bluuebunny/crossref_metadata_2025 huggingface dataset:
Cadmium Refining in Chloride Melts Using a Bipolar-Electrode Electrolyzer
Authors: Kozin Valentin F. , Blyznyuk Antonina V. , Savchuk Ruslan N.
Published: February 2020

The kinetics and mechanism of the formation of subvalent cadmium complexes in the Cdo – CdCl2 – ZnCl2 – NH4Cl system were studied spectroscopicaly. The results indicate that metallic cadmium reacts with Cd2
2+ and Cd2
3+ complex cations. The formation of Cd2
2+ and Cd2
3+ is evidenced by the absorption bands around 270 and 335 nm, respectively, in the electronic spectrum of the melt.

The variation of the intensity of absorption bands during the reaction between Cd2+ and metallic cadmium was used to evaluate the kinetics of Cd2
2+ and Cd2
3+ formation. The rate constants for the formation of Cd2
2+ and Cd2
3+ complex cations evaluated from the slop of plot of lg(Ao - A∞) versus time are 4.22∙10-3 and 3.50∙10-3 s-1 , respectively.

The effect of the electrolysis conditions on the rate of cadmium exchange between the electrodes was examined. The anode current efficiency of cadmium dissolution was found to increase with current density and temperature and to exceed the theoretically predicted value, which was attributed to the formation of subvalent cadmium compounds.

The present results may be helpful in assessing parameters of cadmium electrorefining.

A method was proposed for electrolytic Cd refining in which electrolysis is performed in molten cadmium chloride containing Cd in lower oxidation states. The technique for the preparation of the electrolyte was described. To prevent impurity transfer from the anode to cathode, bipolar Cd electrodes were used.

The distribution ratios evaluated for typical metallic impurities in Cd show that high-purity Cd can be obtained in a single electrolysis cycle.
(Invited) Lithium Recovery and Lithium-6 Enrichment Using Innovative Electrodialysis with Lithium Ionic Conductor Membrane
Authors: Hoshino Tsuyoshi
Published: February 2020

As a means of addressing global warming, the world is increasingly turning to the use of Li-ion batteries in electric vehicles and as storage batteries in the home; therefore, there is a growing need for Li. Furthermore, as a fuel for fusion reactors, tritium is produced by the reaction of lithium with neutrons in a tritium-breeding material.

Li is primarily recovered from salt lakes in South America but is also present in seawater. Thus, I propose a method for recovering Li from seawater by using innovative dialysis, wherein Li only permeates from the negative electrode side to the positive electrode side through a Li ionic superconductor functioning as a Li separation membrane (LISM) (Fig.1). Measurements of the Li ion concentration at the positive electrode side as a function of dialysis duration showed that the Li recovery ratio increased to approximately 7% after 72 h with no applied electric voltage, and an electrical power of 0.04 V and 0.1 mA was generated. Moreover, other ions in the seawater did not permeate the LISM. With both ends of the LISM bound with a negative and positive electrode, hydrated Li ion was transformed to Li ion only because Li ion can permeate through the LISM [1].

Furthermore, tritium needed as a fuel for fusion reactors is produced via neutron capture by lithium-6 (6Li). However, natural Li contains only about 7.8% 6Li, and enrichment of 6Li up to 90% is required for adequate tritium breeding in fusion reactors.

Therefore, new Li isotope separation technique using a Li ionic rconductor functioning as a LISM have been developed. Because the mobility of 6Li ions is higher than that of 7Li ions, 6Li can be enriched on the cathode side of a cell. Using Li0.29La0.57TiO3 (LLTO) as the Li ionic superconductor was prepared, and the relationship between the 6Li separation coefficient and the electrodialysis time was investigated. After electrodialysis, we obtained a maximum of 1.05 for the 6Li isotope separation coefficient. This result showed that the 6Li isotope separation coefficient of this method is the same as that of the amalgamation process using mercury (1.06). Thus, this method has the potential to be a superior 6Li enrichment method to produce 90% enriched tritium breeder for fusion reactors.

[1] T. Hoshino, Desalination, 359, 59-63 (2015).

Figure 1
Electrochemical Processes for Improved Efficiency of the Environmental Control and Life Support System
Authors: Vijapur Santosh H. , Wang Dan , Hall Timothy D , Pena Armando , Taylor E. J. , Cabrera Carlos R
Published: February 2020

In order to facilitate extended human space travel, solutions and innovations are required to enable efficient long life operation of life support systems with limited earth availability. The existing supply of air and water on the International Space Station (ISS) is managed by Environmental Control and Life Support System (ECLSS) which recovers and recycles water and oxygen from human waste. The best estimates available show that this system works at efficiencies between 75% to 85% water recovery which requires relatively frequent refueling to sustain life upon the ISS. As human missions travel further into the solar system the available of earth to resupply will be diminish due to cost. Therefore, next-generation systems to recycle water, oxygen, and improve system sanitization are required to sustain life and improve efficiency. When evaluating the existing ECLSS system we find that this system has lifetime/durability limitations due inefficiencies within existing process like vapor compression distillation (VCD), reverse and forward osmosis (RO/FO), and disinfection. Requiring complex hazardous chemicals to treat and sterilize to each system in order to maintain their performance.

