11), 113508 (2010).

[5] This work is supported by U.S. Army Research Office (Grant No. Army W911NF-10-1-0524 and monitored by Dr. William Clark) through the MURI program, Nanoscience Foundation, France and DOE BES DEFG02-01ER45923.

Figure 1
Numerical Study on Flow Distribution in PEMFC with Metal Foam Bipolar Plate
Authors: Kim Kyoungyoun , Song Myeongho
Published: February 2020

It is important to uniformly supply the fuel gas into the reaction activity area in polymer electrolyte membrane fuel cell (PEMFC). Recent studies have shown that the cell performance can be significantly improved by employing metal foam gas distributor as compared with the conventional bipolar plate types. The metal foam gas distributor has been reported to be more efficient to fuel transport. In this study, three-dimensional computational fluid dynamics (CFD) simulations have been performed to examine the effects of metal foam flow field design on the fuel supply to the reaction site. Darcy's law is used for the flow in the porous media. By solving additional advection equation for fluid particle trajectory, the gas transport has been visualized and examined for various geometrical configuration of metal foam gas distributor.

†This work was supported by the International Collaborative Energy Technology R&D Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) (No. 20148520120160)
Effect of Gdl(+MPL) Compression on the PEM Fuel Cell Performance
Authors: Carcadea Elena , Varlam Mihai , Ingham Derek B. , Patularu Laurentiu G , Marinoiu Adriana , Ion-Ebrasu Daniela , Stefanescu Ioan
Published: February 2020

Two components of the PEM fuel cells play a critical role in obtaining a good performance, namely the gas diffusion layer (GDL) and the micro porous layer (MPL). The target of the reported investigation was the influence of the required gas diffusion layer compression, during stack assembly, onto PEM fuel cell performance. For developing a fuel cell it is necessary to assembly all the components together in order to ensure a good connection and to reduce the leakage problem, and this is done under a compression load. The compression applied can deform the GDL and modify its thickness, porosity, hydrophobicity and electrical resistance, and these can result in damaging or decreasing the performance of the PEM fuel cell. Also, the GDL may intrude in the flow field channels and can lead in significant disturbance of the reactants flow in the channels and consequently to a drop in the performance.

Numerical simulations based on ANSYS software were carried out in order to investigate the effect of the clamping force on the fuel cell performance. Therefore, 4 geometries were considered in our study, by taking into account the uncompressed and compressed GDL and the presence or absence of MPL. Different levels of GDL compression and intrusion were considered and simulated. The 3D multiphase model revealed that the GDL compression and intrusion influence the in-plane gradient in liquid saturation, oxygen concentration, membrane water content, and especially current density profiles. Also, our study showed that inserting a micro porous layer between catalyst layer and GDL can lead to an improvement of the cell performance because it helps ensuring a good water management, reducing liquid saturation.
Influence of Binder Porosity on Gdl Gas Phase Transport
Authors: Eller Jens , Lamibrac Adrien , Marone Federica , Büchi Felix N
Published: February 2020

In polymer electrolyte fuels (PEFC) carbon fiber based gas diffusion layers (GDL) are used for fine distribution of reactant gases from the flow field channels to the catalyst layer (CL). It is a key component for PEFC as it serves also for water removal from the CL as well as heat and electricity transport between CL and the flow field plates. GDL materials can be classified as woven, felts, papers, where the later type requires a binder to mechanically stabilize the fiber arrangement.

While most GDL binders are solid, the binder of SGL GDLs appears porous and it’s influence on gas phase transport is unclear [1]. In SEM surface images of SGL, GDL binder domains of appear as flake like fine-structure with particles of about 100 to 300 nm (see Fig. 1a). Here, we apply multi-dimensional X-ray imaging techniques and multi-scale numerical simulations to clarify possible contributions of the binder porosity to overall GDL gas transport.

Absorption contrast X-ray tomographic microscopy measurements at the TOMCAT beamline of the Swiss Light Source (SLS) with voxel sizes of minimum 0.16 µm revealed a high porosity (59 %) of SGL 24 BA binder domains of (Fig. 1b). Computational transport simulations on the segmented binder structures showed, that the binder domains provide isotropic effective diffusivity of 0.30. In order to quantify the contribution of the porous binder to the overall fluid transport in the GDL, the obtained binder diffusivity values were used in multi-scale transport simulations of ternary segmented XTM data of representative GDL samples with 2.2 µm voxel size. If the binder was treated as solid, through-plane effective diffusivity of the GDL of 0.1 was obtained. If we applied a multi-scale simulation approach, that treats the binder domain as porous and uses the transport parameters of the binder domain as input values for the coarse scale simulations of the whole GDL domain, the through-plane effective diffusivity increased to 0.4 (+300 %). These numbers will be verified by X-ray ptychograptic computed tomography measurements of the binder fine structure at the cSAXS beamline of the SLS that proved resolutions of up to 16 nm [2].

References

[1]Rashapov, A; Gostick, J.T., In-Plane Effective Diffusivity in PEMFC Gas Diffusion Layers, Transport in Porous Media, 2016, In press.

