bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrochemically-Controlled Dimerization in Ferrocene Ureidopyrimidone Derivatives. the Effect of Ferrocene Position
Authors: Mikhaylova Veronika , Smith Diane K 
Published: February 2020

Ureidopyrimidones (UPy’s) are well-known to dimerize in weakly polar solvents such as CH2Cl2, via the formation of four strong, linear H-bonds. This, coupled with their relative ease of synthesis, has led to their use as a linker in supramolecular polymers and gels. The attraction of such materials is their inherent self-healing properties, whereby a defect can be repaired by using heat or mechanical stress to reversibly break the polymer at the H-bond sites. This increases the fluidity of the material, allowing the defect to fill in. Upon cooling or relief of stress, the H-bonds reform and the defect is repaired. However, while the use of heat or mechanical stress as stimuli are clearly useful, neither is inherently very selective. On-going research in our lab is focused on increasing the versatility of the UPy system by creating electroactive UPy’s in which dimerization strength can be controlled in a more selective manner through oxidation and reduction.
Previously, our group has shown that dimers based on the ferrocene-UPy derivative, 1, break apart upon oxidation of the ferrocene to the ferrocenium form at mM concentrations in CH2Cl2. This could be due both to the creation of electrostatic repulsion and a decrease in H-bond strength due to the reduced H-donor ability of the O and N on the pyrimidone side. In this project, another Fc-UPy has been prepared, 2, in which the ferrocene is attached to the urea side of the molecule. In contrast to 1, oxidation of 2 shows a single reversible ferrocene CV wave in CH2Cl2 at mM concentrations. Under these conditions, 1H NMR indicates that 2 is fully dimerized, thus, it appears that, unlike with 1, oxidation has no significant effect on dimerization of 2. In both cases, oxidation would increase electrostatic repulsion. However, unlike in 1, oxidation of 2 should actually increase H-bond strength by making the urea NH a stronger H-donor. Therefore, it appears that the effect of oxidation on the H-donating or accepting ability is a more crucial factor for dimerization control than electrostatics in these systems.

Figure 1
Imaging Electrochemistry at the Nanoscale By Liquid Cell Transmission Electron Microscopy
Authors: Hietzschold Sebastian , Sepunaru Lior 
Published: February 2020

Direct optical visualization of electrochemical processes at the nanoscale is an exciting field of research. It became more and more feasible through the development of enclosed liquid cells for transmission electron microscopes over the past years [1]. The liquid cell itself is built by stacking two silicon chips with electron transparent silicon nitride windows, which are then sealed by a gasket against the surrounding high vacuum in the microscope column. Microfabrication of electrode structures onto the chips opened up the opportunity to control the electric potential and current within the cell in order to perform in-situ potentiometric measurements and impedance spectroscopy. This unique feature enables the correlation of real-time optical imaging at the nanoscale and electrochemistry. So far, most of the experiments have focused on batteries and corrosion studies [2,3]. While there have been numerous reports on the diffusion and agglomeration of nanoparticles [4], the visualization of nanoparticle dynamics coupled to voltammetry in the vicinity of an electrode surface has received less attention. Herein, we investigate the diffusion, deposition and stripping of nanoparticles at an electrode under an applied electric bias. We give insight into how a nanoparticle collision event quantitatively transfers into an electrochemical current signal and disentangle electron beam effects. These results might pave the way towards observation and understanding of reactions catalyzed by nanoparticles in general.
References:
[1] N. de Jonge and F. M. Ross, Electron microscopy of specimens in liquid. Nat. Nanotechnol., 6 (2011), 695-704
[2] B. L. Mehdi, J. Qian, E. Nasybulin et al., Observation and quantification of nanoscale processes in lithium batteries by operando electrochemical (S)TEM. Nano Lett., 15 (2015), 2168-2173
[3] S. W. Chee, S. H. Pratt, K. Hattar et al., Studying localized corrosion using liquid cell transmission electron microscopy. Chem. Commun., 51 (2015), 168-171
[4] H.-G. Liao, K. Niu and H. Zheng, Observation of growth of metal nanoparticles. Chem. Commun., 49 (2013), 11720-11727
(Invited) X-Ray Reflectivity Studies of Interfaces in Lithium-Ion Batteries
Authors: Steinrueck Hans-Georg 
Published: February 2020