Within this context, Faraday Technology Inc. and the University of Puerto Rico (UPR) are working on developing a technology to neutralize or eliminate many of the contaminants that commonly foul the VCD and RO/FO systems while improving system maintenance and disinfection. Specifically, Faraday and UPR are developing a custom bioelectrochemical system to remove urea and a peroxide generation system to disinfect systems and surfaces. The initial goal of this development is to produce systems that will be compatible within the existing ECLSS while also identifying new pathways for improve recovery efficiencies and sustainability far earth life.

Acknowledgements: The financial support of NASA Contracts No. NNX17CA30P, NNX16CA43P, and NNX17CJ12C is acknowledged.
Interfacial Stability, Impact on Surface Stabilization and Charge Transfer
Authors: Pawar Gorakh , Liaw Boryann , Dufek Eric J.
Published: February 2020

The science behind the nucleation growth and stability of deposited metal is crucial for a wide range of commercially relevant electrochemical applications including: energy/hybrid energy storage systems, semiconductors, and catalysis. The combined impact of thermal, mechanical, chemical and electrochemical factors create a complex and convoluted set of possible thermodynamic pathways related to the overall stability and growth of deposited metal. This convolution of pathways has long-ranging impacts on the durability, reliability and safety of the devices and can ultimately lead or inhibit the successful development of advanced technologies.

Routes to better understand the stability and initial structure of nucleation events and the subsequent reactivity of the metals are necessary to determine more efficient and dynamic routes to optimize performance for systems which require the electrodeposition of reactive metals. This presentation will focus on a modelling approach that looks at the combined stability and variation in stability of Li metal.

Included in the discussion will be results showing that deviation from classical theories are expected as the size of the initial Li cluster is varied. The work will also discuss how interfacial structures impact surface stability, the formation of surface interphases and ultimately how charge transfer is impacted.
Nucleation and Surface Passivation in Li-Air Batteries
Authors: Shen Chao , Andrei Petru , Zheng Jim P.
Published: February 2020

Recently, there has been increased evidence that the lithium peroxide in Li-oxygen batteries forms as a result of a continuous nucleation process followed by a growth process [1, 2]. This deposition mechanism is intrinsically heterogeneous and is microscopically different from the traditional approach in which the final product grows uniformly as a thin resistive layer on the surface of the electron conductive material [3, 4]. Similarly to the nucleation and growth of lithium sulfide in Li-S batteries, the deposition of Li2O2 in Li-oxygen batteries starts with the formation of initial Li2O2 seeds and subsequent growth of the Li2O and/or Li2O2 product on the surface of the seeds. This growth can be in the form of direct precipitation of Li2O2 molecules or disproportionation reactions involving LiO2 and Li2O2. In this presentation we introduce a mathematical model that describes the precipitation and growth mechanism in the form of a system of differential equations appropriate for implementation in finite element simulators. In agreement with the classical nucleation theory, the driving force of the nucleation process in our model is the oversaturation of the depositing species. Therefore, the nucleation seeds appear when there is a critical oversaturation condition on the surface of the carbon; the number of nucleation seeds increases in time during the discharge of the battery at a rate which is proportional to the discharge rate of the battery. The model explains quantitatively well the decrease of the specific capacity with the discharge rate and also explains the relatively large Li2O2 grains observed in the cathode of discharged Li-air batteries.

[1] S. Lau, L.A. Archer, Nucleation and Growth of Lithium Peroxide in the Li–O2 Battery, Nano Letters, 15 (2015) 5995-6002.

[2] Y. Yin, A. Torayev, C. Gaya, Y. Mammeri, A.A. Franco, Linking the Performances of Li–O2 Batteries to Discharge Rate and Electrode and Electrolyte Properties through the Nucleation Mechanism of Li2O2, The Journal of Physical Chemistry C, 121 (2017) 19577-19585.

[3] A.C. Luntz, V. Viswanathan, J. Voss, J.B. Varley, J.K. Nørskov, R. Scheffler, A. Speidel, Tunneling and Polaron Charge Transport through Li2O2 in Li–O2 Batteries, The Journal of Physical Chemistry Letters, 4 (2013) 3494-3499.

