bluuebunny/crossref_metadata_2025 huggingface dataset:
Crystalline Mesoporous Films of Titanium Oxides with Various Degree of Substoichiometry for Fuel Cells
Authors: Bienkowski Krzysztof , Kulesza Pawel J.
Published: February 2020

The first results of the synthesis of mechanically stable, crystalline mesoporous films of titanium oxides with various stoichiometry, which will be applied either as an anode or a cathode for fuel cell electrodes, will be presented. The composition of TiO2 and substoichiomteric TinO2n-1 Magneli phases which has been obtained in a high temperature and in reductive atmosphere is expected to have a potential to serve as an anode for enhanced oxidation of organic fuel and to be employed as a cathode when modified with the co-catalyst (NiO/Ni) to allow an effective oxygen reduction. These applications require high degrees of conductivity and a large contact area with the reaction media. In addition, highly crystalline oxides are desired in order to optimize the properties such as electroactivity or electronic conductivity. The synthesis approach of substoichiometric TinO2n-1 oxides and the structural characterization in view of their potential application in fuel cell systems will be the objective of the presentation.
Development of Nanofiber Ceria-PFSA Interlayers to Mitigate Membrane Chemical Degradation
Authors: Zaton Marta , Jones Deborah , Roziere Jacques
Published: February 2020

The attack by radical intermediates like hydroxy and hydroperoxy (∙OH, ∙OOH) radicals on the polymer chain is the current generally accepted mechanism of chemical degradation of perfluorosulfonic acid membranes [1]. The formation of the reactive oxygen species (ROS) occurs through decomposition of hydrogen peroxide in the presence of trace metal ions originating from the corrosion of cell components, including the cathode platinum catalys [2,3]. Different approaches have been adapted to introduce the radical scavenger into membrane electrode assembly (MEA) such as [4] preparation of electrode with the addition of hydrogen peroxide decomposition catalyst or development of composite Nafion® membrane with dispersed inorganic hydroxyl radical scavenger in nanoparticles or ionic form. It has been demonstrated that incorporation of radical scavenger lowers the polymer degradation rate [5, 6]. We will report the development of a nanofiber-network material enriched with cerium oxide nanoparticles as radical trap at the membrane electrode interface. The mitigation properties of such modified MEAs were verified in in situ OCV hold test conditions at low relative humidity 50 % and high temperature 90 ºC, with the radical scavenger interlayer oriented preferentially to the anode or to the cathode side. Reference membranes with an additional nanofiber layer but no cerium component were also examined to ensure that observable effects are due to the presence of radical scavenger. The result of OCV hold testing under these conditions show that whereas MEAs integrating non-modified Nafion®-212, or Nafion®-212 modified by an interlayer of nanofibre PFSA (no cerium oxide) only, show a marked drop in OCV with time, and end of life at <200 hours, an MEA comprising a cerium oxide nanofiber interlayer at the anode side gave very stable open circuit voltage and a significantly longer lifetime. Post mortem analysis of the MEAs and analysis of eluent water by liquid chromatography were combined to better understand the overall degradation process occurring in cerium enriched and cerium free MEAs, including X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and scanning electron microscopy (SEM) analyses.

D.E. Curtin, R.D. Lousenberg, T.J. Henry, P.C. Tangeman, and M.E. Tisack Journal of Power Sources, 131, 41-48 (2004).

J. Peron, Y. Nedellec, D.J. Jones, and J. Roziere, Journal of Power Sources, 185,1209-1217 (2008).

Y. Nosaka, K. Ohtaka, N. Ohguri, and A.Y. Nosaka, Journal of The Electrochemical Society, 158, B430-B433 (2011).

F.D. Coms, H. Liu, and J.E. Owejan, ECS Transactions, 16, 1735-1747 (2008).

P. Trogadas, J. Parrondo, and V. Ramani, Electrochemical and Solid-State Letters, 11, B113-B116 (2008)

P. Trogadas, J. Parrondo, and V. Ramani, ACS Applied Materials & Interfaces, 4, 5098-5102 (2012)
Regioselective Electrochemical Fluorination of Open-Chain Dithioacetal Derivatives Bearing Electron-Withdrawing Substituents at the α-Position: Product Selectivity Depending on Supporting Fluoride Salts
Authors: Fuchigami Toshio , Yin Bin , Inagi Shinsuke
Published: February 2020

Selective fluorination of organic molecules is of much importance to develope new pharmaceuticals and agrochemicals. We have systematically studied electrochemical fluorination of various heteroatom compounds including heterocycles.1-3)

In this study, we have investigated fluorinated product selectivity depending on ionic liquid fluoride salts.Anodic fluorination of dithioacetals bearing various electron-withdrawing substituents was achieved with high regioselectivity in the presence of Et3N-3HF to give α-fluorinated products in good to excellent yields. On the other hand,Et3N-5HF and Et4NF-5HF containing high HF content was used as a fluorinating reagent, fluorodesulfurization of dithioacetals such as ethyl α,α-bis(phenylthio)acetate and α,α-bis(phenylthio)acetone was promoted markedly; however, α-fluorination of α,α-bis(phenylthio)acetonitrile proceeded without desulfurization exclusively to provide the corresponding α-monofluorinated product in excellent yield regardless of fluoride salts.

References:

1) Fuchigami, T.;Inagi, S. Chem. Commun. (Feature Article)
2011, 47, 10211.

2) Sawamura, T.; Takahashi, K.; Inagi, S.; Fuchigami, T. Angew. Chem. Int. Ed. 2012, 51,4413.

