bluuebunny/crossref_metadata_2025 huggingface dataset:
New Titanate Negative Electrode Materials for Na-Ion Batteries
Authors: Fielden Ryan I , Obrovac Mark N
Published: February 2020

Introduction

Lithium-ion batteries are widely used because they are lightweight, have a high energy density, and can be cycled many times. Sodium-ion has shown promise as a potentially lower cost, more sustainable battery chemistry [1]. Titanates have been investigated for use as anode materials in Na and Li cells [2]. However they are non-conductive, requiring the use of large amounts of carbon black to cycle [3]. We have found new titanate phases that can reversibly intercalate Na as bulk micron-sized particles without the need for large amounts of carbon black.

Experimental

Samples were synthesized via heating precursors to 900 °C for 10 hours in argon. A 10 % Na excess was added due to the volatility of Na at these elevated temperatures. Products were found to be air or moisture sensitive. Samples for X-ray diffraction measurement were loaded under argon into an air-tight sample holder with an aluminized Mylar window. The sample holder was purged with He gas during XRD measurement. Electrodes comprising active materials, carbon black and PVDF binder in a 80:10:10 weight ratio were cast using NMP as a solvent and dried at 120°C. Electrodes were cycled in 2325 coin type cells at a rate of C/10 (assuming a 100 mAh/g capacity) using Na metal counter/reference electrodes and 1M NaPF6in PC electrolyte.

Results and Discussion

Figure 1 shows a voltage curve of a new titanate negative electrode material. In-situ XRD shows that reversible Na-insertion occurs via an intercalation mechanism in which the titanate's volume only expands by 1.6% after full sodiation. The volumetric capacity of the titanate is 400 Ah/L, which is comperable to that of hard carbon.

To our knowledge, this is the first demonstration of intercalation of sodium into bulk oxides at such low voltages without the use of large amounts of carbon black. The use of these new titanate phases presents a new strategy towards making negative electrodes for Na-ion cells, from which high energy density bulk intercalation materials may be developed.

References:

[1] M.D. Slater et al., Adv. Funct. Mater., 23(2012) 947-958.

[2] L. Zhao, Journal of Power Sources, 242(2013) 597-603.

[3] P. Senguttuvan et al., Chem. Mat., 23(2011) 4109.

Figure 1 Voltage curve of a new titanate negative electrode vs. sodium metal.
Application of a New Co-Polyimide Binder Material to Improved High-Temperature Performance for Lithium-Ion Batteries
Authors: Choi Jaecheol , Song Seonghyun , Cho Insung , Cho Kuk Young , Lee Yong Min
Published: February 2020

Lithium-ion batteries (LIBs) have been widely used for mobile IT devices and various electric vehicles (xEVs). Especially, since large-format LIBs are operated in the severe environments like -30 or 60 oC, their electrochemical performances and safety should be secured for at least 10 years. Recently, Yoon et al. reported that the degradation was closely related to the contact loss at the electrode/current collector interface and between active material particles1. Thus, the dimensional stability of electrode should be maintained even at high temperatures.

In this study, the effects of a thermally stable co-polyimide-based polymeric binder on the performance of a cathode electrode are investigated. The introduction of co-polyimide (P84) into a conventional polymeric binder system based on polyvinylidene fluoride (PVdF) enhances the cycle performance under high temperature conditions (60 oC). Because of the inherent mechanical and thermal stabilities of the co polyimide, P84 retains outstanding adhesive/cohesive strength within the electrode composite, as well as between the electrode composite and the aluminium current collector. These findings are further supported by electrochemical impedance spectroscopic analysis, scanning electron microscope, and studies using a Surface and Interfacial Cutting Analysis System (SAICAS®) 2.

References

[1] T. Yoon, S. Park, J. Mun, J.H. Ryu, W. Choi, Y.-S. Kang,J.-H. Park, and S.M. Oh, J. Power Sources 215(2012) 312-316

[2] B. Son, M.-H. Ryou, J. Choi, T. Lee, H. K. Yu, J. H. Kim, and Y. M. Lee, ACS Appl. Mater. Interfaces, 6 (2014) 526-531

Acknowledgements

This research was financially supported by Chungcheong Leading Industry Promotion Project of the Korean Ministry of Trade. The authors also thank Sungmoon Systech Corp. in Korea for SAICAS® measurement.
Synthesis and Characterization of Flexible and Free-Standing Carbon Nanotube, Graphene Films and Their Composites for Li-Ion Batteries
Authors: Mery Adrien , Luais E. , Autret C. , Van F. Tran , Ghamouss F.
Published: February 2020

The objective of this communication is to present our results on the synthesis and the characterization of flexible and free standing films made from Carbon Nanotube (CNT), reduced graphene oxide (rGO) [1] and their composites (CNT/rGO). The films were obtained by filtration method from aqueous suspension of CNT, rGO, or CNT/rGO. The obtained materials are used as negative electrode in Li-ion systems. CNT films with a thickness below 50 µm are integrated on an electrodeposited Cu current collector (15 µm thick) according to the method describe by
Luais et al

[2], whereas CNT or CNT/rGO flexible free standing films with a thickness of 50 µm can be directly used without the need of a metallic current collector as anode material for battery cycling. All results will be discussed on the basis of SEM observations (as synthetized films and after cycling for post-mortem characterizations), Raman spectroscopy analysis, galvanostatic cycling, and electrochemical impedance spectroscopy. CNT free standing electrodes exhibit specific discharge capacities up to 300 mA.h.g-1 at C/20 and 200 mA.h.g-1at 5C. The effect of rGO/CNT ratio in composite electrodes will be presented as an improvement of the electrochemical performances compared to CNT free standing electrodes.

