bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) HydroGEN Benchmarking: Developing Best Practices for Water Splitting Technologies
Authors: Ayers Katherine E. , Gross Karl
Published: February 2020

The need for renewable sources of hydrogen is increasing rapidly based on global goals for decarbonization. Interest and investment has also increased with the advent of the Hydrogen Council and the DOE H2@Scale initiative. There are several pathways which could eventually be part of the overall mix, but are currently at different maturities and have different challenges. Low cost renewable energy provides a potential pathway for low temperature electrolysis to make a large impact in the short term, while high temperature baseload such as nuclear matches well with high temperature electrolysis based on solid oxide technology. Photoelectrochemcal and solar thermal chemical water splitting are earlier stage technologies, but could be viable in the long term especially in areas without current infrastructure, if the materials targets can be achieved and manufacturing capability is developed. In the nearer term, understanding of these challenges can also provide valuable perspective for the more mature pathways.

In any of these technologies, appropriate comparisons of test results is important to measure overall progress in the field and identify promising directions, as well as to provide credibility to published results. The DOE Fuel Cell Technologies Office previously funded the development of a detailed reference guide of common methodologies, protocols, and important limitations for measuring critical performance properties of advanced hydrogen storage materials, which has served as a resource to the hydrogen storage materials development community to aid in clearly communicating the relevant performance properties of new materials as they are discovered and tested. The project was coordinated with the IEA and involved 46 co-authors and contributors from 9 countries. The final documents are available to the public on-line: https://www.energy.gov/eere/fuelcells/downloads/recommended-best-practices-characterization-storage-properties-hydrogen-0

A similar effort is now underway for water splitting technologies, framed by questionnaires distributed to the community, frameworks for materials and device testing, and workshops and discussions for feedback. A series of protocols is being drafted to provide easy to follow procedures for materials characterization. The team is also identifying gaps in methods and materials for possible development, and drafting technology roadmaps to highlight research needs. This talk will describe the success of the storage effort, and status for the water splitting benchmarking project.
(Invited) Multiscale Modeling of Reactive Interfaces in Support of the DOE Energy Materials Network
Authors: Wood Brandon C.
Published: February 2020

Energy storage and conversion devices rely on chemical process occurring at solid-gas, solid-liquid, and solid-solid interfaces. Probing behavior of these interfaces under operating conditions presents significant challenges; however, predictive modeling offers an opportunity for providing key insights into interface chemistry, particularly when operating in tandem with high-fidelity experimental characterization techniques.

Within the DOE Hydrogen Materials—Advanced Research Consortium (HyMARC) and the HydroGEN Advanced Water Splitting Materials Consortium, we are using multiscale models to understand properties of reactive interfaces for the production and storage of hydrogen. I will provide an overview of our materials modeling strategy within these consortia, ranging from first-principles calculations of interface chemistry to continuum methods for microstructure-level properties. I will then review some of our recent activities for simulating thermodynamic and kinetic properties of hydrogen-related materials. Specific examples will be given of how these computational models have helped to elucidate mechanisms of interface chemical reactions, the formation of new phases, and the impact of solid-state interfaces on key reaction pathways. I will also show how simulations have been combined with experimental probes to improve models and obtain new understanding of materials interfaces under operating conditions. Finally, I will discuss how this understanding is being used to guide new strategies for improving materials functionality for hydrogen storage and production.

This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
(Invited) Mesoscale Modeling of Solid-State Hydrogen Storage Mechanisms
Authors: Heo Tae Wook , Kang ShinYoung , Zhou Xiaowang , Shi Rongpei , Wood Brandon C.
Published: February 2020

Metal hydrides have been considered as a promising class of solid-state hydrogen storage materials owing to their excellent volumetric and gravimetric storage densities, which can overcome critical technological limits of the currently available high-pressure hydrogen gas storage approach. Solid-state hydrogen storage mechanisms involve the complicated coupling of chemical/physical processes over vast ranges of multiple length and time scales. These include surface reactions with hydrogen gas; surface/bulk/interface mass transport processes; structural modifications occurring under operation; and intermediate phase nucleation-and-growth processes associated with hydrogen incorporation. Essentially, these are collective dynamic processes of atomic/molecular species that determine the thermodynamics and kinetics of nano- or micro-level characteristics. The mesoscale continuum modeling framework can provide a unified platform for integrating the necessary atomistic approaches, which typically provide higher accuracy for nanoscale chemical processes, and continuum approaches, which offer far greater flexibility and scalability and can describe materials at the microstructural level. In this presentation, we demonstrate our integrated effort as part of the DOE Hydrogen Storage Materials—Advanced Research Consortium(HyMARC) under the Energy Materials Network(EMN) towards the multiscale modeling of hydrogen storage mechanisms in metal hydrides for hydrogen storage. Specifically, we will report our recent efforts on the development of an integrated mesoscale modeling framework that can directly incorporate parameters derived from predictive atomistic modeling approaches such as ab initiocalculations and molecular dynamics simulations. Representative case studies will be presented, including beyond-ideal thermodynamic modeling of complex hydrides, effective mass transport/mechanical response modeling for complex hydride microstructures, and phase-field modeling of reaction-induced phase transformations of simple or complex metal hydrides during the (re/de)hydrogenation.
(Invited) Development of a Multiscale Approach for Modeling Fuel Cell Electrodes
Authors: Pant Lalit M. , Chowdhury Anamika , Weber Adam Z.
Published: February 2020

