bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation of NiCo2S4 Thin Films As Counter Electrodes for Dye-Sensitized Solar Cells Using Dip-Coating Method
Authors: Su An-Lin , Chang Chin-Yu , Lin Jeng-Yu
Published: February 2020

Dye-sensitized solar cells (DSCs) have attracted intensive attention due to its high efficiency, low cost, and easy fabrication process. The main components of a typical DSC include a photo anode, an I−/I3
− redox electrolyte and a Pt counter electrode (CE). To speed up the commercialization of DSCs, the manufacturing cost of DSCs should be further significantly reduced. Both of exploring alternative CE materials to noble Pt and developing facile and low-cost fabrication process of CEs are crucial for achieving this purpose. In this study, NiCo2S4 (NCS) counter electrodes (CEs) were successfully fabricated via a facile dip-coating method for the first time. Prior to the CE preparation, the NCS particles were synthesized via a hydrothermal method. Afterward, the as-synthesized NCS were ball milled and then dispersed in de-ionized water or ethanol solutions. The bare fluorine-doped tin oxide (FTO) glass substrates were dipped in the surface-conditioner solution for 1 min and subsequently dipped in the as-prepared NSC suspension solution for different times. The Inductively Coupled Plasma Mass Spectrometry (ICP-MS) results showed the mass loadings for both kinds of NCS CEs first increased with immersion time, and then retain almost the same while the immersion time was over than 10 min The NCS CEs prepared by dipping in de-ionized water solutions for 10 min is designated as NCS CE. According to the electrochemical and photovoltaic measurements, NCS CE demonstrated superior electrocatalytic activity. Moreover, NCS showed the low charge-transfer resistance of 1.56 Ω. As a result, the photovoltaic conversion efficiency of the DSC based on the NCS CE was up to 7.36%, significantly higher than the Pt CE (7.29%).
Non-PGM ORR Catalysts Based on Transition Metals Alternative to Iron
Authors: Martinez Ulises , Holby Edward F. , Dumont Joseph H , Chung Hoon T , Zelenay Piotr
Published: February 2020

Non-platinum group metal (non-PGM) catalysts with high volumetric activity and low hydrogen peroxide yields are potential replacements for platinum-based catalysts for the oxygen reduction reaction (ORR). State-of-the-art non-PGM ORR catalyst synthesized from dual nitrogen precursors (cyanamide and polyaniline) have been presented before by our group [1]. These complex heterogeneous catalyst systems are formed from high-temperature synthesis of nitrogen, carbon, and transition metal precursors. Although Fe-N-C catalysts have demonstrated high ORR activity and low peroxide yields, Fenton (Fe2+/H2O2) and Fenton-like (Fe3+/H2O2) reactions generating hydroxyl radicals are a great concern for the durability of polymer electrolyte fuel cells due to membrane degradation. In an effort to mitigate these risks, development of iron-free non-PGM catalysts with similar ORR activity to the Fe-N-C system but enhanced durability, alternative transition metal precursors are being pursued. In this presentation, we will present further development of the dual nitrogen precursor synthesis approach replacing Fe with precursors of alternative transition metals: Co, Mn, and Ni. A systematic approach to compare structural and electrochemical characterization of all Me-N-C systems (Me = Fe, Co, Mn, Ni) will be developed for better understanding and further optimization of alternative-metal non-PGM ORR catalysts.

Furthermore, atomic-scale structures of simplified Me-Nx active site(s), obtained from density functional theory (DFT), aiding in the synthesis of non-PGM catalysts with high concentration of active site (those with simultaneously high ORR activity and practical stability), will be presented. Relative formation energies serving as descriptors of active-site structure stability will be calculated via DFT with uniform atomic reference states. Previously, O-binding had been utilized as an activity descriptor for ORR catalysts [2], but for non-PGM catalysts, OH-binding is often the potential determining step in the ORR reaction pathway. Thus, this study will present the ORR activity of simplified Me-Nx structures on zig-zag edge of graphene nanoribbons, providing a comparison of both *OH-coordinated and uncoordinated structures and predicting the ORR activity trends from such alternative metal sites to those of iron.

Acknowledgement

Financial support for this research by DOE-EERE through Fuel Cell Technologies Office is gratefully acknowledged.

[1] Chung, H.T., Holby, E.F., Purdy, G.M., Babu, S.K., Litster, S., Cullen, D.A. More, K.L., Zelenay, P. (2015). “Combining Nitrogen Precursors in Synthesis of Non-Precious Metal ORR Catalysts with Improved Fuel Cell Performance.” ECS Meeting Abstracts, MA2015-02 (37), 1278.

[2] Norskov, J.K., Rossmeisl, J., Logadottir, A., Lindqvist, L., Kitchin, J.R., Bligaard, T, Jónsson, H. (2004). “Origin of the Overpotential for Oxygen Reduction at a Fuel-Cell Cathode.” The Journal of Physical Chemistry B, 108 (46), 17886-17892.
Electrochemical Conversion of Cis,Trans-muconic Acid to Trans,Trans-muconic Acid and Trans-3-Hexenedioic Acid for Bio-Based Polymer Production
Authors: Matthiesen John Edward , Carraher Jack M , Vasiliu Monica , Dixon David A , Tessonnier Jean-Philippe
Published: February 2020

The production of biorenewable chemicals has significantly evolved over the past years and numerous processes either have reached commercial stage or are close to commercialization.1 Recently, the biological synthesis of diacids has been receiving greater attention for the manufacture of green polyesters and polyamides.2 Muconic acid, an unsaturated C6 diacid, is quickly evolving as a high interest intermediate for the production of a wide variety of renewable chemicals from biomass (Fig. 1). The increased interest is due to the increasing market size of adipic acid and the need for greener synthesis.