[2]Holler, M.; Diaz, A.; Guizar-Sicairos, M.; Karvinen, P.; Färm, E.; Härkönen, E.; Ritala,M.; Menzel, A.; Raabe, J. & Bunk, O., X-ray ptychographic computed tomography at 16 nm isotropic 3D-resolution, Sci. Rep., 2014, 4, 3857.

Figure 1: SGL 24 binder fine structure a) SEM image and b) X-ray tomographic microscopy with 0.16 µm voxel size.

Figure 1
Electrical Conductivity Behavior of Impregnated Lstm on Selectively Ni Removed Ni/YSZ Anode Substrate
Authors: Park DaeSoo , Kim Jung Hyun
Published: February 2020

Generally, nickel and yttria-stabilized zirconia (YSZ) have been preferred as anode materials for Solid Oxide Fuel Cells (SOFCs), because the Ni-YSZ cermet anode shows excellent performance while operating using hydrogen as a fuel. However, Ni-YSZ anodes are known to undergo degradation due to sulfur poisoning, carbon deposition, and mechanical instability when hydrocarbon-containing fuels have been used. One of the strategies to solve these problems is to modify the Ni-YSZ cermet by altering the nickel or YSZ, adding oxide material catalysts, and carrying out surface treatment.

In this study, electrical conductivity behavior of impregnated La0.4Sr0.6Ti0.8Mn0.2O3±δ(LSTM) on selectively Ni removed Ni/8YSZ anode substrate have been investigated when hydrocarbon fuels are being used for SOFC applications. Abrupt weight losses were measured when reduced Ni/YSZ substrates were exposed to HNO3 at the initial stage reaching 5 minutes, indicating that within these first 5 minutes Ni metals on the surface of Ni/YSZ substrates were removed. After 5 minutes, Ni metals were removed with relatively lower removal rate (2.3 x10-3wt%/min) than first 5 minutes. At values below than 3 wt % of impregnated LSTM on Ni removed substrate, electrical conductivity increase and at values greater than 3 wt %, electrical conductivity decreases as it is related to the effective percolation of electrically conducting phase caused by LSTM present on Ni removed Ni/8YSZ anode substrate. Significantly, the electrical conductivity values with 3 wt % of impregnated LSTM on Ni removed substrate were 2.04 x103 and 1.88 x103 S/cm at 700 and 800oC under H2 condition.
Thermoplastic Polyurethane (TPU) Based All-Solid-State Lithium-Ion Batteries
Authors: Liu Yadong , Aliahmad Nojan , Xie Jian , Agarwal Mangilal
Published: February 2020

The rapidly growing flexible/wearable electronic market drives the research and development of flexible power source systems, especially lithium-ion batteries with high specific energy/power, long cycle life and high safety1. Conventional lithium-ion batteries with fixed shapes and liquid electrolyte are not suitable for flexible applications as they can electrically short and/or cause fire when bended or stretched. However, the use of solid-state electrolytes can replace the liquid electrolytes, thereby leading to all-solid-state batteries that can eliminate the safety issues caused by traditional, flammable liquid electrolytes. Typical solid-state electrolytes for Li-based batteries fall into two categories:(1) inorganic glass/ceramic/crystalline electrolytes and (2) polymer electrolytes. Inorganic electrolytes including some oxides, sulfides, NASICON-type, perovskite-type, garnet-type materials, etc. have promising conductivity2. However, these inorganic electrolytes are typically fragile and not bendable, and therefore cannot be used for flexible electronic devices. In contrast, polymer electrolytes such as polyethylene oxide (PEO), polyvinylidene fluoride (PVdF), Poly(methyl methacrylate) (PMMA), thermoplastic polyurethane (TPU), etc. are elastic and represent good candidates for electrolytes in flexible batteries.

In this work, TPU/Lithium bis(trifluoromethane sulfonyl) imide (LiTFSI) was selected as the polymer electrolyte. The conductivity and electrochemical window of this electrolyte are shown in Fig. 1. The 10 mS/m conductivity of the TPU/LiTFSI should be adequate for low-power-consumption flexible electronic devices. The 0~6.2 V electrochemical window is beneficial for most cathode materials for lithium-ion batteries. A LiNi1/3Co1/3Mn1/3O2 (NCM, 4.0 V vs. Li/Li+, specific capacity: 278 mAh/g) and a Li4Ti5O12 (LTO, 1.5 V vs. Li/Li+, specific capacity: 175 mAh/g) was used as cathode and anode materials, respectively, for the all-solid-state battery (Fig. 2). The LTO was chosen to be the anode because the TPU is sensitive to lithium metal, and the LTO has a relative higher potential vs. Li/Li+so is safe for the TPU electrolyte. The all-solid-state cell could be a promising candidate power source for the flexible electronic devices.

(1) Zhou, G.; Li, F.; Cheng, H.-M. Energy & Environmental Science
2014, 7, 1307.

(2) Bachman, J. C.; Muy, S.; Grimaud, A.; Chang, H.-H.; Pour, N.; Lux, S. F.; Paschos, O.; Maglia, F.; Lupart, S.; Lamp, P.; Giordano, L.; Shao-Horn, Y. Chemical Reviews
2016, 116, 140.

