bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of Electrochemical Reaction Mechanism with LSC-GDC Composite Cathode Based on 3D Reconstructed Microstructures
Authors: Kim Y. T. , Shikazono Naoki
Published: February 2020

In the present study, electrochemical reaction mechanisms of La0.6Sr0.4CoO3 (LSC)-Gd0.1Ce0.9O1.95 (GDC) composite cathodes were investigated by a Lattice Boltzmann Method (LBM) based on 3D reconstructed cathode microstructures with different volume ratios. In the simulation, the exchange current density for the surface reaction was fitted using an experimental data of pure LSC cathode. On the other hand, the exchange current density for the TPB reaction was fitted using composite cathodes. Overpotentials and potential distributions were quantified. Then, the results were compared with those of LSCF-GDC composites reported in our previous work (Y.T. Kim, Z. Jiao, N. Shikazono, J. Power Sources, 342, pp. 787-795, 2017). LSC surface area density was 1.4 μm2/μm3, which was smaller than the LSCF cathode. Compared with the LSCF-GDC composite cathode, it is considered that TPB reaction is more contributed for the LSC-GDC composite cathodes.
Chemical and Structural Stability of SrxNiyOz Chromium Getter for Application in SOFC Systems
Authors: Aphale Ashish N , Uddin Md Aman , Hu Boxun , Liang Chiying , Webster Justin , Singh Prabhakar
Published: February 2020

Cost effective alkaline earth and transition metal complex oxides (SrxNiyOz) have been synthesized and electrically tested as chromium getter to mitigate Cr poisoning in solid oxide fuel cell (SOFC) power generation systems. In this study, we report the chemical and structural stability of the SrxNiyOz powder under simulated synthesis and operational conditions. High temperature in-situ X-ray diffraction (XRD) has been used to determine the phase stability of SrxNiyOz in the temperature range of 850 °C to 1000 °C while SEM-EDS technique was used to study the surface morphology and elemental distribution in bulk phases. XRD results indicate that the synthesized SrxNiyOz remains stable at 850 °C and 900 °C with no/negligible phase separation of SrO and NiO compounds, whereas exposure to temperatures 950 °C and 1000 °C leads to the decomposition of parent phase and formation of SrO and NiO. Further, it was observed that the powder samples sintered at 950 °C and 1000 °C showed volume expansion and pulverization when exposed to the humid air atmosphere for 24h. Samples sintered at 850°C and 900°C maintained structural stability and shape.
Protecting Battery and Energy Technology: Trade Secrets
Authors: Aruda Kenneth
Published: February 2020

Protecting Battery and Energy Technology: Trade Secrets

by Charles Collins-Chase, and Kenneth Aruda, Ph.D.

Finnegan, Henderson, Farabow, Garrett & Dunner LLP

Patents and trade secrets coexist as separate intellectual property regimes, and as a result, businesses and inventors must often choose between patent and trade secret protection. Recent legislative changes, including the Defend Trade Secrets Act (DTSA) in 2016 directly affect this choice.

Manufacturers have long faced a dilemma when trying to protect some of their most valuable assets—the manufacturing methods behind their products. Method patents can be difficult to draft, license, and assert. But trade secrets offer limited protection absent misappropriation. The DTSA aims to place trade secrets on equal footing with other forms of intellectual property by creating a new federal civil cause of action for trade secret misappropriation, and includes an ex parte seizure provision and whistleblower protections.

Under current legislation, the prior user defense preserves the right to continue the practice of a trade secret invention in the United States despite subsequent issuance of a third party patent. The availability of this defense limits the need to patent every commercial improvement and simplifies freedom to operate analysis for commercial processes.

With these advantages in mind, for technologies such as catalysis, electrode production processes, and complex processing of gas diffusion layers, trade secrets could in some instances be a desirable alternative to patents. One should consider developing a trade secret protection plan that fits your business, and assess the sensitivity level of various types of information and establishing security measures that should be in place at each level. To qualify as a trade secret, federal law requires that “reasonable measures” be taken to keep the information secret. This presentation aims to inform how courts have treated various types of secrecy measures mentioned in recent cases.
Degradation of Separator after Calendar Ageing in 18650 Li-Ion Battery: Impact on Safety and Performances
Authors: Fleury Xavier , Geniès Sylvie , Thivel Pierre-Xavier
Published: February 2020

Lithium ion batteries (LIBs) are the most popular types of rechargeable battery with their superior gravimetric and volumetric capacities for electric and hybrid vehicles. But more than energy density, cost, lifetime or recyclability, safety issues is the most challenging parameter to investigate especially after ageing. Even if separator is considered as electrochemically inert, it play a major role in all of these properties. It is so crucial to evaluate its evolution in time, to observe its degradation and its impact on safety and performances of LIBs.

The aim of this study is to determine the evolution of chemical, morphological and mechanical properties of a polyethylene separator under two different ageing conditions: calendar ageing and fast charge cycling in 18650 LFP/G batteries systems. Its porosity is evaluated by Helium pycnometry, its mechanical properties by tensile test. Surface chemical composition is also investigated by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Surface state is observed by scanning electronic microscopy (SEM) and by atomic-force microscopy (AFM). Electrochemical performances are analyzed by impedance spectroscopy and C-rate tests to investigate the consequences of the separator ageing. Safety tests are also performed by overcharge in an Accelerating Rate Calorimeter (ARC) and by in-situ dendrites growing in coin cells.