Figure : a-Evolution of the specific capacity of CNT free standing film in Li-ion half-cell. SEM images of b1: as synthetized free standing CNT film, and b2: after cycling in EC/PC/3DMC 1M LiPF6 electrolyte; Photographs of c1: a flexible free-standing film, and c2: the same film roll up around a plastic rod

[1] Qian Cheng, Jie Tang, Jun Ma, Han Zhang, Norio Shinya, Lu-Chang Qin, CARBON 49 (2011) 2917–2925

[2] E.Luais, J. Sakai, S. Desplobain, G. Gautier, F. Tran-Van, F.Ghamouss. Journal of Power Sources, 242, 2013,166-170
Template-Free Electrochemical Synthesis of Cuprous Oxide and Its Application to Anode of Lithium Ion Batteries
Authors: Shin Jeong Ho , Park Sun Hwa , Hyun Seungmin , Park Hyun Min , Song Jae Yong
Published: February 2020

Cu2O has been investigated as a candidate of the promising anode materials for Lithium ion batteries (LIB) due to its several advantages such as reversible mechanism with Li ion, relatively low-cost, non-toxicity, and higher theoretical capacity than graphite. However, the Li ion charge and discharge (C-D) processes accompany huge volume expansion and shrinkage, by which mechanical stresses are induced and lead to poor C-D cycle life due to the failure of the contacts between anode material and current collector. In order to avoid the drawbacks of large volume change in anode material, several efforts have been taken to use Cu2O nanopowders as an anode. However, the usage of nanopowders requires additional conductive carbon sources or binders which are disadvantageous in simplifying fabrication process and lowering cost.

In this talk, we present a template-free and surfactant-free electrochemical nanosynthesis of single crystalline Cu2O nanostructures. The electrochemical growth of Cu2O nanostructures originated from filamentary effect related to the electric field enhancement on the pyramidal Cu2O grains in an ultra-dilute CuSO4 aqueous electrolyte. The synthesized Cu2O nanorods showed much more excellent electrochemical properties as an anode material for LIBs than Cu2O films; the electrochemical capacities exceptionally increased from 340 to 1249 mAh/g during 500 cycles exceeding the theoretical capacity of Cu2O. The capacity enhancement was due to the phase transformation from Cu2O to CuO, nanostructuring from nanorods to fragmented nanoparticles, and progressive generation of electroactive polymeric gel-like layer on the surface of the nanoparticles. The present nanostructuring of Cu2O is expected to contribute to the development of higher capacity LIBs in near future.
Characterization of a Lithium Ion Battery Based on Carbon-Coated Lithium Sulfide Cathode and Electrodeposited Silicon Based Anode
Authors: Agostini Marco , Liu Jun , Jeong Moongook , Nara Hiroki , Momma Toshiyuki , Scrosati Bruno , Sun Y.-K. , Osaka Tetsuya , Hassoun Jusef
Published: February 2020

In the latest years there has been an increasing interest in the wide spread of electric vehicles (EVs) and hybrid vehicles (HEVs) with the final goal of the reduction of greenhouse gas emission and atmosphere pollution in large metropolitan areas. Clearly, the success of this operation depends on the availability of an efficient power source for the electric engine. Due to his high energy density, the lithium-ion battery is as an ideal candidate.
1
However, although appropriate for the consumer electronic market, the present lithium-ion battery technology is still inadequate for the electric road transportation one. Improvements in energy density and safety, as well as reduction in cost, are mandatory steps to meet the EV and HEV severe targets.
2
To achieve these operative improvements, battery chemistries alternative to intercalation are required.
3-4
A very promising example is provided by the lithium-sulfur battery, characterized by a conversion chemistry leading to high specific energy, i.e. of about 2600 Wh kg-1,combined with the low cost of the earth abundant sulfur. However, several issues still prevent the practical development of this battery, including the solubility of polysulfides in the course of the discharge process and the high resistance, almost insulating nature of both reactants and products; furthermore the safety hazard associated with the use of lithium metal as anode. These issues have been recently addressed by modifying the electrolyte formulation and developing microstructured/nanostructured carbon conductive matrixes.
5
Despite the replacement of the lithium metal anode with an alternative material is mandatory to assure the practical development of Li/S battery, surprisingly there are not many examples of efficient Li-ion sulfur batteries. In this work we report a new type of rechargeable lithium-ion battery based on the combination of a high capacity Si-O-C anode with a high-rate Li2S-MCMB (Mesophase Carbon Micro Beads) composite in a tetraglyme electrolyte. We show that this Si/Li2S battery operates around 1.4V, delivering a very stable capacity of about 280 mAh gLi2S-1 with a resulting theoretical energy density of the order 400 Wh kgLi2S-1.

[1] B. Scrosati, J. Garche, J. Power Sources 2010, 195, 2419

[2] M. Armand and J.M. Tarascon, Nat. 2008, 451, 652.

[3] K. Cai, M.K. Song, E.J. Cairns, Y. Zhang, Nano Lett. 2012, 12, 6474.

[4] Y.K. Sun, S.T. Myung, B.C. Park, J. Prakash, I. Belharouak, K. Amine, Nat. Mater. 2009, 8(4),

320.