Figure 1
Gel Electrolytes Incorporated with Graphene-Oxide Quantum Dots for High Performance in Lithium Ion Batteries
Authors: Chen Yen-Ming , Teng Hsisheng
Published: February 2020

This study incorporates graphene oxide quantum dots (GOQDs) in to a gel polymer electrolyte (GPE) designed for lithium ion batteries (LIBs). The GPE comprises poly(acrylonitrile-co-vinyl acetate) copolymer (PVA) blending poly(methyl methacrylate) (PMMA) as a host swelled by a liquid electrolyte (LE) of 1-M LiPF6 in a carbonate solvent. The major concerns for GPE-based LIBs is the capacity retention and cycle life under high-rate operation. Among numerous functional polymer segments used for GPEs,1 poly(acrylonitrile) (PAN) exhibits excellent thermal stability, ion-solvating ability, material processibility, and electrochemical stability,2 whereas poly(vinyl acetate) (PVAc) strongly absorbs solvent molecules to facilitate polymer swelling and ion transport. The segmental motion of PVA can be further promoted by blending PMMA; therefore, the polymer framework developed in this study represents an ideal host for GPEs.

Previous studies have used inorganic oxide nanoparticles, such as SiO2, TiO2, Al2O3, ZrO2, as fillers to improve both the mechanical strength and ionic conductivity of GPEs.3 GOQDs,which contain numerous oxygen functional groups on the surface, have strong affinity to polymer chains for uniform dispersion in GPEs. The present study finds that the incorporated GOQDs substantially increase the mobility of lithium ions in the developed GPE by accelerating lithium-ion hopping along the polymer chains. A resulting Li/GPE/LiFePO4 battery delivers a high discharge capacity of 70 mAh g-1 at 17 C-rate, which is much higher than that of a Li/LE/LiFePO4 battery (35 mAh g-1).

References

P. Hu, Y. Duan, D. Hu, B. Qin, J. Zhang, Q. Wang, Z. Liu, G. Cui, L. Chen, ACS Appl. Mater. Interfaces 2015, 7, 4720-4727.

S.H. Wang, P.L Kuo, C.T Hsieh, H. Teng, ACS Appl. Mater. Interfaces 2014, 6, 19360−19370

M. Osińska, T. Jesionowski, K. S-S. Tefańska, M. Walkowiak, Cent. Eur. J. Chem. 2010,8(6),1311-1317

 

Acknowledgments: This research was supported by the Ministry of Science and Technology, Taiwan (104-2221-E-006-231-MY3, 104-2221-E-006-234-MY3, 105-3113-E-006-005, and 104-3113-E-006-011-CC2), and by the Ministry of Education, Taiwan, The Aim for the Top University Project to the National Cheng Kung University.
Local Mass Transport Resistance of Low-Loaded PEM Fuel-Cell Catalyst-Layers
Authors: Freiberg Anna Teresa Sophie , Schuler Tobias , Tucker Michael C , Secanell Marc , Weber Adam Z
Published: February 2020

To this day, the content of noble metals in the catalyst layers of proton exchange membrane fuel cells (PEMFCs) is still accounting for up to 60 % of the total stack cost and is therefore needed to be reduced for large-scale applications as automobile industry. Though a lot of effort was put into fabrication of catalyst-layers (CLs) with sufficiently low platinum loading, the performance below a certain content starts to decay rapidly. Within the CL, a complex interplay of mass and charge transport takes place, making the identification and quantification of the limiting parameters especially difficult and laborious. Finally, this resistance was found to be due to a local mass transport resistance scaling inversely with the electrochemical active surface area (ECSA).

In this presentation, the results for the local transport resistance measured in-situ via our unique hydrogen limiting current setup for CLs of varying loading, ionomer content and fabrication are shown. The effects of temperature and relative humidity on this intrinsic property are discussed, allowing a deeper understanding of the processes occurring close to the catalyst surface. Though water production, oxide effects and possible peroxide formation can make oxygen limiting currents hard to quantify in detail, data is included, allowing a direct comparison of the transport properties and pathways of both reactants. The data provided shows the potential of this measurement technic to identify the transport limitations in a fast and easy way, which helps to optimize the electrode structure, composition and fabrication for several operation-conditions and therefore applications.

Acknowledgements

This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Fuel Cell Technologies Program of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 and by CRADA agreement LB08003874 between Lawrence Berkeley National Laboratory and Toyota Motor Company.