First results show a decrease of the separators porosity after calendar ageing which causes a decrease of the cell performances at high capacity rate. A deposit is observed on the extreme surface. A mechanistic model of ageing will be proposed which integrate a porosity gradient and an evolution in time.
Effective Transport Property Simulation on Three-Phase Mesoscale Electrode Reconstructions across Manufacturing Parameters
Authors: Trembacki Bradley L. , Noble David R. , Ferraro Mark E. , Brunini Victor E. , Roberts Scott A.
Published: February 2020

Advances in the three-dimensional imaging and subsequent computational representation of lithium-ion battery electrodes have made it possible to perform detailed simulations on reconstructed electrode mesostructures. These particle-scale simulation capabilities can be utilized to analyze the effect of the manufacturing process and can also inform macroscale (cell- or module-level) battery models, most notably through effective transport properties. For these simulations to be realistic and accurate, quality computational meshes and sufficient domain sizes (1000+ active material particles) must be achieved.

Additionally, imaging techniques, such as x-ray tomography, that can provide sufficiently large domain sizes are often unable to clearly differentiate between the non-active electrode phases (binder, conductive additive, and void/electrolyte). This forces models to make assumptions about the morphology of non-active phases or neglect their contributions altogether. Our recent work has focused on addressing these challenges, and we have developed a novel “binder bridge” placement algorithm to introduce a composite binder morphology to a large many-particle domain that mimics morphologies seen in high-resolution imaging where nonactive phases can be differentiated.

We use this approach to study the effect of the electrode manufacturing process on effective electrode properties by simulating electrodes manufactured using various calendaring pressures and slurry compositions.
Surface Contamination of Metal Oxide-Based Battery Active Materials: Performance Implications and Mitigation Strategies
Authors: Metzger Michael , Sicklinger Johannes , Pritzl Daniel , Beyer Hans , Gasteiger Hubert A.
Published: February 2020

The performance of metal oxide-based battery active materials is compromised by surface contaminants formed during storage and handling in ambient air. We present a detailed analysis of the true nature and the quantity of these surface contaminants on three different cathode active materials (CAMs), the widely used LiNi1/3Mn1/3Co1/3O2 (NMC111), the high surface area Li- and Mn-rich xLi2MnO3•(1-x)LiNiaMnbCocO2 (HE-NMC), and the Ni-rich LiNi0.6Mn0.2Co0.2O2 (NMC622) and LiNi0.8Mn0.1Co0.1O2 (NMC811). We process these materials in three distinct conditions “dry” (as-received materials dried at 120 °C), “wet” (excessive air exposure at high relative humidity) and “calcined” (high temperature treatment) and identify surface contaminants by X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis coupled with mass spectrometry (TGA-MS) and diffusive reflectance infrared fourier transform spectroscopy (DRIFTS). We test the CAMs’ reactivity with an ethylene carbonate-based electrolyte using on-line electrochemical mass spectrometry (OEMS) and evaluate their performance in Li-ion battery cells. We demonstrate that not only the commonly assumed LiOH and Li2CO3 residues account for performance deterioration, but also transition metal hydroxides/carbonates formed on the material surface during exposure to atmospheric moisture and CO2. Finally, we showcase a thermal treatment that removes these transition metal based surface contaminants and leads to superior cycling stability.
Carbide-Derived Carbon As Electrode Materials of Electrochemical Double Layer Supercapacitors in Ionic Liquid Electrolytes
Authors: Messner Matthew , Penney Christopher M. , Johnson Kevin , Caldwell Benjamin V. , Hettinger Jeffrey D. , Yu Lei
Published: February 2020

Carbide-derived carbon (CDC) is a type of porous pure carbon material that is prepared by chlorination or oxidation of metal carbide precursors, which remove the metal elements from the carbides leaving the porous structure. CDC has been shown to be an advanced electrode material for electrochemical double layer supercapacitors (EDLS) bearing large specific energy and power densities, excellent compatibility with various electrolytes solutions, and a long shelf-life. In this work, we investigate the properties of the electrode materials when room temperature ionic liquids (ILs) are used as the electrolytes for the EDLS. ILs have excellent thermal stability and negligible vapor pressures which can improve the safety and longevity of the electrochemical devices. The CDC electrode materials are synthesized by the chlorination method and a newly developed electrochemical oxidation method. Pure ILs with various cations and anions, IL solutions with different solutes such as organic acids, Li+, Cl-, and propylene carbonate are used in the EDLS systems. In addition to the electrochemical measurements, the morphology and structure properties of the CDC electrode are characterized by Raman spectroscopy, SEM, and XRD techniques.
Tungsten Trixode Nanoparticles-Carbon Nanohorns Composite As Anode Material for Lithium-Ion Batteries
Authors: Sahu Sumit Ranjan , Rikka Vallabha Rao , Prathap Haridoss , Gopalan Raghavan , Prakash Raju
Published: February 2020

Lithium-ion batteries (LIB) are currently the most promising energy storage systems used in wide range of applications from portable electronic devices to electric vehicles. Tungsten oxide (WO3) has recently been studied as anode material for LIB due to its high theoretical capacity of 693 mAhg-1 and four times higher volumetric capacity than that of graphite. Due to its high melting point (1473 °C) and strong mechanical stability, WO3 could be used as safe anode material for LIB. However, large first cycle irreversibility as well as long-term cyclic stability are the major bottlenecks associated with this material. Several approaches like controlling morphology, creating oxygen vacancy and composite with carbon materials have been tried to overcome these problems.