[5] X. Ji, K.T. Lee, L.F. Nazar, Nat Mater. 2009, 8(6), 500.
Lithium Polysulfide Flow Batteries Enabled By Percolating Nanoscale Conductor Networks
Authors: Chiang Yet-Ming , Fan Frank , Woodford William , Li Zheng , Baram Nir , Smith Kyle C. , Helal Ahmed , McKinley Gareth , Carter W. Craig
Published: February 2020

The high solubility of lithium polysulfides in nonaqueous electrolytes and associated loss mechanisms have long been a barrier to the development of Li-S batteries. The same attribute allows lithium polysulfide solutions to be used in a flow battery architecture, where the high cell voltage and redox-active species concentrations (>2M) compared to conventional aqueous flow batteries provides significantly higher energy density and potentially lower cost (<$100/kWh at system level). Here we demonstrate a new design approach wherein diffusion-limited aggregation of nanoscale conductor particles at ~1 vol% concentration is used to impart mixed electronic-ionic conductivity to redox-active solutions, forming flow electrodes with embedded current collector networks that self-heal after shear. As illustrated in Fig. 1, flow cells of this architecture can distribute electrochemical activity throughout the volume of flow electrodes rather than being confined to surfaces of stationary current collectors. Applying this concept to lithium polysulfide semi-flow batteries, we demonstrate that the nanoscale network architecture enables cycling of polysulfide solutions deep into precipitation regimes that otherwise show poor capacity utilization and reversibility. Figure 2 compares results for identical 2.5 mol S/L solutions (as Li2S8 in TEGDME with 1 wt% LiNO3 and 0.5M LiTFSI) tested in half-cells using a conventional fibrous carbon current collector, and using the nanoscale conductor network approach without the current collector. At C/4 rate, the latter exhibits specific capacity of 1200 mAh g-1 (vs. theoretical capacity of 1460 mAh g-1 for this solution), about a factor of 5 greater than with the carbon fiber current collector.

Lithium polysulfide half-flow cells are demonstrated for the first time, operating in two modes: 1) Potentiostatic cycling under continuous flow (the typical configuration for flow batteries), in which at C/10-C/15 rates reversible capacity is ~380 mAh g-1 and catholyte energy density is ~60 Wh/L (with respect to Li/Li+), and 2) Galvanostatic cycling with intermittent flow (in which fluid is pumped in discrete volumes with complete charging or discharging of the electroactive region in between), in which reversible capacities are ~650 mAh g-1 and catholyte energy density is ~100 Wh/L. An example of potentiostatic cycling results appears in Figure 3; the performance of such devices from fundamental Li-S reaction kinetics to non-Newtonian rheology to electrochemical cell design will be discussed.

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.
Boron Doped Defected Graphene: A Promising Anode Material for Li-Ion Battery
Authors: Singh Abhishek Kumar , Das Deya , Hardikar Rahul P , Lee Kwang-Ryeol , Han Sang Soo
Published: February 2020

Li ion batteries (LIB) are most promising energy storage devices for today’s technologies due to their size, portability, and superior performance. In the search of an anode material having specific capacity far beyond that of the existing commercially used graphite (372 mAh g−1 ), graphene emerges as a strong candidate for anode materials in Li ion battery due to its high surface area, high electrical conductivity, robust mechanical integrity and high capacity of about 540 mAh g−1. The success of graphene as an anode material depends strongly on the diffusion kinetics of Li, through and across the graphene sheet. Here, we study the Li diffusion through and across the graphene sheet using first principle calculations. We found that for pristine graphene, across diffusion barrier is several orders less than the through diffusion barrier. In order to reduce the energy barrier more, we investigated Li diffusion through and across the graphene with most commonly observed defects. The barriers reduce significantly by the presence of defects, with di-vacancy having lowest barrier of 1.34 eV for through diffusion and Stone Wales having 0.13 eV for across diffusion. We explore doping as another alternative to manipulate Li diffusion rate. We studied the effect of both boron and nitrogen doping by calculating the energy barrier through the defected doped graphene sheets. The height of the barrier depends sensitively on the concentration and type of dopants. While, nitrogen doping in defected graphene leads to strong binding, boron doped defected graphene show consistently low barriers. Boron doping in mono-vacancy and di-vacancy graphene leads to better anode materials for across and through diffusion, respectively.

Reference

D. Das, S. Kim, K-R. Lee, and A. K. Singh, Li diffusion through the doped and defected graphene, PCCP 15, 15128 (2013)

R. P. Hardikar, D. Das, S. S. Han, K-R. Lee, and A. K. Singh, Boron doped defected graphene as promising anode materials for Li-ion batteries, submitted
An Alternative Electrolyte Based on Sebaconitrile for Thermally-Stable Lithium-Ion Batteries
Authors: Cho Sung-Ju , Choi Keun-Ho , Park Joo-Sung , Lee Sang-Young
Published: February 2020

Volatile, flammable carbonate-based liquid electrolytes, although they show good electrochemical performance suitable for practical use, have posed a critical threat to safeties of lithium-ion batteries. This safety concern becomes more serious in newly-emerging application fields such as (hybrid) electric vehicles and grid scale energy storage systems, which employ large-sized, high-capacity lithium-ion batteries. One promising solution to address the liquid electrolyte-induced safety issues is to replace with nonflammable, thermally-stable electrolytes. Here, we demonstrate a new electrolyte system composed of 1M LiTFSI (lithium bis-trifluoromethanesulphonimide) in sebaconitrile (SBN). The SBN is featured with high boiling temperature (~ 375 oC) and nonflammability, which are expected to enable significant improvements in high-temperature performance of SBN-based electrolytes. Based on the characterization of thermal/electrochemical properties of SBN-based electrolytes, their application to lithium-ion batteries is explored as a function of operating temperature. Notably, the cell incorporating SBN-based electrolytes show stable cycling performance at 80 oC. This advantageous effect of SBN-based electrolytes on thermal stability of cell, in comparison to conventional carbonate-based liquid electrolytes, is discussed by scrutinizing the variation in AC impedance of cells and ionic conductivity of the electrolytes as a function of temperature.
A Multi-Scale Computational Homogenization Formulation for Li-ion Battery Cells
Authors: Salvadori A , Grazioli D , Geers M.G.D.
Published: February 2020