3) Takahashi, K.; Inagi, S.; Fuchigami, T. J. Electrochem. Soc. 2013, 160, G3046.
Synthesis and Characterization of Imidazolium Chiral Ionic Liquids Prepared from Low-Cost Chiral Amines for Its Use in Asymmetric Organic Electrosynthesis
Authors: Frontana-Uribe Bernardo A. , Rodríguez-Cárdenas Esdrey
Published: February 2020

Room temperature ionic liquids (RTIL’s) are organic salts with low melting points (less than 0°C) and are in the focus of green chemists as alternative solvents, due to their attractive properties such as chemical electrochemical and thermal stability, non-flammability, low vapor pressure, high ionic conductivity and designable structure.[1],[2] These solvents are constituted of organic cations and inorganic or organic anions. So there is a great possibility to design and tune their properties for various applications just by careful selection of the cation or anion to obtain the desired properties.[3],[4] In the last few years, researchers have turned their interest to synthesis of chiral ionic liquids (CILs). Many CILs have been designed, synthesized and used in organic reactions.[5] Nevertheless, the use of RTIL’s in organic electrosynthesis is well known,[6] the use of the CILs has been overlooked. Chiral imidazolium ionic liquids derived from both enantiomers of a-phenylethylamine using a simple and low cost methodology were synthesized. In this communication it is reported their physicochemical properties, thermal behavior, water content and hydrophilicity, density and electrochemical behaviour. The first studies of the application of these chiral solvents in organic electrosynthesis will be discussed, using the classical pinacolic coupling and CO2activation looking for asymmetric electrochemical reactions.

The authors thank the financial support of PAPIIT-UNAM project IN202011.

[1] Li, R. X. China Chemical Industry Press: Beijing. 2005, 298-300. 

[2] Earle, M. J.; Seddon, K. R. Pure Appl. Chem.
2000, 72, 1391–1398.

[3] Torrecilla, J. S.; Palomar, J.; García, J. N.; Rodríguez, F. J. Chem. Eng. Data. 2009, 54, 1297– 1301.

[4] Davis, J. H. Chem. Lett. 2004, 33, 1072–1077.

[5] a)Baudequin, C.; Baudoux, J.; Levillain, J.; Cahard, D.; Gaumont, A.-C.; Plaquevent, J.-C. Tetrahedron Asymmetry
2003, 14, 3081–3093. b) Ding, J.; Armstrong, D.W. Chirality
2005, 17, 281–292. c)Baudequin, C.; Brégeon, D.; Levillain, J.; Guillen, F.; Plaquevent, J.-C.; Gaumont, A.-C. Tetrahedron Asymmetry
2005, 16, 3921–3945.

[6] Bornemann, S., Handy, S.T. Molecules
2011, 16, 5963-5974.
Overview of Emerging Technologies and Challenges for Large Scale Energy Storage
Authors: Virden Jud W.
Published: February 2020

Energy storage will play a critical in the electrification of the transportation industry and modernization of the power grid infrastructure. Currently, many technologies are investigated, including Li-ion, redox flow, Li and Na sulfur batteries. Li-ion batteries have attracted wide attention for automobile applications, and redox flow, sodium and new sulfur chemistries are under intense development. Significant breakthroughs in performance, cost and safety is needed to meet the requirement of various applications, but no single technology will be able to address all the challenges. This seminar will summarize our recent progress in developing analytical tools to understand the energy storage requirements for balancing service and other applications in different regions in the United States, and the cost and life cycle requirements for such applications. The current status, advantages and limitations of some key technologies will be discussed. This seminar will also discuss our recent breakthroughs in a new generation of low cost, redox flow batteries that can increase the energy density by several times, and Na batteries that can operate at temperatures at below 100°C.
A Novel Aluminium–Air Secondary Battery with Long-Term Stability
Authors: Mori Ryohei
Published: February 2020

A metal-air secondary cell with the abundant metal aluminium has been assembled by placing the aluminium ion conductor Al2(WO4)3 both on top of the aluminium anode and underneath the air cathode. It was possible to enhance the cell capacity and suppress the yield of by-products, by modifying the cell structure. When aqueous NaCl was used as an electrolyte, byproducts such as Al(OH)3 or Al2O3were not detected. We suggested that this is one of the reasons for obtaining secondary battery with Aluminium -Air cell. When the condition was optimized, the battery functioned for approximately one month. We found that the impedance was increased after 1 week of charge-discharge reaction. Moreover, by combining the air cathode active material and the solid electrolyte, we were able to achieve a higher cell capacity. This provides a snapshot of future Al-air secondary batteries.

Figure A Schematic Figure of Aluminium-Air Secondary Battery
Nitrogen-Doped Mesoporous Carbon Promoted Chemical Adsorption of Sulfur and Fabrication of High-Areal-Capacity Sulfur Cathode with Exceptional Cycling Stability for Lithium-Sulfur Batteries
Authors: Song Jiangxuan , Xu Terrence , Gordin Mikhail L , Wang Donghai
Published: February 2020

Lithium-sulfur batteries have attracted increasing attention as next-generation energy storage devices for plug-in hybrid and all-electric vehicles, owing to the extremely high theoretical specific capacity (1672 mA h/g) and energy density (2600 Wh/kg) of sulfur. In addition, sulfur is low-cost, abundantly available, and eco-friendly, making Li-S batteries even more attractive.1-3

As one important component of sulfur cathodes, the carbon host plays a key role in the electrochemical performance of lithium-sulfur batteries. In this talk, mesoporous nitrogen-doped carbon (MPNC)-sulfur nanocomposite is reported as a novel cathode for advanced Li-S batteries. The nitrogen doping in the MPNC material can effectively promote chemical adsorption between sulfur atoms and oxygen functional groups on the carbon, as verified by X-ray absorption near edge structure spectroscopy, and the mechanism by which nitrogen enables this behavior is further revealed by density functional theory calculations. Based on the advantages of the porous structure and nitrogen doping, the MPNC-sulfur cathodes show excellent cycling stability (95% retention within 100 cycles) at a high current density of 0.7 mAh/cm2 with a high sulfur loading (4.2 mg S/cm2) and a sulfur content (70 wt.%). A high areal capacity (~3.3 mAh/cm2) has been demonstrated by using this novel cathode, which is crucial for the practical application of Li-S batteries. We believe that the important role of nitrogen doping promoted chemical adsorption can be extended for development of other high performance carbon-sulfur composite cathodes for Li-S batteries.

