bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrochemical Studies of Cysteine
Authors: Worosz Matthew A. , Cheek Graham T.
Published: February 2020

Introduction

 L-Cysteine is an important amino acid because of its role in various biochemical pathways (1). The sulfhydryl functional group gives L-cysteine significant redox characteristics, prompting an investigation of its electrochemical behavior in various media and electrode surfaces. The interaction of protein cysteine residues with Zn2+ (“zinc fingers”) also suggested a voltammetric study of the effect of Zn2+ on L-cysteine electrochemistry.

 

Experimental

 L-Cysteine was obtained from Sigma-Aldrich. Electrochemical experiments were carried out using a Gamry Interface 1000 potentiostat and Gamry Framework software. Potentials are referenced against a Ag/AgCl reference electrode. Platinum and glassy carbon electrodes were obtained from BASi. Gold electrodes were purchased from eDAQ. 

 

Results and Discussion

 The voltammetric behavior of 5 mM Zn2+ in 0.10 M KNO3 is shown in the figure. Zinc deposition at -1.0 V was not very distinct, and there was no well-defined stripping peak. Addition of equimolar L-cysteine produced a definite stripping peak at -0.8 V, evidently an effect of complexation of Zn2+ by L-cysteine. The L-cysteine voltammetry was also affected by the presence of Zn2+. At platinum and gold with no addition of Zn2+, oxidation of L-cysteine occurred as merged peaks at +0.8 and +1.0 V (2), with no oxidation feature at +0.6 V. Even with Zn2+ added to L-cysteine n solution, an initial positive-going scan gave no +0.6 V peak, and scanning through the zinc reduction/stripping region was necessary to produce the +0.6 V feature on the second sweep to more positive potentials as shown in the figure.  The stripping of the zinc layer from the gold surface may produce a renewed gold surface which allows strong adsorption of L-cysteine on gold. In general, L-cysteine is known to interact strongly with gold surfaces (3).

 

References

C. K. Mathews, K. E. Van Holde, D. R. Appling, and S. J. Anthony-Cahill, Biochemistry, 4th Edition, Pearson Canada, Toronto, 2013.

J. Koryta and J. Pradac, J. Electroanal. Chem., 1968, 17, 185-189.

A. J. Tudos, P. J. Vandeberg, and D. C. Johnson, Analytical Chem., 1995, 67, 552-556.

Figure 1. Cyclic voltammograms at gold (1 mm diameter) in aqueous 0.10 M KNO3. 100 mV/s.

[ Dashed line : 5.0 mM ZnSO4 ]  [ Solid line : 5.0 mM ZnSO4 + 5.3 mM L-cysteine ]

Figure 1
Rationalized Onion-like Non-PGM Catalyst Development for Oxygen Reduction Reaction
Authors: Narvaez Villarrubia Claudia Wuillma , Yen Hung-Ju , Chen Gen , Li Hombo , Zhou Ming , Jiang Ying-Bing , Artyushkova Kateryna , Atanassov Plamen , Gupta Gautam , Wu Gang , Wang Hsing-Lin
Published: February 2020

Fuel cell technology is a green alternative to conventional combustion engine technology. At the cathode of the fuel cell, the oxygen reduction reaction (ORR) takes place. The state-of-the-art catalysts for this reaction are platinum (Pt)-based materials. At the fuel cell’s anode, Pt-based catalyst is also needed. The limited activation and reduction of oxygen on the cathode force to increase the loading of Pt-catalysts when compared to the anode. As a result, the practical fuel cell application is constrained by the expensive and volatile price of the Pt-market; the Pt-catalysts represent the 40% of the cost of the fuel cell.

The development of inexpensive non-Pt catalysts are the center of investigation in the last decades and the development of non-Pt group metal (Non-PGM) catalysts, nitrogen-doped carbon materials, are promising alternatives. These are, typically, synthesized from metal salts and organic nitrogen and carbon precursors. The precursors are pyrolyzed at elevated temperatures, in an inert environment, to form the active structures for oxygen reuction catalysis. N-doped onion-like carbon nanostructures have being developed to achieve ORR catalysis. However, the mechanism of formation of these structures is not very well understood nor controlled.

In this research, we aimed to rationally control the active site nanoarchitectures for ORR in acid media. Onion-like nanoarchitectures are developed as catalytic structures by handling the chemistry of the carbon and nitrogen precursors and the reaction leading to the formation of the onion-like nanostructures. These structures are inserted in a carbon-based conductive matrix that serves as electron collector. Results show these controlled nanoarchitectures are promising Non-PGM materials for ORR catalysis.

Steele, B. C. H.; Heinzel, A. Materials for Fuel-Cell Technologies. Nature 2001, 414, 345–352.

Shao, Y. Y.; Liu, J.; Wang, Y.; Lin, Y. H. Novel Catalyst Support Materials for PEM Fuel Cells: Current Status and Future Prospects. J. Mater. Chem. 2009, 19, 46–59.

Wu, G.; Nelson, M.; Ma, S.; Meng, H.; Cui, G.; Shen, P. K. Carbon. 2011, 49, 3972-3982.
(Invited) Plasmon-Induced Charge Separation: Mechanisms and Applications
Authors: Tatsuma Tetsu , Nishi Hiroyasu
Published: February 2020

Plasmonic nanoparticles, which are characterized by strong light absorption, scattering, and their controllability, attract much attention as new photofunctional materials. Plasmonic metal nanoparticles in contact with semiconductor exhibit charge separation under visible and near infrared light, i.e. plasmon-induced charge separation (PICS, Fig. 1).1 PICS involves carrier transfer from plasmonic nanoparticles (e.g. gold or silver nanoparticles) to semiconductor (e.g. TiO2)1-3 due to external photoelectric effect, hot carrier injection, or interfacial electron transition. In addition, PICS and/or accompanying redox reactions are accelerated by localized electric field (i.e. optical near field).4,5