Electrocatalytic hydrogenation (ECH) represents a promising approach to combine the fermentative synthesis of muconic acid with its chemical catalytic diversification to produce these value-added chemicals. ECH typically proceed by applying a -0.3 to -1.8 V potential vs. Ag/AgCl on a transition metal electrode. In contrast to high pressure hydrogenations using noble metals, the electrocatalytic hydrogenation of muconic acid is facilitated through the reduction of protons on the surface of base metal catalysts, yielding interesting selectivities and conversion rates. We demonstrate that the use of Earth-abundant catalysts such as Pb also mitigate the necessity to separate amino acids from the fermentation broth that have been shown to readily poison archetypical hydrogenation catalysts such as Ni, Pd, and Pt3.

Herein we screen a wide variety of early, late, and post transition metal catalysts in an attempt to identify key parameters that govern ECH selectivity and faradaic efficiency. In particular, we differentiate the selected transition metals based on the free energy of hydrogen absorption ΔGH on ECH performance (Fig. 2). Our studies detail the synthesis of trans,trans-muconic acid and trans-3-hexenedoic acid, two bio-based intermediates for the production of polyamides and polyesters, using low hydrogen overpotential metal catalysts. In contrast, high hydrogen overpotential metals produced trans-3-hexenedioic acid with high yield and faradaic efficiency. Conversion and selectivities after 1 h reaction durations for two particular electrocatalysts are displayed in table 1. In all cases, the need to identify binding strengths of the organic reactant will necessitate further correlations that determine hydrogenation product selectivity.

 

References

 

1. Choi, S.; Song, C. W.; Shin, J. H.; Lee, S. Y. Metab. Eng.
2015,28, 223-239.

2. Becker, J.; Lange, A.; Fabarius, J.; Wittmann, C. Curr. Opin. Biotechnol.
2015,36, 168-175.

3. Schwartz, T.; Brentzel, Z.; Dumesic, J. Catal Lett
2015,145, 15-22.

4. Greeley, J.; Jaramillo, T. F.; Bonde, J.; Chorkendorff, I.; Norskov, J. K. Nat. Mater.
2006,5, 909-913.

5. Trasatti, S. J. Electroanal. Chem. Interfacial Electrochem.
1972, 39, 163-184.

Figure 1
Mushroom-Derived Flow Battery Electrolytes
Authors: Cappillino Patrick J , Huang Haobo , Wheeler Joseph , Howland Rachael
Published: February 2020

There is a strong and growing need for reliable, cost-effective grid storage to support a transition from fossil fuels. Non-aqueous redox-flow batteries (NRFB) are a promising technology to meet this need but they are currently limited by poor stability of solution-phase, charge-carrying metal complexes. A major mechanism of decomposition of these redox electrolytes is substitution of ligands that have weak interactions with substitution-labile metal ions. Presented herein is an approach to mitigate these thermodynamic and kinetic challenges with a naturally occurring compound that is produced biologically. Mushrooms of the genus Amanita synthesize a molecule known as Amavadin, in which a vanadium ion is tightly coordinated by a pair of 2,2’-(hydroxyimino)dipropionic acid (HIDPA) ligands. Millions of generations of evolution have optimized the stability of this molecule. As a result, under physiological conditions in which most vanadium compounds would decompose, ligand substitution is suppressed.

The electrochemical properties of redox molecules based on Amavadin as NRFB electrolytes will be presented. This will include data on electrochemical reversibility and stability to deep redox-cycling under various conditions. In addition, we will present the results of computational investigations that have guided ligand-design efforts. These are focused on optimization of the properties of Amavadin-based compounds for application in energy storage devices without losing their extraordinary ability to bind metal ions.
(Invited) Α-Mn2O3 Electrodes for the Oxygen Evolution Reaction - Catalytic Activity As a Function of Electrode Preparation
Authors: Fiechter Sebastian , Kölbach Moritz , Kratzig Andreas , Hillebrand Philipp , Ramirez-Caro Alejandra , Ellmer Klaus , Bogdanoff Peter
Published: February 2020

In photosynthesis nature uses transition metal complexes as catalysts to evolve oxygen and hydrogen from water. In this process the catalytic centers are separated from the light capturing and absorbing co-factors in photosystem I and II integrated in the thylakoid membrane. To develop bio-inspired catalysts and to mimic e.g. the Mn3CaO3MnO complex in PSII, different manganese oxides as well as alkaline metal and earth alkali metal manganates were investigated with respect to the oxygen evolution reaction (OER) in the process of water oxidation. In this contribution special attention will be turned to the structure - morphology– function relationship of these materials.