Acknowledgements

This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy under Contract No. DE-EE0005475.

References

[1] P. G. Bruce, S. A. Freunberger, L. J. Hardwick, J.-M. Tarascon, Nat. Mater.
2012, 11, 19.

[2] X. Ji, L. F. Nazar, J. Mater. Chem.
2010, 20, 9821.

[3] A. Manthiram, Y. Fu, Y.-S. Su, Acc. Chem. Res.
2013, 46, 1145.
Novel Conducting Polymer Hydrogels for Electrochemical Energy Storage Devices
Authors: Yu Guihua
Published: February 2020

Conductive polymer hydrogels (CPHs) represent a unique class of polymeric materials with 3D hierarchical networks of crosslinked polymer chains, and can synergize the advantageous features of hydrogels with electrical and optical properties of ‘organic metals’. They provide an excellent interface between the electrode and the electrolyte in electrochemical devices, as well as between soft and hard materials, and have been explored for a range of important technological applications from biosensors and medical electrodes, to energy storage devices such as supercapacitors and lithium-ion batteries. This talk will discuss our recent progress on rational syntheses and device studies of nanostructured CPHs with tunable structures and electrochemical properties for high-performance energy storage devices. Given their 3D hierarchical architecture and multi-scale porosity, high electrical conductivity and redox activity, the CPHs can enable the design of high-performance electrochemical storage devices, offering high power and energy densities as well as excellent cyclability. Two examples will be presented: 1) CPHs function as active electrodes for making flexible solid-state supercapacitor devices; 2) CPHs serve as functional components to chemically integrate with silicon particles to make stable, high-energy-density battery anodes.
Title III Lithium-Ion Battery Project – Lithium Cobalt Oxide, Lithium Nickel Cobalt Aluminum Oxide & Meso Carbon Micro Beads Domestic Manufacturing Development
Authors: Visco Vincent , Nakahara Hiroshi
Published: February 2020

The US government has recognized the need to provide a trusted domestic material and cell source for the lithium-ion batteries for aerospace use. Quallion has been awarded this contract and will give an update on the installation on the establishment of the material lines. In addition, preliminary data on the Quallion Lithium Cobalt Oxide, Lithium Nickel Cobalt Aluminum Oxide and Meso Carbon Micro Beads anode material manufactured will be presented. This data will include capacity and cycle life characterization on test cells, as well as material analysis.
Energy Storage Coaxial Cable
Authors: Yu Zenan , Thomas Jayan
Published: February 2020

Developing lightweight, space saving, and multifunctional integrated device has become a critical task for numerous fields including displays, military and aviation. Components like electrical cables and supercapacitors have been widely and separately used as connectors and energy storage devices, respectively for many applications. Here we demonstrate a novel device architecture to develop an integrated coaxial supercapacitor cable (CSC) that functions both as electrical cable and energy storage device. Similar to typical coaxial cables, the inner core is used for electrical conduction and overlying layer is used for energy storage. A template-free method was developed to fabricate large area, high aspect ratio, nanowhisker-structure based cable electrodes. This unique design provides high specific capacitance (1,376 F g-1) and exceptional reversible redox reactions for CSC electrodes. The integrated CSC device shows excellent flexibility and bendability, long and stable cycle lifetimes, and high energy and power densities. All these remarkable results demonstrate that CSC design can be very promising to club electrical conduction and energy storage into one cable for many technologically critical applications.
Enhanced Electrochemical Performance of Li1.17Ni0.25Mn0.58O2 Cathode Material for Lithium-Ion Battery Via Fluorine Doping and LiCrMnO4 Coating
Authors: Fan Li-Zhen , Li Hongxiao
Published: February 2020

The layered lithium-enriched and manganese metal oxides are considered to be an attractive cathode with a high capacity of 250 mAh g-1 when charged above 4.5 V [1]. However, the irreversible loss of oxygen and undesirable dissolution of transition metal ions during charge/discharge process cause the poor cycling performance and unsatisfactory thermal stability [2]. Many strategies are applied to overcome the large irreversible capacity loss during the first cycle and the following-up capacity fading. Substitutions and surface coatings are considered to be effective ways to solve these problems [3,4].

In this study, in order to improve the electrochemical performance of Li1.17Ni0.25Mn0.58O2 cathode material, fluorine doping and LiCrMnO4 coating were applied. F- is more electronegative thus fluorine substitution may change the energy bond between the transition metal ions and the anion. The spinel LiCrMnO4 with three-dimensional Li+ diffusion channels exhibits high electronic conductivity and the Cr3+ can be oxidated to Cr6+, which provides a higher capacity. Therefore, we synthesized the fluorine doping materials by the co-precipitation method followed by a high-temperature solid-state reaction. And the LiCrMnO4 coated Li1.17Ni0.25Mn0.58O2 was prepared by a chemical deposition method followed by a high-temperature calcination.

The result reveals that irreversible loss of oxygen was reduced during the first charge and cycling performance was enhanced dramatically by fluorine doping and LiCrMnO4 coating. For fluorine substitution materials, the improvement in cycling performance was more visible at high temperature. For LiCrMnO4 coating materials, the rate capability was largely improved. The modified cathode materials exhibit excellent cycling stability.

References

[1] C.S. Johnson, N. Li; C.Lefief, M.M. Thackeray, Electrochemistry Communications, 9, 787 (2007).

[2] T.A. Arunkumar, Y. Wu, A. Manthiram, Chemistry of Materials, 19, 3067 (2007).

