bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigating Phase and Electrical Properties of Calcium-Doped Yttrium Iron Garnet
Authors: Zhang Zheyu , Singh Kalpana , Thangadurai Venkataraman
Published: February 2020

Literature studies have shown that Ca0.5Y2.5Fe5O12-δ can be a promising cathode material for intermediate temperature solid oxide fuel cell (IT-SOFC) 1. As it exhibits higher electrical and ionic conductivity compared to several other kinds of rare-earth garnets 2. However, given the high resistivity (> 1012 Ω cm at room temperature) and less-explored oxide ion conductivity of its parent phase yttrium iron garnet (Y3Fe5O12, YIG), the effect of calcium doping on the electronic and ionic properties has not been fully studied yet 3. In this work, polycrystalline samples of Ca-doped YIG, with general chemical formula CaxY3-xFe5O12-δ (x=0, 0.1, 0.3, 0.5 and 0.7), were prepared and phase characterized by powder X-ray diffractometer. The oxygen non-stoichiometry was determined by iodometric titration at room temperature and thermogravimetric analysis (TG) at elevated temperatures. Total electrical conductivity was measured by four-probe DC method, and ionic conductivity was calculated by using a modified Hebb-Wagner polarization method. As a result, the ionic transference number was calculated and discussed in relation to its potential applications.

Reference:

Zhong, W., Ling, Y., Rao, Y., Peng, R. & Lu, Y. Calcium doped Y3Fe5O12 as a new cathode material for intermediate temperature solid oxide fuel cells. J. Power Sources
213, 140–144 (2012).

Kharton, V. V. et al. Ionic Transport in Gd3Fe5O12- and Y3Fe5O12-Based Garnets. J. Electrochem. Soc.
150, J33 (2003).

Lehmann-Szweykowska, A., Wojciechowski, R. J., Gehring, G. A. & Tobijaszewski, I. Quasiparticles in Calcium Doped Yttrium-Iron Garnets. Acta Phys. Pol. A
91, 423–426 (1997).
(Invited) In Situ Grown Metal Nanoparticle Catalysts from Perovskites: Properties and Control
Authors: Oh Tae-Sik
Published: February 2020

The ability to produce supported metal nanoparticle catalysts via exsolution from a perovskite type oxide support under reducing conditions has been known for some time and is used in solid oxide electrochemical cells. The ability to re-dissolve and exsolve the metal via redox cycling has led to these systems being referred to as smart or regenerable catalysts. While this phenomenon is well known, the mechanism by which the transition metal is exsolved from the oxide host is still poorly understood. The relationships between the exsolution process and the resulting structure of the metal nanoparticles are also not well understood. In this talk I will discuss our recent mechanistic studies of the exsolution process. Using well-defined model systems and detailed structural analysis by electron microscopy and atomic force microscopy, the nucleation and exsolution of Ni particles from Ni-doped strontium titanate was monitored. These studies show how exsolution produces unique surface structures consisting of metal particles partially submerged in pits on the oxide surface. I will show that this particle-in-a-pit morphology imparts unusually high thermal stability as well as significantly decreased carbon filament formation. Metal exsolution control will be discussed for host oxide lattices in thin film form.
Surface Cation Segregation on La0.6Sr0.4Co0.2Fe0.8O3
Authors: Ostrovskiy Yevgeniy , Huang Yi-Lin , Wachsman Eric D.
Published: February 2020

The high oxygen activity of perovskites makes them effective as solid oxide fuel cell (SOFC) cathodes. However, surface cation precipitation, especially Sr segregation, on La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) cathodes is a well-known issue that limits the cathode stability. Moreover, CO2 is known to cause cathode degradation, but how CO2 affects surface cation segregation is still unclear. Here, the formation of Sr-rich secondary phases on the surface of LSCF were evaluated systematically in a variety of conditions; including time, temperature, and oxygen partial pressure. This was done to better understand the mechanism and the contribution of each variable to surface cation segregation. Additionally, the CO2 effect on the SrO segregation is also discussed. Our results demonstrate that SrO segregation on LSCF is thermodynamically favored as temperature increases, and a different segregation mechanism is observed above 850 °C. The nucleation sites are also determined, and the 3-step surface segregation process of nucleation, surface migration, and agglomeration, is proposed. We also observed that different gases (N2, O2, and CO2) have different effects on the surface segregation. Meanwhile, the effects of underlying grain orientation on surface cation segregation is further discussed.
New Electrochemical Synthesis of Fe2TiO5 Photoanode from Metal-Catechol Complexes
Authors: Lee Dongho , Choi Kyoung-Shin
Published: February 2020

Solar water splitting in a photoelectrochemical cell (PEC) is an attractive approach to generate hydrogen fuel from the abundant solar energy source in a benign and environmentally friendly manner. In this field, TiO2 and Fe2O3 are some of the most extensively studied candidates for use as photoanodes. This is because they consist of naturally abundant elements and are photostable in a wide pH range. However, the major drawback of TiO2 for water splitting is its wide bandgap (3.2 eV). Though Fe2O3 has a narrow bandgap (2.0–2.1 eV), its conduction band minimum (CBM) is still ~200 mV below the water reduction potential. Recently, Fe2TiO5, one of the Fe-Ti-O ternary oxide compounds, has received a considerable interest as a new candidate material to overcome the intrinsic limitations of TiO2 and Fe2O3 while maintaining their strengths. That is, Fe2TiO5 has a favorable bandgap (2.1 eV), chemical robustness, and band edges that straddle the water oxidation and reduction potentials. These properties make Fe2TiO5 a promising photoanode candidate for solar water splitting.

