bluuebunny/crossref_metadata_2025 huggingface dataset:
Porphyrins As Excellent Sensitizers for Dye-Sensitized Solar Cells
Authors: Imahori Hiroshi
Published: February 2020

Recently we have developed aromatic ring-fused, unsymmetrically pi-elongated porphyrins (i.e., naphthalene-fused and quinoxaline-fused porphyrins) that showed broadened, and red-shifted light absorption properties compared to the corresponding porphyrin references, resulting in the power conversion efficiencies of 4.1% and 6.3%, respectively. As demonstrated for other sensitizers in DSSCs, introduction of both electron-donating and electron-withdrawing substituents to a core of pi system would be appealing for the modulation of the light-harvesting properties of sensitizers. In this talk I will present our recent advance in porphyrin-sensitized solar cells.1-10 In particular, I will focus on novel push-pull porphyrins for porphyrin-sensitized solar cells.1-10 For instance, we synthesized for the first time a push-pull porphyrin dye bearing two diarylamino groups and two carboxyphenylethynyl groups as electron-donating and electron-withdrawing anchoring groups, respectively. The absorption spectrum displayed broad and red-shifted absorption, achieving panchromic light-harvesting in visible and NIR regions. Introduction of multiple push-pull groups into meso-positions is a promising strategy for the rational design of porphyrin sensitizers for light-harvesting applications. The preliminary photovoltaic performance is moderate (3.0%), but the extensive photocurrent generation matches with the excellent light-harvesting ability. Further modulation of the photovoltaic properties of porphyrin DSSCs will be possible by suitable selection of electron-donating and electron-withdrawing groups as well as introduction of the substituents into the porphyrin core.

[1] H. Imahori, T. Umeyama, and S. Ito, Acc. Chem. Res.
42, 1809 (2009).

[2] H. Imahori, S. Kang,  H. Hayashi, M. Haruta, H. Kurata, S. Isoda, S. E. Canton, Y. Infahsaeng, A. Kathiravan, T. Pascher, P. Chabera, A. P. Yartsev, and V. Sundström, J. Phys. Chem. A, 115, 3679 (2011).

[3] H. Imahori, H. Iijima, H. Hayashi, Y. Toude, T. Umeyama, Y. Matano, and S. Ito, ChemSusChem, 4, 797 (2011).

[4] M. Simon, H. Iijima, Y. Toude, T. Umeyama, Y. Matano, S. Ito, N. V. Tkachenko, H. Lemmetyinen, and H. Imahori, J. Phys. Chem. C, 115, 14415 (2011).

[5] H. Imahori, T. Umeyama, K. Kurotobi, and Y. Takano, Chem. Commun. (Feature Article), 48, 4032 (2012).

[6] H. Hayashi, A. S. Touchy, Y. Kinjo, Y. Toude, K. Kurotobi, T. Umeyama, Y. Matano, and H. Imahori, ChemSusChem, 6, 508 (2013).

[7] S. Ye, A. Kathiravan, H. Hayashi, Y. Tong, Y. Infahsaeng, P. Chabera, T. Pascher, A. P. Yartsev, S. Isoda, H. Imahori, and V. Sundström, J. Phys. Chem. C, 117, 6066 (2013).

[8] K. Kurotobi, K. Kawamoto, Y. Toude, Y. Fujimori, Y. Kinjo, S. Ito, Y. Matano, and H. Imahori, Chem. Lett., 42, 725 (2013).

[9] K. Kurotobi, Y. Toude, K. Kawamoto, Y. Fujimori, S. Ito, P. Chabera, V. Sundström, and H. Imahori, Chem. Eur. J., 19, 17075 (2013).

[10] T. Higashino and H. Imahori, Dalton Trans. (Perspective), in press.
Out of the Blue! Azuliporphyrins and Related Azulene-Containing Porphyrinoids
Authors: Lash Timothy D.
Published: February 2020

Carbaporphyrinoids, porphyrin analogues that have one or more of the usual pyrrolic units replaced by carbocyclic rings, have been widely studied in recent years. These systems exhibit a wide range of properties and varying degrees of macrocyclic aromaticity. Azuliporphyrins have an azulene ring incorporated into the porphyrin framework and exhibit intermediary aromatic character. They were first prepared by reacting tripyrranes with 1,3-azulenedicarbaldehyde under acid-catalyzed conditions, although several alternative routes have been developed for preparing this intriguing carbaporphyrinoid system. Azuliporphyrins are easily protonated and this greatly enhances the diatropic properties for the macrocycle. Azuliporphyrins are also superior organometallic ligands and afford stable derivates with Ni(II), Pd(II), Pt(II), Ir(III) and Rh(III). Furthermore, tetraarylazuliporphyrins have been shown to undergo an oxidative metalation with copper(II) salts to generate a nonaromatic copper(II) complex. Treatment of azuliporphyrins with tert-butyl hydroperoxide under basic conditions triggers a ring contraction reaction to afford benzocarbaporphyrins. This appears to involve initial nucleophilic attack onto the seven-membered ring, followed by a Cope rearrangement and elimination of tert-butyl alcohol. These observations have led to investigations into related macrocyclic systems, including heteroazuliporphyrins with furan, thiophene or selenophene rings. In addition, an azulisapphyrin has also been reported. Dicarbaporphyrinoids with azulene-subunits have also been investigated. Azulene-containing fulvene dialdehydes have been shown to react with dipyrrylmethanes under acidic conditions to give 22-carbaporphyrins, and this system also shows intermediary aromatic character. In addition, a bis-azulenylmethane dialdehyde was shown to react with dipyrrylmethanes to give, following oxidation with DDQ, examples of diazuliporphyrins. This system was only stable in a protonated form but retained a degree of diatropic character. Reaction with palladium(II) acetate gave an unusual zwitterionic palladium(II) organometallic complex. These results demonstrate that azulene-containing porphyrinoids have unique properties and are superior precursors to organometallic derivatives.
Chemistry of Novel Non-Aromatic, Meso-Alkylidenyl Carbaporphyrinoids
Authors: Lee Chang-Hee
Published: February 2020