PICS attracts increasing attention, because it can be applied to wet1 or solid-state6 photovoltaics under visible and near infrared light. It is also applied to photocatalysis1 and LSPR sensors,7 in which stable gold nanoparticles are used. In the case where less stable silver nanoparticles are used, PICS gives rise to oxidative dissolution of silver to silver ions. This process can be applied to multicolor photochromism,8 near infrared photochromism,9 single nanoparticle multicolor changes,5 and photomorphing hydrogels.10

1. Y. Tian and T. Tatsuma, J. Am. Chem. Soc., 127, 7632 (2005).

2. T. Tatsuma, Bull. Chem. Soc. Jpn., 86, 1 (2013).

3. E. Kazuma and T. Tatsuma, Adv. Mater. Interfaces, 1, 1400066 (2014).

4. E. Kazuma, N. Sakai, and T. Tatsuma, Chem. Commun., 47, 5777 (2011).

5. I. Tanabe and T. Tatsuma, Nano Lett., 12, 5418 (2012).

6. Y. Takahashi and T. Tatsuma, Appl. Phys. Lett., 99, 182110 (2011).

7. T. Tatsuma, Y. Katagi, S. Watanabe, K. Akiyoshi, T. Kawawaki, H. Nishi, and E. Kazuma, Chem. Commun., 51, 6100 (2015).

8. Y. Ohko, T. Tatsuma, T. Fujii, K. Naoi, C. Niwa, Y. Kubota, and A. Fujishima, Nat. Mater.,
2, 29 (2003).

9. E. Kazuma, and T. Tatsuma, Chem. Commun., 48, 1733 (2012).

10. T. Tatsuma, K. Takada, and T. Miyazaki, Adv. Mater., 19, 1249 (2007).

Figure 1
Platinum Electrodeposition on in-Situ Grown Prussian Blue Nanostructures and Reduced Graphene Oxide Composite for Synergistic Methanol Oxidation
Authors: Kim Kyuwon , Kang Inhak , Manivannan Shanmugam
Published: February 2020

We report a synthesis for in-situ growth of Prussian blue nanostructures (PB NSs) at the amine functionalized silicate sol–gel matrix (TPDT)–RGO composite via the electrostatic interaction. Pt nanostructures are electrodeposited onto the preformed ITO/TPDT–RGO–PB electrode to prepare the RGO/PB/Pt catalyst. The significance of the present method is that the PB NSs are in-situ grown by inter-connecting the RGO layers, led to 3D porous nanostructure. The modified electrodes are characterized by FESEM, EDAX, XRD, XPS and electrochemical techniques. The RGO/PB/Pt catalyst exhibits synergistic electrocatalytic activity and high stability towards methanol oxidation. The porous nature of the TPDT and PB, and unique electron transfer mediating behavior of PB integrated with RGO in the presence of Pt nanostructures, facilitated synergistic electrocatalytic activity for methanol oxidation.
Structure, Electronic Properties and Electrochemical Behavior of a Boron-Doped Diamond/Quartz Optically Transparent Electrode
Authors: Swain Greg M , Jarosova Romana , Wachter Naihara , Munson Catherine
Published: February 2020

This presentation will review the morphology, microstructure, chemistry, electronic properties and electrochemical behavior of a boron-doped nanocrystalline diamond (BDD) thin film grown on quartz. Diamond optically transparent electrodes (OTEs) are useful for transmission spectroelectrochemical measurements offering excellent stability during anodic and cathodic polarization and exposure to a variety of chemical environments.1,2 An example will be shown of how the OTE in a spectroelectrochemical measurement can be used to study the redox mechanism of the model analyte, chlorpromazine.1 We will also report on the characterization of the BDD OTE by AFM, optical spectroscopy, Raman spectroscopic mapping, AC Hall Effect measurements, XPS and electrochemical methods. Cyclic voltammetry was used to investigate the background current response as a function of potential, scan rate and electrolyte composition. Cyclic voltammetry and digital simulation were used to determine the heterogeneous electron-transfer rate constants (ko) for IrCl6
2-/3-, Fe(CN)6
3-/4-, ferrocene carboxylic acid, Ru(NH3)6
3+/2+ and methyl viologen. The diamond OTE supports relatively rapid electron transfer for a wide range of redox systems with formal potentials from ca. 0.9 to -1.0 V vs. Ag/AgCl. Capacitance-potential measurements were made in aqueous electrolyte solutions and ionic liquids to better understand the organization of electrified interfaces formed at this electrode. The work constitutes the first comprehensive study of the relationship between the physical and chemical structure and electronic properties of a diamond OTE, and the electrode’s electrochemical activity.

1. Stotter, J; Zak J; Behler Z; Show Y; Swain GM. Optical and Electrochemical Properties of Optically Transparent, Boron-Doped Diamond Thin Films on Quartz. Anal. Chem. 2002, 74, 5924-5930.

2. Stotter J; Show Y; Wang S; Swain GM. Comparison of the Electrical, Optical and Electrochemical Properties of Diamond and Indium Tin Oxide Thin-Film Electrodes. Chem. Mater. 2005, 17, 4880-4888.
Tunable Electrocatalytic Performance of Metal Nanocrystals By Tailoring Surface Electronic Structures
Authors: Xiong Yujie
Published: February 2020

Nanocrystals of noble metals have been widely used as electrocatalysts in various reaction systems.  As heterogeneous electrocatalytic reactions take place at catalyst surface, the efficiency relies on the interactions of surface with reaction species.  For this reason, the electrocatalytic performance can be tuned by tailoring the surface electronic structures of solid materials.  In this talk, I will demonstrate a new approach to maneuvering the surface electronic structures through interfacial or interatomic charge polarization between noble metals and other materials.  The charge polarization provides a versatile tool for tailoring the charge densities and d-band centers of surface catalytic sites.  Leveraging chemical bonding, we have developed methods for forming material interfaces at atomic precision in core-shell or alloy nanostructures, which allows to implementing the charge polarization mechanism in multiple electrocatalytic systems.  The number of active sites and their activity can be controlled by altering the interfacial dimensions.  It is anticipated that this work will provide insights into the rational design of hybrid catalytic nanomaterials through interface engineering.