Manganese oxide electrodes have been prepared by reactive magnetron sputtering from a Mn target in an Ar/O2 atmosphere as well as by anodic electrodeposition and a subsequent annealing step. Besides amorphous MnOx obtained at low temperatures, crystallized oxides, such as γ-MnO2 and α-Mn2O3, were tested as electrocatalysts. Thin (60-70 nm) and dense layers were deposited by reactive magnetron sputtering using conductive glass (FTO) slides as substrates. Cross section transmission electron micrograph (Figure 1a) clearly revealed that the sputtered α-Mn2O3 layers consist of nanocrystals of

10 - 20 nm edge length. These layers show current densities of 10 mA/cm-2 at an overpotential of 370 mV (pH 13.8). Similar overvoltages were also obtained with electrodeposited α-Mn2O3 layers (10mA/cm-2 at 340 mV overvoltage). In contrast, the electrochemically deposited α-Mn2O3 layers are several 100 nm thick and appear highly porous (Figure 1b). Obviously, the specific activity related to the active surface area of the sputtered material is about one order of magnitude higher than the one of the electrodeposited samples. Nevertheless, higher current densities can be achieved with the electrodeposited material because high electrochemically active surface areas can be provided.

This behavior will be discussed as a function of defect chemistry and will be compared with the structure – function relationship of other OER electrocatalysts.

References

[1] A. Ramírez, P. Hillebrand, D. Stellmach, M. May, P. Bogdanoff, S. Fiechter; J. Phys Chem. C, 118 (2014) 14073-14081 and SI.

[2] M.M. Najafpour, T. Ehrenberg, M. Wiechen, P. Kurz; Angew. Chem. Int. Ed., 49 (2010) 2233-2237.

Figure 1: α-Mn2O3 deposited a) by reactive magnetron sputtering and b) by electrochemical deposition.

Figure 1
Experimental Analysis of Thermal Runaway in 18650 Cylindrical Li-Ion Cells Using an Accelerating Rate Calorimeter
Authors: Lei Boxia , Ziebert Carlos , Zhao Wenjiao , Melcher Andreas Markus , Rohde Magnus , Seifert Hans Jürgen
Published: February 2020

In this work commercial 18650 lithium ion cells with LiCoO2 and LiMn2O4 cathodes were exposed to external heating in an Accelerating Rate Calorimeter (es-ARC, THT Company) in order to investigate the thermal behavior under abuse conditions.

During the experiments the temperature and the internal pressure changes of the cells were measured in the ARC.  Furthermore, external pressure changes were measured in order to detect venting of the cells. Before the measurement the cells were fully charged and the so-called Heat-Wait-Seek method was applied. This procedure starts by heating the sample in small incremental steps. At the end of each step the calorimeter “waits” if the battery is generating heat that can be measured by a temperature rise (so called "seek" step). When self-heating of the cell is detected, the ARC switches to the adiabatic mode in which the temperature of the calorimeter follows instantaneously the surface temperature of the cell, i.e. the cell cannot exchange heat with the surroundings anymore. This procedure is repeated until a thermal runaway occurs. For the external pressure measurements, the cell was placed in a gas-tight cylindrical compartment inside the calorimeter chamber. This compartment was equipped with an outlet where a pressure line is connected with a pressure sensor. In contrast to the external pressure measurement for internal pressure measurements this pressure line was directly inserted into the cell. Therefore, a suitable place had to be found by using images from X-Ray Tomography.  In a second experiment a current profile was applied to the cell with maximal C-rate and cycled until a thermal runaway occurs. During these experiments again the internal and external pressure was measured as well as the cell temperature. In addition the heat capacity was measured to calculate the heat of reaction.

From the results of the thermal runaway experiments, three stages (low rate reactions stage, medium rate reactions stage and high rate reactions stage) have been observed. Both pressure and temperature change indicated different stages of exothermic reactions, which would produce gases or/and heat. The onset temperature of thermal runaway was estimated according to temperature and pressure changes in the measurements. Moreover, the different activation energies for the exothermic reactions could be derived from Arrhenius plots.

Finally, the experimental data were compared with the results of numerical simulations based on an electrochemical-thermal model which was extended with additional source terms in order to describe the exothermic reactions inside the cell during thermal runaway. The experimentally determined activation energies have been used as input parameters for these simulations. It could be shown that the above mentioned reactions stages can also be found in the simulations.
The Roles and Characterizations of Activated Carbon in Printed Air Cathode for Flexible Zinc-Air Battery
Authors: Kheawhom Soorathep , Suren Sira
Published: February 2020

Flexible zinc-air batteries were fabricated using an inexpensive screen-printing technique. The anode and cathode current collectors were printed using commercial nanosilver conductive ink on a polyethylene terephthalate (PET) substrate and a polypropylene (PP) membrane, respectively. Air cathodes made of blended activated carbon with MnO2, were fabricated. Further, the effects of the structure of the air cathode layers and their electrochemical characterizations were studied. We also studied the effects of type and concentration of the activated carbon on the performances of the battery. Increasing porosity of the air cathode layers resulted in achieving more power from the batteries.  Finally, the batteries were tested for their flexibility by bending them so that their length decreased from 100% to 50%. The results showed that the bending did not affect characteristics on voltage and discharging time of the batteries.
Electrochemical Studies of Halogens at Carbon Graphite Electrode in Aqueous Solutions
Authors: Quintero Pulido Diego Fernando , Ten Kortenaar Marnix Victor , Hurink Johann , Smit Gerard
Published: February 2020