We developed new class of porphyrinoids and core-modified porphyrinoids that have not been well studied previously. So called, meso-alkylidenyl porphyrins and their congeners are rather recently developed porphyrinoid family that have shown several unique properties including tautomerization, unusual protonation selectivity and spectroscopic properties. We here report the chemistry of meso-diethyl malonylidene-(m-benzi)porphyrin and meso-diethyl malonylidene-(m-benzi)pentaphyrins such the reaction with in-situ generated azomethine ylides and redox reactions. This 1,3-dipolar cycloaddition reaction has well documented and become an important alternative to the synthesis of pi-extended porphyrin analogs. The versatility and synthetic utilities associated with these reactions is useful in the synthesis of pi-extended analogs of the meso-alkylidenyl porphyrinoids. Successive 1,3-dipolar cycloaddition reaction combined with oxidation could be good tool for the pi-extended porphyrin analogs bearing region-selectively fused pyrrole rings. The 1,3-dipolar cycloaddition of the corresponding Pd(II) complexes also resulted in bis-cyclized adducts which are resistant to DDQ oxidation. All adducts are liable to core N-methylation. The adducts exhibit large bathochromic shift of absorption.

References  1.   E.-K. Sim, S.-D. Jeong, D.-W. Yoon, S.-J. Hong, Y. Kang and C.-H. Lee, Org. Lett., 2006, 8, 3355–3358.  2.   S.-D. Jeong, S.-J. Hong, K.-J. Park, S. Ham, J. L. Sessler, V. M. Lynch and C.-H. Lee, J. Org. Chem. 2007, 72, 6232–6240.  3.   S.-D. Jeong, K.-J. Park, H.-J. Kim and C.-H. Lee, Chem. Commun. 2009, 5877–5879.  4.   S.-D Jeong; A. Nowak-Kro; Y. Kim; S.-J. Kim; D. T. Gryko; C.-H. Lee, Chem. Commun. 2010, 46, 8737–8739.  5.   J. Yoo; H.-J. Kim; H.-J. Kim; C.-H. Lee, J. Porphyrins Phthalocyanines, 2011, 15, 676–677.  6.   D. Park, S.-D. Jeong, M. Ishida and C.-H. Lee, Chem. Commun. 2014, 50, 9277-9281.  7.    D. Park, N.-Y. Choi, S.-J. Hong and Chang-Hee Lee, Chem. Commun., 2014, 50, 3689-3691.

Figure 1
Functionalization of the Corrole Ring: A Neverending Game
Authors: Paolesse Roberto , Nardis Sara , Monti Donato , Mandoj Federica , Pomarico Giuseppe , Naitana Mario Luigi , Di Natale Corrado , Stefanelli Manuela
Published: February 2020

Corrole has been one of the first porphyrinoids reported in the literature, but only in the last few years it has been observed an impressive boost in corrole researches, because it has shown some peculiar properties, different from those of the corresponding porphyrins, which are promising for practical applications.

From this point of view, it has been important to study the possible synthetic modifications of the corrole framework, with the aim to tune the properties of the resulting macrocycle to the corresponding application.

Although the impressive progress of the corrole preprative chemistry, the functionalization of this macrocycle  is still a challenging research area.

We have contributed to this area by studying the definition of synthetic protocols for the insertion of different substituents, both into the meso and b-positions of the macrocycle, with the aim of building more complex structures.

In these reaction, corrole has demonstrated a peculiar regioselectivity, with the substituents introduced in the directly linked pyrroles A and D. However we have recently observed that the substitution pattern can be modulated by the different substituents introduced in the peripheral positions.

In the present work we summarise our recent achievements in the functionalization of the corrole ring.
Ion-Pairing Assemblies Comprising Pyrrole-Based π-Electronic Systems
Authors: Maeda Hiromitsu
Published: February 2020

π-Electronic systems responsive to metal ions and anions are very fascinating because they can form a variety of ion complexes as building subunits, providing supramolecular assemblies that exhibit attractive electronic and electrooptical properties.1  In fact, anion complexes of the anion-responsive π-systems have been found to construct ion-pair-based assembled structures as crystals, supramolecular gels, and thermotropic liquid crystals by combination with cationic species.  Derived from favorable overlap of charged π-planes, ion-pair-based materials with the contribution of charge-segregated arrangements provided charge carrier mobilities, which are often larger than corresponding charge-by-charge-based materials, showing superior semi-conductive properties.  Highly ordered arrangement of charged species, not only the ion complexes but also charged π-systems, has been found to be a key factor to exhibit the enhanced performance as fascinating electronic materials.

1. A recent review: Maeda, H. Bull. Chem. Soc. Jpn.
2013, 86, 1359–1399.
Synthesis of Phthalocyanines Using Triorganoindium Reagents
Authors: Fernández-Lázaro Fernando , Font-Sanchis Enrique , Molina Desiré , Sastre-Santos Angela
Published: February 2020

Phthalocyanines (Pcs) have attracted much attention due to their singular electronic properties, exceptional chemical and photochemical stabilities, and strong absorption of visible light [1]. Although there is a great variety of methods for the preparation of substituted phthalocyanines, introducing the substituents either on the phthalonitrile precursor or on the already formed phthalocyanine core, we have decided to explore the palladium-catalysed coupling reaction between haloaromatics and triorganoindium reagents [2]. The latter benefits from high reactivity, efficiency, versatility and chemoselectivity, together with the low toxicity associated with indium derivatives. We have indeed already experimented with this process, first exploring some basics about the scope [3] and new procedures for the synthesis of the triorganoindium reagents [4], and later using it in the preparation of hole transporting materials [5]. In this occasion we will discuss our more recent results in the preparation of substituted phthalocyanines using triorganoindium reagents.