 

References.

1. Du, N.; Wang, C.; Wang, X.; Lin, Y.; Jiang, J.; Xiong, Y.*,
Adv. Mater.

2016
,
28, 2077-2084.

2. Ma, L.; Wang, C.; Xia, B. Y.; Mao, K.; He, J.; Wu, X.; Xiong, Y.;* Lou, X. W.*, Angew. Chem. Int. Ed.
2015, 54, 5666-5671.

3. Bai, S.; Wang, C.; Deng, M.; Gong, M.; Bai, Y.; Jiang, J.; Xiong, Y.*, Angew. Chem. Int. Ed.
2014, 53, 12120-12124.

4. Ma, L.; Wang, C.; Gong, M.; Liao, L.; Long, R.; Wang, J.; Wu, D.; Zhong, W.; Kim, M.;* Chen, Y.; Xie, Y.; Xiong, Y.*, ACS Nano
2012, 6, 9797-9806.

5. Liu, D.; Xie, M.; Wang, C.;* Liao, L.; Qiu, L.; Ma, J.; Huang, H.; Long, R.; Jiang, J.;* Xiong, Y.*, Nano Res. DOI: 10.1007/s12274-016-1053-6.
Integrating Enzymes into Cytochrome c –Based Multilayer Architectures – General Considerations and Example with Fructose Dehydrogenase
Authors: Lisdat Fred , Wollenberger Ulla , Kano Kenji , Wettstein Christoph
Published: February 2020

The creation of artificial electron transfer (ET) chains based on the defined arrangement of enzymes and redox proteins on electrode surfaces represents an interesting field in bioelectronics1. One approach exploits the self exchange properties of cytochrome c (cyt c) to build up new sensing electrodes2.

In this study we have investigated the ET reaction of the flavin-dependent enzyme fructose dehydrogenase (FDH) with the redox protein cyt c. Two different pH optima are detected for the reaction of both proteins in solution - at acidic and neutral pH. When one reaction partner - cyt c - is immobilized on a thiol-modified gold electrode and FDH is in solution ET proceeds efficiently at neutral pH which can be concluded from well-shaped catalytic currents obtained in cyclic voltammetry. In addition, a defined dependence on the substrate concentration has been found. In acidic media the reaction can also be verified but appears to be less efficient.

Furthermore, it can be demonstrated that both partners can be assembled in a stable multilayer architecture, using the biopolymer DNA as a negatively charged polyelectrolyte building block. The defined layered deposition of DNA and a mixture of FDH and cyt c is confirmed by surface plasmon resonance (SPR) measurements. Prepared on electrodes, substantial catalytic currents are recorded upon addition of fructose. The response can be enhanced by the number of layers deposited on the surface. This shows that an artificial signal chain can be constructed through multiple protein layers.

FDH is not the only enzyme which can be immobilized and connected to the electrode by means of the redox protein cyt c. Cellobiose dehydrogenase, sulfite oxidase or billirubin oxidase are other examples3,4. This may indicate that cyt c based multilayers can have some general applicability when some preconditions are fullfilled.

1. Feifel et al , in Biosensors Based on Aptamers and Enzymes, Springer 2014, 140, 253-298

2. Lisdat et al., Chemical Communications 3 2009, 274-283.

3. Feifel et al., Angew. Chemie 126(22) 2014 5782-86

4 Dronov et al. JACS 2008 130(4) 1122.
Electrochemical Reduction of Atrazine at Carbon and Silver Cathodes
Authors: Martin Erin Theresa , Peters Dennis G
Published: February 2020

Since its introduction in the 1950s, atrazine (6-chloro-N2-ethyl-N4-(1-methylethyl)-1,3,5-triazine-2,4-diamine) has become one of the mostly widely used pesticides in the world. Although atrazine has been banned in the European Union since 2004, it is still applied extensively in the US, and can be detected in water sources, soil, and even air.1 Environmental persistence of atrazine and its metabolites has caused contamination to spread away from regions of herbicide application, and some studies have shown evidence of endocrine disruption in amphibians exposed to these chemicals.1 For these reasons, the degradation of atrazine to less environmentally harmful compounds is of great concern.

In this study, we have employed electrochemical reduction for the degradation of atrazine at different cathode materials. Previous electrochemical studies of atrazine have been performed at mercury cathodes, and were successful in both the detection of atrazine by means of square-wave voltammetry and its degradation through controlled-potential (bulk) electrolyses.2-4 At mercury cathodes, long electrolyses resulted in both the breaking of the carbon–halogen bond and reduction of the triazine ring.4 To avoid the use of mercury, we have explored the use of carbon and silver cathodes; glassy carbon provides a simple, environmentally friendly alternative, whereas silver has been shown to be catalytic for the cleavage of carbon–halogen bonds. Reduction of atrazine at carbon and silver cathodes, respectively, in dimethylformamide (DMF) containing 0.050 M tetramethylammonium tetrafluoroborate (TMABF4), results in a single cyclic voltammetry peak at –1.77 or –1.62 V vs. a Cd(Hg) reference electrode. Investigations of the products arising from controlled-potential electrolysis by means of gas chromatography–mass spectrometry indicate the presence of dechlorinated atrazine (N2-ethyl-N4-(1-methylethyl)-1,3,5-triazine-2,4-diamine) after electrolyses at both carbon and silver cathodes.

References

1. Jablonowski, N. D.; Schäffer, A. Environ. Sci. Pollut. Res.
2011, 18, 328–331.

2. dos Santos, L. B. O.; Silva, M. S. P.; Masini, J. C. Anal. Chim. Acta
2005, 528, 21–27.