In this presentation, we report a new electrochemical method to prepare a high quality Fe2TiO5 film to systematically investigate its photoelectrochemical properties. The synthesis is based on the interaction between metals and catechol where catechol acts as a chelating agent to solubilize metal ions in a plating solution. When the catechol ligands are removed by applying electrochemical bias, the resulting insoluble metal ions or metal-catechol complexes are deposited onto the FTO surface. Using this method, we deposit a film that contains atomically well mixed Fe and Ti, which are then converted to crystalline Fe2TiO5 after annealing at a moderate temperature. This method also allows facile doping of the Fe2TiO5 film, enabling us to investigate the effect of both bulk and surface composition tuning on its photoelectrochemical properties.
(Invited) Nanostructured Photoelectrodes for Unassisted Solar Water Splitting with Enhanced Stability and Surface Catalysts
Authors: Pan Shanlin
Published: February 2020

Nanostructured photoelectrodes with high surface area and tunable optical and electrical properties can potentially benefit a photoelectrochemical (PEC) water splitting system. PEC performance of a nanostructured photoelectrode is usually quantified in a standard three-electrode configuration under potential-assisted conditions because of the additional overpotentials for the two half-reactions of water splitting. However, it is a necessity to fully recognize their potential to split water under unassisted conditions by designing a tandem cell that can provide sufficient voltage to split water. Herein, we present a tandem cell comprised of a photocathode (e.g., carbon-modified cuprous oxide (C/Cu2O) nanoneedles and MoS2-coated Cu2O) and a photoanode (e.g., Co modified BiVO3
and oxygen-deficient titanium dioxide (TiO2−x
) nanorods) for unassisted solar water splitting. The synthesized photoelectrodes were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and electrochemical impedance spectroscopy (EIS) techniques. The tandem cell performance was analyzed by measuring the current-voltage responses in various photoelectrode configurations to validate the collective contributions of both photoelectrodes to unassisted solar water splitting. The PEC properties of these paired photoanodes and photocathodes in a tandem configuration exhibited reasonable photocurrent in the absence of any redox mediator and external bias. Surface active species of photoanode are studied with an ultra-micro electrode of a scanning electrochemical microscope (SECM) to reveal the relationship to substrate and photoexcitation.
(Keynote) Transient Absorption Studies of Charge Carrier Dynamics in Photocatalysts and Photoelectrodes for Solar Driven Water Splitting
Authors: Durrant James
Published: February 2020

In my talk I will focus on the underlying charge carrier dynamics which determine the efficiency of solar driven water splitting by a range of photoelectrodes and photocatalyst suspensions, including metal oxide photoanodes and carbon nitride and polymer based photocatalysts. The key kinetic challenge in these materials is to match the lifetimes of photogenerated carriers with the timescales of water oxidation / reduction catalysis. I will discuss our studies addressing this kinetic challenge on timescales from picoseconds to seconds. Key factors which will be considered will include the relevant timescales of bulk carrier recombination, and how these differ between materials, the timescales of catalysis, the role of space charge layers and junctions in separating charges, the impact of charge trapping on charge carrier lifetimes and reactivity, and the impact of polaron formation.
The Role of MnOx and Ni:MnOx Co-Catalysts on the Photoelectrochemical Properties of Ta-O-N Photoanodes
Authors: Irani Rowshanak , Plate Paul , Harbauer Karsten , Bogdanoff Peter , Abdi Fatwa Firdaus , van de Krol Roel
Published: February 2020

The ever-increasing energy demand and environmental concerns associated with fossil-based fuels have driven the urgent need for sustainable methods to produce chemical fuels. One approach is to perform solar water splitting to produce hydrogen and oxygen. For this purpose, metal oxide-based semiconductor are promising photoelectrode materials due to their relatively high abundance and stability in aqueous solutions. However, metal oxides typically have only slow surface reaction kinetics for water oxidation [1]. To overcome this, water oxidation co-catalysts, such as CoPi, FeOOH, NiFeOx, and MnOx, have been deposited on the surface of numerous metal oxide semiconductors resulting in an improved performance [2-6]. However, the processes at the semiconductor/co-catalyst interface are not yet well understood. Here, we investigate the role of MnOx and Ni:MnOx co-catalysts (thickness < 10 nm) deposited by atomic layer deposition (ALD) on Ta-O-N thin films as a model system. By systematically controlling the partial pressure of NH3, H2 and H2O during post-annealing of Ta thin films, different phases (e.g. Ta2O5, TaOxNy, Ta3N5) with varying valence band maximum positions were successfully prepared. The valence band position of the co-catalyst was also varied by modifying the Ni content. Photoelectrochemical studies with and without hole scavenger reveal that MnOx and Ni:MnOx enhances the photocurrent of Ta-O-N films by a factor of ~ 4, but they do not affect the charge injection efficiency. Instead, the photocurrent increase is likely a result of higher charge separation efficiency. We attribute this to the formation of a band bending at the Ta-O-N/MnOx and Ta-O-N/Ni:MnOx interface, as suggested by the open circuit potential (OCP) and in-line X-ray photoelectron spectroscopy (XPS) data. This is further supported by analyzing Ta-O-N films with varying thickness of the co-catalysts; thicker co-catalysts result in increasing band bending, which correlates with the photocurrent trend as well as the effective carrier diffusion length measured by time-resolved microwave conductivity (TRMC). Finally, the influence of the band offsets between the different photoanode in the Ta-O-N systems and the co-catalysts is discussed.