Taking advantage of the previously commented properties of Pcs, the synthesized compounds are excellent candidates for the preparation of photovoltaic devices, either Dye-Sensitized Solar Cells (DSSCs) or Bulk Heterojunction (BHJs) [6,7].

 
Acknowledgements. This work has been supported by the Spanish Ministerio de Economía y Competitividad, Generalitat Valenciana and the European FEDER funds (grants CTQ 2010-20349, CTQ2011-26455, CTQ2013-47922-R, PROMETEO 2012/010 and ISIC/2012/008).

 References

Phthalocyanines: Properties and Applications, Leznoff, C. C.; Lever, A, B. P. Eds.; VCH Publishers, Weinheim, 1990-1996, Vols. 1-4.

Pérez, I.; Pérez-Sestelo, J.; Sarandeses, L. A. Org. Lett.
1999, 1, 1267-1269.

Font-Sanchis, E.; Céspedes-Guirao, F. J.; Sastre-Santos, A.; Fernández-Lázaro, F. J. Org. Chem.
2007, 72, 3589-3591.

Font-Sanchis, E.; Sastre-Santos, A.; Fernández-Lázaro, F. Dalton Trans.
2009, 2470-2473.

 Lana-Villareal, T.; Font-Sanchis, E.; Sastre-Santos, A.; Fernández-Lázaro, F.; Gómez, R. ChemPhysChem
2011, 12, 1155-1164.

Martín-Gomis, L.; Fernández-Lázaro, F.; Sastre-Santos, A. J. Mater. Chem. A
2014, 2, 15672-15682.

Molina, D.; Guerrero, A.; García-Belmonte, G.; Fernández-Lázaro, F.; Sastre-Santos, A. Eur.
J. Org. Chem.
2014, 4585-4591.

Figure 1
Design, Synthesis, and Electronic Properties of Near-Infrared Absorbing Phthalocyanine Analogues
Authors: Muranaka Atsuya , Uchiyama Masanobu
Published: February 2020

In recent years, much effort has been made to develop various types of near-infrared organic compounds because of their potential applications in organic solar cells, photodynamic therapy for cancer, and fluorescence bioimaging. Although a common strategy to achieve bathochromic shifts of the absorption maximum of a dye is the extension of the π-electron system, chemical stability of the π-extended system usually decreases with increasing extension. Phthalocyanine derivatives are an important group of visible-light-absorbing compounds, because they are more stable to heat and light than other types of organic dyes. In order to develop stable near-infrared dyes, we designed and created new types of phthalocyanine analogues, azulenocyanines (1), aromatic hemiporphyrazines (2), benziphthalocyanines (3), and expanded phthalocyanines (4). Design strategy, synthesis, and unique properties of these compounds are reported.

Figure 1
Bioinspired CO2 Reduction with Iron Porphyrin Catalysts in High Efficiency
Authors: Naruta Yoshinori
Published: February 2020

Conversion of CO2 to useful carbon resources as well as water splitting is the important ways to store renewable energy as chemical energy.  Both reactions are typical multi-electron ones, thus, they tend to require large overpotentials (or activation energies) unless one uses proper catalysts.  Particulary, CO2 reduction potentially gives several reduced products, CO, HCO2H, (CO2H)2, CH3OH, etc.  CO2 reduction also competes proton reduction.  Thus, the product selectivity is another important factor on its reaction.  Following issues are keys on the development of CO2 reduction catalysts: (1) low overpotential, (2) high turnover frequency, (3) robustness, (4) product selectivity, (5) easy separation of product(s), and (6) use of base metal (complexes) on the elemental strategy aspect.  Carbon monoxide dehydrogenase (CODH), an enzyme in bacteria, catalyzes the mutual conversions between CO2 and CO.  The active site of the enzyme is consisted of Ni-Fe cluster and this enzyme realizes selective CO2 reduction to CO at very low overpotential (η < 100 mV).  We develop new catalysts to fulfill the above criteria referring the enzyme structure.  We developed iron porphyrin dimers as bio-inspired catalysts, which realized electrochemical CO2 reduction at the lowest overpotentials and high TOF in high selectivity and robustness by choosing suitable functional groups.  In a homogeneous solution, continuous electrocatalytic reduction of CO2 for 12 h gave a good Faradaic efficiency as well as a good product selectivity by keeping a constant current through the electrolysis and any decrease of the catalyst activity is not observed.  We will discuss the importance of the dinuclear center in the CO2 reduction.
Solid-State Electrochemistry of Organic Macrocycles and Mofs; Application to Organic Electronics and Energy Storage
Authors: Awaga Kunio
Published: February 2020

Solid-state electrochemistry is a powerful tool to control the electronic properties of organic materials through charge/carrier injections. In contrast to the numerous studies on organic polymers, its application to small molecules has been limited, because most of them become soluble into solvents after redox reactions. In this perspective, the organic macrocycles and MOFs are promising materials due to their structural robustness. We will discuss the following three topics

1. Electric-double-layer field-effect transistors of organic macrocycles. Electric-double-layers (EDLs), formed at solid-electrolyte interfaces, induce extremely large electric fields. This results in a high charge carrier accumulation in the solid, much more effectively than solid dielectric materials. We investigated the EDL thin-film transisotrs of porphyrazines and octathio[8]circulene (sulflower) with gate dielectrics of ionic liquids, which have attracted much attention due to their wide electrochemical windows, low vapor pressures, etc. We revealed the factors, controlling the mobility and threshold voltage in these types of FETs.