[4] P. Andrei, J.P. Zheng, M. Hendrickson, E.J. Plichta, Some Possible Approaches for Improving the Energy Density of Li-Air Batteries, Journal of the Electrochemical Society, 157 (2010) A1287-A1295.
Transient Study of Adsorbed Oxygen Species Arising from Exposure to Dissolved Oxygen
Authors: Rodríguez Oliver , Denuault Guy
Published: February 2020

Recently, adsorbed oxygen species (adspecies) have been detected at the millisecond scale on different metallic microelectrodes after being exposed to dissolved oxygen 1,2 . Comparing the experimental current of the oxygen reduction reaction (ORR) with a theoretical diffusion controlled current, it was revealed that both, the adsorbed and diffusion controlled species, were being reduced at the same time. To study the adspecies independently, it is necessary to decouple the contribution of each process. Here, we show that this can be done by controlling the availability of the gas present in solution as well as the potential waveform applied. After the separation, the diffusion controlled current reveals how n
app, the apparent number of electrons for the ORR, depends on km
, the mass transfer coefficient. On Pt microdiscs, n
app decreased from 4 to 2 as the mass transfer coefficient was increased by decreasing the disc radius or the timescale of the experiment. This effect was previously observed at the steady state with rotating disc and microelectrodes, but its dependency on transient conditions has never been reported 3, 4. Meanwhile, the decoupled desorption current was found to follow a second order process which would be consistent with the production of H2O2 via dimerization of OH radicals. These desorption currents were used to estimate the desorption rate constant and maximum coverage of the adspecies as a function of the applied potential. Our results indicate that the amount of adsorbed species left after exposure to dissolved oxygen is below 0.1 of a monolayer, in agreement with previously reported values 1, 2. The high sensitivity of the methodology presented here reveals the subtle effects arising from exposure to dissolved oxygen.

(1) Perry, S. C.; Denuault, G. Transient Study of the Oxygen Reduction Reaction on Reduced Pt and Pt Alloys Microelectrodes: Evidence for the Reduction of Pre-Adsorbed Oxygen Species Linked to Dissolved Oxygen, Chem. Chem. Phys.
2015, 17 (44), 30005-30012.

(2) Perry, S. C.; Denuault, G. The Oxygen Reduction Reaction (ORR) on Reduced Metals: Evidence for a Unique Relationship Between the Coverage of Adsorbed Oxygen Species and Adsorption Energy, Chem. Chem. Phys.
2016, 18, 10218-10223.

(3) Pletcher, D.; Sotiropoulos, S. A Study of Cathodic Oxygen Reduction at Platinum Using Microelectrodes. Electroanal. Chem. 1993, 356 (1-2), 109-119.

(4) Sosna, M.; Denuault, G.; Pascal, R. W.; Prien, R. D.; Mowlem, M. Development of a Reliable Microelectrode Dissolved Oxygen Sensor. Sensors Actuators, B Chem. 2007, 123 (1), 344-351.
High Magnetic Field Effects on Al Electrodeposition in AlCl3-Emic Ionic Liquid
Authors: Matsushima Hisayoshi , Takahashi Hitomi , Mogi Iwao , Ueda Mikito
Published: February 2020

1.Introduction

Aluminum is a very important material because of its distinctive features of a bright silvery appearance, light weight and high corrosion resistance. Also, it is used as a base in light-emitting diodes owing to its high reflectance of more than 90% in the visible light region. We have been investigating Al electrodeposition in a magnetic field. The surface morphology changed remarkably in the presence of a magnetic field, where the large grains with tabular-face were created [1]. This is explained by MHD convection induced by Lorentz force.

We consider that the MHD convection can act more effectively as compared with an aqueous solution system, since an ionic liquid consists of only ion species. In this report, Al films were electrodeposited in EMIC-AlCl3 ionic liquid under a superconducting magnet. Their morphology and crystal orientation were analyzed by scanning electron microscopy and X-ray diffractometry.

Experimental

Electrodeposition was carried out with a three-electrode system. The electrolyte used was EMIC-AlCl3 (1:2). The cathode was a Cu plate and the anode was an Al plate. All experiments were conducted in a glove box purged using by Ar gas at 60°C. The Al electrodeposition was conducted galvanostatically until the amount of electrical charge reached 29 C cm−2, which corresponds to a deposition 10 µm thick. A superconducting magnet up to 5 T was applied parallel to the electrode surface. The surface morphology of the electrodeposited Al films was observed using SEM, while the crystal orientation was measured by XRD using the Cu-Kα line.

Results and discussion

Figure 1 shows the SEM image of the Al electrodeposited surface without a magnetic field and with a magnetic field of 5 T. When no magnetic field is applied, there were many grains on the surface and the deed groove was seen (Fig. 1 (a)). On the other hand when 5 T was applied parallel to the electrode surface, the grooves between the grains were buried and a very smooth surface was observed (Fig. 1 (b)). Because the MHD convection was generated by the magnetic field, the ions were supplied to the vicinity of the trench between the grains. This was attributed to the uniform electrodeposition.