In lithium-ion batteries (LIBs), the arrangement of electrolyte molecules directly at the electrode interface, and the corresponding electric double layer (EDL) are expected to govern the interfacial ion transport during charge/discharge and the electrochemical stability, i.e. the origin and properties of the solid electrolyte interphase (SEI). The SEI is formed on anode surfaces due to electrolyte decomposition at low potentials outside the electrolyte's electrochemical stability window, and dictates cell chemistry, cycle life, and electrochemical reversibility.
Towards this end, the first topic of this talk covers an Ångstrom-resolution combined experimental and theoretical structural determination of solid–liquid interfaces relevant to LIBs, specifically a baseline organic electrolyte containing various concentrations of lithium hexafluorophosphate (LiPF6) salt at a metal oxide interface. We find good agreement between our x-ray reflectivity (XRR) and molecular dynamics (MD) simulations. These show well defined interfacial layering of electrolyte molecules and that solvent molecules in the first interfacial layer are aligned surface-parallel. Furthermore, we observe reorientation of solvent molecules in the presence of ions [1,2].
The second portion of this talk describes a multi-property characterization study of the physical and chemical properties as well as the nucleation and growth of the SEI on silicon anodes relevant to LIBs. We combined in situ XRR, linear sweep voltammetry (LSV), and ex situ x-ray photoelectron spectroscopy (XPS) to develop a holistic understanding of the SEI formation mechanism and properties on native oxide terminated single crystalline Si electrodes. Our self-consistent findings show the formation of two distinct inorganic SEI layers, and reveal the critical role of the surface oxide in the surface electrochemistry of silicon anodes. These novel insights will be discussed with regard to the performance of LIB in general [3,4,5]. Finally, we will present recent results from combining in situ XRR and precision electrochemical measurements to understand origins of coulombic efficiencies, capacity fading, and charging rate capabilities in thin film silicon batteries.
­­­­References

H.-G. Steinrück, C. Cao, Y. Tsao, C. J. Takacs, O. Konovalov, J. Vatamanu, O. Borodin, M. F. Toney, Energy Environ. Sci., 11, 594-602 (2018)

Horowitz, H.-G. Steinrück, H.-L. Han, C. Cao, I. I. Abate, Y. Tsao, M. F. Toney, G. A. Somorjai, Nano Lett. 18, 2105-2111 (2018)

Cao, H.-G. Steinrück, B. Shyam, K. H. Stone, M. F. Toney, Nano Lett.16, 7394-7401 (2016)

Cao, H.-G. Steinrück, B. Shyam, M. F. Toney, Adv. Mater. Interfaces 4, 1700771 (2017)

C. Cao, I. I. Abate, E. Sivonxay, B. Shyam, C. Jia, B. Moritz, T. P. Devereaux, K. A. Persson, H.-G. Steinrück, M. F. Toney, Joule (accepted 2018)
Cross Sectional Mapping of Nano-Mechanical Properties of Composite Electrodes for Lithium Ion Batteries Using Bimodal Mode Atomic Force Microscopy
Authors: Masuda Takuya , Sakai Hiroki , Taniguchi Yukinori , Uosaki Kohei 
Published: February 2020

Lithium-ion batteries (LIBs) have been widely used for various applications including portable devices and electric vehicles. Improvement of the cyclability and capacity is an important challenge. In the manufacturing process, active materials, conductive additives and binders are mixed in a solvent at a certain ratio and the slurry is casted, dried and pressed on a metallic foil current collector to yield a composite film. The composite films are assembled together with an electrolyte solution and a separator in coin or laminate cells. The packing density and mechanical strength of each material are important parameters for the cell performance because the volume expansion and resulting mechanical stress may cause a destruction of the electrical connections between binders, current collectors and the active materials during the charge/discharge processes. Young's modulus is one of the most important mechanical properties because it is an indicator of the mechanical strain in a material under a certain amount of stress.
Nanoindentation has been used to measure the Young's moduli of various materials. However, it has a few restrictions as follows: (i) sample surface has to be destructed in nanoindentation and (ii) it has a limited spatial resolution, typically a few micrometers, due to the size of the disruption. Although recent atomic force microscopy (AFM) techniques allow non-destructive and high-resolution Young's modulus mapping by measuring force curves at each point using relatively weak force of<100 nN, this method is not applicable for stiff materials with modulus larger than 100 GPa because their sample deformation is too small to be detected by the cantilever deflection. Here, a newly developed technique, bimodal AFM that allows nanoscale mechanical mapping for a wide range of Young's modulus from 0.1 to 200 GPa in a non-destructive manner, was applied to LiCoO2-based positive and graphite-based negative composite electrodes before and after the charge-discharge cycles in a coin cell for a demonstration.
Reference: H. Sakai, Y. Taniguchi, K. Uosaki, T. Masuda, “Quantitative cross-sectional mapping of nanomechanical properties of composite films for lithium ion batteries using bimodal mode atomic force microscopy”, 2019, 413, 29-33.
Study of Sulfur-Based Electrodes By Operando Acoustic Emission
Authors: Lemarie Quentin , Idrissi Hassane , Thivel Pierre-Xavier , Alloin Fannie , Roué Lionel 
Published: February 2020