2. Electrochemical doping to nano-porous single crystals of Li-phthalocyanine (LiPc). The crystal structure of a neutral π radical, LiPc in the x from, consists of 1D stacking chains of LiPc and nano-channels parallel to them. We found that the LiPc crystals were electrochemically oxidized in an acetonitrile solution of tetrabutyl ammonium chloride (TBA·Cl), exhibiting a crystal-to-crystal transformation to LiPc·Cl
x
(0<x<0.5). The crystal structures of the LiPc·Cl
x
series were successfully solved and refined by the X-ray single-crystal analysis, and the obtained structures clearly indicated the presence of the Cl−ions in the 1D channels and a systematic structural change in the π stacking chain of LiPc.

3. Synthesis and solid-state electrochemistry of a redox-active MOF, Cu(2,7-AQDC), toward high-capacity lithium battery. We synthesized a microporous redox-active MOF, Cu(2,7-AQDC) (2,7-H2AQDC=2,7-anthraquinonedicarboxylic acid), and utilized it as a cathode active material in lithium batteries. With a voltage window of 4.0-1.7 V, both metal clusters and anthraquinone groups in the ligands were found to exhibit reversible redox activity. By controlling the voltage window of operation, extremely high recyclability of batteries was achieved.
Copper Nanoparticles Effect on the Corrosion Behavior of Different Types of Nickel-Based Super Alloys
Authors: Abdullah Aboubakr Moustafa , Mohamed Adel M. A. , Sliem Mostafa H
Published: February 2020

Nickel-based alloys are usually used for a wide range of applications like petrochemical processing, oil and gas extraction, marine engineering and high temperature applications in power generation industry e.g., heat exchangers or turbine blades due to their excellent corrosion resistance and good mechanical properties. Nickel-based alloys are designed to resist high loading and severe corrosive environments during operations. 

The aim of this study is to investigate the effect of  depositing copper nanoparticles of different sizes on top of the surface of different nickel-based alloys (e.g.alloys 825, 625 and 276) on their corrosion behavior in different electrolytes of different pH values and chloride and sulfide ions concentrations. The study included, electrochemical and non-electrochemical characterization techniques. Also, the surfaces of the corroded alloys were checked using optical and scanning electron microscopy, energy dispersive x-ray and atomic force microscopy.
Inhibition Effect of Some Benzotriazole Derivatives on Carbon Steel in 1M H2so4 Medium
Authors: Branzoi Florina , Pacuretu Catalina , Branzoi Roxana
Published: February 2020

The inhibition effect of some benzotriazole derivatives (1-hydroxybenzotriazole, 5-chlorobenzotriazole and 3-amino-5-mercapto-1,2,4-triazole) on the corrosion of two carbon steels (OL 37 and OLC 45) in 1M H2SO4 was studied potentiostatic and potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and metallurgical microscopy techniques.

The inhibition activity analysis of these organic inhibitors was made by assuming that the mechanism of inhibition by organic molecules is chemisorptions and that the energetic of the corrosion process per se is unaffected by the addition of substituents on the parent compound. We presume that, these organic inhibitors inhibit corrosion of carbon steel by a protective mechanism, forming insoluble iron complexes and repairing the porous oxide layers. The addition of the organic inhibitors led in all the cases to inhibition of the corrosion process. Polarization curves indicate that they are mixed type of inhibitors. The inhibition efficiency was high in all the studied cases. The corrosion parameters obtained from polarization curves and from EIS spectra are in good concordance and point out the inhibitory action of derivatives benzotriazole. The adsorptions of the organic compounds on the carbon steels surface obeyed Langmuir’s isotherm. The thermodynamic parameters of adsorption enthalpy (ΔH0), adsorption free energy (ΔG0) and adsorption entropy (ΔS0) were calculated. Further characterization using Fourier transform infrared spectroscopy (FT-IR) demonstrates the adsorption of organic inhibitors and the formation of corrosion products on the carbon steels surface. The inhibition process was attributed to the formation of the adsorbed film on the metal surface that protects the metal against corrosive agents. The EIS measurements have confirmed this protection and pointed out the formation of adsorption layers on the electrode surface.
Scaling Kinetics and Scale Microstructure of Chromia Scales Formed on Ni25Cr Model Alloy during Oxidation in H2o-Containing High and Low pO2
Test Gas at 1000°C
Authors: Hänsel Michael , Shemet Vladimir , Kijatkin Ivan , Simon Dirk , Gorr Bronislava , Christ Hans-Jürgen
Published: February 2020

The ability of water vapour to alter chromia scaling rates has long been recognised, but is poorly understood because of the diversity of scale-water vapour interactions possible. One obstacle is the complex defect structure of thermally growing chromia scales. For technological reasons a protective oxide scale needs to be essentially gas-tight to ensure that its growth is governed by diffusion. A gas-tight thermally growing chromia scale is commonly assumed to be in equilibrium with the atmosphere the scale is growing in, as well as the metal the scale is formed on. Consequently the type of defects may change throughout a thermally growing chromia scale. Another difficulty lies in the fact that the concentration and the mobilities of the intrinsic defects depend strongly on the pO2 and pH2O in the test gas used for the experiments.

At high pO2 test gas containing O2 and H2O, the pO2 is independent of the H2O content in the test gas. However both types of oxygen species O2 as well as H2O contributing to the chromia scaling reaction. The effect of specimen thickness on chromia scaling allows to change the concentration of the intrinsic defects and their diffusivities in thermally grown chromia scales independently from the test gas applied. Chromia scales are under pressure during scale growth. For thermodynamic reasons the concentration and diffusivity of the intrinsic, native defects in oxides under hydro-static pressure varies with the amount of pressure applied. The chromia growth kinetics was found to be depending on the thickness of the specimens used for the oxidation experiments. In dry Ar/N2-O2 gas the effect was very clear with the 0.25 mm thick specimen producing a twice as thick chromia scale compared to the 1.0 mm thick specimen. The addition of water vapour into the test gas levelled the differences in chromia scaling kinetics and the chromia scale thickness decreased with increasing water vapour content in the gas.