In order to evaluate the crystal orientation of the Al films obtained by electrodeposition, XRD measurement was carried out. When the magnetic field was not applied, the (200) plane showed a very strong orientation compared with other crystal faces. In the magnetic field, the orientation of the (200) plane decreased with the increase of the magnetic flux density, while the crystal growth of the (111) and (220) planes were progressed.

[1] H. Takahashi, H. Matsushima and M. Ueda, J. Electrochem. Soc., 164, H5165 (2017).

Figure 1
Activity and Selectivity Control in CO2 eectroreduction through Catalyst and Electrolyte Design
Authors: Roldan Cuenya Beatriz
Published: February 2020

The electrochemical conversion of CO2 (CO2RR) into chemicals and fuels is of industrial significance since it might lead to a more efficient storage of renewable energy while closing the carbon cycle.

This talk will focus on model nanostructured plasma-activated dendrites and nanoparticle (NP) electrocatalysts (Cu, Ag, Zn, Cu-M with M = Co, Zn and Ag-Sn) for the electrocatalytic reduction of CO2. We will show how to tune catalytic selectivity based on rational catalyst and electrolyte design involving controlling the NP size, shape, support interaction, as well as the electrolyte properties by adding cations and anions (Cs+, Li+, Na+, K+, I-, Br-, Cl-). 1-5

In situ and operando spectroscopic and microscopic methods have been used to gain insight into the correlation between the structure, chemical state, and reactivity of ligand-free size- and shape-controlled spherical and cubic NPs as well as plasma-activated dendritic structures and Cu single crystals during CO2RR. Dynamic changes in the morphology and composition were monitored under potential control via electrochemical atomic force microscopy, X-ray absorption fine-structure spectroscopy and quasi in situ X-ray photoelectron spectroscopy. Additionally, density functional theory calculations were used to provide new insights on the active sites and reaction mechanism of the former electrocatalysts, including the role of different electrolytes. Our results are expected to open up new routes for the reutilization of CO2 through its direct selective conversion into higher value products.

1. P. Grosse, D. Gao, F. Scholten, I. Sinev, H. Mistry, B. Roldan Cuenya, Angewandte Chemie (2018) in press.

2. H. S. Jeon, S. Kunze, F. Scholten, B. Roldan Cuenya, ACS Catal. 8 (2018) 531

3. H. Mistry, Y. Choi, A. Bagger, F. Scholten, C. Bonifacio, I. Sinev, N. J. Divins, I. Zegkinoglou, H. Jeon, K. Kisslinger, E. A. Stach, J. C. Yang, J. Rossmeisl, B. Roldan Cuenya, Angew. Chem. 56, 11394 (2017)

4. D. Gao, F. Scholten, B. Roldan Cuenya, ACS Catal. 7, 5112 (2017)

5. D. Gao, I. Zegkinoglou, N. J. Divins, F. Scholten, I. Sinev, P. Grosse, and B. Roldan Cuenya, ACS Nano 11, 4825 (2017)
(Invited) Polymer-Ceramic Composite Electrolytes for All-Solid-State Lithium Ion Batteries
Authors: Yang Hui , Wu Nianqiang
Published: February 2020

This presentation deals with the polymer-ceramic composites, which are used for all-solid-state lithium batteries. The ceramic Li-ion conductor nanofibers are fabricated with electrospinning technique. The polymer-ceramic composites are formed by in-situ polymerization of monomers, which are cast onto the ceramic nanofibers. The Li-ion batteries with the polymer-ceramic composite electrolytes are testes.
Design of Ion Conductive Core-Shell Bilayer Nanoparticles By Site-Selective Quaternization
Authors: Isawa Yuta , Nakabayashi Kazuhiro , Chen-Tsyr Lo , Mori Hideharu
Published: February 2020

Triazolium-based ion conductive nanoparticles (NPs) with cross-linked cores were synthesized using a self-assembled block copolymer comprising N-vinyl-4-ethyl-1,2,4-triazolium bis(trifluoromethanesulfonyl)imide (NVETri-NTf2) and N-vinyl-1,2,4-triazole (NVTri) and a site-selective cross-linking quaternization in a selective solvent. Their solution behavior and ionic conductivity were evaluated. DLS analyses demonstrated the formation of stable NPs with uniform sizes (about 190 nm). Furthermore, high ionic conductivity was observed by the addition of an ionic liquid (MEI-NTf2) into NP.