[3] H.X. Li, L.Z. Fan, Electrochimica Acta, 113, 407 (2013).

[4] Y.K. Sun, M.J. Lee, C.S. Yoon, J. Hassoun, K. Amine, Advanced Materials, 24, 1192 (2012).
Synthesis of Li
x
Mn0.54Ni0.13Co0.13O
y

cathode Materials for Lithium-Ion Batteries Via Mechanochemical Activation
Authors: Kahvecioglu Feridun Ozgenur , Shin Youngho , Krumdick Gregory , Dermer Mikel
Published: February 2020

Mn0.54Ni0.13Co0.13CO3 precursor materials were prepared via mechanochemical activation using a high energy planetary ball-mill and subsequently lithiated at high temperatures to form Li
x
Mn0.54Ni0.13Co0.13O
y

cathode materials. Optimal ball-milling conditions, including the milling time, rate, ball to powder weight ratio, milling media, and ball diameter were investigated to produce precursor materials with high tap density. Precursor and cathode materials were characterized via X-Ray powder diffraction (XRD), scanning electron microscope (SEM), Brunauer-Emmett-Teller (BET) surface area measurements, inductively coupled plasma mass spectrometry (ICP-MS), particle size analysis, and galvanic charge-discharge cycling. Preliminary results indicate that increasing the milling time, rate, and ball diameter yield precursor material with a higher tap density up to 1.7 g/mL. The tap density approaches an apparent upper limit at longer time durations when holding other variables constant. The mean particle size decreases to 9.42 µm as a function of longer time durations, higher rates, and smaller ball sizes. Ongoing work will comprehensively evaluate the effects of altering ball-milling conditions on the particle morphology and the electrochemical performance of cathode materials.
Mechanism Study of Li/Se Rechargeable Batteries in Different Electrolytes
Authors: Cui Yanjie , Abouimrane Ali , Amine Khalil
Published: February 2020

Lithium-seleniume battery has been reported as one of the promising new high energy density energy storage systems considering its high theoretical gravimetric capacity of 678 mAh/g and volumetric capacity density of 3268 mAh/cm3, which is comparable to that of S (3467 mAh/cm3). It has been reported that Se cathode could be cycled versus both Li and Na at room temperature. Moreover, a long cycle life up to 1000 cycles with high efficiency have been reported by Wang et al recently. We have proved that Se is reduced into Li2Se through the formation of intermediate polyselenide in the ether-based electrolyte by in-situ synchrotron techniques. However, a different mechanism is expected in the carbonate-based electrolyte based on the different voltage profiles. Then we experimentally demonstrated that the Se is directly transformed into Li2Se without any intermediate phase formation. These results further proved that the electrolytes have a significant effect on this battery system. This mechanism study provides essential information on strategy selection for furhter performance improvement of Li-Se baterry.
Synthesis of Porous 3D Metallic Current Collectors for High Performance Lithium Batteries
Authors: Gullapalli Hemtej , Kalaga Kaushik , Arava Leela , Ajayan Pulickel M
Published: February 2020

Conventional thin film lithium ion batteries are built on a planar design where electrode material is coated on to a conducting current collector substrate. Contact resistance between the current collector and the electrode always hinders the overall performance of the battery. In order to better utilize the electrode material, 3D current collector architectures with nanoscale roughness have been proposed which would increase the electrode-current collector surface contact area thereby significantly reducing interfacial resistance. The nanoporous current collector configuration is one of several 3D designs which have shown high potential for the development of high energy and high power microbatteries. We present here a scalable process for the synthesis of three dimensional porous metallic current collectors with conformal graphene coating on the surface. One step chemical vapor deposition technique has been used for controlled etching and simultaneous graphene growth on the surface of metals such as copper and stainless steel. The 3D structures can be directly used as a cathode in lithium ion battery as graphene has lithium intercalating capability. The structural and morphology of the current collector/electrode hybrid structures were characterized by X-ray diffraction, X-ray photoelectron spectroscopy (XPS) analysis, scanning electron microscopy and energy-dispersive X-ray spectroscopy. The contribution of 3D current collectors resulted in excellent cyclic stability and capacity compared to using conventional 2D configuration.
Polyaniline–carbon Nanotube Composites As Electrocatalysts for Fuel Cells
Authors: Zheng Haitao
Published: February 2020

Conducting polymers have been investigated as carbon-substitute supports for fuel cell catalysts due to their high accessible surface area, low resistance and high stability. Conducting-polymer-supported metal particles present higher tolerance to poisoning due to the adsorption of CO species, in comparison to the serious problem of tolerance of bulk and carbon-supported metals. Polyaniline(PANI)-carbon nanotube (CNT) composites indicate favourable interaction between PANI and CNTs. The CNT provides higher surface area and better electronic conductivity while PANI facilitates the electron transfer through the conducting matrix. The CNT content in these composites controls their conductive, mechanical, and thermal properties. In this work, we have synthesized PANI-CNT composite using stablizer. The structure and properties of the composites have been studied. the electrochemical performance of the composites have been carried out.
Novel Si/Carbon Nanofibers Composite Anodes for Lithium-Ion Batteries
Authors: Yao Meng , Zhang Hui , Liu Xingbo
Published: February 2020

Si/Carbon nanofibers composite films have been deposited on the copper foil by means of cost-effective electrophoretic deposition (EPD). In the meantime, the distribution uniformity of Si particles in the composite materials and the bonding force between Si and CNFs can be improved through individual surface pretreatment of Si and CNFs materials. As an anode material for lithium-ion batteries, the pretreated Si/CNFs composite anode exhibits better capacity retention than the pristine one. The relationship between discharge/charge capacity and the weight ratio of Si and CNFs in the composite has been also investigated. The results show that the composite of with a weight ratio 2:1 (Si:C) shows the most stable cycle performance with a reversible capacity of 574 mAh/g after 100cycles at a current density of 400 mA/g.
Interactions Between LiFePO4 and Binders in Water-Based Electrode Slurries
Authors: Li Chia-Chen , Tsai Feng-Yen , Hsieh Han-Wei , Tung Chih-An
Published: February 2020

Since 1997, lithium iron phosphate (LiFePO4) has been well-known as a potential cathode-active material for a lithium-ion battery because of its advantages of having large theoretical capacity, good cycle-life performance and better safety. Nevertheless, LiFePO4 has other disadvantages, such as its poor electrical conductivity and low diffusion for lithium ions (Li+), and thus it is common for the commercial LiFePO4 to have surface coating of conductive materials, which carbon is the most popular one, to enhance the electrical conductivity and the Li+ diffusivity.