The experimental findings will be discussed with strong focus on the oxide growth mechanism, the chromia microstructure of the scales formed under the various conditions and the concentration and mobility of the native defects in the chromia scales and its interactions with H-containing species originating from water vapour in the test gas.
The Time and Temperature Dependence of AISI 316L Corrosion in Chlorosilane Environments
Authors: Aller Joshua L , Ellingwood Kevin , Gannon Paul E.
Published: February 2020

Chlorosilanes are used abundantly at high temperatures in the production of ultra-pure silicon and silicon containing materials. The presence of both chlorine and silicon presents a unique corrosion environment for the metallic materials that must handle these compounds. It is known that in chlorosilane environments, 316L can form either a protective metal silicide layer or a volatile metal chloride layer on the substrate. However, it is not known what dependence this surface reaction has on temperature, time, or gas composition. In this study, AISI 316L stainless steel was exposed to vaporized silicon tetrachloride (STC, SiCl4), pure hydrogen (H2), and anhydrous hydrogen chloride (HCl) at temperatures (>500°C), times (1-150 hours), and compositions relevant to industrial processes. Metal silicide and metal chloride formation was evaluated using surface and gravimetric analysis, with metal silicide formation causing a gain in sample mass and metal chloride formation causing a loss in sample mass. It was revealed that the transition between chloride and silicide formation depends on time of exposure, temperature, and mole fraction of HCl present in the gas stream. Lastly, some discussion is provided on the underlying mechanisms of silicide and chloride formation, and how to prevent excessive corrosion in industrial applications.
Formation of NiAl2O4 Layer on High Temperature Oxidation of Ni/Al2O3 Nanocomposites
Authors: Nanko Makoto , Maruoka Daisuke
Published: February 2020

Al2O3 composites dispersed with nano-Ni particles, Ni/Al2O3 nanocomposites, are candidates for high temperature structural applications because of excellent mechanical properties. Those nanocomposites have a self-healing function for surface cracks via high-temperature oxidation.  In high temperature oxidation of Ni/Al2O3 nanocomposites, inward diffusion of oxide ions occurs mainly to form oxidation zone consisting of NiAl2O4 and Al2O3.  Outward diffusion of cations also occurs to develop NiAl2O4 layer on the surface of Ni/Al2O3 nanocomposites.  Surface cracks of Ni/Al2O3 nanocomposites are filled out by the surface NiAl2O4 developed by high temperature oxidation.  Kinetics on growth of an NiAl2O4 layer was discussed in order to understand kinetics of oxidation and self-healing of Ni/Al2O3nanocomposites at high temperatures. 

Starting powder of Ni/Al2O3 nanocomposites was prepared by drying and reducing Al2O3 aqueous slurry with Ni nitrate.  Volume fraction of Ni was ranged from 1 to 10 vol%.  The powder was densified by pulsed electric current sintering at 1400°C for 5 min under 40 MPa in vac.  Grain sizes of Al2O3 matrix and Ni particles were equal to 1 μm and 300 nm, respectively.  The Ni/Al2O3 nanocomposites were oxidized at 1300°C in air.  Thickness of the NiAl2O4 layer was measured as well as the oxidized zone of Ni/Al2O3nanocomposites. 

Growth of surface NiAl2O3 developed on Ni/Al2O3 nanocomposites,, as well as the oxidized zone, followed a parabolic manner.  The parabolic rate constant on the growth of NiAl2O4 layer was proportional to the Ni volume fraction until 5 vol%.  Reaching to 10 vol% in Ni volume fraction, the value of the parabolic rate constant increased remarkably.  The fast growth of NiAl2O4 layer on 10 vol% Ni/Al2O3 nanocomposite would be caused by connection of NiAl2O4 grains in the oxidized zone because Ni diffusion in NiAl2O4 is faster than that in Al2O3 matrix.
Measurements of Gas Shielding Factors for Cu, Fe, Ni
Authors: Markus Torsten , Thaler Florian , Schulz Michal , Fritze Holger , Stenzel Christian
Published: February 2020

Knowledge of the vaporization behavior of different metals in dependence of temperature, pressure of the ambient atmosphere as well as its purity, is a crucial issue for high temperature materials. It has even been proven in the literature that the amount of mass loss of a sample due to vaporization strongly depends on the purity of the atmosphere in which the sample is heated. This coincides with the value of partial pressures of specific impurities. The so called gas shielding factor describes the ratio of the evaporation rate in a specific gas atmosphere and the evaporation rate under UHV.

The dependence of the gas shielding factor on the pressure and the purity of the process gas is remarkable. The range can extend over several orders of magnitude [1].

Within the framework of the presented work, vaporization experiments using a HT- Thermobalance with UHV supply have been carried out for the elements Fe, Cu, and Ni under inert gas atmosphere and with defined oxygen partial pressures. Thereby, the oxygen partial pressure has been maintained using an oxygen ion pump. Here, an electric current between +10 and -10 mA is applied to an yttrium-doped zirconia tube operated at a temperature of 600 °C. The current flow results in oxygen being transferred into or out of the ambient gas provided to the experimental set-up with a flow rate of about 2 cm3/min. The ion pump yields accuracy in oxygen flow of 10-9 l/min and, therefore, enabled precise adjustment of pO2 within the area of interest.

The gas shielding factor not only depends on the gas purity but also on the investigated material itself. The dependency from the oxygen partial pressure for example is influenced by the partial vapor pressure of the corresponding oxides and their dissociation pressure.