Abstract

The electrochemical behaviour of halogens redox couples is studied on carbon graphite electrode by voltammetry under different conditions (pH, Concentration, Cation and Temperature). It is found that there is a large difference in current density behaviour between the different halogen electrolytes at a concentration of 2M (I- 400mA/cm2 and Br- 250mA/cm2 oxidation peak at 1.5V) as shown in Figure 1. Besides this, it is found that changing the cation salt  (e.g. NaBr and ZnBr2) affected the current density to a great extent, the effect is observed more clear when the concentration of the electrolytes are changed from 3M to 8M. This effect may be related to pH changes caused by the identity of the cation (Na and Zn). In general, the pH is found to affect oxidation of halogens substantially at pH lower than 5. In line with these results, the diffusion coefficient increases when acid is added to the electrolytes. As expected, the current density increased when temperature is raised and the activation energy have a value of 45kj/mol for the Br- oxidation at carbon graphite. Finally, It is found with UV-Vis experiments that halogen oxidation at carbon graphite shifts to a lower peak wavelength when cation is change and differs from pure halogen spectra. 

Key words: Halogens, Voltammetry, graphite

Figure 1
Experimental and Theoretical Investigation on the Structures and Relative Reactivity of Pr@C74 and Pr@C74(C6H3Cl2)
Authors: Zhao Yanli , Yu Haitao , Lian Yongfu
Published: February 2020

Pr@C74(C6H3Cl2), a novel dichlorophenyl-functionalized derivative of the Pr-containing monometallofullerene Pr@C74, was successfully prepared and isolated. Its molecular structure was determined as Pr@D
3h
(14246)-C74(C6H3Cl2) by a combined mass spectrometry (MS), UV-visible-near-infrared (UV-vis-NIR) absorption spectroscopy, and quantum-mechanics characterization. Using the computed theoretical data, we evaluated the isomeric structures, metal-to-cage electron transfer, and metal-cage interactions of Pr@C74(C6H3Cl2) and the pristine Pr@C74. Furthermore, the relative reactivity of C74, Pr@C74, and Pr@C74(C6H3Cl2) was estimated by the calculated electronic structures and bandgaps, and the results indicated that the open-shell structure and relatively small bandgap should be responsible for the unsuccessful isolation of C74 and Pr@C74.
Electrochemical Refrigeration and Energy Harvesting with the Vanadium-Bromide Couples
Authors: McKay Ian Salmon , Schwalbe Jay , Cargnello Matteo , Majumdar Arun
Published: February 2020

Thermogalvanic cells exploit the entropy changes inherent in redox reactions to couple a flow of ions to a flow of heat. While these systems have been studied in the past in the context of thermal energy harvesting, few chemistries have been identified with the requisite low activation energies, high entropy changes, and high overall reversibility for effectively coupling thermal and electrical energy flows. However, recent developments in the redox flow battery community have opened up many avenues for improvement in thermogalvanics, especially in the nearly-unstudied but complementary field of electrochemical refrigeration, which offers a potentially environmentally and climate-friendly means of climate control.

In this presentation, we develop the thermogalvanic concept from basic principles, derive the fundamental relationship between cold-side activation energy and overall entropy change required to yield a cooling effect, provide an accounting of the dominant loss mechanisms encountered in these systems, and review a number of proposed chemistries and system configurations, including charge-cycling, static electrolyte, and flow systems with and without membrane separators. We present a matrix of candidate redox couples and describe the criteria for their utilization in thermogalvanic systems, as well as favorable operating regimes for each in terms of temperature, partial pressure of gaseous reactants, electrolyte composition, and catalyst and support materials.

Finally, we present a novel 4-electrode vanadium-bromide flow cell for electrochemical refrigeration. The 4-electrode cell is projected to produce a cooling power up to 20mW/cm^2 of device area with a cooling COP of 0.9, based on a model accounting for activation losses (based on Butler-Volmer kinetics and measured exchange current and transfer coefficient values), concentration polarization, and thermal losses. This model is described in full, and power curves are derived for varying temperature, pressure, pump power, and electrolyte concentration and composition. Additionally, we present the results from preliminary electrochemical and thermal testing in a 2-electrode static-electrolyte cell. The preliminary test cell consists of two identical carbon paper electrodes separated with a 50um polyethylene mesh, and built into a carbon-aerogel insulated glass calorimeter, with a total interior volume barely exceeding that of the porous electrodes and separator so as to minimize the heat capacity of the cell. The cell also includes a porous frit connection to a reference electrode. This system is characterized via potentiostatic and galvanostatic techniques, and its transport characteristics are established via impedance spectroscopy. Finally, measured cooling power is compared to a model of the 2-electrode cell, and used to validate the model of the full 4-electrode flow-cell electrochemical refrigerator.
Multivalent Zinc Ion, Nickel Ion and Magananese Ion Batteries: Recent Progress and Battery Products
Authors: Xu Chengjun
Published: February 2020

Due to the energy crisis and environmental deterioration, our society seeks the safety, environmentally friendly, and low cost batteries to meet the demand of the “next generation” electric or electrical devices. The state-of-the-art batteries generally utilize univalent ions (i.e. H+ Na+ or Li+) as media for energy storage. More recently, we have firstly proposed a storage mechanism of multivalent ion (Ni2+, Zn2+, Mg2+, Ca2+, Ba2+, or La3+ ions) as a new strategy for energy storage, in which multivalent ions rather than conventional univalent ions are used as medium for energy storage. This is a new strategy providing possibility for invention of new safety and ecofriendly energy devices based on various multivalent ions instead of conventional univalent ions.