The acoustic emission (AE) technique has been widely used since the 70’s for detecting anomalies such as leakages and cracks on large structure (e.g. bridges, pressure containers, and pipe lines). The analysis of the AE signals (transient elastic waves) can also be used to characterize the degradation mechanisms (crack growth, friction, delamination, matrix cracking, corrosion, etc) of various materials subjected to a stress by mechanical, pressure or thermal means. Recently, AE technique has also been used to evaluate the degradation of metal hydride electrodes for Ni-MH [1] and Si-based electrodes for Li-ion batteries [2,3]. Cracking of the active material and gas evolution are the main sources of AE signals identified in these studies.
In the present study, the AE technique is used for studying upon cycling the mechanical degradation of S-based electrodes for Li/S batteries. The AE signals were recorded by a piezoelectric transducer fixed on the back of the working electrode. S-based electrodes made with two different binders (PVdF vs. CMC) and two different current collectors (standard Al foil vs. porous 3D carbon paper) were studied. In all cases, AE signals were mainly detected during the first plateau of the first discharge, suggesting that the electrode degradation mostly occurs during the initial dissolution of the S8 particles. AE signals were also detected during a few subsequent cycles when CMC binder is used. This is attributed to a better propagation of the AE signals through the electrode thanks to an improved adhesion of the electrode to the current collector in comparison to PVdF binder. This is confirmed by further mechanical resistance testing (peel and scratch tests). The use of a carbon paper as a current collector combined to CMC binder greatly improves the electrochemical performance of the S electrode by preventing the collapse of the electrode upon cycling. This electrode also presents an increased amount of AE signals, suggesting that the carbon fibres of the C paper act as an AE waveguide.
This study demonstrated that AE could be used as an efficient tool to monitor the morphological degradation of S-based electrodes upon their cycling and offers relevant information for optimizing their formulation and architecture.

A. Etiemble, H. Idrissi, P. Bernard, L. Roué. New insights into the pulverization of
LaNi5-based alloys with different Co contents from electrochemical acoustic emission measurements. Electrochim. Acta 186 (2015) 112-116

A. Tranchot, A. Etiemble, P-X. Thivel, H. Idrissi., L. Roué. In-situ acoustic emission study of Si-based electrodes for Li-ion batteries, J. Power Sources 279 (2015) 259-266.

A. Tranchot, P-X. Thivel, H. Idrissi, L. Roué. Influence of the Si particle size on the mechanical stability of Si-based electrodes evaluated by in-operando dilatometry and acoustic emission. J. Power Sources 330 (2016) 253-260.

Figure 1
Battery Charakterisation Using Optical Methods
Authors: Rahe Christiane 
Published: February 2020