Reference

[1] E. Fromm, METALLURGICAL TRANSACTIONS A, VOLUME 9A , DECEMBER 1978, 1835-1838
Isothermal Pressure-Swing Cycling of Strontium Doped Lanthanum Manganite Oxides for Fuel Production
Authors: Ignatowich Michael Joseph , Davenport Tim , Yang Chih-kai , Handler Sheila , Yamazaki Yoshihiro , Wilke Stephen , Haile Sossina M
Published: February 2020

Water splitting for fuel production via isothermal pressure-swing cycling has recently emerged as a means of converting solar heat to a storable medium [1]. For the generation of hydrogen, the process involves the high temperature reduction of a variable valence oxide under an inert gas of low oxygen content followed by oxidation by steam at the same high temperature. Due to thermolysis, the higher the temperature the greater the oxidizing power of the steam, providing a means of converting thermal energy to chemical energy. In comparison to a more conventional temperature-swing cycle, the isothermal, pressure-swing cycle offers the potential for greater efficiency because the need for solid state heat recovery is eliminated, although the demands on gas-phase heat recovery are increased. To date, isothermal, pressure-swing process has been demonstrated only using ceria. Here, we explore the behavior of perovskite-structured oxides as candidates for this cycle.

In principle, fuel production capacity can be determined, a priori, from knowledge of the thermodynamic properties of a non-stoichiometric oxide. Accordingly, as a first step, the thermodynamics of various compositions of lanthanum strontium manganite oxides (LaxSr1-xMnO3) were modeled at high temperature from literature data [2]. The theoretical, equilibrium fuel production capacity at 1500°C is found, on the basis of this analysis, to exceed that of undoped ceria, by almost a factor of two (and more than a factor of three at 1400°C). Motivated by this result, samples of x = 0.1, 0.2, 0.3 and 0.4 were synthesized via solid state reaction and then experimentally evaluated for fuel productivity using in an in-house constructed thermochemical reactor. Cycling between Ar (with 10 ppm oxygen) and 20% steam (balance Ar) at 1500°C shows that indeed the series of materials offer higher fuel production capacity under conditions of long-cycle times. In addition, oxygen release rates are higher for the perovskites than they are for ceria, indicating that more fuel is produced for a given cycle with finite periods.

References:

[1] Y. Hao, C.-K. Yang and S. M. Haile, Phys. Chem. Chem. Phys., 2013, 15, 17084–17092.

[2] J. Misuzaki, et al. Solid State Ionics, 2000, 132, 167–180
A Thermodynamic Study of Evaporation of the CaO-MgO-Al2O3-FeO-SiO2 System Melts
Authors: Shornikov Sergey I.
Published: February 2020

Within the framework of the developed semi-empirical model based on the theory of ideal associated solutions, the concentration changes in the CaO-MgO-Al2O3-FeO-SiO2 system melts during high-temperature evaporation were calculated.
A Combined Computational and Experimental Approach to Determine Mg(BH4)2 Electrolyte Parameters
Authors: Chadwick Alexander Fredenburgh , Vardar Gulin , Thornton Katsuyo , Siegel Donald
Published: February 2020

Metallic magnesium is a promising material for rechargeable battery anodes, as it offers higher theoretical volumetric capacities than lithium-ion chemistries and is less prone to dendrite formation upon repeated cycling [1]. Magnesium borohydride (Mg(BH4)2) in dimethoxyethane (DME) is a candidate electrolyte for metal-anode batteries because of its stability in highly reducing electrochemical environments. Additionally, magnesium borohydride is not corrosive towards typical electrode materials to the same extent as some halogenated electrolytes [2]. To date, however, little is known about the electrochemical behavior of this system.

We have developed a computational model capable of determining the redox and transport properties of an electrochemical system. In this model, used to simulate the cyclic voltammetry of an electrochemical cell, we solve the Nernst-Planck equation for electrolyte transport coupled with the Poisson equation for electrostatics. The Butler-Volmer equation is used to describe the electron transfer reaction at the electrode/electrolyte interface. This methodology is based on models previously presented in the literature, but enhancements have been made to account for the nucleation overpotential and coulombic efficiency.  These enhancements are required to predict the experimentally observed electrodeposition and stripping behavior [3,4].

To obtain the input physical parameters for this model, cyclic voltammetry experiments were performed with 75mM Mg(BH4)2 in DME. A gold microelectrode was used as the working electrode. The counter and reference electrodes were magnesium. Several scan rates were explored within the voltage range –1V to 1V vs. Mg/Mg2+. By matching the simulated voltammogram to those obtained experimentally, we determine the values for the heterogeneous rate constant, diffusion constants, and the extent of dissociation of Mg(BH4)2in the electrolyte. The results will be presented and discussed. These parameters enable future investigations of the cycling behavior of the electrolyte system, such as cyclability and rate capabilities.

This work was supported as part of the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences.

References:

[1] Hyun Deog Yoo, Ivgeni Shterenberg, Yosef Gofer, Gregory Gershinksy, Nir Pour and Doron Aurbach, Energy Environ. Sci., 6, 2265-2279 (2013).

[2] Rana Mohtadi, Masaki Matsui, Timothy S. Arthur and Son-Jong Hwang, Angew. Chem. Int. Ed., 51, 9780-9783 (2012).

[3] Timothy R. Brumleve and Richard P. Buck, J. Electroanal. Chem., 90, 1-31 (1978).