References

[1] M. De Respinis, Chem. Mater. 2015, 27, 7091.

[2] F. F. Abdi, ChemCatChem 2012, 5, 490.

[3] W. D. Chemelewski, J. Am. Chem. Soc. 2014, 136, 2843.

[4] J.-W. Jang, Nat. Commun. 2015, 6, 7447.

[5] D. Xu, Electrochim. Acta. 265, 2018, 10.

[6] A. Ramirez, J. Phys. Chem. C. 2014, 118, 14073.
(Invited) Quantum-Sized Metal Nanoparticles: Bridging Photons and Chemical Transformations
Authors: Sun Yugang
Published: February 2020

The incompatibility of the energy of a solar photon and the absorption band of a chemical bond prevents the use of light to activate the chemical bond for interesting chemical reactions directly. This presentation will focus on a strategy that enables the efficient coupling of photon energy into chemical bonds to selectively promote the desired chemical reactions. The strategy relies on the generation of hot electrons in quantum-sized metal nanoparticles (QSMNPs, with size < 10 nm) upon photo-illumination and the next efficient injection of the hot electrons into specific chemical bonds. The redistribution of hot electrons in the chemical bonds dissipates the kinetic energy of hot electrons to the chemical bonds, activating the chemical bonds to promote the target chemical reactions. These sequential processes occur in a confined space, representing a series of quantum transitions, i) optical-to-electronic transition in quantum-sized metal nanoparticles (i.e., hot electron generation), ii) electronic-to-electrical transition at the nanoparticle/adsorbate interface (i.e., hot electron injection), and iii) electrical-to-electronic transition in adsorbate molecules (i.e., chemical bond activation).

Selective oxidation of alcohols to aldehydes rather than ketones/acids, a class of important chemical reactions for many industrial processes (e.g., esterification), will be used as an example to highlight the use of QSMNPs for photo-driven selective chemical transformation on platinum group metal (PMG) nanoparticle catalysts, which do not exhibit strong optical absorption. Current practices primarily rely on the use of strong oxidants (e.g., permanganate and dichromate), which are too strong in oxidizing power to prevent over-oxidation of alcohols to ketones. These strong oxidants are usually toxic and have to be removed from the products. In contrast, using ambient oxygen as oxidant is promising to develop an environmentally friendly synthesis strategy that does not require additional separation. However, ambient oxygen is lack of the power to oxidize alcohols at mild temperatures. Therefore, precisely controlling the oxidizing power of the oxidants becomes crucial to promote the selective oxidation of alcohols to aldehydes. The PMG QSMNPs are used to improve the selective oxidation with ambient oxygen by converting the molecular oxygen adsorbed on the catalyst to more active species when the QSMNPs absorb visible light.
(Invited) Effects of the Electrochemical Double Layer on CO Reduction and Hydrogen Evolution on Cu Electrodes
Authors: Waegele Matthias
Published: February 2020

The electrochemical reduction of carbon dioxide to fuels and high-value commodity chemicals is of great technological interest. Cu is the only pure electrocatalyst that facilitates the conversion of carbon dioxide to hydrocarbons at significant reaction rates. Cu is therefore an important prototypical catalyst for the reduction of carbon dioxide. However, the product selectivity of this process for specific desired products is poor. This product selectivity is not only controlled by the electrode material and its morphology, but also by the cations of the supporting electrolyte. While it has been shown that the identity and concentration of cations can greatly change the reaction selectivity of the process, a fundamental understanding of these effects is mostly lacking to date. Herein, we systematically explored the effects of quaternary alkyl ammonium ions on the reduction of CO to ethylene on Cu electrodes. With differential electrochemical mass spectrometry (DEMS), we determined that ethylene is produced in the presence of methyl4N+ and ethyl4N+. By contrast, we did not observe the formation of this product in the presence of propyl4N+ and butyl4N+. Using surface-enhanced infrared absorption spectroscopy (SEIRAS), we determined that the changes in selectivity are likely not due to blocking of catalytic sites or changes in the interfacial electric field. However, SEIRAS showed that the interaction of surface-adsorbed CO and water is disrupted in the presence of the two larger cations. This finding indicates that the interaction of interfacial water with surface-adsorbed CO is critical for the formation of ethylene. We will discuss the mechanistic implications of these findings. Furthermore, we will discuss the effects of alkali cations on the hydrogen evolution reaction, which is an undesired side-reaction in electrochemical carbon dioxide reduction. Using electroanalytical techniques, we showed that the effects are strongly dependent on the pH of the electrolyte. We rationalize these observation with dependence of the reaction mechanism of the hydrogen evolution reaction on pH, and the resulting differential interactions of cations with the intermediates in the different pH regimes.
Multilayer Photosystem I Films within Porous Indium Tin Oxide Cathodes for Enhanced Photocurrent Generation
Authors: Dervishogullari Dilek , Wolfe Kody , Stachurski Christopher , Jennings G. Kane , Cliffel David E.
Published: February 2020