Since I invented three kinds of rechargeable multivalent ion batteries, named as zinc ion, nickel ion and manganese ion batteries, the researchers around the world have paid much attentions on the multivalent ion batteries. At first, I will summarize the recent progress on these multivalent ion batteries. And the ion storage mechanism of multivalent ions (Ni2+, Zn2+, Mg2+, Ca2+, Ba2+, Sr2+ or La3+ ions) and univalent ions (Li+, Na+ or K+) in specific nanostructure materials will be discussed in detail[1,2].

Subsequently, we firstly introduce the battery produts of multivalent zinc ion batteries. The cylinder and prismatic zinc ion battery products show promising performance. They are totally eco-friendly, low cost and safety. These multivalent ion products exhibit a high energy density up to 110 Wh/Kg, cycle life up to over 500 times at 1C/1C, and fast charge/discharge ability up to 20C/20C over 2000 times. This is the first step to commercialize the multivalent zinc ion, nickel ion and manganese ion batteries. With the future improvement both on the charge storage mechanism and technology, I believe that the multivalent ion batteries are the altinatives to the unsafety lithium batteries.

Reference

[1] Xu, C., et al, Secondary batteries with multivalent ions for energy storage, Scientific reports, 2015, 1283: 14120;

[2] Xu, C., et al, Energetic zinc ion chemistry: the rechargeable zinc ion battery. Angew. Chem. Int. Ed., 2012,
51, 933

Acknowledgements: We thank the financial surppots from NSFC, 973, and Shenzhen Technical Plan Projects.
Cycle and Calendar Aging Study of Lithium-Ion Batteries in the Context of Grid-Scale Energy Storage Systems
Authors: Devie Arnaud , Dubarry Matthieu
Published: February 2020

The Hawai‘i Natural Energy Institute (HNEI) is leading a team engaged in the research, development, deployment, and analysis of grid-scale battery energy storage systems (BESS) that are designed for system control and power quality support at the generation, transmission, and distribution levels. The program aims to identify high value BESS applications at various system levels, develop control algorithms that maximize the benefit to the grid/customer and the lifetime of the BESS, and evaluate and optimize those algorithms under real world operating conditions.

The focus is to deploy, operate, and validate the performance of four grid-scale BESS for various ancillary service applications on grid systems across the state. Large scale battery energy storage systems will become an important part of the electric grid in the near future and it will be essential to ensure their reliability. The objective of this project is to understand the degradation of the individual batteries to anticipate failures. Laboratory testing of advanced Li-ion battery cells is performed to support life-time analysis of technologies targeted for large-scale grid energy storage applications.

HNEI’s battery testing efforts have focused on grid scale deployment lithium ion titanate battery technology which is successfully being used for a variety of purposes including frequency and power regulation of large scale wind and solar energy generation. There is currently a lack of understanding of long term performance of battery technology in general, and specifically lithium ion titanate, used under large scale, grid conditions.  This work aims to fill that gap in knowledge through laboratory scale battery testing and the development predictive lifetime models of performance of grid battery technology.

Accelerated testing of identical lithium ion titanate battery technology was performed in the laboratory and those results will be used to develop predictive performance models. This model will combine existing modules [1-4] that account for single cell asymmetric degradation, single cell heat generation, string imbalance, and cell paralleling. As real world data is collected from the grid batteries, the predictive models will be compared and assessed for accuracy and ability to predict performance. This work will present preliminary results of the cycle and calendar aging long-term studies.

[1] M. Dubarry, N. Vuillaume and B. Y. Liaw, J. Power Sources 186(2), (2009) 500-507.

[2] M. Dubarry, C. Truchot and B.Y. Liaw, J. Power Sources 219 (2012) 204-216.

[3] https://www.soest.hawaii.edu/HNEI/alawa/

[4] M. Dubarry, C. Truchot, A. Devie and B. Y. Liaw, J. Electrochem. Soc 162(6), (2015) A877-A884.
Opto-Electrochemical Spectroscopy
Authors: Habib Khaled
Published: February 2020

Opto-electrochemistry is the state of the art and technology of not only imaging surfaces of a condensed matter, i.e., solid metal, submerged in aqueous solutions, but also, the science of measuring electrochemical properties of the condensed matter by solely light.   In the present investigation, holographic interferometry was utilized for the first time to determine the rate change of the electrical resistance of aluminium samples during the initial stage of anodisation processes in aqueous solution. In fact, because the resistance values in this investigation were obtained by holographic interferometry, electromagnetic method rather than electronic method, the abrupt rate change of the resistance was called electrical resistance–emission spectroscopy. The anodisation process of the aluminium samples was carried out by electrochemical impedance spectroscopy (EIS) in different sulphuric acid concentrations (1.0–2.5% H2SO4) at room temperature.   In the   meantime, the real time holographic interferometry was used to determine the difference between the electrical resistance of two subsequent values, dR, as a function of the elapsed time of the EIS experiment for the aluminium samples in 1.0, 1.5, 2.0 and 2.5% H2SO4 solutions. The electrical resistance–emission spectra of the present investigation represent a detailed picture of not only the rate change of the electrical resistance throughout the anodisation processes but also the spectra represent the rate change of the growth of the oxide films on the aluminium samples in different solutions. As a result, a new spectrometer was developed based on the combination of the holographic interferometry and electrochemical impedance spectroscopy for studying in situ the electrochemical behavior of metals in aqueous solutions.