[4] Ian Streeter and Richard G. Compton, J. Phys. Chem. C, 112, 13716-13728 (2008).
Structural Causes of Electrochemical Hysteresis and Voltage Fade in Lithium- and Manganese-Rich Composite Cathodes
Authors: Dogan Fulya , Long Brandon R. , Croy Jason R. , Gallagher Kevin G. , Iddir Hakim , Russell John , Balasubramanian Mahalingam , Key Baris
Published: February 2020

Layered lithium- and manganese-rich, TM oxide (LMR-NMC) intercalation cathode structures have been widely investigated as the next generation cathodes for advanced lithium-ion batteries. This class of materials, denoted as xLi2MnO3•(1-x)LiMO2 (M=Mn, Ni, Co), possesses complex nanocomposite structures consisting of two distinctly different average local environments one rich in Li and Mn (e.g., Li2MnO3) and the other in the constituent TMs (e.g., LiMO2)1. In order to achieve reversible capacities greater than 200mAh/g, electrochemical activation of the Li- and Mn-rich component above ~4.4V is necessary.  However, activation followed by cycling above ~4.0V results in continuous structural changes to the material. Hysteresis in the open-circuit voltage is one manifestation associated with high-voltage cycling after the activation process.  In addition, a continuous decrease in the average voltage of cells, known as voltage fade, occurs 2,3. 6Li NMR spectroscopy is the only structural probe currently available that can quantitatively characterize local lithium environments that dominates the free energy for site occupation and can be used to monitor the evolution of local order and low concentration defect formation with the goal of correlating local structural changes with hysteresis and voltage fade phenomena. Here, we show direct evidence of path-dependent lithium site occupation, correlated to structural reorganization of the metal oxide and the electrochemical hysteresis, during lithium insertion and extraction.

1) Croy, J. R., Gallagher, K. G., Balasubramanian, M., Long, B. R. & Thackeray, M. M. Journal of the Electrochemical Society
2014 161, A318-A325

2) Bettge, M.; Li, Y.; Gallagher, K.; Zhu, Y.; Wu, Q.; Lu, W.; Bloom, I.; Abraham, D. P. Journal of the Electrochemical Society
2013, 160, A2046

3) Gallagher, K. G.; Croy, J. R.; Balasubramanian, M.; Bettge, M.; Abraham, D. P.; Burrell, A. K.; Thackeray, M. M. Electrochemistry Communications
2013, 33, 96.
Coupling Tof-SIMS and XPS for a Better Understanding of Lithiation Mechanism of Silicon Electrodes for Li-Ion Batteries
Authors: Bordes Arnaud , Haon Cédric , Secouard Christophe , Montani Alexandre , Marcus Philippe , De Vito Eric
Published: February 2020

Li-ion batteries technology is an attractive energy storage system for many specific applications like portable devices. To follow the growing energy demand of new devices, their energy density needs to be improved. Silicon-based anode is a serious option since it offers a specific capacity almost ten times higher than carbonaceous materials. However, cycling performances of Si electrodes, particularly in term of coulombic efficiency, remain so far inadequate for a use in practical LIBs, due to huge volume changes upon alloying and de-alloying with lithium. A fine understanding of the lithiation mechanism of silicon electrodes will help to design more robust architectures. Indeed, the degradation mechanisms upon electrochemical cycling are still under debate.

In this work, an amorphous silicon thin film has been used as a model for a better understanding of lithiation mechanism appearing in more complex systems such as Si composites electrodes. Lithium distribution in the Si layer has been thoroughly investigated by coupling powerful characterization tools: X-ray Photoelectron Spectroscopy (XPS) and Secondary Ion Mass Spectroscopy (ToF-SIMS). In particular, cross-analyses of different lithiation states have been carried out by using an airtight transfer vessel between a glove box and XPS and ToF-SIMS spectrometers.

Results reveal a lithiation front moving forward over the state of charge. The quantification of the LixSi alloy indicates a higher lithium amount compared to literature[1]. This anomaly leads to a description of the lithiation mechanism based on the presence of fast diffusion paths for Li throughout the Si layer reaching the Cu collector. These paths would be a second driving force for silicon alloying. To corroborate this mechanism, complementary analyses were performed: SEM observation of a FIB cut, TEM involving cryo-ultramicrotomy under protected atmosphere and Auger spectrometry.

1.            Radvanyi, E., De Vito, E. and al., Study of lithiation mechanisms in silicon electrodes by Auger Electron Spectroscopy. Journal of Materials Chemistry A, 2013. 1(16): p. 4956-4965.

Figure 1
Comparisons of the Performance of Combustion Derived Undoped LiCo1/3Ni1/3Mn1/3O2, and Doped LiCo0.3Ni0.3Mn0.3Fe0.1O2, LiCo0.3Ni0.3Mn0.3Cr0.1O2, and LiCo0.3Ni0.3Mn0.3Ti0.1O2 Cathode Materials
Authors: Kamarulzaman Norlida , Elong Kelimah , Rusdi Roshidah , Jaafar Mohd Hilmi
Published: February 2020

Improving the performance of cathode materials is an on-going effort amongst battery scientists. Doping the materials with other transition elements is a good way of obtaining improvements in the performance of the materials. This work focuses on the Fe, Cr and Ti doping of LiCo1/3Ni1/3Mn1/3O2, producing LiCo0.3Ni0.3Mn0.3Fe0.1O2, LiCo0.3Ni0.3Mn0.3Cr0.1O2, and LiCo0.3Ni0.3Mn0.3Ti0.1O2 materials. X-Ray diffraction (XRD) results show that the materials are pure and single phase. Highly ordered hexagonal structures with R-3m space group were obtained. Galvanostatic charge-discharge cyclings were performed and results showed differences in the specific capacity as well as capacity retention of the materials. In order to further understand the behaviour of the cathode materials, X-Ray Photoelectron spectroscopy were done. Results showed that the binding energy of lithium affects the specific capacity of the electrochemical cells. The existence of the transition metals in several oxidation states also seem to affect the materials’ performance and cycling.
Durable Sno-Lto Composite Anode for Lithium Ion Batteries
Authors: Chen Yi-Chih , Liu Guan-Hung , Chu Peter Pojen
Published: February 2020