On the other hand, for considerations of environmental consistency and low cost, the technique of fabricating electrodes based on a water-based process by using water as the mixing solvent and water compatible polymer as the binder is gaining favor and has attracted significant interest. In this investigation, the interactions between the cathode active powder, LiFePO4, and the water soluble binder, SBR and CMC binder blend, in the water-based electrode slurries were discussed. The experimental results showed that the factor of the quality of the surface carbon coating on LiFePO4 dominated the interactions between LiFePO4 and the binder. When the surface carbon coating on the active powder was less completed and showing more exposure of the inner LiFePO4, the active powder gelled with the binder significantly and caused the as-prepared water-based electrode slurry to exhibit poorer dispersion property and higher elastic flow behavior. The poorer dispersion of slurry resulted in a less-uniform distribution of compositions in the dried electrode sheets and harmed the electrochemical performance. In addition, the initial mechanism for the gelation of LiFePO4 with the binder blend had also been proposed, which was highly probable due to the chemical chelation between the exposed iron from the inner LiFePO4 and the hydroxyl group of CMC.
Soft Chemical Approach to Surface Modification of Olivine-Type LiFePO4 nanoplatelets and Their Electrochemical Properties
Authors: George Chandramohan , Paolella Andrea
Published: February 2020

Abstract:Olivine phosphate (LiFePO4) is a remarkable cathode material1-4 for lithium ion (Li-ion) batteries due to its high theoretical capacity (Q= 170 mA h g-1), exceptional cycling stability, low cost, environmental compatibility and safety. Conventionally, on this material a carbon coating5 has widely been attempted for better Li ions kinetics and cycling (charge/discharge). Here, we report a colloidal synthesis route to prepare platelet-shaped (~10 nm thick) LiFePO4 nanocrystals (NCs). We then explore soft chemical strategies for the surface preparation of phospho-olivine platelet NCs by a treatment with either lithium fluoride (LiF) or lithium hexafluorophosphate (LiPF6). The NCs were given, for instance, a coating of LiF to yield core-shell type structures (LiFePO4 core and LiF shell) as shown in Figure.1a-b. The core-shell NCs were extensively characterized with the aid of several structural and compositional techniques (via X-ray diffraction, high-resolution electron microscopy, and electron energy loss spectroscopy), highlighting their morphological/structural features relevant for high-rate capable electrodes. We then illustrate the electrochemical properties (via cyclic voltammetry, galvanostatic charge/discharge, and impedance spectroscopy) of core-shell NCs in Li metal half-cells by comparing their carbon coated NC counter parts.

Reference:

(1) Padhi, A. K.; Nanjundaswamy, K. S.; Masquelier, C.; Okada, S.; Goodenough, J. B. J. Electrochem. Soc.
1997, 144, 1609-1613.

(2) Kang, B.; Ceder, G. Nature
2009, 458, 190-193.

(3) Gibot, P.; Casas-Cabanas, M.; Laffont, L.; Levasseur, S.; Carlach, P.; Hamelet, S.; Tarascon, J.-M.; Masquelier, C. Nat.Mat
2008, 7, 741-747.

(4) Nishimura, S.-i.; Kobayashi, G.; Ohoyama, K.; Kanno, R.; Yashima, M.; Yamada, A. Nat.Mat
2008, 7, 707-711.

(5) Wang, J.; Sun, X. Energy & Environmental Science
2012, 5, 5163-5185.

Figure.1 a) Transmission electron microscopy (TEM) image of LiFePO4NC samples a) pristine; b) after a treatment with lithium fluoride (LiF)
Probing Active Particle Assembly in Lithium-Ion Battery Electrode Processing
Authors: Liu Zhixiao , Mukherjee Partha P.
Published: February 2020

Lithium-ion batteries (LIB) are currently considered as the primary choice for electric drive vehicles. The electrode microstructure and composition play an important role in determining the performance of the LIB. To this end, the processing of the multi-phase slurry consisting of active nanoparticles, conductive additives, binder and solvent determines the electrochemical properties and performance of the electrode. Morphology and the size of the active nanoparticles affect the LIB performance due to large active surface area, short diffusion length and fast kinetics. On the contrary, the aggregation of the active nanoparticles might have a detrimental effect. Therefore, fundamental understanding of the aggregation behavior of the active particles in the slurry is of paramount importance.

In this regard, the evaporation dynamics of the slurry is a key factor which determines the microstructural heterogeneity of the electrode. The morphology of the aggregated particles is governed by a variety of physicochemical factors such as interaction between nanoparticles, diffusion rate of the nanoparticles and evaporation rate of the solvent. In this work, we present a mesoscale modeling approach in order to investigate the influence of evaporation on active particle assembly in LIB electrode processing. Our mesoscale model is based on a coarse-grain formalism combining lattice gas and kinetic Monte Carlo methodologies. We will present a comprehensive study of the active particle aggregation behavior and resultant influence due to the (1) evaporation rate of the solvent, (2) active particle and binder interaction, and (3) active particle morphology. Figure 1 shows representative aggregation characteristics of different active particle morphology.