Figure 1
Preparation of Large Pore Volume Carbon Materials for High Performance Li-S Battery
Authors: Cui Yanhui , Baker Andrew , Huang Kevin , Wu Junwei , Zhang XinHe
Published: February 2020

Carbon matrix is effective in enhancing electrochemical performance of lithium sulfur battery due to its high surface area and electronic conductivity. Here, porous carbon matrix (PCM), derived from cotton and using ZnCl2 as an activator, has a surface area of 1070 m2 g-1 and a pore volume of 2.0 cm3 g-1. The prepared carbon-sulfur composite from PCM mixed with sublimed sulfur showed excellent electrochemical proprieties, because the hierarchy porous structure of PCM keeps sulfur electrochemical activity when sulfur dissolves into electrolyte from inner pores of PCM. To improve sulfur loading and electrochemical proprieties, the pore volume of PCM was enlarged by concentrated H2SO4 and KOH. The larger pore volume is beneficial to sulfur loading, cycling performance, and rate performance. Especially, KOH was used to enlarge the bottom of the pores and keep bore diameter nearby top of the pores invariant. This novel structure also can restrain polysulfide escaping to electrolyte from the pores effectively. Furthermore, PCM-S composite was coated by conductive polymer, like polyaniline (PANI) and Poly (3, 4-ethylenedioxythiophene) (PEDOT), to restrain the shuttle effect of polysulfide and improve the cycling performance.
Achieving Long Life Time Batteries: Understanding and Controlling Non-Faradaic Reactions
Authors: Takeuchi Esther S , Marschilok Amy C , Takeuchi Kenneth J
Published: February 2020

Characterization of electrochemical properties determines the energy content for new materials and possible viability for a potential application. Equally critical yet more challenging is determining the non-Faradaic parasitic reactions of the active materials in a battery environment and their relationship to useful battery life. In order to be successful in long calendar life battery applications, only very low levels of parasitic reactions can be tolerated. For example, calendar life is a particularly important consideration for implantable medical batteries, especially for devices powering essential life functions such as cardiac rhythm management devices. Determining stability by direct systems level testing is slow and expensive as it can require many years and many batteries to affirm.

The dissolution of cathode materials including manganese, cobalt and vanadium oxides in battery systems has been identified as a specific battery failure mechanism. However, dissolution studies including kinetic analysis of the dissolution of active battery materials in non-aqueous electrolytes are largely absent from the literature. We developed a quantitative approach to assess battery materials for their solubility and then validated the approach with battery testing. In this study, a series of vanadium oxide and vanadium phosphate based cathode materials were studied relative to their dissolution in battery electrolyte. Kinetic analysis of the results provided a quantitative approach for understanding the impact of structure and composition on the dissolution of active materials. Negative electrode surfaces from cells using cathodes displaying different levels of solubility were analyzed. A conceptual model of the negative electrode surface electrolyte interphase was developed to rationalize the observed cell impedance and performance. Implications for lifetime prediction for these and other battery systems will be discussed.
A Computational Analysis of Battery Response during Onset of Internal Short Under Mechanical Abuse Conditions
Authors: Allu Srikanth , Kalnaus Sergiy , Kumar Abhishek , Pannala Sreekanth , Simunovic Srdjan , Wang Hsin , Turner John A
Published: February 2020

The impact testing of batteries revealed multiple layers of current collectors come into contact leading to internal short. The local short generates large currents and cause immense heat generation. The dynamics of discharge during this internal short process is not completely understood. In this work we present a three-dimensional electro-chemical and thermal model for Li-Ion batteries that captures onset of internal short under mechanical abuse conditions. The governing differential equations are discretized using ﬁnite element method and solved using implicit non-linear solvers with robust stability and convergence. A simulation study of various contact areas for multiple Li-Ion battery capacities is reported.
Meeting Anode Material Cost Goals through Understanding Performance Drivers and Production Processing Costs
Authors: Deveney Bridget
Published: February 2020

Lithium Ion has the potential to convert transportation in the United States over to fully electric green technology. The major remaining barrier is not technical but cost. The cell level component cost is close to half of the overall cost of a Li Ion battery pack for an electric vehicle. Traditionally the cathode material has been the main cost driver but with the move to cathodes containing less Cobalt and Nickle and more Manganese and Iron the anode has become an equal cost driver. Synthetic graphite offers high performance in cycle and calendar life with well controlled production quality but significantly higher cost. Natural graphite materials are generally known to offer lower cost, but with limitations in quality consistency, environmental concerns, and finished cost that is still not low enough to allow Lithium ion to dominate vehicle and grid markets.  This talk will detail the performance drivers and tradeoffs of various types of graphite anode materials and how the traditional graphite industry can bring capital equipment infrastructure and production scale knowledge to produce low cost high performance anode materials.
Novel Electrolyte Additives for Improving the Stability of High Voltage Electrode/Electrolyte Interface
Authors: Xing Lidan , Li Weishan
Published: February 2020

Development of high specific capacity and high operating voltage cathode material is critical in making next generation high energy density lithium ion battery to satisfy the ever-growing demands for portable electronic devices and electric vehicles. However, interfacial instability of high voltage electrode/electrolyte such as electrolyte decomposition and electrode structural destruction has been found to be the main reasons hindering the development of high energy density lithium ion battery [1]. It has been widely accepted that preventing the direct contract of high voltage electrode and electrolyte would effectively improve the interfacial stability of electrode/electrolyte, which can be achieved by surface coating and electrolyte additive [2-4]. In this work, we will propose several novel film-forming electrolyte additives that dramatically improved the cyclic stability and rate capability of high voltage cathode, including lithium-rich layered nickel manganese cobalt oxide [Li(Li0.2Ni0.13Mn0.54Co0.13)O2], layered lithium nickel cobalt manganese oxide (LiNi1/3Co1/3Mn1/3O2) and lithium nickel manganese oxide (LiMn1.5Ni0.5O4). The mechanism of the additives will be discussed via combination of theoretical calculations and experimental characterizations. 