In a recent contribution the Computational Homogenization technique was tailored to model the multi-physics processes that take place in Li-ion batteries. An improved formulation is presented here. Novelties incorporated are: i) electroneutrality - which is assumed (yet not imposed as for the balance equations); ii) Maxwells equations - considered in a quasi-static sense in a rigorous way; steady motion of charges is used for the mere estimation of the magnetizing field along the electrolyte/active particle interface; iii) time dependent scale transitions - formulated as required by the length/time scales involved in Li-ion batteries processes; iv) scale separation in time - a concurrent time modeling between the macro and micro scales is carried out. Preliminary numerical results of this multiscale approach are shown.
Insights into Structural and Chemical Evolution in Novel Energy Storage Materials Using Hard X-Rays
Authors: Wiaderek Kamila M , Kinnibrugh Tiffany L. , Borkiewicz Olaf J , Chapman Karena W , Chupas Peter J , Pereira Nathalie , Amatucci Glenn G
Published: February 2020

Reversible electrochemical conversion reactions represent a potential path towards exceptionally high energy density batteries. Although promising from fundamental energy perspectives, conversion electrodes still face challenges related to reversibility and cycle life, which limit widespread technological implementation. In contrast to current intercalation-based technologies where the electrode host structure is only minimally perturbed by Li-insertion and extraction, during conversion an electrode material completely restructures at the atomic level, expanding the scope of potential processes that can degrade reversibility, reduce cycle life and contribute to failure. Identifying how the electrochemical performance characteristics emerge from the complex correlation of atomic and electronic constituents is a significant characterization challenge magnified by the nanoscale nature and chemical heterogeneity of the electrode and reaction products. Using Pair Distribution Function measurements applied operando, during electrochemical cycling, we can gain insight into these complex multiphase behaviors and identify transient intermediates to develop a full understanding of the processes governing energy storage in these materials.
The Oxygen Transport Properties of La2NiO4+
Î´ Infiltrated La0.6Sr0.4Co0.2Fe0.8O3-
Î´ By Electrical Conductivity Relaxation
Authors: Zhang Xinxin , Liu Xingbo , Zhang Hui
Published: February 2020

La2NiO4+
δ(LNO) infiltration in La0.6Sr0.4Co0.2Fe0.8O3-
δ (LSCF) cathodes have performed excellent cell electrochemical properties in our previous work. However, the effect of the infiltration phase on oxygen transport properties is still lacking and the mechanism for the enhancement of electrochemical properties is unclear. In this work, the electrical conductivity relaxation (ECR) is used to characterize the oxygen transport properties in La2NiO4+
δ(LNO) covered La0.6Sr0.4Co0.2Fe0.8O3-
δ (LSCF)materials. The ECR experiment was performed at 700oC in different oxygen particle pressure in the range of 0.21 to 0.02 atm. The ECR data suggested that there are fast oxygen transport path along the hetero-structured interface La0.6Sr0.4Co0.2Fe0.8O3-
δ (LSCF)/La2NiO4+
δ(LNO). The interface oxygen exchange coefficient k was estimated by assuming the invariable oxygen flux and the ignorable oxygen diffusion in LNO layer due to its minimal relative thickness. The calculated k value was 7.94-3.31 cm﹒s-1, which is larger than that value of the surface of single LSCF or LNO by 3-4 times. XPS analysis shown that Co and Sr diffused from LSCF into LNO layer and an additional low energy state Co peak appeared after ECR measurement resulting from Co disproportionate reaction probably, which are the possible reasons for the enhancement of surface and interface exchange coefficients.
Lithium Metal Polymer Battery Interfaces Studied By Hard X-Ray Microtomography
Authors: Devaux Didier , Harry Katherine J. , Parkinson Dilworth Y. , Yuan Rodger , Hallinan Daniel T. , MacDowell Alastair A. , Balsara Nitash P.
Published: February 2020

Conventional Lithium-ion batteries contain volatile liquid compounds that can leak and violently react with the environment leading to a fire.1 Solid polymer electrolytes (SPEs) are one solution as these flexible materials do not contain any volatile components. Additionally, they enable the use of high energy density lithium (Li) metal anodes.2 However, Li metal battery utilization is hampered by the dendrite growth.3 Upon cycling lithium metal is plated unevenly on the lithium metal anode side. Such dendrites can grow through the electrolyte and cause the battery to fail by short circuit.

Solid block copolymer electrolytes are a class of SPEs that contains a mechanical reinforced block and an ion conducting block doped with a Li salt.4 The block immiscibility induces microphase separation, producing ordered morphologies on the nanometer scale.5 The seminal work done by K.J. Harry et al.
6 on solid polystyrene-b-poly(ethylene oxide) (SEO) block copolymer electrolyte led to a better understanding of Li dendrite formation and growth. Using Li symmetric cells dendrite evolution was observed and imaged by a non-destructive tool, hard X-ray microtomography.

To go toward the application, batteries were imaged by hard X-ray microtomography. The batteries are made of a Li metal anode, a SEO electrolyte layer and a composite cathode. The cathode deposited onto on Aluminum (Al) foil, contains LiFePO4 as active material, SEO electrolyte as binder, and carbon black. Hard X-ray microtomography enables to visualize the microstructural changes at the Li/SEO and SEO/cathode interfaces to get insight on the battery failure mechanisms.

The batteries were cycled at 90°C at a C/20 charge rate and a C/8 discharge rate (Figure 1a). Prior and after battery cycling, the electrode-electrolyte interfaces were imaged by hard X-ray microtomography as shown in figure 1b and 1c, respectively. We found that the supposed intimate Li/SEO interface undergoes a strong delamination phenomenon that leads to the formation of voids (Figure 1b). Using a rendering image software, the void fraction can be measured all along the Li/SEO interfaces, and its effect on the battery capacity fading be estimated.