Keywords: Holographic interferometry; Electrical resistance; Anodisation process; Electrochemical impedance spectroscopy (EIS); Sulphuric acid; Aluminium.
Crevice Corrosion of Nickel Alloy 625 in an Ocean Water Environment: New Insight into the Crevice Environment
Authors: Salgado Diana M. , Lillard Scott
Published: February 2020

Nickel alloy 625 is widely used in marine applications due to its excellent corrosion resistance when exposed to highly oxidizing and reducing environments. However, nickel alloy 625 has been found to be susceptible to localized corrosion when crevices with a large aspect ratio (depth/gap) are exposed to seawater. In this study, two different electrochemical techniques were used to evaluate the mechanisms of crevice corrosion in nickel alloy 625: potentiostatic polarization of remote crevice assemblies (RCAs) exposed to ASTM artificial ocean water and potentiodynamic polarization curves in simulated critical crevice solutions (CCSs).

From the electrochemical response of the RCAs, i.e. current vs. time curves, it was found that crevice corrosion damage under potentiostatic conditions occurred in three stages: Stage (I) CCS development, stage (II) crevice corrosion under IR control, and stage (III) crevice corrosion under diffusion control. It was also found that the CCS formed near the crevice tip and moved toward the crevice mouth. Once the CCS reached a critical distance from the mouth, presumably IR*, the corrosion rate drastically increased and severe damage occurred.

During the RCA experiments, light green deposits around the outside edge of the RCA were found. When the crevices were opened after the test, additional corrosion products were found. For short exposure times, dark green and brown corrosion products were found spread out over the etching damage while at longer exposure times, accumulation of dark brown corrosion products were found closer to the crevice mouth. Energy Dispersive Spectroscopy (EDS) analysis showed that the crevice corrosion products formed inside the crevice were rich in Mo, Nb, and O, suggesting the possible formation of Mo and Nb oxides. The crevice corrosion products outside of the crevice were rich in Ni, Cr, Fe, Mo and O.

The behavior of 625 in the CCS was characterized using potentiodynamic polarization in concentrated metal salt solutions prepared by dissolving NiCl2∙6H2O, CrCl3∙6H2O, FeCl2∙4H2O, MoCl3, and NbCl5 salts in deionized water at concentrations ranging from 3 to 5 molal. It was found that Mo and Nb content increased the current density of the active peak. The properties of these simulated CCSs were determined using thermodynamic calculations via the OLI Stream Analyzer software. Specifically, OLI software was used to predict the precipitation products and solution pH at 25°C. The predictions were used to compare the polarization data generated with the traditional simulated CSS using HCl base solutions.
Steel Surface Conversion By Flavonoid Model Molecules
Authors: Veys-Renaux Delphine , Rocca Emmanuel , Reguer Solenn , Mirambet Francois
Published: February 2020

In the framework of new ecological challenges, many plant extracts appear as promising green corrosion inhibitors. Their efficiency is generally attributed to the antioxidant properties of secondary metabolites, as flavonoid molecules, which are produced by plants in order to fight against environment attacks. However, due to the large number of molecules contained in plant extracts, the corrosion inhibition mechanisms remain largely unknown. This paper focuses on the inhibiting effect on steel corrosion of different model flavonoid molecules with various structures.

In acidic medium, polarization measurements and electrochemical impedance spectroscopy (EIS) measurements, performed in HCl 0.1 M in a water/ethanol medium, show slight inhibition efficiency (both anodic and cathodic) of pure flavonoid molecules, through an adsorption mechanism, directly linked to their structure. Actually, the best performances are obtained with molecules characterized by two adjacent OH groups on the B-ring (catechol group), which explains the chelation of Fe2+. Regarding the anticorrosion efficiency of a diluted natural extract (from orange peel as example in this work), it is enhanced compared to isolated flavonoid molecules (naringin, neohesperidin) thanks to the formation of a thick surface film with organic macromolecules, limiting the diffusion of oxidant species, as revealed by both SEM observations and EIS data.

In more alkaline medium, at pH 4, the corrosion behavior is governed by the formation of a tri-dimensional conversion film made of iron and flavonoid, as revealed by SEM observations. For a deeper understanding, the corresponding organo-metallic compounds were synthesized from precipitation at pH 4 of iron salt in presence of flavonoid molecules (rutin) and investigated by Raman spectroscopy and X-ray Absorption Spectroscopy measurements (XAS). Results show that the formation of conversion products requires the octahedral coordination of Fe3+ by the O atoms of the catechol group attached to the B-ring. From an electrochemical point of view, a cathodic inhibition attributed to the oxygen scavenger role of the antioxidant molecules was observed. Nevertheless, the anodic protection depends on the covering properties of the conversion film (when it is formed), related to the molecule structure.