3. Maleki, N.; Absalan, A.; Farjami, S. E. Anal. Chim. Acta
2007, 581, 37–41.

4. Caetano, J.; Homem-de-Mello, P.; da Silva, A. B. F.; Ferreira, A. G.; Avaca, L. A. J. Electroanal. Chem.
2007, 608, 47–51.

Figure 1
Characterization of the Electrochemical Behavior of a Li-Bi Reference Electrode for the Molten LiCl-Li
Authors: Phillips William , Merwin Augustus , Singh Vickram , Chidambaram Dev
Published: February 2020

In order to maximize uranium resources and minimize the need to store radioactive material in geologic repositories, it is necessary to reprocess used nuclear fuel (UNF) to recycle the fissile material and transuranic isotopes that remain. The pyroprocessing operation developed by Argonne National Laboratory as part of the integral fast reactor project was designed to accomplish this goal while minimizing the risk of proliferation (1). Inclusion of oxide based UNF from the current light water reactor fleet into the metallic fuel based fast reactor cycle will require electrolytic oxide reduction in a LiCl-Li2O electrolyte (2). As a side reaction during the electroreduction of U, Li is codeposited on the cathode surface and subsequently dissolves, forming a ternary LiCl-Li2O-Li electrolyte (3, 4). The presence of metallic Li in the electrolyte negates the possibility of using the reference electrodes typically used for molten salt electrochemistry. The Li-Bi couple has been used as a reference electrode previously but has not yet been well characterized (5, 6). This work investigates the stability of the Li-Bi reference couple in varying solution chemistries typical of those found during electrolytic reduction of UO2.

Acknowledgements: This work was performed under the auspices of the Department of Energy (DOE) under contracts DE-NE0008262 and DE-NE0008236, and the US Nuclear Regulatory Commission (NRC) under contracts NRCHQ-11-G-38-0039, NRC-HQ-10-G-38-0027, NRC-HQ-13-G-38-0027. W.P. and A.M acknowledge the Fellowship Award from the USNRC. Dr. Kenny Osborne serves as the program manager for the DOE award and Ms. Nancy Hebron-Isreal serves as the grants program officer for the NRC awards.

References:

1. J. J. Laidler, J. E. Battles, W. E. Miller, J. P. Ackerman, E. L. Carls, Development of Pyroprocessing Technology. Progress in Nuclear Energy
31, 131-140 (1997).

2. S. D. Herrmann, S. X. Li, M. F. Simpson, S. Phongikaroon, Electrolytic Reduction of Spent Nuclear Oxide Fuel as Part of an Integral Process to Separate and Recover Actinides from Fission Products. Separation Science and Technology
41, 1965-1983 (2006).

3. T. Takenaka, K. Shigeta, H. Masuhama, K. Kubota, Influence of Some Factors upon Electrodeposition of Liquid Li and Mg. ECS Transactions
49, 441-448 (2009).

4. A. S. Dworkin, H. R. Bronstein, M. A. Bredig, Miscibility of Metals with Salts. VI. Lithium-Lithium Halide Systems. The Journal of Physical Chemistry
66, 572-573 (1962).

5. M. Iizuka, Y. Sakamura, T. Inoue, Electrochemical reduction of (U-40Pu-5Np)O2 in molten LiCl electrolyte. Journal of Nuclear Materials
359, 102-113 (2006).

6. X. Ning et al., Self-healing Li-Bi liquid metal battery for grid-scale energy storage. Journal of Power Sciences
275, 370-376 (2015).
CO Gas Production by CO2 Gas Decomposition in Molten Salt Electrolysis
Authors: Suzuki Ryosuke O. , Matsuura Fumiya , Natsui Shungo , Kikuchi Tatsuya
Published: February 2020

If CO2 gas can be efficiently decomposed, the produced carbon can be used as the raw material of the reducing agent of iron ore. Oxygen can be also used as the blowing gas into converters. In addition, CO gas can be used as an effective fuel in industrial plants. Thus, all the products arising from CO2 decomposition can become raw materials or energy resources.

The decomposition of CO2 gas to carbon or CO gas by electrolysis is examined via the use of a combination of CaCl2-CaO melt as a media and ZrO2 solid-state electrolyte as anode. The schematic of the reactor used in this study is shown in Figure.

CO2 gas is injected through the cathodic pipe, and it is reduced near the cathode by metallic Ca that is electrochemically deposited from CaO, leading to formation of carbon or CO gas. However, CO2 gas partially dissolves to form CO3
2- with coexistence of CaO in the melt. CO3
2- precipitates carbon on the cathode. A part of carbon reacts with the blown CO2 gas to form CO gas. These two mechanisms work for effective CO2 decomposition.

The anode contained 8 mol% Y2O3 to ensure stability of the ZrO2 cubic crystal structure. By means of utilizing platinum paste as the conductor inside the ZrO2 tube instead of carbon powder, its tube can work as a good anode, and a large amount of CO gas is stably produced in the exhaust gas.

At a higher electrolysis temperature, CO2 gas is preferentially converted to CO gas. At 1273 K, the conversion ratio approached the maximum value of 88.2%.

The highest concentration of CO gas is generated by application of a cell voltage of 2.55 V, which is lower than the theoretical decomposition voltage of CaO, E
0
CaO (2.65 V at 1173 K). Therefore, CO2 gas decomposes preferentially via the decomposition reaction of carbonate ions.

We believe that our approach can contribute in reducing atmospheric CO2.