Light-to-charge carrier converting proteins involved in oxygenic photosynthesis can be utilized in biohybrid photovoltaic electrodes, and have a wide range of applications in solar energy conversion. Photosystem I (PSI) is one of the two primary protein complexes involved in photosynthesis within plants, algae and cyanobacteria. Photosystem I (PSI) is capable of inducing directional electron transfer upon illumination. Further improvement of the photocurrent performance of both PSI cathodes and anodes is necessary for the implementation of these low-cost and low-impact devices for energy conversion. One route for improving electrode performance is to incorporate PSI into porous electrodes. In this study, indium tin oxide (ITO) nanoparticles were used to fabricate porous, translucent and conductive host electrodes for PSI. Mesoporous and macroporous ITO electrodes were prepared, characterized and modified with PSI. In comparison to planar PSI-ITO cathodes, both mesoporous and macroporous ITO cathodes were found to enhance photocurrent generation in the presence of the electrochemical mediator. The photocurrent produced by macroporous ITO cathodes, 42 ± 5 μA/cm2, is on par with other porous electrode studies and is the highest reported value for a PSI-ITO cathode. Additionally, macroporous ITO cathodes displayed, on average, a 112% greater photocurrent per active surface area, when compared to mesoporous cathodes. Larger pore sizes improve performance by achieving a higher PSI loading, increasing the active surface area, and taking advantage of the spherical diffusion of redox mediators within the pores. This work shows the capabilities of porous ITO electrodes for biohybrid PSI photovoltaics and discusses directions for further improvement; namely the continued development of structurally stable macroporous electrodes.
(Invited) Thermochemical Properties of Non-Stoichiometric Oxides for Solar Fuel Generation
Authors: Qian Xin , He Jiangang , Baldassarri Bianca , Huang Ruiyun , Wolverton Christopher , Haile Sossina M
Published: February 2020

Solar-driven thermochemical production of chemical fuels using redox active oxides has emerged as an attractive means for storing solar energy for subsequent use on demand. In this process a reactive oxide is cyclically exposed at high temperatures to an inert gas, which induces partial reduction of the oxide, and to an oxidizing gas of either H2O or CO2, which oxidizes the oxide, releasing H2 or CO. The capacity for fuel production is dictated by the thermodynamic properties of the oxide, specifically the enthalpy and entropy of reduction. Less appreciated is the fact that the fuel production rate is also highly dependent on the thermodynamic properties. Here we review progress made in measuring the thermodynamic functions for a range of materials and in identifying suitable thermodynamic values for efficient fuel production.
(Invited) Benchmarking and Round Robin Testing for Proton Exchange Membrane Water Electrolyzers
Authors: Bender Guido , Carmo Marcelo , Lickert Thomas , Fischer Stefanie , Kadam Pankajkumar , Kang Zhenye , Young James L. , Smolinka Tom
Published: February 2020

Hydrogen generation via proton exchange membrane water electrolysis is one technology that offers a pathway to store large amounts of electrical energy in the form of hydrogen and enables the integration of renewables into the grid. In order to realize a large market penetration of carbon free hydrogen, produced through PEM water electrolyzers, high capital and operating costs need to be reduced via rapid and successful research and development. This is only possible if a meaningful comparison of performance across laboratories can be achieved and demonstrated. As shown in Figure 1, performance data in the literature of nominally identical systems vary significantly. For example, up to 200 mV deviation was reported at current densities of 1 A/cm2for cells that employed Nafion 117 membranes (Figure 1) [1]. These deviations may originate from using different materials, hardware, test equipment, and operating conditions and procedures. The data confirm an obvious need for standardization of materials and testing protocols to enable such a comparison in the low temperature electrolysis field. Herein, we address this need by reporting on the latest results of a round robin test effort conducted by contributors to the IEA Electrolysis Annex 30. Building upon a method and equipment framework developed and verified in an iterative process, the work recently expanded to include titanium based porous transport layer materials and pressure capable hardware. As shown in Figure 2, initial results with these material sets between laboratories (Figure 2, right) indicate a similar if not reduced deviation between laboratories when compared to the results of the first study (Figure 2, left). The presentation will address the method and thought process selected for harmonizing low temperature electrolysis performance experiments and defining equipment requirements. Latest results and progress of the round robin phase II effort will be reported and discussed and further action summarized.

References:

Bender, M. Carmo, T. Smolinka, A. Gago, N. Danilovic, M. Mueller, F. Ganci, A. Fallisch, P. Lettenmeier, K.A. Friedrich, K. Ayers, B. Pivovar, J. Mergel, D. Stolten, „Initial approaches in benchmarking and round robin testing for proton exchange membrane water electrolyzers”, International Journal of Hydrogen Energy, Vol. 44, Issue 18, 2019, P. 9174-9187, https://doi.org/10.1016/j.ijhydene.2019.02.074

Lickert, M. Carmo, G. Bender, B. Pivovar, T. Smolinka, S. Fischer, J. Young, A. Kang, P. Kadam, A. Fallisch, „Round Robin Testing Activities – Phase 2”, IEA Annex 30 Workshop, Hannover, March 2019

Figure 1
Quasi-2D Hybrid Organic-Inorganic Perovskites: DFT Modeling Approach
Authors: Allam Omar Adel , Lee Ilgeum , KIM Dong Ha , Jang Seung Soon
Published: February 2020