Figure 1
Investigations of the Structural and Electrochemical Properties of Partially Abused Li-ion Batteries for Advanced Diagnostics
Authors: Deichmann Eric , Torres-Castro Loraine , Lamb Joshua , Karulkar Mohan
Published: February 2020

Establishing a framework for understanding the degradation mechanisms of lithium-ion batteries (LIBs) subjected to abusive conditions has become increasingly important in recent years, as LIBs continue to capture new markets involving an array of abuse-prone applications such as electric vehicles, aircraft, and mobile energy storage systems. Characterization techniques used to identify the state-of-health (SoH) of LIBs can identify a range of degradation mechanisms, which can be broadly categorized as loss of lithium inventory (LLI), loss of active material (LAM), and conductivity loss (CL). These degradation mechanisms, which have been well characterized in literature, are established using a variety of in-situ and ex-situ techniques. The most common in-situ technique for determining cell SoH involves monitoring temperature and voltage as a function of state of charge (SOC) throughout cell cycling. For abusive conditions, however, this measurement is a particularly poor indicator of battery SoH and does not provide valuable insight into cell degradation until failure is imminent. It is particularly difficult to determine SoH for LIBs, as the voltage curve maintains a relatively uniform profile until moments before cell failure. A more versatile in-situ technique capable of monitoring battery degradation mechanisms is Electrochemical Impedance Spectroscopy (EIS), which quantifies cell SoH by measuring system response to a range of sinusoidal excitation signals at varying frequencies. Although extensive characterization of battery degradation has been conducted using traditional EIS hardware, no research has been conducted on impedance analysis of active load cells subjected to abusive conditions.

This work attempts to identify failure markers by linking impedance measurements captured using the EIS toolbox to previously established degradation mechanisms for abused cells. In-situ EIS measurements were collected, followed by identification of failure markers using ex-situ material characterization of harvested electrodes. Failure markers were established by linking degradation behavior identified by material characterization methods to changes in impedance behavior observed by the toolbox. This data can be extrapolated for use with general LIB chemistries in a wide range of BMS’s. Although data extrapolation is outside the scope of this work, data obtained will help facilitate future extrapolation of failure markers to a wide range of LIB chemistries.

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and 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.
The Role of DMSO As an Electrolyte Additive in Alkaline Zinc-Air Flow Battery
Authors: Hosseini Soraya , Kheawhom Soorathep
Published: February 2020

Zinc-air batteries are attractive electrical energy storage due to their cost effectiveness, high specific energy density, and safety. Traditionally, the batteries use alkaline solution as an electrolyte. Besides, electrolyte additives such as potassium sulfide, zinc oxide, ethanol, surfactants, bismuth oxide, and iron oxide were introduced to suppress zinc anode passivation and corrosion. Dimethyl sulfoxide (DMSO) is one of the potential additives capable of inhibiting zinc anode passivation and corrosion effectively. This work investigates the application of DMSO in an alkaline zinc-air flow battery. Adding DMSO to potassium hydroxide (KOH) aqueous solution electrolyte revealed the positive effects on zinc dissolution.

The effects of DMSO were studied by cyclic voltammetry of Fe(CN)6
3-/Fe(CN)6
4- redox couple reaction using the scan rate of 0.05 mV/s. A pair of sharp cathodic and anodic peaks were observed at 0.2 and 0.7 V (vs. Hg/HgO), corresponding to the redox reaction related to Fe(CN)6
3-/Fe(CN)6
4-. The reduction peaks between 0.04 and 0.2 V (vs. Hg/HgO) were observed for all electrolytes (KOH, DMSO/KOH). With increasing DMSO concentration from 1 to 20 v/v %, the redox peaks shifted towards less positive values. The results suggested that KOH undergoes an interaction with DMSO.

Besides, the effects of DMSO (0, 1, 5, 10 and 20 v/v %) in 0.1 M KOH electrolyte on the electrochemical performance of air-cathode using MnO2 oxygen reduction reaction (ORR) electrocatalyst was examined by a rotating disk electrode technique. Linear sweep voltammetry was recorded in a potential window from 0 to -1 V (vs. Hg/HgO) at a scan rate of 0.05 mV/s and rotation rates of 100 to 3600 rpm. The Koutecky-Levich equation was applied to study kinetics and mass transfer processes of ORR in the electrolyte containing DMSO and KOH. The presence of DMSO in KOH solution causes significant improvement in the limiting current density. Also, it was observed that the limiting current density for the 5 v/v % DMSO/KOH at 3600 rpm is higher than that of 20 v/v % and also higher than that attained by KOH. The calculated number of electron transfer in 5 and 20 v/v % DMSO/KOH were 3.2 and 2.75, respectively, whilst the number of electron transfer of 2.24 was obtained for KOH electrolyte without DMSO. Overall, the results indicated that using DMSO as an electrolyte additive significantly improve zinc anode performance as well as ORR electrochemical performance.