References:

[1] Kang Xu, Electrolytes and interfaces in Li-ion batteries and beyond, Chem. Rev. 2014, 114:11503-11618.

[2] Jianhui Li, Lidan Xing*, Ruiqin Zhang, Min Chen, Zaisheng Wang, Mengqing Xu, Weishan Li, Tris(trimethylsilyl)borate as an electrolyte additive for improving interfacial stability of high voltage layered lithium-rich oxide cathode/ carbonate- based electrolyte, J. Power Sources, 2015,285:360-366.

[3] Wenna Huang, Lidan Xing*, Ruiqin Zhang **, Xianshu Wang, Weishan Li*, A novel electrolyte additive for improving the interfacial stability of high voltage lithium nickel manganese oxide cathode, J. Power Sources, 2015,293:71-77.

[4] Wenna Huang; Lidan Xing*; Yating Wang; Mengqing Xu; Weishan Li*; Fengchao Xie; Shengan Xia, A novel electrolyte additive for lithium nickel manganese oxide cathode of high voltage lithium ion battery, J. Power Sources,2014,267:560-565.
New Insights on Aromatic Pathways in Porphyrinoids
Authors: Fliegl Heike
Published: February 2020

Electronic and spectroscopic properties of porphyrinoid macrocycles are, to a large extent, determined by the number of π-electrons participating in the conjugation network. Full control of the number of π-electrons implies full control of the aromatic or antiaromatic character of the molecule. To achieve this, knowledge about the electron mobility pathways within a molecule is essential. Experimentally, these pathways are not easily accessible. Therefore theoretical studies are necessary to complement experiments that aim at systematically synthesizing porphyrinoids with distinct properties. A possible way to achieve this is the systematic investigation of magnetically induced current densities to determine reliable aromatic pathways in molecules.[1]

In my talk I will present an overview of different ways to systematically calculate and analyze the magnetically induced current density in porphyrin based molecules. The computational approach used in my group is the gauge including magnetically induced current density method (GIMIC).[2,3] GIMIC is a independent program that is used for the calculation of magnetically induced current densities using London orbitals.[2, 3] Numerical integration of the current flow around molecular rings and along selected chemical bonds can be used for determining current pathways and the degree of aromaticity of various molecules according to the magnetic criterion.[4,5] A new feature of the GIMIC program is the calculation of the anisotropy of the magnetically induced density using gauge including atomic orbitals.[6] Very recent results obtained for various porphyrinoid molecules will be highlighted illustrating the potential and challenges of the method.[7-9]

References:

 [1] D. Sundholm, H. Fliegl and R. J. F. Berger, Wiley Interdisciplinary Reviews (WIREs), 6, 639-678 (2016).

[2] J. Jus´elius, D. Sundholm and J. Gauss, J. Chem. Phys., 121, 3952-3963 (2004).

[3] H. Fliegl, S. Taubert, O. Lehtonen and D. Sundholm, Phys. Chem. Chem. Phys., 13, 20500- 20518 (2011).

[4] R. Valiev, H. Fliegl and D. Sundholm, Phys. Chem. Chem. Phys., 16, 11010-11016 (2014).

[5] H. Fliegl, F. Pichierri and D. Sundholm, J. Phys. Chem. A, 119, 2344-2350 (2015).

[6] H. Fliegl, J. Jus´elius and D. Sundholm, J. Phys. Chem. A, 120, 5658-5664, (2016).

[7] R. Valiev, H. Fliegl and D. Sundholm, J. Phys. Chem. A, 119, 1201-1207 (2015).

[8] R. Valiev, H. Fliegl and D. Sundholm, Phys. Chem. Chem. Phys., 17, 14215-14222 (2015).

[9] I. Benkyi, H. Fliegl, R. R. Valiev and D. Sundholm, Phys. Chem. Chem. Phys., 18, 11932, (2016).
Triplet-Triplet Annihilation in a Single Dendritic Macromolecule with Pt Porphyrin As a Sensitizer-Core
Authors: Vinogradov Sergei , Cember Abigail , Plunkett Shane
Published: February 2020