Porous electrodes form a critical part of electrochemical energy systems such as polymer electrolyte fuel cells (PEFCs). In order to improve their performance and reduce cost, novel designs for porous electrodes are being envisioned, e.g., non-PGM catalyst layers, ultra-thin Pt/Pt-Ni based catalyst layers, or NSTF catalyst layers.1 These electrodes have features spanning multiple length scales: from nano-scale catalyst particles to micrometer thick catalyst layers; with meso-scale porous structure in between. In order to understand the impact of these new designs on cell performance, a detailed understanding of the multi-scale structure is required. Furthermore, the physical processes at each length scale must be understood and up-scaled in order to evaluate the macro-scale cell performance.

The aim of this work is to develop multi-scale models which can account for the effect of micro and meso scale structure on macro-scale performance. Figure 1 shows a schematic of the multi-scale approach for modeling PEM fuel cells. This approach can be used for conventional Pt based electrodes, or for non-PGM based electrodes where large catalyst particles induce significant local flooding and reactant losses. The microstructure is generated using stochastic techniques.2,3 The crucial micro-structural properties such as pore sizes, ECSA, phase distributions are obtained using physical characterization methods such as imaging, Cyclic voltammetry, and BET. The generated microstructures will be used to simulate pore-level physics, where local transport, and reactions will be modeled. The pore scale performance will then be upscaled and used with macro-scale models to simulate system level performance.

To analyze critical parameters for fuel cell performance, sensitivity studies will be performed using the macro-scale model. The aim is to identify parameters which affect the cell performance significantly and therefore must be measured accurately and provide a way to optimize cell performance. Apart from macro-scale parameters, the multi-scale sensitivity study can also be used to optimize ionomer and catalyst distribution.

Acknowledgements

The work is funded under the Fuel Cell Performance and Durability Consortium (FC-PAD), by the Fuel Cell Technologies Office (FCTO), Office of Energy Efficiency and Renewable Energy (EERE), of the U.S. Department of Energy under contract number DE-AC02-05CH11231.

References

P. K. Sinha, W. Gu, A. Kongkanand and E. Thompson, J. Electrochem. Soc., 158, B831 (2011).

F. C. Cetinbas, R. K. Ahluwalia, N. N. Kariuki and D. J. Myers, J. Electrochem. Soc., 165, F1051 (2018).

L. M. Pant, S. K. Mitra and M. Secanell, Phys. Rev. E, 92, 063303 (2015).

Figure 1
(Invited) The Impact of Defects on the Efficiency of Rare Earth Doped Oxides Under Vacuum Ultraviolet Excitation
Authors: Diaz Anthony L
Published: February 2020

Understanding the factors that govern efficient host-sensitized luminescence remains an important element in the development of more efficient luminescent materials. In a doped phosphor system, absorption of high energy photons leads to the creation of an electron-hole (e-h) pair in the host that must be captured by the dopant for emission to occur. While many materials have been developed for these applications, fundamental questions remain regarding the details of this energy transfer process. One aspect of research in this field that has not received much systematic attention is the study of the role various defects play in decreasing the efficiency of phosphors under host-sensitized excitation. The work presented here focuses on the effect of oxygen vacancies in rare earth doped YBO3 and YPO4, which are created via doping with Ca2+. Excitation and reflectance spectroscopy are combined to quantify the fraction of e-h pairs that are trapped by a dopant. The impact of oxygen vacancies depends on the particular rare earth present in the host, which is likely related to differences in the e-h trapping mechanism.
Analysis of Energy-Structure Relationship for Ce3+ in Garnet-Type Oxides Based on First-Principles Calculations
Authors: Ogasawara Kazuyoshi
Published: February 2020

The 4f-5d transitions of Ce3+ in crystals are utilized for various optical materials such as solid-state lasers, scintillators, and phosphors. Since the 4f-5d transition energy of Ce3+ in crystals strongly depends on the local structure around Ce3+, it is important to understand the relationship between the energy levels and the local structure for theoretical design of novel optical materials based on Ce3+. In order to control the local structure, garnet-type oxides are useful as host crystals since there are three types of cation sites and the local structure around the impurity Ce3+ ion can be modified widely by cation substitution. In garnet-type oxides, Ce3+ usually occupies the dodecahedral site with D2 symmetry. The arrangement of eight nearest neighbor O2- ions can be understood as interpenetrating two tetrahedrons. Therefore, the geometry of CeO8 cluster can be specified by six structural parameters corresponding to the coordinates of two representative ligand positions. However, investigation of the energy-structure relationship depending on six structural parameters is not straightforward.