Reference

J. Li, B. L. Armstrong, J. Kiggans, C. Daniel and D. L. Wood, Langmuir, 28, 3783-3790 (2012).

J. Li, C. Daniel and D. L. Wood, Journal of Power Sources, 196, 2452-2460 (2011).

H. Zheng, R. Yang, G. Liu, X. Song and V. S. Battaglia, Journal of Physical Chemestry C, 116, 4875-4882 (2012).

E. Rabani, D. R. Reichman, P. L. Geissler and L.ha E. Brus, Nature, 426, 271-274 (2003).
Dynamic Behaviour of Pt Microelectrode Arrays during the Galvanostatic Oxidation of CO
Authors: Bonnefont Antoine , Crespo-Yapur Alfonso , Bozdech Sébastien , Schuster Rolf , Krischer Katharina , Savinova Elena R.
Published: February 2020

The electroxidation of carbon monoxide has been used as a prototype reaction in fundamental electrocatalysis1. On Pt electrodes, the CO bulk electroxidation is a typical example of a bistable electrochemical system2. The bistable kinetics of the reaction stems from the interplay between the competitive Langmuir-Hinshelwood mechanism and the controlled mass transport of CO toward the electrode. On macroscopic Pt electrodes, different kinds of spatio-temporal instabilities may occur during the CO oxidation depending on the nature and the strength of coupling existing between different parts of the electrochemical system3,4.

In this presentation we will discuss the influence of the size, the interelectrode distance and the supporting electrolyte concentration on the dynamic behaviour of a Pt microelectrode array in the electrooxidation of saturated CO solutions. A custom built galvanostat allows the individual currents flowing through each of the microelectrodes to be measured. Three different kinds of cooperative behaviour could be evidenced for the first time and explained with the help of mathematical modelling. When the applied reaction current value is linearly increased, sequential activation of the microelectrodes was observed (cf. Fig.), while a complex dynamical switching regime was obtained when the current was kept constant5. At low supporting electrolyte concentration, spontaneous oscillations of the potential emerged through the coupling of individual electrodes.

Acknowledgements: Financial support from the International Center for Frontier Research in Chemistry (University of Strasbourg) and of the Labex “Chemistry of Complex Systems” is gratefully acknowledged

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109, 16230, 2005

M.T.M. Koper, T.J. Schmidt, N.M. Markovic, P.N. Ross, J. Phys. Chem. B
105, 8381, 2001

R. Morschl, J. Bolten, A. Bonnefont, K. Krischer, J. Phys. Chem. C,
112, 9548, 2008

P. Bauer, A. Bonnefont, K. Krischer, ChemPhysChem, 11, 3002, 2010

D. A. Crespo-Yapur, A. Bonnefont, R. Schuster, K. Krischer, E.R. Savinova, ChemPhysChem, 14, 1117, 2013
Thin Layer Sonoelectrochemistry
Authors: Duda Chester G , Null Emily M , Leddy Johna
Published: February 2020

Ultrasound irradiation of electrodes in a thin electrolyte layer improves heterogeneous electron transfer kinetics.1,2

A bulk fluid irradiated with ultrasonic energy of sufficient intensity generates bubbles by compression and rarefaction. On bubble collapse, extremes of temperature (T ≳ 5000 K) and pressure (P ≳ 10³ atm) are generated at the narrow interface between the fluid and bubble void3. In bulk fluids, ultrasound enhances transport and impacts homogeneous reactions, but the energy attenuates. In prior sonoelectrochemical studies (first by Coury), bulk electrolyte was irradiated with sufficient ultrasonic intensity to generate cavitation. Cavitation increased homogeneous reaction rates, transport, and turbulence. No effects on heterogeneous electron transfer were found.

In a thin layer sonoelectrochemical system (Figure 1), heterogeneous electron transfer rates increase. Thin layers have two advantages for harvesting sound energy2. Sound waves reflect back into the thin layer | air interface to retain energy. Losses from attenuation are less within thin layers. No frank cavitation is observed in thin layers.

Electrolyte fills the well to form a meniscus. Cyclic voltammograms are recorded for each Ru(bpy)3
2+ and Fe3+ with and without sonication (Figure 2). Sonication intensity can be varied. Sonication has no impact on the voltammetry for Ru(bpy)3
2+ for which electron transfer rates are rapid compared to the scan rate. Sonication does not impact transport. Rates of Fe3+ reduction increases with sonication intensity, as shown by the more rapid rise in current on sonication. Peak potentials shift because the reference is shifting. Where rates are slow, sonication increases heterogeneous electron transfer rates without significantly impact on diffusional transport1.

References and Acknowledgments: Support of the National Science Foundation and the University of Iowa is gratefully acknowledged. With thanks to Andrej Wieckowski for his explorations and contributions to understanding electrocatalysis.

[1] Chester G. Duda, Ph.D. dissertation, University of Iowa, 2012.

[2] J. Leddy, C.G. Duda, and W.J. Leddy III, Provisional U.S. Patent application, 2013.