References

J.-M. Tarascon, M. Armand, Nature, 414 (2001) 359.

M. Armand, J.-M. Tarascon, Nature, 451 (2008) 652.

M. Rosso, C. Brissot, A. Teyssot, M. Dollé, L. Sannier, J.-M. Tarascon, R. Bouchet, S. Lascaud, Electrochimica Acta, 51 (2006) 5334.

M. Singh, O. Odusanya, G.M. Wilmes, H.B. Eitouni, E.D. Gomez, A.J. Patel, V.L. Chen, M.J. Park, P. Fragouli, H. Iatrou, N. Hadjichristidis, D. Cookson, N.P. Balsara, Macromolecules, 40 (2007) 4578.

V. Abetz, T. Goldacker, Macromolecular Rapid Communications, 21 (2000) 16.

K.J. Harry, D.T. Hallinan, D.Y. Parkinson, A.A. MacDowell, N.P. Balsara, Nature Materials, 13 (2014) 69.

Figure 1
Subphthalocyanines: Supramolecular Organization and Self-Assembling Properties
Authors: Torres Tomas , Guilleme Julia , González-Rodríguez David , Sánchez-Molina Irene , Claessens Christian G , Zango German , Martínez-Díaz M. Victoria , Guzman David , Vazquez Purificacion , Koji Naoda , Rodriguez-Morgade M. Salome , Trukhina Olga
Published: February 2020

Subphthalocyanines (SubPcs), phthalocyanine analogues, are intriguing compounds made of three diiminoisoindoline units N-fused around a boron atom. Their 14 pi-electron aromatic core associated with their curved structures render them appealing building blocks for the construction of multicomponent photo- or electroactive assemblies. Recently, the development of an improved synthetic methodology for axially substituted SubPc allowed the efficient synthesis of a variety of SubPc-based hybrids.

 To enhance the understanding of the nature of these curve pi-extended surfaces, we have undertaken a series of studies, including the synthesis and characterization of subphthalocyanine-based capsules. These supramolecular systems have been successfully been employed for the encapsulation of fullerenes. Furthermore, it was possible to evaluate the binding constants of the host-guest complexes. Finally, a full study of the photophysical properties revealed that the subphthalocyanines can undergo an energy transfer transduction of singlet excited state energy to the fullerene inside the cavity upon photoexcitation.

 SubPc pi-systems can be organized at supramolecular level. Thus, the self-assembly of axial dipolar subphthalocyanine molecules in the presence of electric fields leads to uniaxially oriented columnar liquid crystalline materials that exhibit permanent polarization.

 References

Sánchez-Molina, I.; Grimm, B.; Claessens, C. G.; Krick-Calderón, R.; Guldi, D. M.; Torres, T. J. Am.
Chem. Soc. 2013, 135, 10503-10511.

Sánchez-Molina, I.; Claessens, C. G.; Grimm, B.; Guldi, D. M.; Torres, T. Chem. Sci.
2013, 4, 1338-1344

Claessens, C. G.; Gonzalez-Rodriguez, D.; Rodríguez-Morgade, M. S.; Medina, A.; Torres, T. Chem. Rev., 2014, 114, 2192−2277.
ORR Catalyst Based on Polypyrrole Nanowires with Electrochemically Immobilized Macrocycles
Authors: Sansiñena José-María , Chlistunoff Jerzy
Published: February 2020

Optimizing the amount of platinum, and eventually avoiding its use, is one of the ultimate goals for polymer electrolyte fuel cells (PEFC). In this regard, different approaches have been investigated such as using platinum alloys with non-precious metals, preparing particles with a non-precious metal core and a platinum shell, and by the use of novel supporting materials [1-3].

As part of the latter effort, carbon has been the most widely used electronically conducting support to obtain higher active surface area and efficiency. In addition, nanostructured conducting materials like carbon nanotubes, nanofibers and mesoporous carbon have also been used for supported metal catalysts [4-7].

The work we are presenting involves the development of a new class of ORR catalysts based on polypyrrole nanowires with immobilized macrocycles, which are incorporated into the polymer during the electropolymerization process as counterions. In this new approach polypyrrole nanowires play the role of a conductive supporting material while the incorporated macrocycles provide the active centers for ORR catalysis (Figure 1).

Electrochemical characterization, including RRDE studies, was performed to determine the catalytic properties of the new conductive nanostructured material. For this purpose, the catalyst was electrochemically deposited on a glassy carbon disk electrode in presence of the macrocycles as supporting electrolyte in order to incorporated them into the polymer as counterions.

 Conclusions

The new ORR catalyst based on polypyrrole nanowires with immobilized macrocycles showed promising RRDE results for ORR catalysis. Furthermore, this catalyst demonstrated good potential as a new class of non-precious metal catalyst without involving pyrolysis steps during the preparation process.

 Acknowledgement

The financial support from the University of California (grant 12-LR-237440) is gratefully acknowledged.

 References

P.H. Matter, E.J. Biddinger, U.S. Ozkan, in Catalysis Book Series, Spivey. J., Editor,  Royal Society of Chemistry, 20, 338-361, Cambridge, (2007).

Mark K. Debe, Alison K. Schmoeckel, George D. Vernstrom, Radoslav Atanasoski, J. Power Sources, 161, 1002–1011 (2006).

W.S. Shi, P. Liang, D. Ge, J. Wang, Q. Zhang, Chem. Commun.,  2414–2416 (2007).