Figure 1
(Invited) Real Time Analysis of the Crystallization Dynamics of Organilead Halide Perovskite
Authors: Miyadera Tetsuhiko
Published: February 2020

Organolead-halide perovskite solar cells have been attracting much attention because of the rapid improvement of its power conversion efficiency. Simple fabrication process can be advantageous for the cost reduction, where just mixing lead halide and amine halide results in the perovskite crystal. Although there have been published numbers of method for the fabrication of perovskite solar cells, reproducibility of the device characteristics is great issue. The fundamentals of crystallization process is important to improve the device performance as well as reproducibility, however, such studies are still underway. We have been conducted in-situ analysis of the crystallization process of organolead-halide perovskite by means of grazing incident wide angle X-ray scattering (GIWAXS) [1]. The measurement was performed at BL46XU in SPring-8 and 2 dimensional X-ray detector (PILATUS 300K) was used, which enables the real time GIWAXS measurement.

 Perovskite film was synthesized on the measurement stage of the beamline to observe the crystallization dynamics. A PbI2 thin film was placed and CH3NH3I solution was dropped onto the PbI2. The reduction in the amount of PbI2 raw material over time was observed as well as the formation process of the perovskite crystal. Analysis of the rate of progression of this reaction revealed that reaction progression did not follow the normal diffusion phenomenon but instead followed an anomalous diffusion process. This can be originated from the anomalous diffusion of CH3NH3I into the PbI2thin film medium, which shows the heterogeneous structure. Next we focus on the angle dependent X-ray diffraction patterns. In the early stage of the reaction the formed crystals were oriented in two specific directions, but with the progress of time they changed to a random orientation. This finding suggests that the crystals changed continuously during the process of formation of the perovskite crystal. The fluctuating characteristics of the crystallization process of perovskites, such as fractal penetration and orientational transformation, should be controlled to allow the fabrication of high-quality perovskite crystals. The characteristic reaction dynamics observed in this study should assist in establishing reproducible fabrication processes for perovskite solar cells.

[1] T. Miyadera et al., Nano Lett., 2015, 15 (8), pp 5630–5634.

This work is financially supported by the new energy and industrial technology development organization (NEDO) and Japan science and technology agency (JST) through its funding program for Precursory Research for Embryonic Science and Technology (PRESTO).

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(Invited) Environmental Resistance of Resistive Random Access Memory
Authors: Kinoshita Kentaro
Published: February 2020

Environmental resistance of memory devices must be clarified for putting them into practical use. This should be emphasized in particular for resistance random access memory (ReRAM), which switching mechanism is still unclear, because responses to environmental stresses are closely related to the mechanism. As for the influence of radiation exposure, with increasing density of memory devices, the issue of the generation of soft errors by the radiation, ex. cosmic rays, is becoming more and more serious. So far, soft errors are concerned about only in some semiconductor memories such as SRAM and DRAM, in which stored data are easily inverted by weak current that is generated by incident secondary cosmic rays. On the other hand, there is very little report on reliabilities of ReRAM against exposure to radiation, which might be due to a common belief that ReRAM, which resistive switching is believed to be caused by ion migration, is free from this kind of error. However, if resistive switching of ReRAM is caused by change in the charge state of oxygen vacancies (VO) as proposed by Kamiya et al. [1], soft errors of data inversion might be occurred by charge excitation such as due to ultraviolet irradiation (UV) irradiation.

In this paper, we fabricated Pt/NiO/indium tin oxide (ITO) structure, which has transparent ITO electrode, and therefore the irradiation of light to the NiO memory layer became possible. By using this structure, we investigated data retention characteristics against UV irradiation to ReRAM [2]. As a result, soft errors were confirmed to be caused by UV irradiation in both low- and high-resistance states. An analysis of the wavelength dependence of light irradiation on data retention characteristics suggested that electronic excitation from the valence to the conduction band and to the energy level generated due to the introduction of VO caused the errors. Based on a statistically estimated soft error rates, the errors were suggested to be caused by the cohesion and dispersion of VO owing to the generation of electron-hole pairs and valence changes by the ultraviolet irradiation. Therefore, it was suggested that establishing a method to improve resistance to UV irradiation in consideration of the band gap, in-gap states, and the charge state of VO in metal oxides may be a key factor for practical use of ReRAM.

The effect of moisture and atmosphere gas on the reliability of ReRAM will also be discussed.

[1] K. Kamiya et al., APL 100, 073502 (2012). [2] K. Kimura et al., APL 108, 123501 (2016).
ALD Coating of Selective Laser Melted 3-D Printed Stainless Steels
Authors: Zhang Kai , Lin Pengtao , Chen Xin , Baumgart Helmut , Bradas James
Published: February 2020

Selective laser melting (SLM), also known as 3-D printing or additive manufacturing process, has been developed for over 2 decades. This technique exhibits the capability to fabricate three-dimensional metal objects of complex geometries & structures from metal powders used in aerospace or medical orthopedics. This additive manufacturing technology has received a lot of attention, because various metals and metal alloys can now be processed to manufacture metal parts or structures, which includes the technologically important metals of stainless steel, cobalt chrome, titanium, tungsten and various other alloys. Typically SLM selectively melts thin layers of fine metal powder above each other by using a focused laser beam with high thermal energy on a substrate plate under argon atmosphere, resulting in production of almost full density metal or alloy parts. In this fashion successive layers of material are formed according to the computer edited 3-D-CAD design. Thereby, SLM could be applied to make functional end-use and geometrically complex products with cost-effect process especially in industry.