Herein, we have investigated the effect of carbon nanohorns (CNH) addition on the irreversibility and long-term cyclic stability of WO3. CNH is a well-studied material as a composite with metal oxides, enhances the cyclic stability of metal oxides due to its good electric conductivity, large surface area and mechanical strength. WO3 was synthesized via microwave synthesis method and CNH were prepared by arc-discharge method. Both the materials were characterized by XRD, Raman spectroscopy, BET analysis, SEM and TEM. WO3 showed spherical morphology with a uniform particle size of <200 nm. Pure WO3 showed first discharge capacity of 887 mAhg-1 at a current density 50 mAg-1 in a voltage range between 0.05 and 3.0V. It showed a capacity of ~235 mAhg-1 after 100 cycles. Electrochemical performance of WO3 was studied by addition of 10, 20, 30 wt% of CNH. Among all, 30 wt % CNH composite electrode exhibited a first discharge capacity of ~998 mAhg-1 and a capacity of ~650 mAhg-1 after 100 cycles at a current density 50 mAg-1. The electrochemical performance of the composites with 10 and 20 wt% of CNH have also been studied. The results of the rate capability and long-term stability of the composites will be discussed in detail during the presentation.
Direct Correlations of Grain Boundary Potentials to Dielectric Properties of Doped CaCu3Ti4O12 Thin Films
Authors: Han Chan Su , Cho Ahra , Kim Ji Won , Cho Yong Soo
Published: February 2020

A direct relation between dielectric constant and surface potential at grain boundary in giant permittivity CaCu3Ti4O12 (CCTO) thin films doped with various dopants of Zn2+, Ga3+, Mn2+ and Ag1+ is proposed here. The CCTO-based materials have been one of emerging dielectric candidates due to a giant dielectric constant of >104, which is different with typical high k materials such as BaTiO3 or Pb(Zr,Ti)O3 in that the CCTO is based on the interfacial (or space charge) polarization mechanism (instead of permanent dipolar polarization). Accordingly, the electrical status of grain boundary has been recognized as the main cause for the exceptionally high permittivity. As a highlight, we suggest a nearly linear relation between the dielectric constant and grain boundary potential, with experimental evidences. As an experimental result for four different choices of dopants, Zn2+, Ga3+, Mn2+ and Ag1+ in terms of dielectric properties, chemical states of involved defects such as Cu1+, Ti3+ and oxygen vacancy are proven to dictate the dopant-dependent dielectric performance. Particularly, the case of Ag-doping exhibited the best dielectric constant as related to the highest grain boundary potential. A direct observation of the grain boundary region by using spherical aberration-corrected scanning transmission electron microscopy (Cs-STEM) with the simultaneous electron energy-loss spectroscopy (EELS) reveals the changed chemical states across the grain boundary.
Amorphous Niobium Oxide Thin Film As Anode for High Rate Lithium Ion Battery
Authors: Kimble Ke'La Amonzie , Adams Jada Imari , Abiade Asha Ain , Tran Nam Xuan , Adkins Joshua Willis , Dangerfield Aaron , Meda Lamartine
Published: February 2020

Electrochemical pseudo-capacitor materials that can deliver high power and store high capacity energy for applications that required faster rate performance than traditional energy storage battery are needed. Amorphous Nb2O5 has been evaluated as a pseudo-capacitor. Amorphous thin film (550 nm) was synthesized by RF magnetron sputtering. The morphology of the Nb2O5 nanoparticle thin films was smooth as evaluating in field emission scanning electron microscope (FE-SEM) with nanoparticle size ranged between 5 and 15 nm. A cross-sectional FE-SEM image shows thickness was approximately 550 nm with excellent adhesion to the SS substrates. XPS revealed that the as-deposited materials are Nb2O5.

To understand the electrochemical redox reactions, cyclic voltammetry (CV) and galvanostatic discharge-charge (GDC) experiments were performed at different rates. The CVs were performed at scan rates of 0.1, 1, 2, and 5 mV/s. For example, for the scan rate at 1 mV/s a sharp peak current is observed at ~0.85 V during the first cycle which has been assigned to the formation of the solid electrolyte interface (SEI) and reduction of Nb+5 to Nb+4. As the cathodic sweep continues to zero volt no conversion reaction took place. The anodic sweep shows two broad and weak peak currents at ~0.7 and ~1.5 V. During the second cycle, the peak current at ~0.85 V disappeared which is typical of irreversibility and loss of capacity in the first cycle. All subsequent cycles were smooth with quasi rectangular CV curves which indicated the pseudo-capacitive characteristics of amorphous Nb2O5. This is opposite to sharp peak currents typically observed in CV that are characteristics of battery electrodes. Ex-situ XPS were performed on the sample stopped at 1.0 V during the reverse potential sweep and 1.84 V during the forward potential sweep. A very thick SEI layer was observed when the sample was stopped and analyzed at 1.0 V. NbOx was observed after fifteen minutes of sputtering at 1 KeV Ar+ and Nb+4/+5 after 90 min of sputtering. The SEI is composed of carbonates (Li2CO3), aliphatic carbon species, and fluorides (LiF). The capacity observed during the first cycle was 436 mAh/g at C/3 rate. After 100 cycles, the coulumbic efficiency was maintained at 100% and the capacity retention was 160 mAh/g. The materials responded very well to different cycling rates.