[3] K.S. Suslick, Y. Didenko, M.M. Fang, T. Hyeon, K.J. Kolbeck, M.M. Mdleleni, and M. Wong, Acoustic Cavitation, Phil. Trans. Royal Soc. A 1999.
Electrocatalysts for Oxidating of Polyhydric and Monohydric Alcohols to Carbon Dioxide on Platinum Alloy Nanoparticles Dispersed on Noble Metal Oxides
Authors: Miecznikowski Krzysztof , Murawska Magdalena , Cox James A.
Published: February 2020

The most important tasks in the previous century are to develop fuel cells as alternative electrochemical devices for efficient generation of energy. The low-temperature acid-type systems, such as hydrogen-oxygen polymer electrolyte membrane fuel cells and direct alcohol fuel cells are, at present, the most commonly studied devices in many laboratories world-wide [1-8]. Among organic compound fuels for anodic reactions in fuel cells, methanol has been historically most extensively studied and, more recently, alternative liquid fuels like a short chain alcohol (such as ethanol, ethylene glycol) becomes essential. It is well established that Pt is rated as the most active material for oxidation of small organic molecules in acidic media but the easily poisoning by intermediate byproduct – CO adsorb species the binary or ternary platinum-based alloys with Ru, Sn, Rh, Pb, Ir, W or Mo were proposed to enhance the electrooxidation activity towards alcohols[1-8]. The splitting of the C–C bonds is particularly difficult at ambient (low) temperatures, and the surface of catalytic platinum readily undergoes poisoning with intermediates of the ethylene glycol or ethanol oxidation. This problem may be partially solved by applying bifunctional electrocatalysts. Metals, like ruthenium, tin or rod may activate molecules of water and supply strong oxidizing agents: –OH groups and thus remove adsorbed species from platinum surface.

In order to increase the overall kinetic of electrooxidation of ethylene glycol or ethanol, we propose modification of bifunctional, metallic catalyst with metal oxide. Our concept involves adsorption onto the surface of commercial available Pt alloys nanoparticles ultra-thin layers of tungsten oxide, molybdenum oxide, zirconium oxide or iridium oxide. Presence of metals oxide (WO3, MoO3, ZrO2, IrO2) on nanoparticle have led not only to the specific interactions but also increased the catalytic surface. Introduction of noble metals oxide to Pt-based alloy nanoparticles lead to the increase of the catalytic current under voltammetric and chronoamperometric conditions.

References:

[1] M. Li, D.A. Cullen, K. Sasaki, N.S. Marinkovic, K. More, R.R. Adzic, J. Am. Chem. Soc. 135 (2013) 132

[2] H. Wang, Z. Jusys, R.J. Behm, Electrochim Acta 54 (2009) 6484

[3] R. Ojani, J.-B. Raoof, S. Fathi, Electrochimi. Acta 54 (2009) 2190

[4] A. Kowal, M.Li, M. Shao, K. Sasaki, M.B. Vukmirovic, J. Zhang, N.S. Marinkovic, P. Liu,A.I. Frenkel, R.R. Adzie, Nature Mater. 8 (2009) 325

[5] D.M. dos Anjos, F. Hahn, J.-M. Leger, K.B.Kokoh, G.Tremiliosi-Filho, J. Braz. Chem. Soc. 19 (2008) 795

[6] P. J. Barczuk, A. Lewera, K. Miecznikowski, P. J. Kulesza, J. Power Sources 195 (2010) 2507

[7] K. Miecznikowski, P.J. Kulesza, J. Power Sources 196 (2011) 2595

[8] K. Miecznikowski, J. Solid State Electrochem. 16 (2012) 2723.
TaOx-Capped Pt Nanoparticles As Active and Durable Electrocatalysts for Oxygen Reduction
Authors: Awaludin Zaenal , Moo James Guo Sheng , Okajima Takeyoshi , Ohsaka Takeo
Published: February 2020

Here we demonstrate the formation of unique structure of TaOx-capped Pt nanoparticles on a Pt/TaOx/GC electrocatalyst (Fig. 1), where at first tantalum oxide (TaOx)and next Pt nanoparticles were electrodeposited on the glassy carbon (GC) substrate, for an oxygen reduction. The surface characterizations show that the nanoparticles of TaOx deposit homogeneously on the GC surface, forming a thin layer and surprisingly, the Pt nanoparticles do not exactly deposit on the top layer of the TaOx, i.e., Ta2O5 but inside their framework and consequently a unique assembly of the TaOx-capped Pt particles is fabricated. The analyses using XPS spectra indicate electronic interactions of TaOxwith the GC, as well as with the Pt nanoparticles. The electrochemical measurements conducted by cyclic voltammetry and rotating ring-disk electrode voltammetry reveal that the novel electrocatalyst possesses an enhanced activity for an oxygen reduction reaction, without any loss of performance even after 250,000 cycles (1,111 h) of a durability test. The plausible reasons for the remarkable activity and durability of this electrocatalyst are proposed.

Fig. 1 Schematic illustrations of (a) Pt deposited on a TaOx-modified GC surface with a TaOx framework, (b) O2 adsorption on Pt-TaOxinterface and (c) bonding formation of Ta with GC and Pt.

Acknowledgement

The present research was financially supported by Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.

References

1) Z. Awaludin, M. Suzuki, J. Masud, T. Okajima and T. Ohsaka, J. Phys. Chem. C, 115, 25557 (2011).

2) Z. Awaludin, J.-M. Sheng Moo, T. Okajima and T. Ohsaka, J. Mater. Chem. A, 1, 14754 (2013).
Spontaneous Phase Segregation in Bare Palladium-Platinum Nanoparticles Evidenced By Superior Hydrogen Absorption
Authors: Januszewska Aneta , Dercz Grzegorz , Lewera Adam , Jurczakowski Rafal Robert
Published: February 2020

Palladium Platinum bimetallic alloys are widely used in heterogeneous catalysis as active components for oxygen reduction reaction, anodes in low temperature fuel cells and hydrogenation of aromatic compounds in fuels. Pd-Pt catalysts often operate at elevated temperatures, for example in catalytic converters for automobile exhausts. Under such conditions segregation/alloying is a particularly important issue. However, in most experimental studies on Pd-Pt nanoparticles the homogeneous alloying is consistently reported or a priori assumed.