Hybrid organic-inorganic perovskites (HOIPs) have developed to become highly promising solution-processable direct-bandgap semiconductors, which have exhibited high solar conversion efficiencies due to their outstanding charge carrier mobilities. HOIPs exhibit superior optical properties due to their relatively high photoluminescence quantum efficiency and high brightness emission. Furthermore, HOIPs have garnered much interest due to their tunable bandgaps; which are controlled by modifying the dimensionality and composition of the perovskites. In this study, we utilize DFT methods to investigate the emission of HOIPs in order to achieve reliable tunability of bandgap. We investigate quasi-2D perovskites which are considered to form multiple quantum wells, in which the inorganic layers act as wells and the bulky organic spacers as barriers. It is well known that the bandgap of these layered perovskites can be tuned by varying the “quantum well” thickness (corresponding to n in Aʹ2An-1BnX3n+1). While it has been shown that the size of the organic cations occupying the cuboctahedral cavity of 3D perovskites indirectly affect bandgap by altering B-X orbital overlap through octahedral distortions, the effect of the spacer size (in the interlayer region) has not been fully understood in 2D perovskites. In this study, we investigate the effects of aliphatic and aromatic spacers on the bandgap and formation energies of HOIPs. Furthermore, we characterize a correlation between the steric size of the spacer cation and band gap, which is a key characteristic for the design of optoelectronics. Overall, we find that the choice of the spacer cation can play a crucial role in tuning the emission of perovskite light-emitting diodes.
Bioelectrochemical Approach for Urea Removal from Synthetic Urine
Authors: Rojas-Pérez Arnulfo , Barreto-Vázquez Delmaliz , Vijapur Santosh H. , Hall Timothy D. , Taylor E. J. , Cabrera Carlos R
Published: February 2020

The recycling of human urine has become a main research area in wastewater treatment due to the increased demand for water. Urine is composed of 95% water, 2% urea and other organic and inorganic compounds. Urea is a toxic molecule that may cause renal failure and gastrointestinal bleeding. Nevertheless, it is difficult to remove by common methods since it is a small, uncharged molecule. In this work, the use of Proteus vulgaris is proposed, a bacterium that contains urease, to catalyze the urea conversion to ammonia. The latter can then be oxidized by a platinum electrode while producing a current leaving a urea-ammonia-free solution. This system was first tested in synthetic human urine (SHU) simulating the ureolytic bacterium behavior. The ammonia oxidation current (AOC) was evaluated by cyclic voltammetry (CV) using Pt electrode in SHU, obtaining better results when less urea was present in solution. Preliminary, AOC was evaluated while the bacterial grew in Enriched Synthetic Human Urine (SHU + growth factors). The experiment was carried out for 24 hours showing not only bacterial viability and actual growth in the medium but an increased AOC over time.
Label-Free Paper Sensor for Picomolar Insulin Detection in Human Serum
Authors: Krishnan Sadagopan , Niroula Jinesh , Premaratne Gayan
Published: February 2020

Insulin measurement systems for artificial pancreas and for managing normal glucose metabolism have been identified to be a critical need due to the ever growing rapid diabetic disorders globally. Our objective is to design a label-free, low-cost paper sensor for directly measuring insulin concentrations in circulating biofluids. As a step forward towards this goal, we present herein a sensor design that can successfully measure picomolar insulin concentrations in a diluted human serum.
A Cross-Linker Free Enzyme Immobilization for Direct Bioelectrocatalysis Using Aqueous Phase Inversion of a High-Ionic-Strength, Liquid Complex Coacervate
Authors: Lim Koun , Sima Monika , Stewart Russell , Minteer Shelley D.
Published: February 2020

Immobilization of enzymes on an electrode surface is critical in facilitating bioelectrocatalysis. Here, we present cross-linker free immobilization using aqueous phase inversion of a high-ionic-strength, liquid complex coacervate to create a porous solid electrode coating for direct bioelectrocatalysis of horseradish peroxidase (HRP) and laccase. The liquid complex coacervate (PGP6) was made by mixing a polycationic polymer with guanidinium moiety (PG) and polyanionic polymer of hexametaphosphate (P6) in 1.4 M NaCl at a 1:1 positive to negative polymer charge ratio. A mixture of 18 µL of the condensed liquid phase (PGP6) and 2 µL of 50 mg ml-1 of laccase or HRP was made. A total of 1.5 µL of this mixture was deposited on a 0.25 cm2 AvCarb electrode and submerged in DI water for 30 minutes to induce phase inversion and solidification of the coating. A confocal microscopic image of fluorescently tagged laccase showed the entrapment of enzymes within the solids, not in the pores. Both immobilized enzymes successfully generated a catalytic current corresponding to the addition of their respective substrates. Also, the square wave voltammograms of these electrode coatings showed no apparent redox peaks which indicated direct electron transfer. These results show the convenience of an aqueous phase inversion coating system for direct bioelectrocatalysis and advance to the potential for mediated electron transfer.
Transition State Structure Modeling and Mechanistic Study of Purine Derivatives
Authors: Abate Mulu Alemayehu
Published: February 2020