Figure 1
Stretchable Array of Wirelessly Charged High Performance Micro-Supercapacitors with Solar Cells for Wireless Powering of the Integrated Strain Sensor
Authors: Yun Junyeong , Song Changhoon , Park Heun , Jeong Yu Ra , Jin Sang Woo , Oh Seung Yun , Ha Jeong Sook
Published: February 2020

Along with the increasing demands for wearable health care and biomedical applications, there has been extensive research on the development of various stretchable electronic devices with mechanical stability even under deformations caused by body or skin movements. Also, energy storage devices which can be integrated with the stretchable active sensor devices have been actively studied for the practical utilization of wearable electronics without any wire-connected external power sources. Among various candidates for integrated energy storage devices, high performance solid-state micro-supercapcitors (MSCs) have been extensively investigated. Furthermore, integration of those MSCs with photovoltaic devices is expected to provide the power for the sensors, leading to the wirelessly driven skin-attachable health monitoring sensor system.

In this work, we report on the fabrication of stretchable array of high performance solid-state MSCs which can be charged via integration with Si-based commercial solar cell so that those can power the integrated strain sensor. The planar MSC consists of electrodes of potentiostatically deposited polypyrrole on spray coated multi-walled carbon nanotubes film and gel-type electrolyte of LiCl/polyvinyl alcohol with redox additive of 1-Methyl-3-propylimidazolium iodide. The fabricated MSC shows areal capacitance 5.2 mF cm-2 at a current density of 100 µA cm-2. The MSC retains 80% of initial capacitance after 5000 charge/discharge cycles at a current density of 100 µA cm-2. A strain sensor was fabricated with a composite film of fragmentized graphene foam and PDMS. Such fabricated MSCs, strain sensor, and the solar cell were integrated on a single deformable polymer substrate with embedded stiff platforms of SU-8 via long serpentine interconnections of Ti/Pt metal film for mechanical stability under stretching. After 1000 repetitive biaxial stretching/releasing cycles by 30%, there appeared no noticeable change in the charge/discharge behaviors. Furthermore, the photo-charge/discharge characteristics and electrochemical performance remained stable under biaxial stretching of 30 %. With the energy stored in MSCs using the solar cell, the integrated strain sensor could detect the externally applied strain and the arterial pulse after attachment of the whole integrated system onto the wrist of the author.

This work successfully demonstrates the potential application of our stretchable self-charging power/sensor system to skin-attachable health monitoring devices.
Polymeric Binder Distribution within LiCoO2 Electrodes By Using a Surface and Interfacial Cutting Analysis System (SAICAS)
Authors: Byun Seoungwoo , Roh Youngjoon , Kim Seokwoo , Jin Dahee , Choi Jaecheol , Ryou Myung-Hyun , Lee Yong Min
Published: February 2020

Polymeric binder distribution of lithium-ion battery (LIB) electrodes becomes as important as using high-capacity electrode materials for highly loaded electrodes. Because, the electrode coating layer can be delaminated from the current collector within the service time unless the binder is well-dispersed. However, due to the limitation of usable analysis tools, to get some information on binder distribution remains one of the unresolved issues in LIBs. Fortunately, we have started to analyse these issues using a new tool, surface and interfacial cutting analysis system (SAICAS, Daipla Witnes, Japan), to measure adhesion properties of LIB composite electrodes as a function of depths. The adhesion strength measured by SAICAS is approximately proportional to the binder content, the polymeric binder distribution within the electrodes can be unveiled with a SAICAS.

In this study, we fabricated two LiCoO2 positive electrodes dried at different temperatures, 130 and 230oC. They were used to analyse the polymeric binder distribution in the electrode by using SAICAS. First, their adhesion strengths were carefully measured at every 10 μm depth from the electrode surface. At the same time, both surface/cross-sectional SEM images and corresponding EDS atomic mapping were confirmed to find correlation with adhesion strength. Finally, their electrochemical property changes such as cycle life, rate capability, DC-IR, etc. at room and high temperatures were also discussed.
Development of Formvar-Based Membranes with Controlled Porosities for Microfluidics and Large-Area Graphene Transfer
Authors: Dervishi Enkeleda , Auchter Eric , Marquez Justin , Stevens Garrison , Li Nan , Mcculloch Quinn , Sheehan Chris , Chamberlin Rebecca , Yarbro Stephen
Published: February 2020

Ultra-thin and strong formvar-based membranes with controlled morphologies were developed via a simple synthesis technique. This thin hydrophilic and oleophilic polymer possesses very interesting morphological properties including being inert to most chemicals and resistant to radiation. Tunable porous membranes (porosity ranges from 20 to 60%) were synthesized by controlling the ratios of formvar, glycerol, and chloroform; and varying the sonication time. While the porosity can be altered, the hydrophilicity and oleophilicity is fundamental to the formvar itself and is independent of synthesis conditions. The formvar-based membranes were found to have an elastic modulus of 7.8 GPa (twice as high as previously reported values) with an average thickness of 125 nm. The figure below shows the SEM images of holey formvar structure (A) and lacey structure (B) along with a 3D render AFM image of a high porosity holey formvar sample (C). To demonstrate the versatility of this membrane, we performed chemical compatibility testing revealing that only chloroform had a destructive effect fully dissolving the formvar in a few minutes. High concentrations of HCl (above 6M) were found to have minor deleterious effects after an hour of exposure. Moreover, a numerical model was used to demonstrate the feasibility of the membranes with a range of porosity in realistic conditions in nano- and micro-devices. These thorough simulations revealed that the membrane with the highest porosity of ~50% exhibited the lowest probability of failure in a pressurized system.