H. Zhao, L. Li, Jun Yang, Y. Zhang, Journal of Power Sources, 184, 375–380 (2008)

R. Dersch, M. Steinhart, U. Boudriot, A. Greiner, J. H. Wendorff, Polym. Adv. Technol., 16, 276–282 (2005).

T. Ochi, Biochem. Biophysic. Res. Commun., 11, 67–70 (2004).

G. G. Wallace, P.C. Innis, J. Nanosci. Nanotechnol., 2, 441–451 (2002)

Figure 1. SEM picture of the new class of ORR catalysts based on polypyrrole nanowires with immobilized macrocycles with ORR catalysis centers.

Figure 1
Heme Ruffling in Cytochrome c As a Mechanism to Control Electron Transfer
Authors: Champion Paul M
Published: February 2020

Recent studies of a variety of heme protein systems demonstrate that impulsively driven Raman vibrational coherence (or vibrational coherence spectroscopy) is a sensitive probe of thermally accessible and functionally relevant distortions of the active site heme chromophore. The observed signals involve otherwise symmetry forbidden optically driven coherent motions that become allowed due to protein-induced distortions of the heme along its out-of-plane normal modes. The low frequency (ℏω < kBT~300K~200 cm-1) of such modes allow the efficient extraction of energy from the thermal bath so that it can be utilized it for barrier crossing. An example of such a situation is the heme doming motion, which is a key reaction coordinate for ligand binding. Generally, the low frequency out-of-plane modes of the heme are prime candidates to serve as biochemical reaction coordinates. The mixing with other delocalized low-frequency modes of the protein, or with binding partners, offers a potential control mechanism.

In order to probe the effect of heme “ruffling” on electron transport, we studied three cytochromes that display a wide variation in the protein-induced distortion along this mode1. As the ruffling distortion is increased, the ruffling mode frequency decreases from ~ 60 cm-1 to ~ 45 cm-1.  The photoreduction cross-section is also measured and found to decrease exponentially as a function of the magnitude of the distortion. Given the similarity in the distance between the heme and the nearest aromatic amino acid for all three proteins, the order-of-magnitude changes in photoreduction rate demonstrate that the ruffling coordinate can serve as a control mechanism for electron transport in heme proteins. For example, major differences in heme ruffling are noted for cytochrome c when bound to the mitochondrial membrane compared to its solution structure.

1.  Y. Sun, A. Benabbas, W. Zeng, J. Kleingardner, K. Bren, and P. M. Champion, Proc. Natl. Acad. Sci.(USA) 111, 6570-6575 (2014).
The Molecular Approach for Artificial Photosynthesis
Authors: Aukauloo Ally , Sircoglou Marie , Herrero Christian , Leibl Winfried , Quaranta Annamaria , Cherdo Stephanie , ElGhachtouli Sanae
Published: February 2020

Nature has provided us with the main clues how to use solar energy to power multielectronic catalytic reactions leading to its storage in form of chemical bonds. A key feature is that nature uses molecular metal complexes based on earth abundant metal ions at the active catalytic sites of most enzymes participating in the main energetic transduction pathways. Therefore, replicating these activities using synthetic molecular complexes is a central research theme. Photosystem II, the enzyme responsible for the water oxidation can be conceptualised as being made up of two parts: a photoactive unit and a catalytic module held at optimised distances through the protein matrix.  We are involved in the design of modular assemblies of photoactive units and molecular based catalytic unit for the photoactivation of water. We will discuss on our work to use Click chemistry to develop a library of modular ensembles for the study of light induced electron transfer and our effort in the understanding of water activation in the oxygen atom transfer reactions. We will also present our latest results in the field of molecular catalyst for the production of H2.
Synthesis of Biologically Relevant Compounds Catalyzed By Metal Porphyrin Complexes
Authors: Gallo Emma , Zardi Paolo , Carminati Daniela Maria , Tseberlidis Giorgio
Published: February 2020

The direct amination of hydrocarbons is a reaction of great synthetic interest because of the biological and pharmaceutical relevance of aza-derivatives. For several years we have studied the formation of C-N bonds using aryl azides (ArN3)1 as nitrogen sources and metal porphyrins as catalysts. Amongst all the metal porphyrin catalysts,2 ruthenium porphyrins show a good catalytic activity in both inter- and intramolecular transfer of a nitrene functionality “ArN” from aryl azides into C-H bonds. The sustainability of the synthetic procedure is related to the high atom efficiency of azides which insert the aza-fragment into the organic skeleton with the formation of benign molecular nitrogen as the only stoichiometric side product.

Herein we report the use of ruthenium porphyrins to promote the synthesis of biologically interesting compounds such us: a)

α-

and β

-

amino ester
by amination of benzylic C−H bonds. The methodology was also effective in synthesizing two derivatives of methyl L-3-phenyllactate in order to convert one of them into the corresponding β-lactam;3
b) dihydrophenanthridines and phenanthridines
, important core structures in a large class of pharmaceutical compounds, through the intramolecular amination of several 2-azido biaryls;4
c) C3-functionalized indoles
by an intermolecular reaction of aryl azides with alkynes. Several derivatives were synthesized with yields up to 95%, high regioselectivity, and without requiring the time consuming prefunctionalization of reagents and the addition of oxidants and/or additives.5

In addition, we describe the catalytic activity of glicoporphyrin derivatives in amination reactions. It is worth noting that the use of these catalytic materials with very low toxicity could enhance the eco-sustainability of the entire synthetic process.