In this work, in order to visualize the energy-structure relationship of Ce3+ occupying the dodecahedral site in garnet-type oxides, two-dimensional energy maps were constructed by performing first-principles relativistic molecular orbital calculations for a series of CeO8 clusters constructed by changing two selected structural parameters. The 4f-5d transition energies of Ce3+ for these clusters were calculated based on the Slater’s transition state method. Then the relationship between the 4f-5d transition energy and the local structure depending on the six structural parameters was clarified by the combination of these energy maps.
Application of Water-Dispersed Quantum Dots to Crack Monitoring in Smart Composite Materials
Authors: Hwang Heesu , Oh Jiwon , Kim Jaehwan , Lee Hyunbae , Yang Heesun , Hwang Jin-Ha
Published: February 2020

Heterostructurally engineered CdZnSeS@ZnS quantum dots (QD) materials are synthesized through surface modification involving ligand exchange, changing the surface chemistry from hydrophobicity to hydrophility. The hydrophilic characteristics of the CdZnSeS@ZnS QDs are exploited in the artificial monitoring of the cracks present in the smart composite building materials. The synthesized CdZnSeS@ZnS QDs demonstrate that the average sizes of CdZnSeS and CdZnSeS@ZnS QDs are 9.5 and 12.7 nm, respectively. The presence of ZnS shell (~1.6 nm) functions as an effective physical barrier in order to enhance the stability of QDs against environmental changes such as the ligand exchange process. The optimized CdZnSeS@ZnS QDs, exhibit high-quality fluorescent features with a peak emission wavelength of 525 nm. The current work chose the shape memory alloy(SMA)/cement composites as a model system of cement-based materials, due to its applicability to self-healing functions mediated through shape memory alloys immersed into the cementitious matrix. The SMA/cement composites are subjected to the hostile mechanical loading, leading to mechanical defects, cracks and subsequently were heated to heal cracks mechanically generated. The insertion of aqueous QD solutions to the recovered SMA/cement composites is evaluated in terms of structural health monitoring. Unlike the previous crack monitoring approaches, the water-dispersed QD materials demonstrate the facilitated infiltration to the crack networks and the effective monitoring capability with the aid of highly luminescent quantum dots. The unique features are discussed with the main emphasis on the hydrophilic properties of the CdZnSeS@ZnS QDs. The aqueous QD solution approach is proven to be suitable for monitoring complex cracks and self-healing features in smart composite materials which will be employed in buildings and infrastructures.
Enrichment in Methane Content in Biogas By External Voltage Supply
Authors: Poudyal Pranita , Prajapati Bikram , Bajracharya Suman , Joshi Jarina
Published: February 2020

The increment in the methane content has a major role to broaden the application of biogas. Enhancement of the methane-generating metabolism of microorganisms known as methanogens is required to increase the methane production. Research has shown that methanogens can use supplied voltage to acquire the electrons for the production of methane from CO2. In this process, methanogens reduce CO2 to CH4 utilizing electrons from externally supplied voltage on integrating with anaerobic digestion. Microbial electrochemical cells (MEC) was developed employing biocompatible fibrous graphite electrodes. Cow manure was assessed for the anaerobic digestion combined with MEC. The objectives of the study were to use manure waste and to enrich methane in biogas even at low temperature condition. The biogas produced contains mainly methane, hydrogen sulphide and carbon dioxide. The maximum gas production was at 37oC. However, biogas could be produced at 18oC with supply of 2V external power. There was found 65 times increment in biogas production with external power supply at 18oC. Besides methanogens, two other bacterial species identified were Serratia liquefaciens and Zoballella taiwanensis respectively.

Keywords: Methane, biogas, methanogens, voltage, anaerobic digestion, microbial ecology
Synthesis and Characterization of Osmium Redox Polymer Mediators for Type II Biosensors
Authors: Calhoun Margaret C , Stachurski Christopher , Gizzie Evan A. , Daniel Aaron W. , Cliffel David E.
Published: February 2020

Electrochemical sensors that utilize enzymes are a sensitive, inexpensive means of detecting biologically relevant analytes. These sensors are further categorized based on their construction and method of signal transport.1 Type I sensors consist of a crosslinked enzyme on an electrode surface, which are subject to interference from byproducts and other biological analytes. However, type II sensors alleviate this problem with the addition of a redox polymer layer, to assist in signal transportation, thus minimizing interference. There are a growing number of Type II sensors in the literature, however few are commercially available and typically suffer from poor structural and optical characterization.

Previously, an osmium-loaded poly(vinylimidazole) polymer (Os-PVI) was synthesized in order to avoid acetaminophen interference in enzyme sensor testing with successful results, yielding a type II sensor.2, 3 Given the success of the polymer, and the potential applications of the polymer for both enzyme and eletrogenerated-chemiluminescent sensors, it was important for Os-PVI to be properly characterized. Using previous literature, the two precursors Os(bpy)2Cl2 and poly(vinylimidazole) were synthesized. However, attempts at replication lead to the synthesis of an unknown osmium precursor. When coupled to PVI, a new osmium polymer was synthesized with new fluorescent and redox properties that did not match with the original Os-PVI polymer. All precursors and osmium polymers were characterized with 1H NMR, fluorescence, mass spectrometry, and cyclic voltammetry in order to provide a better understanding of these compounds and assist in the building of new sensors.

Wang, J.; Ju, H.; Zhang, X., Electrochemical Sensors, Biosensors and Their Biomedical Applications. Academic Press: Amsterdam, 2008; Vol. 1st ed.