The fast advance of electromobility demands the maximizing of energy density and lifetime of any given battery. Such needs for precise information can only be satisfied with the help of adequate simulation models. During the last years, several battery models have been proposed [1, 2, 3].
This publication focuses on physical-chemical battery (p-c-b) models as they allow insights into single electrochemical processes and their effect on the whole system and reliable predictions of the battery behavior. P-c-b models are based on the underlying chemical and physical equations describing the internal battery processes. They require input parameters, which need to be adapted to the specific characteristics of the examined cell and especially the used materials. Input parameters need to be determined in detailed analyses on the opened cell. However, existing methods for model parameterization are insufficient and time intensive: Existing methods are limited in terms of mathematical constraints.
In this work, a measurement method for determining the material diffusion parameter is described and applied to different samples based on microscopy. An optical cell is used to track the lithiation progress of graphite anodes introducing color changes upon intercalation. Out of these data, the diffusion coefficient of lithium in graphite is calculated. Furthermore, a parameter study on different graphite anodes is conducted. Single parameters of the graphite anodes are changed to execute a parameter study: the influence of porosity and particle size is shown and analyzed.
The results of the parameter study can be used to define the input parameters for the next generation of battery models. Furthermore, the results indicate that the proposed measurement method offers several advantages (as easy adaptable and quick measurable) compared to existing methods. The proposed method can be adapted to other cell types and models.
[1] M.Ecker, et all. Parametrization of a Physico-Chemical Model of Alithium-Ion Battery doi:10.1149/2.0551509 J. Electrochem. Soc. 2015 volume 162, issue 9, A1836-A1848
[2] D.Cittanti, et all. Modeling Li-ion batteries for automotive application: A trade-off between accuracy and complexity, doi: 10.23919/EETA.2017.7993213, IEEE Xplore 27.07.2017
[3] A. Kashkooli, Multiscale modeling of lithium-ion battery electrodes based on nano-scale X-ray computed tomography, doi: 10.1016/j.powsour.2015.12.134, J. Power Sources, 2016, vol. 307, p. 496-509
Hybrid Graphene/Metal Oxygen Reduction Reaction Catalyst: An Insight at Sandwiched Single Layer Graphene Interdiffusion Barrier, Preserving Sharp Metallic Interface for Atomically-Thin Core@Shell Architectures
Authors: Abdelhafiz Ali , Vitale Adam , Alamgir Faisal M. 
Published: February 2020

The concept of a core–shell metallic structures, with well defined atomically-thin “shell” material delineated from the “core” support with atomic-scale sharpness opens the door to a multitude of surface-driven materials properties that can be precisely controlled. However, in practice, such architectures are difficult to preserve due to the entropic cost of a segregated near-surface architecture, and the core and surface atoms inevitably mix through interdiffusion over time or under processing conditions (e.g. in Proton Exchange Membrane Fuel Cells (PEMFC)).
Herein, We present a systematic study of interdiffusion in a Au@Pt Core@Shell architectures and the role of an interrupting monolayer graphene sandwiched in between. The physical and chemical structure of the near-surface is probed via mean-free-path tuned X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy (HRTEM), and probing the oxygen reduction reaction (ORR) as an electrochemical performance indicator. We find that at operating temperatures above 100 °C, there is a potential for interdiffusion to occur between the shell and support metals, which can diminish the catalyst activity toward ORR. The introduction of a single-layer graphene, at the interface between the core and shell metals, acts as a barrier that prevents unwanted core leaching and/or surface-alloying between the layered metals. STEM imaging shows that fully wetted Pt monolayers can be grown on stand-alone single graphene template, allowing a high level of surface utilization of the catalyst material. We present how the use of graphene as an interdiffusion barrier mitigates the loss of surface catalytic sites, showing much improved retention of Pt monolayer surface at elevated temperatures.
Development of Bimetallic Non-Platinum Group Metal Catalysts Based on Metal Organic Framework Precursors
Authors: LaRochelle Richard Lynne , Jia Qingying , Mukerjee Sanjeev 
Published: February 2020