Triplet-Triplet Annihilation (TTA) is a process in which two molecules in their triplet spin states interact to produce one excited and one ground state singlets. In traditional diffusive TTA systems, Pt or Pd porphyrins are typically used as 'sensitizers'. Upon excitation, followed by ultrafast intersystem crossing, they transfer the excitation energy to molecules of an 'annihilator' by way of collisional triplet-triplet energy transfer (TTET), thus sensitizing the annihilator triplet states. Annihilator triplets undergo TTA, followed by emission of delayed fluorescence, which usually occurs at wavelengths shorter than the wavelength required for the excitation of sensitizer. The resulting energy upconversion may present interest for bioimaging applications. However, TTA in diffusive systems requires very high local concentration of the sensitizer and annihilator, making realization of this process in a biological system practically non-feasible. Here we present a rare example of a system where the TTA process occurs in a single dendritic macromolecule, charting a path to a new class of upconverting imaging probes. The sensitizer (donor) is a metalloporphyrin, which constitutes the core of the dendrimer, while multiple annihilator (acceptor) perylenes are positioned at the dendrimer periphery. Two consecutive cycles of photon absorption by the sensitizer, intersystem crossing and sensitization of a peripheral annihilator moiety by intramolecular triplet-triplet energy transfer (TTET) create a single dendrimer bearing two triplet excitons, which subsequently undergo TTA followed by the annihilator fluorescence. The overall efficiency of the process greatly exceeds that of conventional multiphoton-induced emission at low excitation energies.
Highly Efficient Multifunctional Interlayer for Lithium Sulfur Battery
Authors: Ramaprabhu Prof S , Seshadhri Garapati Meenakshi , Ajay Piriya Vijaya kumar Saroja , Chandrabhan Shende Rashmi , Dharavath Ravindar , Biswas Sanjay , Loganathan S , Balasubramanian T S , Rambabu K
Published: February 2020

Increase in the energy demands has attracted attention towards energy conversion and storage devices. Li ion batteries have played a major role in this aspect. The Li ion battery applications are limited portable electronic devices because of its low energy density and specific capacity. To overcome the limitation of LIB, high energy density batteries like Lithium Sulfur (LiS) batteries have gained more attention. The high abundance, low cost, high theoretical capacity (1675 mA h g-1) and high energy density (2600 Wh kg-1) of sulfur made it a comprising candidate for LiS battery. Although LiS battery is having very high energy density, but not yet commercialized due to its poor cycle life, and low coulombic efficiency. The major challenges of LiS are the dissolution of higher order polysulfides intermediates in the organic electrolyte. These higher order polysulfides migrate to the lithium metal anode and get reduced which leads to overcharging, accumulation of insulating sulfur on the anode and capacity fading. This mechanism is known as shuttle mechanism. On the other hand, the dissolution of polysulfides is also important, which provides the fresh sulfur available for the further reaction to takes place. Using a polysulfide trapping interlayer between cathode and separator can minimize the shuttle effect. This interlayer should highly either attractive or repulsive to polysulfides such that they cannot penetrate through it and migrate to anode. Sulfur (S) to polysulfides (Li2S) reduction happens in presence of the carbon, with high conductivity and high surface area. In the present work, a highly hydrophobic interlayer with high nitrogen content is designed, which can trap the intermediate polysulfides before they reach the anode. The use of partially exfoliated carbon nanotubes (PCNTs) as sulfur host can increase the reaction kinetics of the polysulfides with its high conductivity and surface area. The structural and morphological studies of the synthesized PCNTs sulfur composite (PCNTs/S) and nitrogen rich highly hydrophobic interlayer were done by X-ray diffraction (XRD) pattern, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The use of PCNTs/S cathode with nitrogen rich highly hydrophobic interlayer for LiS battery has shown excellent cyclic stability for more than 100 cycles at 1C (1C = 1675 mA g-1), high rate capability up to 2C and specific capacity more than 1000 mA h g-1 at 0.1C.
All-Organic Rechargeable Battery with Reversibility Supported By “Water-in-Salt” Electrolyte
Authors: Dong Xiaoli , Wang Yong-Gang , Xia Yong-Yao
Published: February 2020

Rechargeable batteries with organic electrodes are preferred to those with transition-metal-containing electrodes for their environmental friendliness, and resource availability, but all such batteries reported to date are based on organic electrolytes, which raise concerns of safety and performance. Here an aqueous-electrolyte all-organic rechargeable battery is reported, with a maximum operating voltage of 2.1 V, in which polytriphenylamine (PTPAn) and 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA)-derived polyimide (PNTCDA) serve as cathode and anode material, respectively. A key feature of the design is use of a “water-in-salt” electrolyte to bind “free” water; this impedes the side reaction of water oxidation, thereby enabling excellent reversibility in aqueous solution. The battery can deliver a maximum energy density of 52.8 Wh kg-1, which is close to most of the all-organic batteries with organic electrolytes. The battery exhibits a supercapacitor-like high power of 32000 W kg-1 and a long cycle life (700 cycles with capacity retention of 85%), due to the kinetics not being limited by ion diffusion at either electrode.

Fig. 1 Electrochemical performance and reaction mechanism of PTPAn in the “water-in-salt” electrolyte.

Keywords: All-organic rechargeable battery, Polytriphenylamine cathode, Polyimide anode, “Water-in-salt” electrolyte

Reference:

[1] Dong, X. L. et al. Chem. Eur. J. 2017, 23, 2560–2565.

[2] Wang, W.; Sprenkle, V. Nature Chem. 2016, 8, 204-206.

[3] Yamada, Y.; Usui, K.; Sodeyama, K.; Ko, S.; Tateyama, Y. Nature Energy, 2016, 1:16129.