Xanthine oxidase is one of the members of molybdo-enzymes known to catalyze the oxidative hydroxylation of various purine derivatives. The mechanistic transformation of the tetrahedral Michaelis-Menten type complex ((EOX)-[Mo(VI)-Oeq-CCRH]) to the product bound intermediate ((EOX)-[Mo(IV)-Oeq-CCR]) is expected to pass through the tetrahedral transition state complex ((EOX)-[Mo(VI)(-Oeq-CCRH---HRH---)(=SMo)]#). Although several accounts are made regarding the events taking place at the transition state, they have never been fully explored nor quite understood. Similarly, the description of the formation of Oeq-CCRH bond, cleavage of CCRH-HRH bond, migration of HRH to SMo terminal, and reduction of (EOX)-Mo(VI) to (ERED)-Mo(IV) was not well understood. In order to understand the events taking place during catalysis, new computational models have been used to perform an electronic structure calculation. The calculations were performed on the active site model compound bound to purine derivatives, mainly 2-hydroxy-6-methyl purine (HMP) that has never been investigated computationally. The transition state modeling also reveals a reactant like transition state for the reaction of HMP with the active site. Understanding the transition state geometry is a prime importance in developing a plausible reaction mechanism. From the four alternative paths, path one has small energy barrier compare to the three alternative paths. Understanding the mechanism may be used in the drug design process. From our mechanistic study HMP favor concerted mechanism rather than step wise mechanism.
New Separator Materials for Lithium-Ion and Lithium Primary Batteries Operating in Extreme Environments
Authors: Brandon Erik J. , Billings Keith J. , Ratnakumar Bugga V. , Jones Simon C. , Pasalic Jasmina , Seong Jessica , Warner William N. , Hu Carl , Morin Brian
Published: February 2020

Lithium-ion battery technology is now pervasive in all areas and at all scales of energy storage, including consumer electronics, automotive applications and grid level storage. Traditionally limited to operation under terrestrial conditions, these limits of lithium-ion technology are being expanded to encompass operation under more extreme conditions, including aerospace applications. These scenarios require the consideration of new cell components, including electrolytes, cell designs and separators. This talk will focus on the development of new separator materials, targeted for operation in high radiation environments, often encountered in space missions. Conventional polyethyelene/polypropylene based separators have been evaluated for their electrical, chemical and mechanical performance. High doses of radiation have been shown to compromise the mechanical performance of these conventional separators. New aramid based separators are under development to address these limitations, and results from this development and testing will be reported. It is anticipated these separator materials may find application in lithium-ion battery cells used in other types of extreme environments.

The work described here was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA) and supported by the Europa Lander Pre-Project.
Adhesive and Heat Resistant Separator for Long-Term Stable Lithium Ion Batteries
Authors: Park Eun Ji , Ahn Jinhyeok , Yoo Minjeong , Im Jinsol , Jang Eun Kwang , Lee Jong Hyun , Cho Kuk Young
Published: February 2020

Next-generation lithium ion batteries (LIBs), the promising energy sources for an electric vehicle and grid energy storage systems, should satisfy the continuous needs for high reliability and safety for long-term high-energy-density operation. A novel separator has a functional multi layer coating on both side of PE separator. It shows superior heat resistance, high electrolyte uptake, long stable cyclability when equipped in the cell, and persistent adhesion with the electrode. Multi coating layers are composed of a 2-μm-thick Al2O3 ceramic layer that enhances mechanical strength and thermal stability of the conventional polyethylene separator, and a 1.5-μm-thick adhesive layer produced from acrylic polymer beads that combine consistently between the electrode and the separator forming electrode/separator assembly during cell operation. These multi-layer coated separators enable high capacity retention and reduce impedance build up with cycling, when used in coin or pouch cells. Fabrication of multi-coating layers by aqueous coating without organic solvents not only offers environmental benefits but is also effective in cost reduction. This approach paves the way for the separator, which has long been considered an inactive major component of LIBs, to contribute towards the energy density as an active component for obtaining longer stable cyclability.
New Electrolyte Additives Formed By in Situ Method for High Voltage Lithium Ion Battery
Authors: Yang Jianzhong , Shkrob Ilya A , Liu Qian , Dietz Rago Nancy L. , Zhang Zhengcheng , Liao Chen
Published: February 2020

Developing high-voltage Li ion batteries (LIBs) is an important trend to fit high energy and power density requirement of electric vehicles and hybrid electric vehicles. This requires the cathode materials and concomitant electrolyte to accommodate the high voltage working condition. However, continually exposed to high voltage, the cathode materials could gradually deteriorate and eventually cause the failure of battery. To address this issue, electrolyte additives can be an economic solution based on current existing electrolyte system, since it can decompose on the electrodes forming thin protective layer during formation cycles to prevent further deleterious reactions. The nominal electrolyte additives here are the precursors, which can spontaneously react with electrolyte when introduced into the electrolyte to yield the target surface-modifying products that can effectively protect the cathode. These additives were proved exceptional, since they delay both the impedance rise and capacity fade in the LIBs. To extend the library of this type of additives and explore more effective additives, we applied the molecular engineering to tune molecular backbone, functionality and substitution to obtain different surface-modifying products and maximize the battery performance. In addition, the in situ method is particularly beneficial to scale up electrolyte preparation, since it doesn’t need any post separation and purification process. By varying the structure of the additive precursor, we clearly see a trend that is governed by thermodynamics which determine the product configuration. The electrochemistry of these additives and their application in composite cathodes will be also discussed. Our strategy of synthesizing new electrolyte additives by in situ method will open up and facilitate the development of the lithium ion batteries toward high energy and high power density.
(Invited) Towards Fast Charging of High Energy Density Li-Ion Batteries
Authors: Du Zhijia , Liu Tianyi , Wu Xianyang , Lin Feng , Zhao Kejie , Wood David L. , Belharouak Ilias
Published: February 2020

The development of Li-ion battery has attracted extensive efforts in the last three decades for its high energy density and long cycle life. The rapid growth of electric vehicle market has a demand for fast charging of Li-ion battery in order to increase the market penetration. The energy density of Li-ion battery has been increased to 225-250 Wh/Kg nowadays thanks to R&D of cell engineering development (mainly increasing electrode thickness). This high energy density ensures longer driving mileage, but also limits the fast charging capability compared to high power Li-ion cells with thinner electrodes.