Additionally, the unique mechanical properties and chemical resistivity of formvar, provide the opportunity for using these type of membranes in certain environmental conditions to transfer and handle various 2D materials, where other polymer types would not be suited for. More specifically, due to the ease at which formvar dissolves in chloroform, for the first time we utilize the formvar-based membranes for large-area graphene transfer. Compared to other polymer-based transfer techniques, our novel method allows for a cleaner and a faster transfer of graphene sheets onto a variety of substrates, including commercial TEM grids, silicon dioxide and glass. Various spectroscopy and microscopy analyses demonstrated the effectiveness of this formvar-based transfer technique for large-area crystalline graphene sheets. The formvar removal is one to two orders of magnitude faster than other reported PMMA-based transfer methods. Moreover, formvar can be applied to large-area graphene sheets limiting the transfer dimensions only to that of catalyst size utilized for graphene growth. Ultimately, the development of ultra-strong and versatile membrane materials can allow for major advances across a wide range of important applications in microscale to nanoscale fluidics and nano-electronic devices.

Figure 1
(Invited) A Role of Graphene Fabricated on Surfaces of Metal Halide Perovskite Compounds. A First-Principles Study
Authors: Sugimoto Manabu
Published: February 2020

Surface fabrication of metal halide perovskite compounds is a challenging issue to enhance energy conversion efficiency of perovskite solar cells (PSCs). Since they are a multi-layered device and the energy band alignment are not necessarily perfectly matched between the adjacent layers, a buffer layer is expected to bring some beneficial effects by intervening between the layers. Such a layer might also give additional effects on surface passivation, surface protection against device deterioration, etc.

In this presentation, we report our first-principles study of graphene fabrication on metal halide perovskite compounds with some types of lattice defects. The sheet-type material has been experimentally reported to improve photovoltaic action of PSCs. Our interest on lattice defects are due to the experimental report indicating the existence of carrier traps near the surfaces of the perovskite compounds.

The present density functional calculations show that single vacancies arising from a loss of either iodine or lead atoms in methyl ammonium lead iodide can be carrier traps near the surface. The calculations on the system after graphene fabrication of the defective crystal predict that the surface coating would suppress carrier trapping at the lattice vacancies. The detailed numerical analyses clarify that electronic interaction by graphene would be significant for the suppression, and would explain a reason why the graphene fabrication of the surface was successful in the previous experiments.
Charge Transfer within Metal-Organic Frameworks: The Role of Polar Node in the Electrocatalysis and Charge Storage
Authors: Deria Pravas , Wyk Andrea Van , Smith Tanner
Published: February 2020

Metal-organic frameworks (MOFs) assembled from photo and redox active building blocks such as porphyrins and pyrenes, as well as numerous post-synthesis processes that enable incorporation of required chemical functionality within the pores, have signified these crystalline molecular assemblies as emerging class of compositions for energy conversion, and storage systems. In particular, electrocatalytic energy conversion and storage applications require efficient charge transport process within the framework. It is known that the difference in the redox potentials between the linkers and metal-oxo nodes enforces a self-exchange/hopping type charge transport processes. For example, porphinato-iron based frameworks are shown to provide high electrode-surface concentration of electrocatalytic reduction of CO2 to CO. However, in such processes, as counter ion migration accompanies a (electrochemical) charge transfer reaction within the narrow pores of the MOFs, it leads to unique situations including a slower kinetic and selective redox reaction [i.e. a modified self-exchange reaction: L⁺—PF₆̅ + L⁰ → L⁰—PF₆̅ + L⁺]. This paper will discuss how the charge-transfer process is inherently different within the pores and that the metal-oxo node can play a critical role in the CT kinetics.
Pyrolysis of Co-Assembled Iron and Cobalt Porphyrin on Carbon As Highly Active Electrocatalysts Toward Oxygen Reduction
Authors: Song Yujiang
Published: February 2020

Herein, we report a new approach for the synthesis of non-precious metal electrocatalysts (NPMEs) relying on ionic self-assembly of oppositely charged iron (III) and cobalt (III) porphyirn on carbon in combination with subsequent pyrolysis, leading to carbonized porphyrins uniformly dispersed on carbon without any noticeable agglomerations at nanoscale. As evidenced by thermogravimetric analysis (TGA), the self-assembled porphyrins show a much better thermal stability than each constituent porphyrin, thus possibly preventing the formation of agglomerations that frequently occurred during a pyrolysis process. Additionally, the strong interaction between self-assembled porphyrins and carbon support should also be responsible for the even distribution of carbonized porphyrins according to Fourier transformation infrared (FTIR) spectra. Compared with mechanically mixed and then heat-treated porphyrins, self-assembled and then pyrolyzed porphyrins exhibit a much higher activity toward oxygen reduction reaction (ORR) in both acidic and alkaline medium likely due to well exposed active sites without any aggregation, which has not been achieved prior to this study.
Synthesis of Tetrabenzoporphyrin Complexes Bearing Peripheral Phenyl Groups
Authors: Okujima Tetsuo
Published: February 2020