Figure 1
Using SEAL and Harpoon to Search for Suitable Water-Splitting Electrodes
Authors: Wilkinson Theron J , Priewe Eva C , Menningen Kenneth L , Riha Shannon C.
Published: February 2020

The search for suitable electrodes for photoelectrochemical water splitting extends across the periodic table. While III-V semiconductors exhibit superior light gathering properties, metal oxide semiconductors generally cost less and are more robust.

The Solar Energy Activity Laboratory (SEAL) 1 and the Heterogeneous Anodes Rapidly Perused for Oxygen Overpotential Neutralization (HARPOON)2 are simple experiments that can quickly scan for suitable oxide semiconductors. The SEAL experiment measures photocurrent and the HARPOON experiment measures oxygen production efficiency. In addition, an electroplating and lithography technique3 can produce nanowires of nearly any composition that can increase the achievable current density at the electrode surface.

Electrodes made of oxides of Fe, Cr, Zn, Al, Bi, Co, and Ni were produced in our laboratory and evaluated using the SEAL and HARPOON experiments. Promising candidates were made into nanowires for additional study. This presentation will communicate the preliminary results.

REFERENCES

J. R. McKone et al., “The Solar Army: A Case Study in Outreach Based on Solar Photoelectrochemistry, “ Rev. Adv. Sci. Eng.
3, 288 (2014).

S. E. Shaner et al., “Discovering Inexpensive, Effective Catalysts for Solar Energy Conversion: An Authentic Research Laboratory Experience,” J. Chem. Educ.
93, 650 (2016).

http://www.unitedsci.com/product-catalog/making-wire-lithograph-pressure-sensor-nanotechnology-stem-kit
Probing Interactions at the Polymeric Filtration Media/ CMP Slurry Interface Using Dynamic Electrochemical Quartz Crystal Nanobalance (EQCN) and Atomic Force Microscopy (AFM)
Authors: Salinas Maria , Saucedo Cynthia , Keleher Jason J. , Hudiono Yeny , Harton Shane , Connor Patrick
Published: February 2020

As devices continue to shrink, the demands on chemical mechanical polishing (CMP) become more stringent, requiring slurries to be modulated in order to enhance surface quality. Achieving angstrom level uniformity and minimizing defects, results in the need to develop polymeric filtration media that also increases polishing efficiency. Probing the interactions that can occur at the particle/polymer/slurry interface is essential in order to understand the impact of altering the chemistry and the filtration media on the filterability, rate of diffusion, adhesion force, surface roughness, and activation energy (EA). This work focuses on investigating the interactions between common abrasive particles, such as ceria and silica (in various chemistries), as well as different polymeric filtration media through the use of an electrochemical quartz crystal nanobalance (EQCN) and atomic force microscopy (AFM). The AFM tip is effectively functionalized in solution using epoxy glue to mimic a nanoparticle, which is used to measure the adhesion force between the particle and membrane via force distance curves. These nanoparticles can be reduced, oxidized, or functionalized and can be used to measure the adhesion force at different filtration time intervals, monitoring the change in the particle-polymer interaction. Preliminary results suggest that altering the complexing agent in the slurry can heavily influence the EA of the interaction between the slurry and filter membrane. Specifically, the activation energy for a copper CMP slurry and an amine-based filter was found to be negative, indicating a barrier-less reaction, due to non-covalent interactions present at the slurry-polymer interface. Changing the complexing agent from glycine to L-alanine and β-alanine revealed the EA to be positive and negative, respectively, which also changed with the structure of the membrane. Ultimately, both the backbone of the filter and the complexing agent alter the interactions on the surface of the polymer membrane and have shown to have a direct impact on CMP performance.
Preparation and Electrokinetic Characterization of Composite Membranes with Various Ion Exchange Moities
Authors: Im Kwang Serb , Son Tae Yang , Han Song I , Yun Jun Seong , Nam Sang Yong
Published: February 2020

In this study, ion exchange membranes were prepared. Prior to the preparation of the ion exchange composite membranes, sulfonation and amination were performed with different equivalents to the same polymer. Then, the most suitable equivalent amount of polymer was selected from the completed polymers. The selected polymer was impregnated into support and reinforced composite membrane excellent in mechanical strength was prepared. When the support was used, the ion exchange capacity value is lowered. In order to compensate, particles were mixed together in polymer solution to maintain the performance. FE-SEM was used to confirm that the particles were sell dispersed in the membrane, FT-IR was used for quantitative analysis, TGA/DSC for thermal characterization and Ion conductivity / membrane resistance / I-V curve were measured for electrochemical properties.
Electrodeposition of a Selective Coating Based on Black Cobalt on Stainless Steel (AISI 304) and Inconel 600 Substrates for Solar-to-Thermal Energy Conversion
Authors: Herrera-Zamora Dallely Melissa , Lizama-Tzec Francisco Iván , Arés-Muzio Oscar , Oskam Gerko
Published: February 2020

Conversion of solar to thermal energy in solar collectors is achieved through selective coatings on metal substrates. The main characteristics of the selective coatings are a high solar absorptance and low thermal emittance, metallic substrates resistant to high operating temperatures and atmospheric corrosion. In this work, selective black cobalt solar coatings electrochemically deposited onto stainless steel (AISI 304) and Inconel 600 substrates, with an intermediate layer of bright nickel as an infrared reflector, are characterized. The transformation capacity of solar-to-thermal energy depends on the thickness of the films, which depends on the galvanostatic deposition time. Hence, by controlling the charge applied in the electrochemical deposition process, the optical properties can be optimized. The black cobalt coating used in this work has the characteristic of high absorption in the solar spectrum and low emission in the infrared, even after a thermal treatment of up to 500 °C on stainless steel substrates (AISI 304).