Due to the geometrically complex form of the SLM manufactured structures, atomic layer deposition (ALD) is uniquely suitable to control the composition, thickness and conformability of thin films in the large scale and complex structures. In this study we report ALD coatings of Al2O3 of SLM stainless steel with the objective of providing corrosion protection by an alumina diffusion barrier and ALD ZrO2 coatings. During the course of this work we found the parts fabricated by 3-D printers tend to be porous and exhibit a rough texture. Figures 1 (a) show FE-SEM micrographs at progressively larger magnification of the surface of the 3-D printed stainless steel samples. As can be seen, the surface is very rough and contain many beads or spheres produced during the SLM manufacturing process, which is a direct result of the laser melting of the metal powder and rapid quenching. In order to reduce the surface roughness of the 3-D printed samples, electropolishing was used to smoothen and streamline the rough surface of the 3-D samples. After electropolishing, the surface of the 3-D printed samples is bright, clean and microscopically smooth and featureless. There are no beads or spheres remaining on the samples as shown in Figures 1 (b).

We used SLM 316 stainless steel samples in a cross-flow ALD reactor with TMA and H2O vapor to attempt ALD coatings, while TDMA-Zr and H2O were used as precursors for ALD ZrO2. The analysis of the ALD Al2O3 and ZrO2 films revealed satisfactory chemisorption on the 3-D printed stainless steel surface. The ALD Al2O3 and ZrO2 films were uniformly grown on the 3-D printed stainless steel surface as shown in Figure 2.

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Silicon-Carbon Nanotube Aerogel Core-Shell Nanostructures for Lithium-Ion Batteries with Long-Cycle Life and High Capacity
Authors: Shim Hyung Cheoul , Woo Chang-Su , Hyun Seungmin
Published: February 2020

Silicon anode for lithium ion battery (LiB) has been attracted considerable attention due to providing theoretical capacity up to about 10 times higher than that of conventional graphite. However, huge volume expansion during the cycle cause crack in the silicon, resulting in degradation of cycling performance and eventual failure. Moreover, low electrical conductivity and unstable solid electrolyte interface (SEI) layer aroused from repeated changes in volume still block the next step forward to commercialization of silicon material. Herein we demonstrate Si-carbon nanotube (CNT) aerogel core-shell nanostructure for LiB via freeze casting followed by RF magnetron sputtering process, exhibiting improved capacity retention as compared to Si only samples while 1,000 times of electrochemical cycle. The freeze casted CNT aerogel as 3D porous scaffold structures could provide buffer volume expansion/shrinkage of Si lattice upon cycling and increase electrical conductivity. In addition, the CNT aerogel could maintain the conducting network between pulverized Si materials during cycling. For this reason, after 1,000 charge/discharge cycles with high current densities (4.0 A g-1), Si@CNT aerogel anode yielded a high specific capacity of 1439 mAh g-1 with low capacity fade. Our approach could be applied to other LiB materials that go through large volume changes, and also affords promising potential for high performance energy applications.
Role of Water Molecules on the Electrochemical Properties of α-MnO2 Hydrate: A Combined Computational and Experimental Study
Authors: Duan Huan , Jiang Baozheng , Li Jia , Xu Chengjun , Gan Lin , Du Hongda
Published: February 2020

Hollandite α-MnO2 and its hydrate compounds synthesized by wet-chemical routes play a vital role in many aspects of technological applications, especially in energy storage devices. The features of lattice water are very peculiar but poorly understood. We present a combined computational and experimental study on the behavior of water molecules to elucidate many aspects of this problem, including the location and aggregation characteristics and the related electrochemical properties of lithium storage. It is shown that the oxygen atom of water is always located at the tunnel center (2b site) as that site is farther away from the inwall O atoms. Moreover, total energy profiles establish that monomeric water can form four stable configurations with different orientations of the two hydrogen bonds in the tunnel which stabilizes the crystal structure, and transform reciprocally by a kinetically preferred H-O bond rotation at a relatively low activation energy. Observations at high water content reveal that the aggregation between water molecules can further enhance the structural stabilization, showing a nearly linear lattice shrink, improving the electronic properties and facilitating the lithium diffusion in the adjacent tunnels. Remarkably, the hydrated α-MnO2 exhibits a much better high-rate capability during the charge/discharge process. But the early cycling deterioration of charge capacity results from the lithium anchoring and tunnel blocking caused by lattice water, which provides a consistent interpretation of the measured rate performance with cyclic voltammetry, hydroxyl vibrational spectra, and other experiments. Subsequently, lattice water can bring benefits to the electrochemical performance of α-MnO2 electrode, the magnitude of which is controlled by the H2O content, suggesting an easily achievable method for tuning the physical and chemical properties.