References:

[1] a) S. Cenini, E. Gallo, A. Caselli, F. Ragaini, S. Fantauzzi, C. Piangiolino Coord. Chem. Rev.
2006, 250, 1234; b) D. Intrieri, P. Zardi, A. Caselli, E. Gallo Chem. Commun., 2014, 50, 11440. [2] S. Fantauzzi, A. Caselli, E. Gallo Dalton Trans, 2009, 5434. [3] P. Zardi, A. Caselli, P. Macchi, F. Ferretti, E. Gallo Organometallics
2014, 33, 2210. [4] D. Intrieri, M. Mariani, A. Caselli, F. Ragaini, E. Gallo Chem. Eur. J.
2012, 18, 10487. [5] P. Zardi, A. Savoldelli, D. M. Carminati, A. Caselli, F. Ragaini, E. Gallo ACS Catal.
2014, 4, 3820.

Figure 1
Semiconductive Properties of Passive Films on Carbon Steel Rebar in Highly Alkaline Environments
Authors: Williamson Jon , Isgor Burkan
Published: February 2020

In the highly alkaline environment of concrete, carbon steel rebar is protected against corrosion by a passive oxide/oxyhydroxide film. Understanding the characteristics of this passive film, and how it depassivates, is the key to mitigate problems associated with steel corrosion in concrete. Although a large number of electrochemical and analytical studies have been conducted on the passivity of steel in concrete, current mechanistic models do not explain all experimental observations about the chloride-induced depassivation process. One area that is not studied extensively is the electronic properties of passive films which show semi-conductive properties; a better understanding of these properties will provide additional information to improve the mechanistic models for chloride-induced depassivation of carbon steel in concrete. The present study uses Mott-Schottky (M-S) analysis along with other electrochemical techniques to study the electronic properties of passive films that form on carbon steel exposed to simulated concrete pore solutions. Both passivation and chloride-induced depassivation processes are investigated, and changes in electronic properties during these processes are monitored. The main parameters of the study include the concrete pore solution composition, pH, and chloride amount. Challenges of using M-S analysis to study the electronic properties of passive films will also be discussed.
Corrosion Monitoring of Reinforcing Steel in Concrete By Electrochemical Impedance Spectroscopy
Authors: Hoshi Yoshinao , Soukura Masanori , Shitanda Isao , Itagaki Masayuki , Kato Yoshitaka
Published: February 2020

The corrosion of the reinforcing steel in concrete is strongly related to the loss of cover concrete and the steel bar diameter. These effects may cause sudden failure of a structure. Therefore, it is important to obtain the corrosion rate of the reinforcing steel in concrete precisely.

An electrochemical impedance spectroscopy (EIS) is the powerful method for evaluating the conditions of the reinforcing steel because the EIS enables us to discriminate the time constants of elementary steps in the dissolution process without causing damage to the electrodes. We applied the EIS to monitor the corrosion rate of the reinforcing steel in concrete. In order to establish the method of the corrosion monitoring by EIS, the effects of the covering depth and the concentration of chloride ions on the corrosion of the reinforcing steel in concrete were investigated. All reinforcing steels were cast using a concrete. The covering depth of the concrete is 10, 20 or 30 mm. The water-cement (W/C) ratio of the concrete is 40, 50 or 60. A NaCl was used as the source of the chloride ions. Impedance measurements were performed by a two-electrode system using potentiostat (Solartron, 1287) and a frequency response analyzer (FRA) (Solartron, 1255B) combined with oscilloscope (IWATSU, SS-7802). The working electrode and the counter electrode were the reinforcing steel. The impedance spectra were measured in the frequency range from 10 mHz to 1 MHz at 5 frequencies per decade with AC amplitude of 10 mV. The impedance spectra of the reinforcing steels in concrete with different covering depth and concentrations of chloride ions were discussed.
The Role of Grain Boundaries during the Initial Oxidation Stages in Cu-Added Austenitic Stainless Steel at 700 °C Studied at the Atomic Scale
Authors: Kim Ju-Heon , Kim Byung Kyu , Kim Dong-Ik , Choi Pyuck-Pa , Raabe Dierk , Yi Kyung-Woo
Published: February 2020

The early stages of the oxidation behavior (≤ 12 h, in air with 20% water vapor at 700°C) of Cu-added austenitic stainless steels with various grain sizes was investigated using atom probe tomography (APT), transmission electron microscopy (TEM), scanning electron microscopy (SEM), electron backscattered diffraction (EBSD), electron probe microanalyzer (EPMA) and X-ray diffraction (XRD). A thin Cr-rich oxide layer is formed over the entire surface of a small-grained (8 µm) sample, which is similar to that formed near grain boundaries of medium-grained (17 µm) and large-grained (27 µm) samples. Oxidation of all samples proceeds via the lattice and grain boundary diffusion of Cr, leading to the formation of a protective Cr-rich oxide first at the grain boundaries and then via lateral growth toward the grain interiors. APT and TEM studies clearly reveal that within 4 μm of the grain boundaries, the oxide layer exhibits a duplex-layer structure consisting of a thin Fe-rich (Fe,Cr)3O4 oxide (~55 nm) above and a protective Cr2O3 oxide (~40 nm) below as a diffusion barrier. In contrast, further away from the grain boundaries, a non-protective Fe-rich (Fe,Cr)3O4 oxide (~160 nm) and a Cr-rich (Fe,Cr)3O4 oxide (~40 nm) are formed as the outer and inner layers, respectively. The oxidation kinetics was studied in terms of mass gain measurements. The critical grain size (< 8 µm) to prevent the formation of fast-growing, non-protective Fe-rich oxides is discussed based on the experimental findings.
Different Vanadium Compounds Ash Corrosion of Boilers Using Heavy Fuel Oil
Authors: Montero Xabier , Galetz Mathias C
Published: February 2020

Vanadate induced or accelerated corrosion is observed in fossil energy conversion systems. The combustion of poor quality fuel oils with high asphaltene mounts and other vanadium and sulfur rich-compounds produces ash deposits on components such as heat exchangers, boilers or turbine blades and vanes. Boiler steel tubes are reported to be highly sensitive to this kind of high temperature corrosion enhanced by liquid phase fuel oil ash deposits.