Ohara, T. J.; Rajagopalan, R.; Heller, A., "Wired" Enzyme Electrodes for Amperometric Determination of Glucose or Lactate in the Presence of Interfering Substances. 1994,
66 (15), 2451-2457.

Forster, R. J.; Vos, J. G., Synthesis, characterization, and properties of a series of osmium- and ruthenium-containing metallopolymers. Macromolecules
1990,
23 (20), 4372-4377.
Electrochemical Behavior of Selenophene in Quaternary Ammonium and Phosphonium Based Ionic Liquids
Authors: Yasugi Noriaki , Tsunashima Katsuhiko , Higashi Toshikazu , Sakaguchi Yuki , Yamada Hirohisa , Matsumiya Masahiko
Published: February 2020

Room-temperature ionic liquids (RTILs) have been regarded as potential electrolytic media for electropolymerization processes.1 Many kinds of RTILs have been investigated for the electropolymerizations. For example, we have reported that a bis(fluorosulfonyl)amide (FSA) anion based imidazolium ionic liquid promoted the electropolymerization reaction of pyrrole and the anion doping into the polymerized film, improving the conductivity of the film.2 We also have applied the phosphonium based RTILs to the electropolymerization of pyrrole and thiophene, investigating the influence of the phosphonium RTILs on the polymerized film properties.3 However, electrosynthesis of polyselenophene in phosphonium RTILs has not been examined. In this work, we report the electropolymerization of selenophene in triethylpentylphosphonium FSA (P2225-FSA) (Fig. 1) and the effect of the phosphonium RTIL on the polyselenophene film properties.

P2225-FSA was prepared according to the procedure we have previously reported,4 and dried under high vacuum at 80°C for 6 h before use. The electropolymerization of selenophene in P2225-FSA was carried out by cyclic voltammetry (CV) method using a three-electrode cell equipped with a working electrode of platinum or transparent glass electrode and an IL-based Ag/Ag+ reference electrode.

Figure 2 showed the cyclic voltammograms for the electropolymerization of selenophene in P2225-FSA. In the first cycle, the oxidation peak current value of about 0.2 mA was shown around +1.7 V vs Ag/Ag+, and the current decayed with each cycle. This closely resembles the electrochemical behavior observed in CVs using π-conjugated aromatic compounds such as pyrrole and thiophene as substrates. 3 After 10 cycles, a black thin film was grown on the surface of the working electrode, and the oxidation current observed in this CV seems to be due to the electropolymerization reaction of selenophene. Furthermore, we will discuss the comparison between the behaviors in various quaternary onium based ionic liquids from the viewpoint of the morphology of the polymer film grown on the working electrode.

References

K. Sekiguchi, et al, J. Electroanal. Chem.
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1, 557 (2003).

K. Tsunashima, et al, ECS Electrochem. Lett., 3, G1 (2014).

K. Nishihata, et al, ECS Trans.,
75, 99 (2016).

K. Tsunashima, et al, Electro
cheml. Commun.
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13, 178 (2011).

Figure 1
Electrochemical Degradation of Phenol and Clorophenol Using Boron Doped Diamond and Composite of Fe3O4 Nanoparticles + Chitosan
Authors: Pujol Alberto Alejandro , León Itzel , Cárdenas Jesús , Sepúlveda-Guzmán Selene , Manríquez Juan , Bustos Erika
Published: February 2020

Phenol (Phen), o-, m- and p-chlorophenol (ClPhen) were electrochemically degraded using a boron doped diamond (BDD) electrode and a composite of Fe3O4 nanoparticles (NPs) and chitosan (CS). Results showed that it was possible to remove Phen, o-, m- and p-ClPhen in synthetic sample by hydroxyl radicals generated during the electrokinetic remediation using BDD||Fe3O4 NPs + CS |Ti in major proportion than BDD||Ti. Additionally, using BDD||Fe3O4 NPs + CS |Ti was possible to obtain 84.92 % of the COD removal and less than 68 % to ClPhens applying a 23 mA current for 4h in acid conditions (H2SO4).
In Situ Vibrational SFG Spectroscopic Study of Au-Catalyzed CO2 Reduction in Aqueous Solution
Authors: Meng Jinhui , Lian Tianquan
Published: February 2020

Electrocatalytically reducing CO2 to useful products, such as alcohols and alkaline, attracts people’s interests in designing more efficient electrocatalysts with better selectivity and universality. As this motivation in catalyst modification requires much deeper understanding in the mechanisms of aqueous CO2 reduction at the heterogeneous interfaces than any learnt knowledge, spectroscopists stand out to utilize in-situ electrochemical spectroscopic techniques to answer these questions. These methods have shed light on considerable questions in the electrocatalysis field. In this system, at a strong optical field in an electrochemical double layer region, how molecules behave with an alternating electromagnetic field and a static electrochemical field is actually the most important question. Among those spectroscopic techniques, vibrational sum-frequency generation spectroscopy (VSFGS) is a recent but powerful tool to be surface-specific and sensitive detecting intermediates during the changes of electrochemical parameters. In this report, potential-dependent behaviors of adsorbed CO from electrocatalytic CO2 reduction on Au is studied as a prototype for further studies of intermediates in a Cu electrode system.
A Kinetic Analysis of the CO Electro-Oxidation Reaction on Pt Bimetallics: Understanding the Interplay of Bifunctional and Electronic Effects
Authors: Baz Adam , Holewinski Adam
Published: February 2020