Figure 1
Transport Properties of Ionic Liquid Mixtures Containing Heterodications
Authors: Lall-Ramnarine Sharon , Fernandez Eddie , Rodriguez Chanele , Wei Sujun , Dhiman Surajdevparkash , Wishart James F.
Published: February 2020

Ionic liquid (IL) mixtures are gaining popularity as a means to access the attractive properties of individual ILs while minimizing less desirable characteristics that impede their large scale adoption. We report here on the transport properties of ionic liquid mixtures that incorporate a series of asymmetrical dications including heterodications. The dicationic ILs were designed to bear triphenyl phosphonium and trimethyl ammonium cationic sites bridged to methylimidazolium, and methylpyrrolidinium cationic sites by a carbon chain, with the Bis(trifluoromethylsulfonyl)imide (NTf2) anion. IL mixtures containing 10%, 25% and 50% dicationic NTf2 by weight with alkoxyalkyl- methylimidazolium and methylpyrrolidinium NTf2 ILs were prepared. The IL mixtures were characterized for their transport properties (temperature dependent conductivity and viscosity) and thermal properties including melting point, glass transition point, and thermal degradation point. The work at BNL was supported by the BNL Office of Educational Programs and the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences under contract DE- SC0012704.
Conductivity Maxima Vs. Temperature: Grotthuss Conductivity in Aprotic Molten Salts
Authors: Aravindakshan Nikhil P. , Kuntz Colin , Gemmell Kyle , Johnson Keith , East Allan
Published: February 2020

The phenomenon of electrical conductivity maxima of molten salts versus temperature during orthobaric (closed-vessel) conditions is further examined. Previously, in a study of molten BiCl3, a new theory was offered in which the conductivity falloff at high temperatures is due not to a shift in equilibrium, but to a rise in the barrier for atomic ions hopping from counterion to counterion. There, conductivity was presented as an ordinary Arrhenius equation in which the frequency prefactor A (for hopping opportunities) and activation energy Ea (for hopping) are density dependent. Here we further test this idea on another high-conducting melt (SnCl2, σmax = 2.81 Ω−1 cm−1) and a low-conducting one (HgBr2, σmax = 4.06 x 10-4 Ω −1 cm−1). First, ab initio molecular dynamics simulations were performed and successfully reproduced the maxima for both these liquids. Second, use of two different ab initio definitions of the Arrhenius prefactor lead to reasonable activation energies for hopping. In the HgBr2 case, a very molecular liquid like water, a clear Grotthuss chain of bromide transfers was observed in simulation when seeding the system with a HgBr+ cation and HgBr3
− anion. The main conclusion is that the Grotthuss mechanism for conduction, currently ignored for all but H+ ions, also occurs with halide ions in “covalent” metal halide melts (involving electronegative metals), and this mechanism is the cause of the conductivity maximum.
Vibrational Observation of Molecular Adsorbates on Various Well-Defined Metal Surfaces Using Gap-Mode Plasmon Enhanced Raman Scattering
Authors: Ikeda Katsuyoshi
Published: February 2020

In the research fields of heterogeneous catalysis and electrocatalysis, it is important to understand interactions between reactant molecules and catalytic surfaces. Molecule-substrate interactions are known to be highly sensitive to the surface geometry on the atomic scale. Therefore, vibrational observation of molecules on atomically defined catalytic surfaces can provide useful information for development of highly efficient catalysts. Although surface enhanced Raman scattering (SERS) is a highly sensitive vibrational spectroscopic method for studying molecule-metal interactions, it is difficult for conventional SERS to observe atomically defined planar surfaces because of the difficulty in excitation of surface plasmons. We have developed gap-mode plasmon enhanced Raman scattering spectroscopy for observing such surfaces and observed SERS spectra of molecular monolayers on various single crystalline metal surfaces . Compared with infrared absorption spectroscopy, SERS has a great advantage for in-situ observation under various conditions. In particular, SERS can detect low frequency vibrations, which can provide direct information on metal-molecule interactions or intermolecular interactions, even in aqueous solution. In this talk, we present vibrational observation of molecular adsorbates on various well-defined metal surfaces in the wide frequency region including low-frequency vibrations.
Copper-Based Electrocatalysts with Multinuclear Catalytic Sites for Oxygen Reduction Reaction
Authors: Kato Masaru , Muto Marika , Oyaizu Nobuhisa , Yagi Ichizo
Published: February 2020

The oxygen reduction reaction (ORR) to water is catalyzed at cathodes in polymer electrolyte fuel cells (PEFCs). For widespread applications of PEFCs, low-cost cathode materials with high catalytic activity and durability are highly desirable. Since natural ORR catalysts such as multi-copper oxidases catalyze the ORR with almost no overpotential (ca. 20 mV)[1]and the enzymatic ORR occurs at a multinuclear copper complex, mimicking enzymatic active sites would allow us to develop non-precious metal-based ORR electrocatalysts for practical applications.

Herein we report our research progress in synthetic and mechanistic studies on copper-based electrocatalysts for the ORR.[3,4]Our findings suggest that the design and synthesis of multinuclear copper cores might be a key to develop highly efficient and durable copper-based electrocatalysts for the ORR.

References. [1] N. Mano, V. Soukharev, A. Heller, J. Phys. Chem. B, 110, 11180 (2006). [2] M.S. Thorum, J. Yadav, A.A. Gewirth, Ang. Chem. Int. Ed.,
48, 165 (2008). [3] M. Kato et al., Phys. Chem. Chem. Phys., 17, 8638-8641 (2015). [4] M. Kato, N. Oyaizu, K. Shimazu, I. Yagi, J. Phys. Chem. C, in press. DOI: 10.1021/acs.jpcc.5b11663
Size Effect of Single Nanoparticle Electrodes on the Electrochemical Interface and Charge Transfer Kinetics and New Insights into Their Size-Activity Relations
Authors: Fan Lixin , Gan Lin
Published: February 2020

Understanding the particle size effects on the electrochemical reaction kinetics is of particular importance for rational design of nanoparticle materials for energy conversion and storages such as fuel cell electrocatalysts and battery materials. Our present knowledge on the size effects of nanoparticle catalysts is generally related to the impact of particle size on the atomic or electronic structures of nanoparticle surfaces. For electrocatalytic reactions, it is well known that the charge transfer kinetics not only depends on the electrode surface structure but also, perhaps more importantly, rely on the electrochemical solid-liquid interfaces, namely, the electric double layers (EDL). Effect of particle size on the latter aspect and thus the charge-transfer kinetics, however, has remained largely unexplored.