The relationship between battery energy density, power density and areal capacity in thick electrodes has been studied by Du et al1. and Gallagher et al2. The results suggested that the rate capability is limited by both the Li-ions mass transport in liquid electrolytes and interfacial overpotential in graphite anodes 2,3. The findings also implied that a significant portion of the available energy in thick electrodes cannot be accessed because of the depletion of Li-ions in the electrolyte phase 1. Therefore, development of electrolyte that has the capability of fast mass transport in the cell is of great importance for fast charging of high energy density Li-ion cells.

The team at ORNL is developing electrolyte that can enable a fast charging of 15 minute for high energy density Li-ion cells. By developing suitable solvent, salt and additives, the Li ion transport properties can be increased by >20%. We will talk about the result in details during the meeting.

Z. Du, D. L. Wood, C. Daniel, S. Kalnaus, and J. Li, J. Appl. Electrochem., 47, 405–415 (2017).

K. G. Gallagher et al., J. Electrochem. Soc., 163, A138–A149 (2016).

S. Ahmed et al., J. Power Sources, 367, 250–262 (2017).
Analyzing the Effects of Lithium Plating on the Safety Performance of Lithium-Ion Batteries
Authors: Deichmann Eric , Torres-Castro Loraine , Karulkar Mohan , Lamb Joshua , Garzon Fernando H
Published: February 2020

As demand for high-performance lithium-ion batteries (LIBs) surges across new civilian and military markets, so does demand for increased charging rates and extended battery life. Unfortunately, this push toward improved battery performance is accompanied by an increased risk of internal lithium plating and subsequent short-circuiting. Both introduce an inherent safety hazard which extends beyond the standard safety concerns associated with lithium ion batteries. It is widely accepted that plated lithium both initiates and increases the rate of reaction of runaway events, however its effects have yet to be quantified and isolated from other exothermic reactions occurring in the cell. Due to lithium’s high physical mobility, volatile high-temperature kinetics, and instability in the presence of humidity, it is important to identify and isolate the unique hazards associated with molten lithium during battery failure. This area of study was of interest to the Power Sources Technology Group (PSTG) at Sandia National Laboratories due to our unique cradle-to-grave capabilities, which allowed for every aspect of the cell development and testing process to be closely monitored. This included fabrication of individual cells (>1 Ah) with preferential nucleation sites followed by electrochemical plating and subsequent abuse testing of each cell at the battery abuse testing laboratory (BATlab). The ability to precisely control the extent of lithium plating allowed for facile correlation between the extent of lithium plating and worsened abuse response. Additionally, the ability to monitor cells during thermal runaway allowed for direct observation of the potential hazards associated with high concentrations of molten lithium being dispersed during a failure event.

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.
Next Generation of Materials for Lithium-Ion Battery Anodes, Cathodes, Separators & Electrolytes
Authors: Yushin Gleb
Published: February 2020

Energy density and cost of conventional Li-ion batteries (LIBs) are closely approaching their limits. The reliance of conventional cathodes on the use of toxic metals additionally endangers health and safety of miners in developing countries. Novel materials for conversion-type cathodes and alloying-type anodes offer an opportunity to double energy stored in LIBs, reduce their cost by the same factor, and improve cell safety. Conventional separators suffer from poor thermal stability, limited mechanical strength in tension and compression, relatively large minimum thickness of 6 micron (typically 10-25 micron for safer versions used in electric vehicle (EV) LIBs) and relatively high ionic resistance, undesired for ultra-fast charging. Ceramic and ceramic-composite nanofiber-based separators enable one to overcome the current limitations and produce safer LIBs with higher energy density and faster charging abilities. Finally, conventional organic electrolytes suffer from flammability, limited electrochemical stability in contact with anodes and cathodes of high-energy LIBs and undesired chemical and electrochemical reactions with cathode materials that accelerate LIB fading, particularly at elevated temperatures. Several classes of solid electrolytes may offer effective solutions to overcome such drawbacks. In this invited talk I will provide an overview of the activities of our group in these complementary fields and share my understanding of the industrial requirements for the technology adoption and successful commercialization.
Copper Delafossites: Diverse Materials for Solar Energy Conversion and Storage
Authors: Farnum Byron
Published: February 2020