The CO electro-oxidation reaction has been one of the most thoroughly studied reaction mechanisms in electrocatalysis, mostly due to its role as a model reaction for the oxidation of larger organics like methanol and ethanol, each of which have important renewable energy applications in direct alcohol fuel cells. Bimetallics of Pt-M (where M is an oxophilic modifier such as Ru or Sn) have been shown extensively to have improved CO tolerance compared to pure Pt. The reason for this enhancement is often attributed to some combination of bifunctional (oxophilic metal provides OH to remove poisoning CO on Pt) and electronic (oxophilic metal weakens the CO binding strength on the Pt sites) effects. However, it has been difficult to determine the extent to which these different effects are operative in a given system.

In this work, we perform a kinetic analysis of the CO electro-oxidation reaction in order to elucidate the roles of bifunctional and electronic effects. We look specifically at the classic Pt-Ru bimetallic system, and determine that the rates of bifunctional coupling are generally lower than the rates of coupling on Pt sites electronically modified by Ru. This indicates that, at least for the Pt-Ru system, the electronic effects that weaken CO binding on Pt are more operative than the bifunctional effect. This implies that that the prospects for bifunctional gains in general may be more limited than once thought, and that a more rational design parameter for bimetallic materials may be the electronic effects between the two components.
Operando Pattern-Enhanced Resonant Scattering for Sub-Nm Interfacial “Spectromicroscopy”­ of Energy Materials
Authors: Wang Cheng , Cordova Isvar A. , Freychet Guillaume , Kilcoyne David , Xu Wei , Hexemer Alexander
Published: February 2020

The advent of highly precise nanofaborication tools has enabled the development of the next generation of mesoscale energy materials, but it requires concomitant progress in the characterization techniques used to address the new challenges and questions inherent to their interfacial behavior at this scale.

We present a powerful, yet simple, patterning approach for interface characterization that takes advantage of the physical processes intrinsic to small angle resonant X-ray scattering in order to 1) decouple the bulk from the interface scattering signal, 2) enhance the strength of said signal, and 3) collect site-specific absorption spectra. In addition to the reconstructing the thickness and shape of the interfacial layer, changes in scattering contrast as a function of energy may be tracked in order to produce a full site-specific x-ray absorption spectrum that can identify small, yet vital, fluctuations in local chemistry. In addition, unlike nm-resolution microscopic techniques, the highly sensitive spatio-chemical information obtained via scattering processes doesn't require a highly focused beam whose flux is more likely to inadvertently affect the chemical reactions at the interface, thus making it more amenable to in-situ/operando characterization.

In this presentation, we demonstrate the ability to selectively probe the interfacial regions of inorganic materials used throughout the fields of energy conversion and storage with nm-scale precision. we leverage a newly-developed in-situ cell for gas/liquid flow and electrical biasing that is compatible with many "soft" and "tender" X-ray beamlines and use it conduct an operando study of Ni/Ni(OH)2 core/shell system undergoing cycling under aqueous conditions. We find that the pattern-enhanced RSoXS approach enables the monitoring of the interfacial region's local morphology as it is electrochemically charged and discharged with millisecond time resolution and sub-nm precision, thus shedding quantifiable insights into the kinetics of the OH- intercalation process. In addition, the Ni L-edge XAS from the metal bulk region that is directly decoupled from that from the hydroxide surface is consistent with previously reported spectra. We will also reveal preliminary results showing how this technique may be applicable to study a variety of interfaces, even if the junction of interest is buried under another solid, liquid, or gas material. Finally, we describe the practical considerations of this characterization technique as it is extended to other material systems, patterning designs, sources, etc.
Balancing Fundamental and Practical Aspects in Nanoelectrochemistry Research and Teaching Involving Non-Traditional Students
Authors: Wang Gangli
Published: February 2020

Many applications in analysis and energy and beyond require fundamental understanding of electrochemistry concepts and techniques. Knowledge from multi-disciplines such as surface/interface, kinetics and thermodynamics, and electronics converges in the interpretation and control of an electrochemical process. Appropriate focus and balance between fundamentals and applications can be important in both research and classroom teaching. This talk will discuss some unique challenges and opportunities at Georgia State where non-traditional students constitute a significant population. There will be basic discussions about the classroom teaching including Ph. D., M. S. and undergraduate students. The focus will be about the research and mentoring of graduate and upper level undergraduate students. Nanoelectrochemistry is a central theme in GWang’s research group. Research results in the area of near infrared electrochemiluminescence from atomic-precision metal nanoclusters will be discussed as examples for the recruitment and training of traditional and non-traditional students. Basics of electrochemiluminescence, atomic-precision nanoclusters, as well as the development of sensing strategies and mechanisms for signal amplification will be introduced. Financial supports from NSF (CHE-1610616) and DOE (DE-SC0019043) are acknowledged.
(Invited) Thin Layer Sonoelectrochemistry: Impacts on Slow Electron Transfer Kinetics without Visible Cavitation
Authors: Duda Chester G , Parke Brenna , Leddy Johna
Published: February 2020

Sonochemistry and sonoelectrochemistry are typically undertaken in a bulk fluid with sonication of sufficient intensity to generate visible cavitation. Sonoelectrochemistry was undertaken in a thin layer of fluid with a quartz crystal oscillator. In the thin layer configuration, no cavitation is visible and mass transport is not impacted, but impacts on electron transfer kinetics are observed.