Exemplified by two redox reactions with different electron transfer kinetics (such as oxygen reduction reaction in fuel cells), we performed finite element analysis of the EDL potential distributions, concentration distributions of redox and intermediate species, and the overall voltammetry behaviors of single platinum (Pt) nanoparticle electrodes as functions of the nanoparticle size for the first time. Our results reveal significant influence of particle size on the potential drop distributions within the EDL of nanoparticle electrodes; decreasing particle size led to an increase of the potential at the compact layer, translating into apparent size effects on the charge transfer kinetics particularly for slow electrochemical reactions. These results provide important new insights into the size effect of nanoparticle materials for fuel cell electrocatalysis and battery electrodes.
Specific Response of Quinone Redox at 2-Aminoethanethiol Modified Electrode
Authors: Naito Kumi , Maeda Yuri , Yasui Takashi , Takada Kazutake , Yuchi Akio
Published: February 2020

Self-assembled monolayers of alkanethiols on electrode surface have been the subjects of intensive studies in both fundamental interests of surface chemistry and their technological significance. The self-assembly is one of the most widely used techniques to construct ordered molecular structures and to control surface characteristics, due to its facile procedure. 2-aminoethanethiol has been used as an anchor to introduce functional molecules to electrode surfaces as it has a reactive amino group and its carbon chain is short.

We have found that a 2-aminotehanethiol modified Au electrode shows a specific electrochemical response to p-hydroquinone in aqueous solution. That is, a peak separation (ΔE
p) in the CV appeared to be very large at the first potential cycle, but it drastically decreased upon successive potential cycling. We have been studying condition where the specific response takes place and its mechanism.

Figure 1A shows typical CVs of an aminoethanethiol modified Au disk electrode in a 0.1 M sodium perchlorate solution containing 5 mM hydroquinone at 100 mV s-1. The ΔE
p for quinone redox was found to be 530 mV for the first cycle, indicating a slow electron transfer (Fig. 1A curve a). After application of +0.9 V vs. Ag/AgCl for 30 min at which hydroquinone is oxidized, the ΔE
p largely decreased to 120 mV (Fig. 1A curve b) and the CV overlapped with that of a bare electrode. On the other hand, application if –0.5 V was applied, the CV remained virtually constant. Interestingly, when the electrode was left in the solution at open circuit or –0.5 V for 3 h, the ΔE
p increased to the original value (530 mV). These results indicate that the changes in the ΔE
p is reversible and not originating from peeling of the film, and the increase can be attributed to an interaction between aminoethanethiol and hydroquinone, whereas the decrease is due to oxidation of hydroquinone. A Au electrode modified with 2-dimethylanimoethanethiol showed similar behavior (Fig. 1B), indicating that Schiff base formation from amino group of 2-aminoethanethiol and p-quinone is not the dominant cause of the changes in the electrochemical response.

At the current stage, we speculate two possible mechanisms for the changes in the electrochemical response. The first one is changes in structure of aminoethanethiol due to changes in an interaction with quinone, although it is known that short alkyl chains on the electrode surface do not block electron transfer. The second one is a chemical reaction between hydroquinone and aminoethanethiol, which produces derivatives with slow electrode reaction rate constant. We currently investigate those two possibilities with STM measurements for an aminoethanethiol modified electrode before and after the electrolysis and with NMR measurements for the reaction.

Figure 1
(Keynote) Artificial Photosynthesis: Progress, Science Outlook and Technology Prospects
Authors: Atwater Harry A
Published: February 2020

The design of highly efficient devices that generate fuels directly from sunlight, water, and carbon dioxide is both a formidable challenge and an opportunity that, if realized, could have a revolutionary impact on our energy system. In the past five years, considerable progress has been made in scientific discovery of key materials and mechanisms needed to realize artificial solar fuels generators, and advances modeling and design have generated a now quite widely embraced conceptual paradigm for a solar fuels generator. While we still lack sufficient knowledge to design solar-fuel generation systems with the ultimate efficiency, scalability, and sustainability to be economically viable, considerable advances have been made, particularly for water-splitting solar fuels devices. I will describe work done in this area by the Joint Center for Artificial Photosynthesis. I will also survey outstanding scientific challenges to realization of artificial photosynthesis for generation of fuels and chemicals by reduction of carbon dioxide and discuss JCAP's approach and recent advances in carbon dioxide reduction.
Recent Progress in Aqueous Organic or Inorganic-Based Redox Flow Batteries at Pnnl
Authors: Li Bin , Nie Zimin , Kizewski James , Duan Wentao , Wei Xiaoliang , Wang Wei , Liu Jun , Reed David , Sprenkle Vincent
Published: February 2020

Redox flow batteries (RFBs), as one of the most promising electrical energy storage systems, provide an alternative solution to the problems of balancing power generation and consumption. RFBs are designed to convert and store electrical energy into chemical energy and release it in a controlled fashion when required. In particular, aqueous RFBs are attracting more attentions because of their good safety, low cost and high power density comparing with non-aqueous RFBs. Therefore, aqueous RFB chemistries with appropriate redox potential, high soluble and low-cost active species are critically required.1

During the past few years, PNNL invented several aqueous RFB systems: inorganic and organic-based systems. Here, we will present the electrode development for zinc-polyiodide RFBs2 (inorganic-based). Two kinds of metal-organic frameworks (MOFs) acting as catalysts were in-situ grown at the cathode carbon electrode.3 The flow cell with MOFs showed largely improved energy efficiency. The chemical stability of MOFs in electrolytes was studied in detail. Also, we will introduce a kind of methyl viologen-based RFBs (organic-based). It represents a great potential to replace expensive vanadium flow batteries because of low-cost active materials. The cell performance and the chemical stability of electrolytes will be discussed.