Anode materials play a pivotal role for high power and high power density lithium ion batteries applications. 1. Graphite was the dominant materials of choice, but still fall short of the goal owing to low rate-capability and specific capacity (372 mAh.g-1). Among other electrochemically active materials, Tin monoxide (SnO) appears promising to replace graphite and is widely explored due to its high specific capacity (875 mAh.g-1). However it suffered from pulverization 2 problem and hampered its commercial implementation. In this study we have developed a novel composite anode material that combined two types of lithium ion insertion and exertion mechanisms with the purpose to reduce pulverization, to improve rate capability and to raise cycling performance. SnO is alloying/de-alloying system, which possess higher specific capability and electrochemical activity. On the other hand, Li4Ti5O12 (LTO) is an intercalation/de-intercalation system, which shows unique rate-capability and zero-strain ability 3 . Combining these two features characteristic of the two materials we are able to stabilize the huge volume change of SnO. Pure SnO and the composite powder with SnO/LTO of 75/25, 50/50 and 25/75 wt% were successfully synthesized by sol-gel method. The decrease of capacity with increasing C-Rate was found to be slower that of generic SnO in SnO-LTO(75/25) composite powders, and a high discharge capacity of 466.2 mAh.g-1 at 1Crate was observed.  Note that this is higher than that in commercial graphite anode materials. The presence of LTO appears to improve simultaneously the rate capability and cycle life through stabilizing the structure of whole active material, and the synergistic mechanism will be discussed.

References:

M. V. Reddy, G. V. Subba Rao, B. V. R. Chowdari. Chem. Rev. 2013, 113, 5364−5457

Md Mokhlesur Rahman, Alexey M. Glushenkov, Thrinathreddy Ramireddy, Tao Tao and Ying Chen. Nanoscale, 2013, 5, 4910–4916

L.J. Fu, H. Liu, C. Li, Y.P. Wu, E. Rahm , R. Holze, H.Q. Wu. Progress in Materials Science 50 (2005) 881–928
Silicon-Germanium Heterostructure Nanowires As High Capacity Lithium-Ion Battery Anodes - an Electrochemical and Structural Investigation
Authors: Kennedy Tadhg , Ryan Kevin M
Published: February 2020

Li-alloying nanowires (NWs) are promising anode materials for next generation lithium-ion batteries due to their large maximum theoretical capacity when compared with conventional graphitic based materials (372 mAh/g). Ge NWs, in particular, have shown great promise, exhibiting stable capacities of   ̴ 900 mAh/g over 1000s of cycles and excellent rate capability due to the high rate of diffusivity of Li in Ge and its inherent high conductivity.1, 2 The superior capacity retention of Ge is attributed to the complete restructuring of the NWs that occurs within the ﬁrst 100 cycles to form a continuous porous network that is mechanically robust. The possibility of incorporating Si into this stable network of Ge is very appealing, resulting in electrodes that combine the very high capacity of Si with the excellent rate characteristics and capacity retention of Ge.

Here we report the formation of high-performance and high-capacity lithium-ion battery anodes from high-density Si-Ge heterostructure nanowire arrays grown directly from the current collector. The unique morphology of the active material consists of Si NW branches grown from a Ge NW backbone.  By tuning the ratio of Si to Ge in the material it is possible to design electrodes for either high-capacity applications (high Si : Ge mass ratio) or high rate capability applications (high Ge : Si mass ratio). We show by ex-situ high-resolution transmission electron microscopy (HRTEM) and high-resolution scanning electron microscopy (HRSEM) studies that the NW array transforms into a mechanically robust, porous network of Si and Ge ligaments. Once this network is formed it is highly stable, maintaining capacities of 1700 mAh/g over 200 cycles.  The electrode material described here also has the advantage of being formed in a low energy, rapid synthetic protocol. Using a very simple reaction protocol, NW growth occurs by thermolytic decomposition of an organometallic precursor onto a preheated substrate in an inert atmosphere.

1.         T. Kennedy, E. Mullane, H. Geaney, M. Osiak, C. O’Dwyer, K. M. Ryan, Nano Letters 14, 716-723(2014),

2.         E. Mullane, T. Kennedy, H. Geaney, K. M. Ryan, ACS Applied Materials & Interfaces
, 6, 18800-18807 (2014).
LiVPO4F : A New Age High Voltage Cathode Material for Lithium Ion-Hybrid Electrochemical Capacitors
Authors: Satish Rohit , Vanchiappan Aravindan , Wong Chui Ling , Srinivasan Madhavi
Published: February 2020

Lithium ion hybrid capacitors are cells that combine the best of both worlds in terms of energy density and power density, where one of the electrodes stores charge via a faradaic mechanism (battery) and the other electrode stores charge using an electrochemical double layer (supercapacitor). This configuration allows it to have a higher power density when compared to batteries and a higher energy density when compared to supercapacitors. Thus making them a potential solution in powering Plug-in Hybrid Electric Vehicles in the future.

LiVPO4F (LVPF) belongs to a class of materials known as tavorites and because of the presence of the poly-anionic phosphate group and fluorine it has a high redox potential of ~ 4.2 V. But because of the high degree of covalency in the molecule it also has very low electronic conductivity, making it unsuitable for use at high current rates in its pristine form, hence we have synthesized LVPF using a carbothermal route in order to ensure good conductivity of the sample , the material was further characterized using X-ray diffraction, scanning electron microscopy and high resolution tunneling electron microscope and was found to have single phase purity with no apparent morphology and a thin layer of conductive carbon which helped form facile electron migration paths in the material.

Comprehensive electrochemical studies were performed on both LVPF and activated carbon (anode) to determine the precise mass loading in a full cell. Because of the relatively high redox potential of LVPF the working potential of the cell is raised allowing for a much higher energy density when compared to other systems in literature. Also because of the synthesis route undertaken the full cell (LVPF/AC) is able to cycle successfully at high current rates with minimal loss in cycleability