Because there is no visible cavitation, cyclic voltammetric responses typical of a quiescent electrolyte are observed. From the voltammograms for species that undergo rapid heterogeneous electron transfer such as outer sphere Ru(bpy)₃²⁺⇌Ru(bpy)₃³⁺+e, voltammetric morphology is unchanged on sonication of a thin layer of fluid. For Fe³+e⇌ Fe² that undergoes quasireversible (slower) electron transfer under cyclic voltammetric perturbation, sonication in a thin layer is found to increase the rate of heterogeneous electron transfer by roughly an order of magnitude.

Sonoelectrochemical catalysis for inherently slow heterogeneous electron transfer processes is generated and observed in a thin layer of electrolyte. In the experiments reported here, the fluid layer was less than the wavelength of sonication. The aqueous electrolyte contains redox species and acid. Experiments were undertaken at a platinum wire electrode using a 41 kHz quartz crystal oscillator. For the same experimental conditions, no impact on the electron transfer reversible Ru(bpy)₃²⁺ was observed. All data were collected at a fixed frequency; impacts varied with oscillator intensity.

As with many sonoelectrochemical experiments, subtle variation in experimental parameters complicate generation of reproducible results. Here, data generated by two different experimentalists yield similar outcomes. Best operating conditions differed slightly for the two experimentalists but the pattern of increased interfacial electron transfer rates for iron on sonication was found by both.

Reference

[1] Johna Leddy, Chester G. Duda, Jacob Lyon, and William J. Leddy III, "Thin Layer Sonoelectrochemistry and Sonoelectrochemistry Devices and Methods," published 28 May 2015 as US Patent Application 20150147594 A1.
Through-Mask Electrochemical Etching of Micropillar Array with Megasonic Agitation
Authors: Du Liqun , Zhai Ke , Wang Shuxuan , Wen Yikui
Published: February 2020

Micropillar array is widely used in bionics, thermodynamics and biomedicine because of its advantages in improving surface tribological properties and enhancing heat transfer [1, 2]. Through-mask electrochemical etching is one of the main methods to fabricate metal micropillar array in large scale [3].

In this study, we studied the etching effect of micropillar array with the method of megasonic assisted through-mask electrochemical etching. An anode vibrating type megasonic source at 1MHz was set up. Micropillar arrays were etched at megasionc intensity of 2W/cm^2. Fig. 1(a) shows the fabrication process of the micropillar array. The mask is prepared by photolithography. During the etching process, anode acts as an acoustic source and radiates megasonic waves simultaneously. Fig. 1(b) shows the micropillar arrays which were etched without megasonic and with megasonic agitation. Uniform micropillars were achieved with megasonic agitation compared to without megasonic agitation. Fig. 1(c) and Fig. 1(d) shows the measured height and diameter of the micropillars. Higher micro columns were obtained with megasonic agitation when the diameters of the micro columns are almost identical. Micropillars with an average diameter of 116.95μm and an average height of 11.31μm were obtained with megasonic agitation. Fig. 1(e) shows the etching factor of the micropillars. Average etching factor of the micropillars etched without megasonic agitation and with megasonic are 2.07 and 2.87, respectively. The method of megasonic assisted through-mask electrochemical etching can achieve much higher etching factor than without megasonic agitation. This work opens new promising fields for development of extensive fabrication methods of micropillar array.

Reference

[1] R. Xiao, R. Enright, E. N. Wang. Langmuir, 26(19) 15070-15075 (2010)

[2] M. Shojaeian, A. Koşar. Exp. Thermal Fluid Sci., 63 45-73 (2015)

[3] T. Baldhoff, V. Nock, A. T. Marshall, J. Electrochem. Soc., 165 (16) E841-E855 (2018)

Figure 1
Simultaneous Neutron and X-Ray Tomography for Non-Destructive Characterization of Rechargeable Batteries
Authors: LaManna Jacob M , Hussey Daniel S , Baltic Elias , Jacobson David L
Published: February 2020

Neutrons are highly sensitive to lithium making them the choice probe to non-destructively investigate lithium-ion transport in rechargeable batteries. Difficulties can arise as hydrogen strongly scatters neutrons which causes strong attenuation in the electrolytes and polymer separators used in batteries. This can be seen in Figure 1 where it is difficult to identify the boundary between the lithium metal and polymer separator. To improve the identification of the interfaces of the various layers within a battery, NIST has the Neutron and X-ray Tomography (NeXT) system that provides truly simultaneous neutron and X-ray tomography. This technique leverages the differences in material interactions between neutrons and X-rays to improve interface and material identification. This presentation will focus on setting limits on the sizes of commercial cylindrical and button style rechargeable lithium-ion batteries so as to avoid the need for custom built batteries using deuterated electrolytes and fluorinated polymer separators. New tools to aid in segmentation of the multimodal datasets will be showcased.