We have successfully synthesized peripheral phenyl-substituted tetrabenzoporphyrins by the precursor methods. Thermal conversion and the oxidative aromatization methods afforded the corresponding tetrabenzoporphyrins. The distorted structures due to the steric hindrance between phenyl groups and insertion of phosphorus atom resulted in marked red-shifted absorptions. The Q bands reached over 700 nm. The X-ray crystallographic analysis revealed the saddle conformation due to steric hindrance between peripheral phenyl groups of the neighboring isoindole moieties and the ruffle conformation similar to tetraazaporphyrin phosphorus complexes. The synthetic strategy based on the precursor method afforded p-expanded porphyrins with the fine tuning of their optical properties.
Photofunctions of Phthalocyanine Complexes
Authors: Ishii Kazuyuki
Published: February 2020

Phthalocyanines (Pcs, Figure 1) have attracted attention as a result of their diverse electronic and optical properties, offer applications in the fields of luminophores, sensors, non-linear optics, photosensitizers for singlet oxygen generation, photovoltaic cells, red or near-infrared light absorbers in optical data storage systems, and photoconductor devices. Because of a recent surge of interest in both the functionalization of various molecules, focusing on photofunctions of Pcs has become essential. I'll present recent topics especially from the viewpoint of photofunctions of Pc complexes, i.e., photoelectrochemical catalysts, singlet oxygen generators, redox-based fluorescent probes, and magneto-optical effects.

Figure 1
Construction of 3D Carbon Nanostructure: Carbon Nanosheets Decorated Carbon Nanofiber As a Three-Dimensional Carbon Hybrid for High Performance Lithium-Sulfur Battery
Authors: Feng Shuo , Song Junhua , Du Dan , Lin Yuehe
Published: February 2020

Among the emerging energy storage methods, lithium-sulfur battery (LiS) has drawn plenty of attentions due to its high theoretical energy density (2600 Wh kg-1),1 economical cost and environmental benignity. Nevertheless, the insulating nature of sulfur and notorious polysulfides shuttling result in a low sulfur utilization and short cycling life.2 To address these problems, carbon material has been confirmed as an ideal sulfur host to promote LiS’s performance because of their low cost, high conductivity and controllable structure such as carbon spheres, carbon nanotube/fibers and carbon nanosheets. For example, one-dimensional carbon nanotube can increase the sulfur utilization by providing better electrical conductivity. However, its “open-to-electrolyte” structures cannot effectively prevent shuttling effect.3 As for zero-dimension carbon materials, core/yolk shell carbon spheres in particular, are less capable of establishing conductive networks, which in turns, compromise the sulfur utilization and rate capability.4 Thus, it is of great necessity to develop three-dimensional (3D) carbon materials with multiple functions in order to achieve high-performance lithium-sulfur batteries.

Along this line, we prepared a three-dimensional carbon nanosheets modified carbon nanofiber (3DCNF) as high porosity sulfur host. After decorated with vertically aligned carbon nanosheets, the surface area of pristine carbon nanofiber was dramatically increased from 30 m2/g to 500 m2/g due to the expanded dimension. Although both 1D nanofiber and 2D nanosheets cannot effectively prevent polysulfides shuttling by themselves, the delicate combination of them endows new functions, where 3D carbon hybrid is capable of accommodating sulfur expansion and deterring polysulfides dissolution by the hierarchical porous structure and interconnected carbon nanosheets. At the same time, the 3D porous carbon nanofiber can also form conductive network that allows rapid electron transfer. With the structural advantages, the 3DCNF and sulfur composite delivered a capacity as high as 1266, 977 mAh/g at 0.1 and 0.5 C, respectively. After 500 cycles at 0.5 C, it still retains a capacity of 607 mAh/g (0.07% capacity fading per cycle), exhibiting excellent cycling capability.

Reference

M. K. Song, E. J. Cairns and Y. Zhang, Nanoscale, 2013, 5, 2186-2204.

Y. Yang, G. Zheng and Y. Cui, Chem. Soc. Rev., 2013, 42, 3018-3032.

X. Liang, Z. Wen, Y. Liu, H. Zhang, J. Jin, M. Wu and X. Wu, J. Power Sources, 2012, 206, 409-413.

Y. J. Hong, J.-K. Lee and Y. Chan Kang, J. Mater. Chem. A, 2017, 5, 988-995.

Figure 1
Expanding the Potential Window of Aqueous Hybrid Supercapacitors with Electrostatically Sprayed Manganese Oxide Composite Cathodes
Authors: Agrawal Richa , Rabiei Baboukani Amin , Wang Chunlei
Published: February 2020