 

References:

Soloveichik, Grigorii L. Chemical reviews 115.20 (2015): 11533-11558.

Li, B et al., Nature communications, 2015

Li, B et al., submitted, 2016
Fluorophosphate-Based Polyanion Cathode Materials for Rechargeable Magnesium Batteries
Authors: Masese Titus , Huang Zhen-Dong , Senoh Hiroshi , Sano Hikaru , Shikano Masahiro , Uchimoto Yoshiharu
Published: February 2020

Rechargeable magnesium-ion batteries are promising candidates to compete with the state-of-the-art lithium-ion batteries for a plethora of large-scale energy storage devices.

The terrestrial reserves of magnesium are plentiful and magnesium metal is safe to handle under ambient atmosphere containing water and oxygen than metallic lithium. In addition, the multivalent nature of magnesium metal itself makes rechargeable magnesium-ion battery very attractive not only due to the inherent low cost and safety, but also as a high-energy density battery system.

However, in spite of the aforementioned advantages, the energy density of rechargeable magnesium batteries reported was low. The low energy density stems from the low voltage and capacity which is mainly constrained by the cathode material. A number of feasible cathode materials that can reversibly (de)insert magnesium ion have been reported in recent years, typical examples being the molybdenum chalcogenides[1] and transition metal oxides such as V2O5
[2]and MnO2
[3]; nonetheless, the energy density attained still remains unsatisfactory. Therefore, high energy density cathode frameworks are highly desirable for rechargeable magnesium battery system to be at par or even outperform the current lithium-ion battery technology.

In pursuit for alternative cathode materials, this study explores a promising broad class of poly(oxy)anion inorganic frameworks based on fluorophosphates[4] that exhibit multi-redox reactions (high theoretical capacity) and high redox voltage. The synthesis, crystal structure and electrochemical magnesium (de)insertion behaviour in representative fluorophosphates cathode materials based on environmentally-benign constituents such as MgFePO4F will be highlighted. Their analogues in the mineral world are hydroxyfluorophosphates, including triplite, panasqueiraite and magniotriplite [(Mg, Fe)2(PO4)(F, OH)], where F- can partially replace an OH- group. Complete substitution of F- is necessary to enhance electrochemical properties because the hydroxyl tends to undergo irreversible redox reactivity. Furthermore, the replacement of PO4
3- with PO4F4-in principle alters the charge balance and the dimensionality of the structure.

References

1. D. Aurbach et al., Nature, 407, 724-727 (2000).

2. D. B. Le et al., Chem. Mater., 10, 682-684 (1998).

3. N. Kumagai et al., J. Power Sources, 97, 515-517 (2001).

4. Z.-D. Huang et al., J. Mater Chem. A, 2, 11578-11582 (2014).
Novel High Energy Density Sodium Layered Oxide Cathode Materials - from Material to Cells
Authors: Smith Katherine , Treacher Joshua , Ledwoch Daniela , Adamson Paul , Kendrick Emma
Published: February 2020

Lithium ion batteries have now been commercially available for the past twenty-five years. There has been a steady improvement in lithium ion battery technology throughout this period and lithium ion batteries are widely considered as the technology of choice to meet the energy demands of the future. However, there is growing research and commercial interest in other metal-ion battery technologies that could also meet certain areas of future energy demand. Sodium-ion technology has commanded an increasing research and commercial interest over recent years due to the high abundance and uniform distribution of sodium across the world, and the reported potential commercial advantages of lower cost, greater sustainability and improved safety characteristics of sodium ion batteries compared with their lithium-ion counterparts.

Sharp Laboratories of Europe Ltd have been developing a new sodium ion cell chemistry based upon a tin-containing nickel based layered oxide cathode and a hard carbon anode. Here we report on the challenges faced during the development of a new sodium-ion technology in moving from a new electrode material, through from half cell results to small full cell development and then larger scale full cell development. We discuss the optimisation of the material choice, electrolyte, electrode parameters and formation process on the gravimetric and volumetric cell energy density along with the lifetime and rate behaviour of the cells.
A Study on Long-Term Cycle Performance of Conventional Tin Anode for Sodium-Ion Batteries
Authors: Kim Changhyeon , Kim Huihun , Sadan Milan K , Cho Gyubong , Kim Ki-Won , Ahn Jou-Hyeon , Ahn Hyo-Jun
Published: February 2020

Tin has been regarded as one of the most promising anode materials owing to its high theoretical specific capacity of 847 mAh g−1, based on the full sodiation of Na15Sn4. However, the pure tin anode has a severe problem of poor cycling properties, as it loses its initial capacity within the first 10 cycles. It is believed that the pulverization of tin induced a rapid degradation of capacity during cycling. The tin anode material expands to 520% of its original volume during sodiation and contracts to its original volume during desodiation. Several approaches have been investigated to overcome this problem. One approach involves stress release by utilizing a buffer layer, decreased tin size, or a thin film. Another approach involved the suppression of volume expansion by encapsulating tin nanoparticles into carbon and coating Al2O3 onto the tin nanoparticles. For example, ultra-small (8 nm) tin nanoparticles embedded in carbon showed 415 mAh g−1 of reversible capacity for 500 cycles, and tin nano-dots (1 ~ 2 nm) encapsulated in porous nitrogen-doped carbon nanofibers showed 483 mAh g−1 for 1300 cycles. Although these previous approaches succeed in improving cycle life, most preparation methods are too complex for commercialization as compared to that of the conventional electrode using tin nanopowder, a conducting additive, and a binder. However, a conventional electrode still showed poor cycling properties. Komaba et al. reported that a conventional electrode demonstrates capacity decay from 758 mAh g−1 to 21 mAh g−1 over the course of 10 cycles, even if using tin nanopowder (< 150 nm). The cycling properties of tin anode could be improved using a conductive binder or polyacrylate binder in short-term cycling of 20 cycles, but improved long-term cycle performance of a conventional electrode has not reported yet.