Figure 1
(Invited) Intramolecular Reactions for Gas-Phase Formation of Carbon-Entrapped Clusterfullerenes
Authors: Dunk Paul W. , Mulet-Gas Marc , Hendrickson Christopher L. , Cerón Maira R. , Echegoyen Luis , Moreno-Vicente Antonio , Rodriguez-Fortea Antonio , Poblet Josep M.
Published: February 2020

Fullerenes that encapsulate clusters of atoms represent a fundamental interest in chemistry, materials, and carbon science due to their unique properties and nanoscale structures. Numerous cages that feature a combination of carbon, metal, and heteroatom-based clusters have been discovered since, for example, Sc3NC@C80 was first reported. Nanocarbon reactions that underlie formation of such compounds, however, are not well understood. Here, we experimentally investigate intramolecular reactions of metallofullerenes in the gas phase by means of laser-based techniques, analyzed by high magnetic field Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. A variety of structurally defined clusterfullerene cages (e.g., Sc3N@C68, Sc3N@C78, etc.) are probed under energetic conditions to decipher reactions that may lead to encapsulation of C atoms, as well as clusterfullerenes that include metal-loss products. An aim of the present work is to identify mechanistic processes and principles that guide formation of metallofullerenes that entrap carbon, metal, and heteroatom-based clusters.
Transition Metal Dichalcogenides Clusters Immobilized on Defective Black Phosphorus As an Efficient Electrocatalyst for Hydrogen Evolution Reaction
Authors: Ou Pengfei , Song Jun
Published: February 2020

Transition metal dichalcogenides (TMDs) have been intensely investigated as attractive noble-metal-free electrocatalysts for the hydrogen evolution reaction (HER). However, it still remains a great challenge to enhance electrical conductivity, maintain high intrinsic activity and increase active site density of TMD-based electrocatalysts in practice. Herein, aided by first-principles calculations, a novel composite electrocatalyst in which the TMD clusters are immobilized on the surface of defective black phosphorus (BP) has been designed, with the promise to combine excellent intrinsic activity, high active site density, and high conductivity. The strong X–P (X = S, Se, or Te) covalent bonds between TMD clusters and defects (single and double vacancies) on the BP surface stabilize the composite structure and avoid the long-standing deactivation problem caused by cluster desorption. TMD clusters possess high active sites density, while BP acts as conducting layer to efficiently transport electrons from the electrode to active sites to ensures high conductivity. In addition, the ab-initio molecular dynamics simulations have been performed on cluster diffusion on the defective BP, illustrating the possibility of synthesizing such composite electrocatalyst by a simple drop-casting procedure at finite temperatures.
Protons Are Transmitted across Single-Layer Graphene in Proton-Exchange-Membrane (PEM) Sandwich Structures More Than 100 Times Faster Than Other Cations
Authors: Bukola Saheed , Korzeniewski Carol , Harris Joel M. , Creager Stephen E
Published: February 2020

Proton transmission rates across single-layer CVD graphene embedded in sandwich structures with proton-exchange membranes made from the perfluorosulfonic acid (PFSA) ionomer Nafion were measured and found to occur more than 100 times larger than for any other cation. Measurements were made for protons and a series of other cations including Li+, Na+, K+, Rb+, Cs+ and NH4
+ using a four-electrode method in which two platinum electrodes drive ionic current through the membrane and two reference electrodes installed in Luggin capillaries sense the transmembrane potential difference induced by the forced ion flow. Proton transmission rates across graphene were between 150 and 350 times larger than for any of the other cations studied. Characterization studies of graphene on Nafion using confocal Raman microscopy and X-ray photoelectron spectroscopy, and defect counting for graphene on copper by chemical etching through graphene on copper will also be reported. Findings are consistent with transport through physical defect structures for all cations except protons. Proton transmission occurs at very high rates and may involve sites that are more widely distributed and that have much higher proton selectivity than the sites responsible for transmission of other ions. Proton transmission rates across graphene were also measured using electrochemical hydrogen pump cells at variable temperature, which provides an activation energy for proton transmission across graphene. Rate constants for proton transmission are interpreted using a charge-transfer resistance model that allows for interpretation of ionic currents in terms of a rate constant for interfacial proton-transfer. Anrhenius analysis of the rate constants gives values for the activation energy and frequency factor for the interfacial proton-transfer reaction.
(Invited) 2D-Metals: From Synthesis to Quantum Phenomena
Authors: Robinson Joshua A.
Published: February 2020

Quantum materials (QMats) are prime candidates for next-generation energy-efficient technologies, such as topological quantum computing, quantum sensing, and neuromorphic computing. While van der Waals 2D materials exhibit a compellingly wide range of exotic and potentially useful properties such as charge density waves, topological insulator edges, and superconductivity, one can also realize these properties by stabilizing new 2D allotropes of traditionally 3D superconductors and magnets. In this talk I will discuss our pioneering work in confinement heteroepitaxy (CHet) that enables the creation of 2D forms of 3D materials (e.g. 2D-Ga, In, Sn) and decouples the growth of the metals from other 2D layers, thereby enabling a new platform for creating artificial quantum lattices (AQLs) with atomically sharp interfaces and designed properties. As a specfic example, we synthesize plasmonic layers that exhibit >2000x improvement in nonlinear optical properties, and 2D-superconductors combined with topological insulators as the building block of next generation “2D” topological superconductors. Confinement heteroepitaxy opens up avenues for enabling a virtual “legoland” of hybrid quantum materials.
Synthesis of Large-Scale Single-Layer Mo1-X
W
x
S2 Alloys with Highly Uniform and Tunable Photoluminescence
Authors: Park Juhong , Choi Wonbong
Published: February 2020