Electrochemical capacitors or “supercapacitors” are a class of electrochemical energy storage devices that bridge the gap between conventional capacitors and rechargeable batteries. Despite their high power handling, their low specific energy densities limit their application in fields that require simultaneous supply of high power and high energy. In the wake of improving the energy density of supercapacitors, the concept of utilizing redox and double layer mechanisms within one system has garnered significant attention in recent years. Such systems typically referred to as asymmetric or hybrid capacitors benefit from the kinetics and cycle life of the double layer material and the high capacitance of the redox material. In this work, electrostatic spray deposition (ESD) derived manganese oxide (MnOx) films were employed as the redox component for the hybrid cell. Three compositions of MnOx were evaluated for the optimal electrochemical characteristics with different amounts of carbon nanotube (CNT) additive. The composition with 10% CNT (MnOx-CNT 9-1) exhibited superior electrochemical performance as compared to both the pristine MnOx and MnOx films with 20% CNT (MnOx-CNT 8-2). The MnOx-CNT 9-1 electrode exhibited a high specific capacitance of 281 Fg-1 in addition to excellent rate handling and high capacitance retention over long term cycling. Upon verifying the viability of the ESD derived MnOx-CNT 9-1 films as electrochemical electrodes, the latter were used in an asymmetric capacitor configuration comprising activated carbon (AC) counter electrodes. The hybrid capacitor with the AC electrode with a mass 2.6 times as that of the MnOx-CNT 9-1 electrode exhibited optimal energy-power trade-off with high rate capability as compared to the other asymmetric capacitors, as well as the symmetric AC//AC and MnOx-CNT 9-1// MnOx-CNT 9-1 systems. The optimized asymmetric capacitor exhibited a maximal energy of 30.3 Whkg-1 and a maximal power density of 4 kWkg-1; the excellent electrochemical characteristics of the optimized hybrid capacitor are ascribed to the wider cell voltage of 2V as well as the high gravimetric capacitance of the ESD based MnOx-CNT composite cathode.
Long-Term Behavior of Carbon Steel in Alkaline Nitrate Solutions Related to Radioactive Waste Storage
Authors: Evans Kenneth , Rollins Brandon , Chawla Sandeep , Beavers John , Sridhar Narasi
Published: February 2020

Radioactive wastes from the processing of nuclear materials used for weapons production have been stored in underground carbon steel tanks for the past several decades. The waste solutions are a complex mixture of a variety of anionic and cationic species, dominated by sodium nitrates, nitrites, and hydroxide. It has been well established that localized corrosion and stress corrosion cracking of carbon steel can occur in these solutions above certain critical potentials that are determined by the anionic species and temperature. Recent studies have shown that the corrosion potential increases significantly over a period of weeks to months, such that there is a concern about exceeding the critical potentials under natural conditions of exposure. This paper discusses the evolution of the corrosion potential of steel in alkaline solutions (pH >11) in comparison to the critical potentials. The impedance behavior of the steel in these solutions shows changes in the semi-conductive behavior over time as well as the density of charge carriers that may influence the evolution of corrosion potential. The effect of the changes in corrosion potential on localized corrosion and stress corrosion cracking is discussed.
Galvanic Corrosion of Mild Steel Under Iron Sulfide Layers
Authors: Navabzadeh Esmaeely Saba , Nesic Srdjan
Published: February 2020

Iron sulfide corrosion product layers have recently become the center of attention in H2S corrosion. The iron sulfides role on mild steel corrosion exposed to H2S containing environments has been reported to be related to their semi-conductive properties. The two most stable phases, pyrite and pyrrhotite have similar resistivity and a more positive open circuit potential (OCP) when compared to mild steel OCP. In an earlier study, the authors reported a comparable electroactivity to what was measured on an X65 mild steel surface. Given conditions for establishing a galvanic cell are present in a conductive electrolyte, a corrosion product layer containing sulfide phases could enhance the rate of cathodic reactions by providing a larger cathodic surface area. Also, the mixed potential established between these layers with the mild steel is often more positive than the OCP for the uncoupled steel. This results in an intensified iron dissolution rate. In conditions where the steel is locally exposed to the corrosive media, this leads to localized corrosion.

The evidence for a galvanic effect related to iron sulfides coupling to mild steel has been mostly circumstantial. The galvanic corrosion that was attributed to such conditions was a conclusion that was reached through deductive reasoning, without direct proof. In the current study, zero resistance ammeter (ZRA) measurements were utilized to measure the magnitude of the galvanic current between coupled X65-pyrite and X65-pyrrhotite electrodes. Pyrite and pyrrhotite electrodes were prepared using geological specimens. The experiments were conducted in a deaerated conductive aqueous solutions at different pH at room temperature with iron sulfide surface area being seven times higher than the X65 steel surface area.

The experimental results for the same cathode to anode ratio showed that a higher galvanic current was measured at the X65-pyrrhotite couple versus X65-pyrite surfaces. It is noteworthy that upon exposure to an aqueous solutions containing H+, pyrrhotite undergoes a surface reduction to troilite and produces H2S. In a more acidic environments the produced H2S does not have a substantial effect on the corrosion currents. However, in aqueous solutions with limited available H+, the produced H2S plays a significant role in enhancing the corrosion currents.

It was shown in a prior publication that at pH 5.0 the currents at the pyrrhotite surface was higher than what was measured at the pyrite or X65 surfaces. This resulted in a much higher galvanic current at the X65-pyrrhotite surface.