The thermal stability of the selective coatings was studied by means of a thermal treatment in the range of 300 and 750 °C in air, observing the change in the optical properties due to the influence on the solar absorptance and the thermal emittance. The coatings were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The Vis – IR reflectance were evaluated before and after the heat treatment using an integrating sphere (2 μm to 15 μm). The black cobalt coatings presented homogeneity, stability, good adhesion and solar absorptance of 96% and thermal emittance of 7% (calculated at 100 °C). Results suggest that the electrochemically deposited black cobalt coating (UV-Vis absorber/IR reflector/metallic substrate) can be scaled-up and applied at medium to high temperatures for the conversion of solar radiation into heat.
Cyclic Voltammetry Studies on Lead Telluride Films for Stainless Steel Working Electrode
Authors: Gite Anil Bhanudas , Jain Gotan Hiralal
Published: February 2020

In the present study, Lead Telluride films are grown by an inexpensive and template free electrochemical technique on stainless steel substrate through an aqueous solution of lead nitrate and Tellurium oxide. The electrodeposition was carried out by cycling between two potentials with different scan rates of 25mV/s, 50mV/s, 75mV/s and 100mV/s. In addition the electrochemical behaviour of PbTe were studied separately. In this method, by selecting precisely the electrolyte concentration, films were synthesized by varying the deposition time and electrode potential. The morphological and structural evolution of as prepared Lead Telluride films was characterized by scanning electron microscopy (SEM) study reveals that the Spherical shape grains are form and spread over the entire surface of the substrate and X- ray diffraction techniques which shows that the films average crystalline size is 27nm on stainless steel substrates and films shows the orthorhombic crystal structure. Fourier Transform infrared spectroscopy gives the transmittance spectra of the synthesized films. The quantitative evaluation of the wetting of a solid surface by a liquid is estimated in terms of the contact angle measurements for the films.

KEYWORDS: Electrode potential, XRD, SEM, EDS etc.
Electrocatalytic Properties of MoS2 In-situ Grown on Graphene Oxide as Counter Electrode for Dye-sensitized Solar Cells
Authors: Pang Beili , Shi Yongtang , Lin Shan , Wang Yingying , Dong Lifeng
Published: February 2020

Dye-sensitized solar cells (DSSCs) have attracted great attention as one of next-generation photovoltaic devices due to low cost and simple fabrication process. A conventional DSSC consists of TiO2 photoelectrode, counter electrode (CE) and liquid electrolytes containing iodide/triiodide (I/I3
-) redox couple sandwiched between the electrodes. The CE serves to collect electrons and catalyze redox couple regeneration; thus, its material and performance determine the cost and photoelectric conversion efficiency of DSSC. Generally, noble Pt is employed as a CE owing to its rapid electron transfer ability and superior electrocatalytic behavior toward I3
- species. However, Pt is expensive and limited in resource. Hence, it is vital to find inexpensive and readily available non-Pt catalysts for the development of DSSCs.

Carbon materials, conductive polymers, transition-metal compounds, metal alloys, and their composites have been explored to replace Pt. Among these alternatives, transition-metal compounds including carbides, nitrides, chalcogenides and oxides have demonstrated some desirable performances. MoS2 consists of three atom layers: one Mo layer sandwiched between two S layers via weak Vander Waals interactions. Advantageously, MoS2 has abundant exposed active sulfur edges for catalytic activity. On the other hand, graphitic carbon nitride (g-C3N4) demonstrates excellent thermal and chemical stability as well as interesting electric properties, which make it have good catalytic activity for a variety of reactions. In addition, g-C3N4 can be economically prepared in large scale. Herein, we present the fabrication and characterization of porous g-C3N4 nanosheet/MoS2 nanoparticle (g-C3N4/MoS2) composite. Such an architecture can provide short diffusion distance for excellent charge transport as well as large contact area for fast interfacial charge separation and electrochemical reactions. As a result, the nanocomposite is anticipated to exhibit good electrochemical and catalytic activities.

In this study, we first developed a solution-based coating method to prepare g-C3N4/MoS2 counter electrode. Through a facile hydrophilization process for g-C3N4 and sintering the Mo-S precursor coated g-C3N4 at 280 °C for 12 h, crystalline MoS2 nanoparticles were formed on g-C3N4 substrate, resulting in strong mechanical adhesion. In addition, low-cost solution-processed g-C3N4/MoS2 electrode had similar electrocatalytic behavior toward I3
- species to Pt. As a result, the DSSC based on g-C3N4/MoS2 demonstrates desirable photovoltaic performance.