Figure 1
Revealing Hidden Chemistry of Anode-Free Lithium Metal Battery
Authors: Huang Chen-Jui , Thirumalraj Balamurugan , Sutiono Hogiartha , Kuo Li-Ming , Su Wei -Nien , Hwang Bing-Joe
Published: February 2020

Lithium metal batteries (LMBs) has been studied extensively over the past four decades and regained great attention then lithium-ion batteries (LIBs) recently due to its higher energy density and volumetric capacity. However, the inevitable formation of high surface area lithium (HSAL) [1,2], also known as dendrites, during the plating/stripping processes among cycling leads to poor capacity retention, low coulombic efficiency (CE), and potential safety concern. One of the major reasons causing serious dendrite formation is the usage of lithium foil as an anode electrode, owing to its soft texture and easily roughened surface. In addition, even if the lithium foil used is ultra-thin, the A/C ratio is still large than 1, which leads to unnecessary excess lithium and sacrifice of higher cathode loading within the cell.

Anode-free lithium metal batteries (AFLMBs), using no excess metallic lithium at the initial state, enable potentially higher energy density than LMBs [3,4]. Nevertheless, the configuration possesses lowest safety risk among the cells with the involvement of metallic lithium due to fewest amount of plated lithium in the charged state. However, low plating/stripping efficiency of AFLMBs leads to rapid capacity decay and very short cycle life. Thus, AFLMBs are often considered having less potential than LMBs or recognized as a failure for this type of cell configuration.

Here in, we fundamentally investigate different parameters which affect the performance of AFLMBs, comparing with LMBs, the hidden chemistry of AFLMBs is unveiled. Base on the obtained results, we tailor down different intrinsic reasons causing irreversible capacity and low CE, and the metallic lithium plating/stripping behavior. Thus, AFLMBs is able to provide extensive cycling performance evaluation, cycle life prediction of LMBs, and approaches to improve reversible lithium metal plating/stripping and suppress of dendrite formation.

Reference:

[1]: J.H. Cheng, A.A. Assegie, C.J. Huang, M.H. Lin, A.M. Tripathi, C.C. Wang, M.T. Tang, Y.F. Song, W.N. Su, and B.J. Hwang, J. Phys. Chem. C, 121, 7761–7766 (2017). [2]: A.M. Tripathi, W.N. Su and B.J. Hwang, Chem. Soc. Rev., 47, 736–851 (2018).
In-Situ Formation of Surface Coatings on Silicon Anodes
Authors: Vaughey John T. , Key Baris , Han Binghong , Dogan Fulya , Lapidus Saul , Liao Chen
Published: February 2020

Silicon anodes have generated significant interest for their exceptional high capacities, relative low cost, and good operating voltage window. For may silicon electrode materials the inhomogeneous nature of the charged electrode yields a highly reduced surface and a less reduced bulk. Using single phase model compounds of the predominant electrodes structures at various states of charge we have examined the role of surface charge on the stability of the electrode to binder, electrolyte, and various salts. In our presentation we have taken these concepts and devised additives that react with the charged surface to coat the material with a more stable interfacial material that extends cycle life and improves performance versus baseline samples.

Notable examples include the synthesis of Li7Si3, a model compound for a 300mV Li-Si electrode. This material contains simple silicon dimers surrounded by lithium cations. Previous modeling has noted these dimers show double bond character, increasing their reactivity with the components of an electrochemical cell. In our studies crystalline samples were synthesized in Ta tubes and exposed to various solvents. Reactivity, as seen by XRD, NMR, and FTIR, confirmed the oxidation of the dimer species to a more oxidized compound (Li12Si7) and ring opening of EC-type solvents.
Bucky-Si-Bucky Sandwiched Structured Anode for Li-Ion Battery
Authors: Chiluwal Shailendra , Sapkota Nawraj , Rao Apparao M. , Podila Ramakrishna
Published: February 2020

Silicon anodes have been of great interest due to their higher theoretical capacity (4200 mAh/g) compared to traditional graphite electrodes (~372 mAh/g). Although Si has a higher capacity, its full potential has not yet been realized due to pulverization of Si anode upon lithiation. Conventionally, Si anodes are made by casting a slurry consisting of Si powder, conductive carbon additives, and a binder on a Cu foil. In such anodes, pulverization of Si particles leads to film delamination from Cu foil ensuing in battery failure. To overcome this challenge, we developed a new sandwich-structured anode by encapsulating ~100 nm Si nanoparticles in between two porous carbon nanotube buckypapers. The buckypaper is a conductive porous structure, which can incorporate active material better than Cu foil facilitating increased mass loading. More importantly, this sandwich-structured anode provides improved electrical contact even under repeated pulverization of Si nanoparticles leading to higher cyclability. We were able to achieve capacities as high as ~700-1200 mAh/g with a stable performance for >100 cycles.
High Performance Silicon Anodes Enabled By Nonflammable Localized High Concentration Electrolytes
Authors: Jia Haiping , Zhang Ji-Guang , Xu Wu
Published: February 2020

High performance silicon anodes enabled by nonflammable localized high concentration electrolyte

Haiping Jia, Ji-Guang Zhang, Wu Xu

Pacific Northwest National Laboratory, Richland, WA, United States.