Previous studies indicate that the long-term cycling of tin electrode with high capacity could be improved by the release or suppression of accumulated stress in a tin due to volume change. In order to release stress of conventional electrode, the tin electrode should be designed using suitable binder, conductive additive, and its optimized structure. Therefore, we study on the long-term cycling of conventional tin anode for sodium-ion batteries by the control these components.
Analysis of Ion Transport in Glyme-Based Electrolyte Solutions for Li-Air Batteries
Authors: Saito Morihiro , Yamada Shinya , Tachikawa Yusuke , Ito Kimihiko , Kubo Yoshimi
Published: February 2020

In order to elucidate the Li+ ion transport in glyme-based electrolyte solutions for Li-air batteries, LiCF3SO3(LiTfO) or LiN(SO2CF3)2(LiTFSI) dissolved glyme (triglyme(G3), tetra-glyme(G4) and pentaglyme(G5)) electrolytes were prepared, and the self-diffusion coefficients D of Li+ ion (7Li), anion (9F) and glyme (1H) solvent were measured individually by a pulsed-field gradient spin echo (PGSE-)NMR [1-3] in the temperature range of 30oC to 60oC. The viscosity η, density d and ionic conductivity σ were also measured to analyze the mechanism of ion transport in the glyme-based electrolytes. Moreover, molecular dynamics (MD) simulation was applied to reproduce the D values and investigate the dissociation of Li salts and solvation structure of Li+ion in the glyme solvents.

As the results, it was found that the glyme with shorter polyethylene glycol (PEG) chains gave lower η (Fig. 1) and higher D values (Fig. 2) and LiTFSI-based electrolytes exhibited higher σ values (Fig. 3) because of high apparent degree of dissociation α
app (Fig. 4), which were estimated by using Nernst-Einstein equation, for an increase in the amount of Li+ carriers. The trend was kept in the examined temperature range from 30oC to 60oC. However, the a value for the Li salts was decreased by an increase in the temperature, implying a reduction of the interaction energy between the Li+ ion and glyme solvents to form a metal complex. On the other hand, the a value was increased by the concentration of both Li salts in the electrolytes up to the molar ratio of 1:1 although the viscosity was also increased. Consequently, the highest σ values were attained both for 1 M LiTfO and LiTFSI-based electrolytes. From the results of MD simulation, the above trend of D values for ions and solvents were clearly reproduced and the larger amount of ion pairs of LiTfO was also confirmed than those of LiTFSI in the glyme solvents. The distance between Li+ ion and anion was much expanded for the LiTFSI compared with that for the LiTfO. Based on those results, we further investigated on the other new Li salt, LiN(SO2F)2(LiFSI), and influence of impurity such as H2O from air to the ion transports. The reports will be presented in the meeting.

 

This study was supported by JST “Next Generation Batteries Area in Advanced Low Carbon Technology Research and Development Program (ALCA)” and “A Tenure-track Program” from MEXT, Japan.

 

References

[1] M. Saito et al., Abstract in The 56thBattery Symposium in Japan, 3G25 (2015).

[2] K. Hayamizu et al., J. Phys. Chem. B, 103, 519 (1999).

[3] Y. Aihara et al., J. Chem. Phys., 113, 1981 (2000).

Figure 1
Unusual Na Storage Behavior of Ordered Mesoporous Carbon on Ether-Based Electrolyte System
Authors: Kim Yunok , Lew Gil Hwan , Oh Woong , Jeong Mihee , Jin Xing , Kim JI Man , Yoon Won-Sub
Published: February 2020

The Li-ion battery (LIB) market increases rapidly due to the development of portable electronic devices and energy storage systems (ESSs). By increasing the demand for commercialization of scale-up LIB, large amounts of accumulated lithium resources will be consumed in the near future. Recently, Na-ion battery (NIB) system is considered as an alternative to LIB system because sodium resources are abundant and distributed around the world as well as sodium storage mechanism is similar to that of lithium. In contrast to LIB, graphite is not suitable for NIB anode material due to the small interlayer for large ionic radius of Na+ ion. Therefore, previous studies have investigated that non-graphitic carbon materials can deliver reversible Na+ ion insertion and extraction with initial capacity up to 300mAh g-1, however, the cycle stability of non-graphitic carbon materials is very poor.

Ordered mesoporous carbon (OMC) has the advantage of large surface area due to the development of nano-sized pores inside a micron-sized particle, which results in large electrode/electrolyte interface, easy penetration of electrolyte, and fast diffusion of Li+/Na+ ion. The ordered hexagonal structure of the OMC was formed as an inverse replica of a mesoporous silica SBA-15 structure and started from phenanthrene as a carbon source. In carbonate-based electrolyte system, the first and second discharge capacities of the OMC were 800 mAh g-1 and 350 mAh g-1 at a current density of 100 mA g-1, respectively, which means a large irreversible capacity loss, whereas in ether-based electrolyte system, the first irreversible capacity decreased considerably, implying an enhanced reaction reversibility. Even though the first discharge capacity in the ether-based electrolyte was about 200 mAh g-1, the capacity in the ether-based electrolyte increased during repeated cycling and achieved 350 mAh g-1 after 100 cycles. In contrast, the cycle retention in carbonate-based electrolyte degraded down to 200mAh g-1 consistently during 100 cycles.

To elucidate the electrolyte system-dependent Na+ storage of the OMC, various electrochemical analyses and synchrotron X-ray based techniques were performed using two-type electrolytes of 1 M NaPF6 in EC/DMC=1/1 and 1 M NaPF6 in DEG/DME.