Single-layer transition metal dichalcogenides (TMDs) exhibit high carrier mobility and photoluminescence; thus, the materials are well suitable for next-generation optoelectronic and nano-electronic devices application. It is essential to fabricate large-scale single-layer TMDs film with uniform and desirable spectral wavelengths. Here, we report the synthesis of optically uniform single-layer Mo1-x
W
x
S2 alloys by a two-step CVD method followed by a laser thinning process and investigations on their excitonic behavior with compositional changes. The amount of W content (x) in the Mo1-x
W
x
S2 alloy is systemically controlled by the co-sputtering technique, and the post-laser process allows layer-by-layer thinning of the as-synthesized few-layer Mo1-x
W
x
S2 alloys down to a single-layer. Photoluminescence (PL) and Raman mapping analyses suggest that the laser-thinning of the Mo1-x
W
x
S2 alloys is a self-limiting process caused via heat dissipation to the substrate, resulting in a spatially uniform single-layer Mo1-x
W
x
S2 alloy films. As W content (x) increases, the single-layer alloys reveal controlled optical band gaps ranging from 1.871 to 1.971 eV. Furthermore, we found that the number of excessive charge carriers decreases as x increases, resulting in the change in the predominant component of the PL emission from trions for single-layer MoS2 to neutral excitons for single-layer WS2.
(Invited) Optical Investigation of Hybrid Perovskite Photophysics
Authors: Kuno Masaru
Published: February 2020

This presentation will focus on recent work to investigate the microscopic photophysics of hybrid perovskite thin films and nanostructures. Of particular interest, are cases of light-induced anion segregation in films. Also of interest are examples of cation segregation under applied bias. These phenomena have been probed using local optical microscopies including recent use of infrared photothermal absorption techniques to monitor cation migration under bias.
Resonance Energy Transfer in Hybrid Plasmonic-Polymetallophthalocyanine Nanoantennas Fabricated By Electropolymerization
Authors: Collins Sean Stevenson Edward , Flatebo Charlotte , Cai Yiyu , Link Stephan , Landes Christy F
Published: February 2020

Metal nanoparticles have exceptionally high photon absorption cross-sections at energies that excite a localized surface plasmon resonance compared to non-metallic particles. The light energy absorbed by these metal “nanoantennas” can be transferred non-radiatively to a coupled semiconductor material. The energy is stored in the semiconductor as electron-hole pairs through the dephasing of localized surface plasmon dipoles. The electrons and holes can then be extracted for charge transfer applications, such as catalysis. Here, we show that individual gold nanorods can be selectively coated via electropolymerization with metallophthalocyanines, a well-established class of oxygen and carbon dioxide reduction catalysts, to produce hybrid plasmonic-polymeric nanoantennas. The semiconducting polymer coatings have a high density of π-π* dipole transitions with energies matching the dipole resonance energy of the gold nanorods, enabling efficient dipole-dipole coupling. Using in situ hyperspectral dark-field imaging, we observed large plasmon resonance linewidth increases in the scattering spectra of single gold nanorods with the anodic deposition of the polymer coating, and attribute this to a greatly decreased plasmon dephasing time due to resonance energy transfer. In situ single particle spectroscopy was required to reveal that the increase in resonance linewidth was dependent on the polymer thickness and the energy of the uncoated gold nanorod longitudinal plasmon resonance. Permeable metallophthalocyanine polymer coatings are spectroscopically and chemically tunable, and have a high effective surface area opening up new opportunities for plasmonic antenna-reactor electrodes in energy sustainability applications.
Ultrafast Photoinduced Charge Separation in Wide-Band Capturing, Bis-Styryl Bodipy-Fullerene Donor – Acceptor Assemblies
Authors: Shao Shuai , Obondi Christopher , Gobeze Habtom , Lim Gary N. , Karr Paul , D'Souza Francis
Published: February 2020