Silicon (Si) anode is regarded as one of the most promising alternatives to graphite for high energy-density lithium-ion batteries (LIBs), but their practical applications have been hindered by high volume change, limited cycle life and safety concerns. In this work we developed nonflammable localized high concentration electrolytes (LHCEs) for Si-based anodes. The LHCEs enabled the Si anodes with significantly enhanced electrochemical performances comparing to conventional carbonate electrolytes with high content of fluoroethylene carbonate (FEC). The LHCE with only 1.2 wt% FEC can further improve the long-term cycling stability of Si-based anodes. When coupled with a LiNi0.3Mn0.3Co0.3O2 cathode, the full cells using this nonflammable LHCE could maintain >90% capacity after 600 cycles at C/2 rate, demonstrating excellent rate capability and cycling stability at elevated temperatures and high loadings. This work casts new insights in electrolyte development from the perspective of in-situ Si/electrolyte interphase protection for high energy-density LIBs with Si anodes.
The Effects of Cycling on Ionic and Electronic Conductivities of 18650 Li-Ion Cells
Authors: Thompson Andrea I , Pouraghajan Fezzeh , Mazzeo Brian A , Wheeler Dean
Published: February 2020

During cycling or other aging processes, the capacity of lithium-ion batteries decreases and it is also observed that cell impedance increases. In order to better understand these processes, we are investigating the electronic conductivity and ionic conductivity of electrodes harvested from 18650 cells that have been cycled by different amounts.

Effective ionic conductivity of a porous electrode film is sometimes expressed in terms of tortuosity, which is correlated by a Bruggeman-type relationship [1]. A reasonably accurate method of measuring tortuosity is using the previously developed blocking electrolyte method [2]. As for effective electronic conductivity of electrodes, our group has developed experimental methods for accurately making this measurement as well [3].

In this work, the effects of cycling on both ionic and electronic conductivities are examined. We investigate different commercially made 18650 (cylindrical) cells, including those with iron phosphate and cobalt oxide cathodes. Each cell was charged and discharged for a different number of cycles, leading to increasing capacity losses. After certain number of cycles, each cell was cut open and the electrodes were harvested for testing. We will provide details on this experimental method as well as the conductivity results.

[1] Zacharias et al, Electrochem. Soc. 160, A306 (2013).

[2] Pouraghajan et al., Electrochem. Soc. 165, A2644, (2018).

[3] Lanterman et al., Electrochem. Soc. 162, A2145, (2015).

Figure 1
The Impact of Particle Size on Cycle Life and Stress Evolution in Silicon-Based Composite Electrodes
Authors: Jin Mok Yun , Guo Kai , Zhang Wei , Xiao Xingcheng , Gao Huajian , Sheldon Brian W.
Published: February 2020

In practical silicon electrodes the coupled mechanical and chemical degradation of the solid electrolyte interphase (SEI) is a critical issue. During electrochemical cycling, the extremely large mechanical strains that are applied to the SEI on Si are a primary factor that limits cycle life. However, the effect of particle size on these strains has not been investigated in prior work.

To address this, we have integrated measurements on silicon nanoparticle composite electrodes with an in situ method for applying controlled mechanical strains to SEI during electrochemical cycling and a finite element model (FEM). Comparisons of electrodes with different particle sizes show lower capacity loss with smaller particles. This finding is explained with the FEM. Variations in the SEI formation were also investigated, using different cycling conditions and electrolyte additives.
Instrument for Measuring Local Ionic Conductivity of Porous Electrodes
Authors: Liu Baichuan , Nielsen Kayci , Mazzeo Brian , Wheeler Dean
Published: February 2020

Due to the nature of how porous battery electrodes are fabricated, their microstructure is not uniform. For instance, there are variations in composition, effective electronic transport, and effective ionic transport. Such heterogeneity has been associated with several battery application issues. For example, variability in transport of ions can lead to a tendency for localized plating of lithium on anodes during fast charging [1-2].

Studying the heterogeneity of electrodes is a growing research topic. Our research group has previously developed a micro-four-line probe that successfully measured the variation of electronic conductivity of electrodes [3]. Another method to study the microstructure of electrodes is by means of SEM and X-ray tomography, and the variation of tortuosity (effective ionic resistance) in electrodes was computed by analyzing the tomographic data of microstructure [4].

We report here on a new technique to measure the local ionic resistance on a sub-mm length scale. A probe was made to detect the local transport of ions through a small aperture. The probe is scanned across the surface of a porous thin-film electrode in order to create maps of tortuosity or MacMullin number. The measurement was performed using electrochemical impedance spectroscopy, and an associated model is needed to invert the experimental results.

[1] Harris et al., The Journal of Physical Chemistry C 117, 6481 (2013).

[2] Vogel et al., Electrochimica Acta 297, 820 (2019).

[3] Lanterman et al., Journal of the Electrochemical Society 162, A2145 (2015).

[4] Kehrwald et al. Journal of The Electrochemical Society 158, A1393 (2011).

Figure 1