Specific interactions of surfaces with monolayers of foreign adatoms (metals and nonmetals) are generally known as a particularly sensitive surface probes [1], among which copper and hydrogen underpotential deposition (UPD) are the most widely used. However, by using this approach little is known about the nanoparticle interior. In contrast, chemical potential of absorbed hydrogen does provide deep insight into the homogeneity on the atomic scale since it is determined by near interactions between metal atoms and absorbed hydrogen occupying interstitials.

In this study we have shown that Pd-Pt nanoalloys are much more susceptible to segregation than their bulk counterparts. The spontaneous segregation and chemical ordering of Pd-Pt nanoalloys was evidenced by hydrogen absorption enhanced nearly by three orders of magnitude with respect to random Pd-Pt alloys [2].

Chemical surface and bulk compositions of the nanoalloys were established by using XPS and ICP-MS, respectively. Carbon monoxide adsorption/oxidation was used as a surface probe and as an indicator of catalytic properties of investigated bimetallic nanoparticles. Hydrogen sorption properties of these alloys were investigated by means of hydrogen UPD and Hydrogen insertion in acidic solutions by using classical transient electrochemical methods. Hydrogen absorption isotherms exhibited a markedly enhanced hydrogen solubility and distinct phase transition in the Pd-Pt-H systems that is absent in Pd-Pt alloys with random atom distribution.

We also report the highest hydrogen sorption in Pd80Pt20 alloy exceeding H/(Pt+Pd)=0.5 at the ambient temperature and hydrogen pressure, which additionally emphasizes the importance of both surface purity and segregation on catalysis and hydrogen storage. Our results clearly show that phase segregation is an extremely important factor that is frequently overlooked in experimental studies yet quite crucial for practical applications.

Literature

[1] Solla-Gullón, J.; Rodríguez, P.; Herrero, E.; Aldaz, A.; Feliu, J. M. Phys. Chem. Chem. Phys. 2008, 10, 1359-1373.

[2] Januszewska, A.; Dercz, G.; Lewera, A.; Jurczakowski, R. J. Phys. Chem. C, Submitted.
Relation Between Thermodynamic and Kinetics Aspects of Pt Deposition Via Slrr and Resulting Properties of Catalyst Monolayers
Authors: Brankovic Stanko , Yuan Qiuyi
Published: February 2020

The deposition method based on surface limited replacement reaction i.e. galvanic displacement of under potentially deposited (UPD) metal monolayers has been extensively used for preparation of highly active catalysts monolayers1-[i],[ii],[iii][iv]. The physical and chemical behavior of these monolayers is altered due to different structural and electronic effects dominating their properties. In the case where ligand (substrate) effect is weak, their properties are predominantly affected by the level of coherent strain.

The two dimensional Pt submonolayers/nanoclusters on Au(111) and Pd(hkl) were used as model system to study size/strain effect on catalyst monolayer properties. The probe ion/molecule was CO and Pb2+, and the Pt submonolayers were obtained by galvanic displacement of Cu UPD monolayers using surface limited red-ox replacement process. The morphology of Pt monolayers was studied by scanning tunneling microscopy and statistical image processing. The electrosorption characteristics of Pt submonolayers were studied using SNIFTIR, STM and conventional electrochemical methods.

The results indicate that Pt submonolayers have quite different electrosorption properties as compared to Pt bulk electrode. In both cases, with strong (Pd(111)) and weak (Au(111)) ligand effect of substrate, a lower reactivity of Pt submonolayers is observed as compared to Pt(111) electrode. In the case of CO adsorption on Pt/Pd(111), the spectroscopic and electrochemical data indicate weaker bond than on both bulk Pt(111) and Pd(111) electrodes. In the case of Pb2+adsorption, (UPD), the Pt sub-monolayers remain passive for UPD process until several hundred milivolts more negative potentials as compared to Pb UPD on Pt(111). These results suggest that lateral strain developed in Pt submonolayers/nanoclusters, which is function of their size, is a dominant force determining their electrosorption behavior.

The presented work correlates the theoretical analysis of the size effects on the active strain in different Pt submonolayer catalysts with their experimentally observed electrosorption properties.

[#] SRBrankovic@uh.edu

[[i]] J. Greeley, J. K. Nørskov, and M. Mavrikakis, Annu. Rev. Phys. Cehm., 53, (2002) 319.

[[ii]] M. Mavrakakis, B. Hammar, and J.K. Nørskov, Phys. Rev. Lett., 81, (1998) 2819.

[[iii]] A. Schlapka, M. Liseihka, A. Gross, U. Kasberger, and P. Jakob, Phys. Rev. Lett., 91, (2003) 016101.

[[iv]]E. Kamshoff, E. Hahn, and K. Kern, Phys.
Rev. Lett., 73, (1994) 704.
Electrical Coupling of Enzymes to Electrodes in Biofuel Cells and Biobatteries
Authors: Bilewicz Renata
Published: February 2020

R. Bilewicz1, K. Stolarczyk1, D. £yp1, M. Kizling1, M. Karaskiewicz1, J.F. Biernat2, K. ¯elechowska3, J. Rogalski4, K.P. Roberts5,

1
Faculty of Chemistry University of Warsaw, Warsaw, Poland

2
Department of Chemistry, Gdansk University of Technology, Gdansk, Poland,

3
Faculty of Applied Physics and Mathematics, Gdansk University of Technology, Gdansk, Poland
of Chemistry

4
Department of Biochemistry, Maria Curie Sklodowska University, Lublin, Poland

5
Faculty of Chemistry and Biochemistry,

The University of Tulsa, Tulsa, USA

Abstract

Single walled carbon nanotubes (SWCNTs) were equipped with aryl residues by chemical reactions. These insoluble materials were used to substitute classical soluble mediators, which help to transfer electrical charge between the conducting electrode and the redox active center of enzyme molecules. The effect of different aryl residues on the efficiency of the catalytic mediatorless reduction of dioxygen in the presence of laccase was systematically studied using voltammetry and measuring the power output of a biofuel cell.