Figure 1
Effect of Magnetic Field on Anodic Dissolution of Nickel in an Alkaline Solution with Chloride Ions
Authors: Ling Sichun , Jia Yibo , Ning Fei , Li Hongjuan , Lu Zhanpeng
Published: February 2020

Localized corrosion is a kind of serious failure that happens frequently in natural and industrial metallic structures. There are some reports on the influence of magnetic fields on pitting corrosion. In this study, the effects of magnetic field on anodic dissolution of nickel in 0.05 mol/L NaOH+0.2 mol/L NaCl system was investigated by potentiodynamic polarization, potentiostatic polarization and morphology observation. The potentiodynamic polarization curves with or without a 0.4 T magnetic field were shown in Fig. 1. The magnetic field has no obvious influence on the polarization curve at low potentials, and the anodic current density increased with the magnetic field at potentials higher than 0.9V(SCE). The results of potentiostatic polarization at 0.1V (SCE) show that the current density decreased rapidly with time starting from the beginning of polarization, and Imposing 0.4T magnetic field at 200s and removing the magnetic field at 400s did not change the current density. The morphological observations results show that the sample surfaces were bright without showing pitting, showing that the applied magnetic field has no obvious influence on the anodic dissolution at 0.1V(SCE). When polarized at 0.6V (SCE) and 0.8V (SCE) potential, current density suddenly increased within a short period of time and then increased gradually. Imposing a 0.4T magnetic field increased the anodic current while withdrawing the magnetic field decreased the anodic current, as shown in Figs. 2 and 3. More small pits were found the electrode surface after polarized at 0.6V (SCE) under 0.4T than that under 0T, implying that magnetic field would promote the pitting initiation at this potential. More large pits were found the electrode surface after polarized at 0.8V (SCE) under 0.4T than that under 0T, showing that the magnetic field would affect the pit growth period.

Figure 1
Electrochemical Investigation of Stainless Steel Cladded Carbon Steel Manufactured Via Powder Bed Selective Laser Melting
Authors: Murkute Pratik , Pasebani Somayeh , Isgor O. Burkan
Published: February 2020

This study aims to investigate the electrochemical and corrosion properties of 316L-stainless steel cladded carbon steel manufactured using powder bed the selective laser melting (PB-SLM) technique in various environments. The PB-SLM technique involves localized melting of a thin layer of 316L-SS powder bed with Yb - fiber laser. Main parameters of the PB-SLM process such as particle size, particle size distribution, laser power, laser-scanning speed and layer thickness were selected to optimize the density of the cladded layer and the quality of metallurgical bond to the substrate. Using the optimized process parameters, carbon steel substrates were cladded with stainless steel of various thicknesses. Several mechanical and microscopic tests (viz. nano-indentation, X-ray diffraction, Scanning electron microscopy) were performed to characterize both the bulk properties of the stainless steel layer and the interface between the cladding and the substrate. Electrochemical and corrosion properties were tested via. open-circuit potential monitoring, electrochemical impedance spectroscopy (EIS) and cyclic polarization (CP) in electrolytes with acidic to alkaline pH range and with increasing levels of chloride, simulating different application conditions. Scanning vibrating electrode technique was employed to study the galvanic corrosion properties of the stainless steel and carbon steel at the clad-substrate interface.
Mechanism and Kinetics of Goethite Dissolution in Water By First-Principles Simulations
Authors: Klyukin Konstantin , Rosso Kevin M. , Alexandrov Vitaly
Published: February 2020

Dissolution of iron oxides including goethite (a-FeOOH) in aqueous solutions plays a key role in a variety of phenomena from materials corrosion to biogeochemical cycling of elements in the environment. Previous experimental studies have made great strides towards better macroscopic understanding of iron-oxide nanoparticle growth and dissolution; however, atomistic picture of these processes is still elusive. Here, we carry out detailed ab initio molecular dynamics (AIMD) based simulations of iron dissolution from the (021) and (110) goethite surfaces. We unveil the mechanistic pathways and rates of both reductive and nonreductive dissolution of iron from both surfaces in aqueous solution at room temperature. Our results clearly demonstrate that the Fe(III) reduction to Fe(II) yields much higher dissolution rates than the nonreductive pathway, while the most rapid dissolution is expected for the proton-assisted reductive mechanism. We also discuss the role of both internal (structural) and external (from solution) protonation as the way to disrupt the breaking Fe-O bonds, as well as to stabilize intermediate reaction configurations of dissolving Fe.
Reactive Molecular Dynamics Modeling of Chloride-Induced Depassivation of Iron Passive Film in Alkaline Media
Authors: DorMohammad Hossein , Pang Qin , Árnadóttir Líney , Isgor O. Burkan
Published: February 2020

Chloride-induced depassivation of iron passive film in 13.5 pH NaOH solution was studied using Reactive Force Field Molecular Dynamics (ReaxFF-MD). The study involved the simulation of the passive oxide film formed in chloride-free 13.5 pH NaOH solution and the effect of incremental chloride addition to the solution on the oxide film. The interactions of chloride with the oxide film and the changes in the oxide film structure were investigated by monitoring different species, charge distributions, and the pair distribution functions over time. The relationship between different surface termination of the passive film (i.e., O-terminated surface vs. Fe-terminated surface) and chloride interactions was also studied. The results of the investigation were linked to existing depassivation models (e.g, the ion exchange model and the point defect model) and to a parallel Density Functional Theory (DFT) investigation of iron oxide and chloride interactions in water.