The mechanisms of hot corrosion by molten sulfate-vanadate deposits were investigated for low and medium chromium steels as well as aluminide coated steels with different ash deposits containing CaSO4, Ca3(PO4)2, NaCl, Na2O and Na2S04 their combinations with V205. All samples were exposed to the ash deposits at 600°C in laboratory air. The deposits and the exposed surfaces were characterized by XRD, SEM and EPMA.
High-Temperature Corrosion Characteristics of Nano-Structured Coatings in Secondary System of Nuclear Power Plants
Authors: Kim Seung Hyun , Kim Jeong Won , Kim Ji Hyun
Published: February 2020

Flow-accelerated corrosion (FAC) of carbon steel pipe systems in secondary system of nuclear power plants is one of the materials degradation issue in nuclear industry. In this study, the feasibility of nano-structured coating application based on electroless nickel plating and high-velocity oxy-fuel (HVOF) is investigated in order to reduce or mitigate the FAC of carbon steel pipes in the secondary system of nuclear power plants. While nano-structured coatings generally show higher corrosion resistance and mechanical properties compared to traditional coating techniques and additionally with low surface roughness, their corrosion characteristics in high temperature water were not evaluated fully enough.  In this study, therefore, their corrosion characteristics in ammonia and mono ethanol amine (ETA) electrolyte at room temperature as well as high temperature are firstly evaluated by potentiodynamic polarization measurement and electrochemical impedance spectroscopy. From this study, it is observed that the metal loss of coated carbon steels are drastically decreased compared to as-polished carbon steels.
Polymer Supported and Freestanding Transparent Electrodes Produced By Ink-Jet Printing and Electrodeposition
Authors: Oriani Andrea Vittorio , Spreafico Marco Alberto , Cojocaru Paula , Marrani Alessio , Triulzi Francesco , Apostolo Marco , Magagnin Luca
Published: February 2020

Transparent conductive electrodes play an important role in different applications, as thin-film solar cells, flat-panel displays and light emitting diodes1-3. With the increasing demand arising from flexible devices, mechanical properties of electrodes are becoming more and more important and alternatives to traditional materials are being investigated4,5. Doped metal oxides, e.g. ITO, are mostly used at the moment, but their main limitation derives from their ceramic nature that makes them brittle and therefore prone to cracking, when deposited on flexible substrates6. We studied the production of metallic micronets, with the aim of finding an alternative to ITO for transparent conductive electrodes. The use of metals, which are the materials owning the highest performances in terms of electrical conductivity, allows maintaining the desired level of transparency of the electrode, given by the optimization of the geometrical parameters of the micro-net.  Both polymer supported and free standing metallic micronets were produced. To obtain the former structure, a conductive Ag pattern was printed on PET substrate using ink-jet printing (an example is shown in Figure 1), and then a copper layer can be grown by electrodeposition on the silver printed lines, to obtain the freestanding structure. Release of the metallic micro-net from the PET substrate is spontaneously obtained during the electrodeposition step. Electrical and optical properties of the produced electrodes were investigated. The free-standing metallic micro-net has resistivity two orders of magnitude lower than a commercially available sample of ITO-coated PET, while maintaining high transparency.

Figure 1: SEM image of Ag pattern printed on PET substrate

References

1. S. Reineke, F. Lindner, G. Schwartz, N. Seidler, K. Walzer and K. Leo, Nat. Lett., 459, 234 (2009).

2. A. C. Arias, J. D. MacKenzie, I. McCulloch, J. Rivnay and A. Salleo, Chem. Rev., 110, 3 (2010).

3. J. J. Shiang, Interface, 18, 37 (2009).

4. H. Chang et al., Adv. Funct. Mater., 20, 2893 (2010)

5. L. Hu et al., ACS Nano, 4, 2955 (2010)

6. Z. Chen, Thin Solid Films, 394, 201 (2001)

Figure 1
Three Dimensional Modeling of Dendrite Growth in Rechargeable Lithium Metal Batteries
Authors: Aryanfar Asghar , Brooks Daniel J , Cheng Tao , Merinov Boris V , Goddard William A , Colussi Agustin J , Hoffmann Michael R
Published: February 2020

One of the most critical issues leading to failure in researchable batteries is the tendency to grow amorphous crystals called dendrites during charge periods. These microstructures cause the internal short circuit between electrodes and lead to possible ignition of organic electrolytes.[1] Lithium batteries, particularly are more prone to form dendrites due to low surface energy of lithium. The tendency for creating more surfaces leads to formation of isolated dendrites known as dead lithium. Particularly rechargeable lithium metal batteries suffer the most from this matter due to dominance of deposition over intercalation on crystalline and compact structure of the metal. [2]

 Herein, we present a new three dimensional framework, extended from our previous Coarse Grained method[3], for predicting the intrinsic properties and internal structure of meta-stable lithium dendrites. A sample of dendrite is given in Fig. 1. We have investigated annealing of dendrites in various temperatures, resulting in stable atomic arrangements. (Fig. 2). We will characterize the physical and mechanical properties of acquired morphologies, such as porosity and compressive strength. 

1.     Armand, M. and J.M. Tarascon, Building better batteries. Nature, 2008. 451(7179): p. 652-657.

2.     Li, Z., et al., A review of lithium deposition in lithium-ion and lithium metal secondary batteries. Journal of Power Sources, 2014. 254: p. 168-182.

3.     Aryanfar, A., et al., Dynamics of Lithium Dendrite Growth and Inhibition-Pulse Charging Experiments and Monte Carlo Calculations. The Journal of Physical Chemistry Letters, 2014.

Figure 1