Metal oxide nanomaterials have a wide range of applications in renewable energy conversion and storage. Many are used as electron transport materials in heterojunction solar cells while others are used directly as light absorbers and catalysts for energy storage reactions such as water splitting. Even further, metal oxides represent a large fraction of electrode materials used in Li-ion batteries which can store solar energy for later use. Copper delafossites (CuMO2) are a unique class of materials capable of achieving all three of these feats. The layered structure of these materials, with Cu(I) atoms sandwiched between M(III)O6 octahedra, along with the tunability of the M(III) atom create a wide range of functionality. Our group has been particularly interested in the delafossite CuGaO2 for applications as a charge transport layer in p-type heterojunction solar cells. Detailed physical characterization and electrochemical studies of these materials reveal the existence and impact of copper vacancies in the crystalline lattice. These vacancies allow for rapid charge transport in CuGaO2 but also introduce a large concentration of recombination trap sites that can be detrimental to solar energy conversion. The importance of these fundamental studies in terms of materials design for delafossite hole transport layers will be discussed throughout.
(Invited) Nanostructured Organic Electrodes for Electrochemical Energy Storage Applications
Authors: Lee Seung Woo
Published: February 2020

Organic electrode materials have significant advantages over conventional inorganic electrodes for rechargeable battery applications, such as low cost, high theoretical capacity, and environmental friendliness. However, the organic electrode materials generally suffer from slow rate-performance and poor cycling stability. Charge storage performance of the organic electrode materials can be significantly improved through the molecular design on conductive carbon substrates, such as carbon nanotube (CNT) and graphene. For example, we have demonstrated the organic positive electrodes by coating redox-active organic molecules on the surface of CNT and graphene substrates.1-4 This presentation introduces various structure-controlled organic electrodes with significantly enhanced charge storage performance. We establish the structure-property relationship of organic electrode materials by combining computations, structure and electrochemical characterizations. Based on the high-capacity organic positive electrodes, we demonstrate hybrid supercapacitors with significantly enhanced energy and power density.

J. C. Bachman, R. Kavian, D. J. Graham, D. Y. Kim, S. Noda, D. G. Nocera, Y. Shao-Horn and S. W. Lee, Nature Communications, 6:7040 (2015).

T. Liu, K. C. Kim, B. Lee, Z. Chen, S. Noda, S. S. Jang and S. W. Lee, Energy & Environmental Science, 10, 205 (2017).

T. Liu, B. Lee, B. G. Kim, M. J. Lee, J. Park, and S. W. Lee, Small, 14, 1801236 (2018).

T. Liu, B. Lee, M. J. Lee, J. Park, Z. Chen, S. Noda, and S. W. Lee, Journal of Materials Chemistry A, 6, 3367 (2018).
Investigation into the Influences of Co-Solvents in Ionic Liquid Based Electrolytes for Lithium-Sulfur Cells
Authors: Meisner Quinton James , Liu Qian , Zhang Zhengcheng
Published: February 2020

Lithium-sulfur (Li-S) batteries remains an energy storage system plagued by many obstructions to their implementation including self-discharge, poor utilization of active material, and the so-called “shuttling effect” of soluble lithium polysulfide species (LiPS). Ionic liquids have been previously studied for application in Li-S cells due to their low solvating ability with LiPS species and elemental sulfur which could lead to better cycling performance. In addition, ionic liquids have great promise in both lithium-ion and beyond lithium-ion systems due to their minimal vapor pressure, high boiling points, and are virtually inflammable. Unfortunately ionic liquids alone are poor electrolyte solvents for sulfur cathodes as that they have insufficient wetting of elemental sulfur ultimately leading to lower material utilization and low specific cell capacity. In order to remedy this issue co-solvents are typically used along with an ionic liquid to increase the specific capacity of the Li-S cell. In this study we have investigated how co-solvent choice and its concentration contribute to the observed capacity of Li-S cells using either a binary or ternary solvent electrolyte systems with 1-butyl-1-methylpyrrolidinium N,N-bis(trifluoromethanesulfonyl)imide (MBPyrTFSI). The consequence of co-solvent choice and ratio will be expressed in terms of Coulombic efficiency and discharge capacity of Li-S cells, as well as the viscosity, density, and conductive properties of the electrolyte solutions.

Figure 1
Rechargeable Aluminum Organic Batteries
Authors: Kim Dong Jun , Yoo Dong-Joo , Otley Michael T , Prokofjevs Aleksandrs , Pezzato Cristian , Owczarek Magdalena , Lee Seung Jong , Choi Jang Wook , Stoddart J.Fraser
Published: February 2020

Since aluminum is the third most abundant element in Earth’s crust, developing rechargeable aluminum-ion offers1 a golden opportunity for delivering a high energy-to-price ratio. Nevertheless, finding appropriate host electrodes for inserting aluminum (complex) ion remains a fundamental challenge. Here, we demonstrate2 a new strategy for designing active materials for rechargeable aluminum batteries. This strategy entails the use of redox-active triangular phenanthrenequinone-based macrocycles which form layered superstructures resulting in the reversible insertion and extraction of cationic aluminum complex. This architecture exhibits an outstanding electrochemical performance with a reversible capacity of 110 mAh g–1 along with a superior cyclability of up to 5000 cycles. Furthermore, we prepared a hybrid electrode by blending the macrocycle with graphite flakes, featuring homogeneous stacking of both macrocycle and graphite flake. These findings lay the groundwork for future design and operation of aluminium-ion batteries and represent a promising starting point for developing affordable large-scale energy storage applications.

References

M. -C. Lin, et al.
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D. J. Kim, D.-J. Yoo, M. T. Otley, A. Prokofjevs, C. Pezzato, M. Owczarek, S. J. Lee, J. W. Choi, and J. F. Stoddart, Nat. Energy, 2019, 4, 51–59.

Figure 1