It has been postulated that non-platinum group metal (non-PGM) catalysts for the oxygen reduction reaction (ORR) must meet four criteria: metal, carbon, nitrogen, and pyrolysis. The precise nature of the catalytic active site remains under debate. Many permutations of metal, nitrogen, and carbon are formed during pyrolysis, only a few of which are catalytically active. Results from multiple studies indicates that metals surrounded by four pyridinic nitrogen atoms form at least part of the active site. It stands to reason that the greater the number of metal-nitrogen-carbon (M-Nx-Cy) sites formed, the greater the active site density will be. However, nanoparticle formation is likely to compete at very high densities. Other groups have demonstrated enhanced catalytic activity in bimetallic catalysts for both ORR and hydrogen evolution reaction (HER) using first and second row non-PGM transition metals in M-N4-Cy centers. The present research focuses on the use of metal organic frameworks (MOFs), primarily zinc imidazolate frameworks (ZIFs), as precursors for bimetallic catalysts. ZIFs are of interest because they are highly porous, contain a high density of M-N4-Cy centers, and are simple to prepare. Metal choice in ZIF precursors (Zn or Co) affects the porosity and graphitization of the heat-treated material. Cobalt catalyzes the formation of carbon nanotubes upon pyrolysis. This research is an investigation of the effects of MOF precursor type, heat treatment, and non-PGM metal pairs (Fe, Co, Mn or Mo) on catalytic activity. It is hypothesized that carbon nanotubes and other graphitic structures formed during pyrolysis of Co-containing ZIFs facilitate the cooperation of proximal metal sites in electron transfer. This will be demonstrated by evaluation of bimetallic Co-containing catalysts in HER or ORR by varying the degree of graphitization while holding the weight percent ratio of Co and another metal (e.g. Fe) constant. Comparison of this data with catalysts prepared from precursors with optimal graphitization and varying the ratio of Co to the other metal will elucidate the relative importance of local carbon structure and electron transfer between two different metal centers.
This work was supported by the U.S. Department of Energy under award number DE-EE0008416. The authors declare no competing financial interests.
Bipolar Electrochemically Exfoliated Graphene for Supercapacitor Application
Authors: Khakpour Iman , Rabiei Baboukani Amin , Allagui Anis , Wang Chunlei 
Published: February 2020

Developing a simple, cost-efficient, and scalable process for the production of graphene attracted a considerable interest, since, the production of graphene-based devices still suffers from various challenges. At one hand, the graphene products are not optimal for practical applications because they contain a large distribution of size and numbers of layers. At another hand, the common processes for production and integration of graphene not only suffers from being costly, time-consuming, and complicated but also the quality, performance and surface condition of produced material are hard to control.
In this study, we used the bipolar concept to design a single step, eco-friendly, cost-efficient, and simple process to simultaneously fabricate and in-situ deposit high-quality graphene-based layers directly on conductive substrates. Formation of graphene oxide and reduced graphene oxide on the substrates are confirmed by different materials characterization methods. The symmetrical 2 electrode systems were assembled and electrochemical performance of produced electrodes was investigated using electrochemical impedance spectroscopy, cyclic voltammetry, and galvanostatic charge-discharge tests. The excellent performance of the supercapacitor electrode was confirmed and promising results for AC/DC filter application were obtained. The results will be presented in detail at the conference.

Key words: bipolar electrochemistry, graphene, supercapacitor, energy storage, AC filter
(Invited) Novel Three-Dimensional Fuzzy Graphene (3DFG)-Based Platform for Interrogation of Excitable Cells
Authors: Rastogi Sahil Kumar , Scopelliti Matteo , Bliley Jacqueline , Johnson Nicholas , Shiwarski Daniel , Garg Raghav , Feinberg Adam , Chamanzar Maysam , Cohen-Karni Tzahi 
Published: February 2020

Investigating and modulating electrical activity of cardiomyocytes and neurons is essential to understanding their physiology, regeneration of excitable cells/tissues, and treatment of various disorders. Recently, microelectrode arrays (MEAs) have gained tremendous popularity since they enable multi-site recordings at sub-msec temporal resolution, provide two-way interaction with cells i.e. recording and stimulation, and have well-established microfabrication methods. However, currently used planar MEAs are not able to record and stimulate at sub-cellular resolution due to significant increase in electrode impedance which reduces the signal-to-noise ratio (SNR) of recorded signal. Currently there is a need to (i) enable high density electrode arrays, (ii) provide high spatial resolution, and (iii) prevent averaging of signals from multiple cells.
To address these needs, we have developed three-dimensional out-of-plane grown fuzzy graphene (3DFG)-based MEA. Out-of-plane growth of single-to-few layers of graphene flakes leverages graphene's outstanding surface-to-volume ratio. The high surface area leads to significant reduction in impedance, thus enabling electrical recordings with high SNR and development of ultra-microelectrode arrays to perform sub-cellular measurements. Furthermore, the high flake density of graphene in 3DFG lead to high photo-absorbance in UV-NIR range. This opens up avenues to enable photo-thermal stimulation of cells with high precision and sub-cellular resolution. Our presented approach would greatly impact our basic understanding of signal transduction in complex cellular assemblies. Furthermore, it would provide a platform for developing and screening of therapeutics, and treatment of various cardiac and neurological diseases.