A series of supramolecular donor-acceptor systems capable of wide-band capture and exhibiting photoinduced charge separation were synthesized, and characterized using various techniques as artificial photosynthetic mimics. Both covalent and noncovalent approaches were developed. In the noncovalent approach, the donor host systems comprise of a 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) containing one crown ether entity at the meso-position and two styryl linkers carrying two electron rich triphenylamine (TPA) or phenothiazine (PTZ) entities. The acceptor host system was a fulleropyrrolidine comprised of mono/bis-alkyl ammonium cation(s). In the second approach of covalent bonding, BODIPY was functionalized with two styryl entities carrying TPA or PTZ as additional donors. Additionally, an electron acceptor, fulleropyrrolidine was connected at the meso-position of the BODIPY ring. Owing to the presence of extended conjugation and multiple chromophore entities, the BODIPY host revealed absorbance and emission well into the near-IR region covering the 300–850 nm spectral range. Using redox, computational, absorbance and emission data, energy level diagrams were constructed to help envision the different photochemical events. Spectral evidence for photoinduced charge separation in these systems was established from femtosecond and nanosecond transient absorption studies. The measured rate constants indicated fast charge separation and relatively slow charge recombination revealing their usefulness in light energy harvesting and optoelectronic device building applications.
Cooperative Dynamics in Oxygen Binding Reaction to Cobalt Porphyrins at the Solution/Solid Interface
Authors: Mazur Ursula , Hipps K W
Published: February 2020

In biology, key molecules for life processes rely on cooperation between metal containing porphyrins to function effectively. In technology, (catalysis and sensing) cooperative interactions between the support and metal porphyrins play a key role in their efficiency. In this study, we present a molecular level study of cooperative surface reaction between O2 ligand and Co(II) porphyrin adsorbates as a function of their spatial proximity at the solution/solid interface. Interactions of note include through-support, through-intramolecular-pi structure, and intermolecular communication. Central metal ion reactivity as a function of surface coverage is measured at varying temperatures and ligand concentrations. Reaction rates and thermodynamic parameters are extracted from measurements made on single molecules. DFT calculations are used to provide electronic insights into the observed results.
Metallomacrocycle-Driven Atomically Dispersed M-N
x
Sites on Carbon Nanostructures for Electrocatlyic Energy Conversion Reactions
Authors: Joo Sang Hoon
Published: February 2020

Developing highly active, durable, and low-cost electrocatalysts is of crucial importance to making renewable energy conversion devices, such as fuel cells and electrolyzers, economically viable. Hence, tremendous efforts have been geared to develop non-precious metal electrocatalysts that can replace expensive precious metal catalysts for energy conversion reactions. Among various classes of non-precious metal electrocatalysts, transition metal and nitrogen codoped carbon (M–N/C) catalysts have demonstrated excellent catalytic activity, which even rivals that of precious metal catalysts. In this presentation, we present our recent efforts toward high-performance M–N/C catalysts for energy conversion reactions, including oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER) [1-7]. We have developed a general “silica-protective-layer-assisted” approach that can preferentially generate the catalytically active M–N
x
sites in M–N/C catalysts while suppressing the formation of catalytically less active or inactive large metallic particles [4,6,7]. The catalyst preparation consisted of adsorption of a metallomacrocyle precursor on a carbon support, low-temperature annealing, silica layer overcoating, high-temperature pyrolysis, and silica layer etching, which yielded a carbon coated with thin layer of metallomacrocyclic carbon catalysts [4]. The prepared catalysts contained a higher density of active M–N
x
sites compared to the catalytic prepared without the silica coating step. This preparation method is generally applicable to various carbon supports and metallomacrocyclic compounds. The prepared Fe-containing catalysts showed very high ORR activity and excellent stability in alkaline media. Importantly, an alkaline anion exchange membrane fuel cell with a CNT/PC-based cathode exhibited record high current and power densities among NPMC-based AEMFCs. Furthermore, using metallomacrocycle precursors with Co, Ni, and Pt metal centers, catalysts showing excellent performances toward HER [7], CO2 reduction reaction [8] were developed.

References

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J. Sa et al., manuscript in preparation (2019).
Erythropoietin Accelerates a Cancer Specific Porphyrins' Accumulation
Authors: Matsui Hirofumi , Kurokawa Hiromi
Published: February 2020

Introduction: Erythropoietin (EPO) is a glycoprotein cytokine which stimulates red blood cell production (erythropoiesis) in the bone marrow. The receptor of it (EPOR) was reported to exist on the cancer cellular membrane: more than 85% cancer cell expresses EPOR. Several reports suggested to play an important role for cancer cellular growth, however, the role of EPOR in cancer cells is not confirmed. The authors have studied the cancer cellular porphyrin accumulation, metabolism and excretion to clear the pathogenic mechanism which involved the high concentration of porphyrins. The authors found that reactive oxygen species (ROS) accelerate both the cancer cellular porphyrin accumulation and the effect of photodynamic therapy. However, we cannot confirm which substrate is a key of signal transduction. EPO has been known used to be up-regulated at the metabolic acidosis via the stabilization of HIF-1α, a nuclear factor. Since HIF-1α can be stabilized by not only acidosis but also the high concentration of nitric oxide (NO), NO rich cancer cells may involve EPOR. Moreover, the purpose of EPO-EPOR system is likely to survive the hypoxic condition, it may keep intracellular heme/ porphyrins. The authors’ hypothesis is EPO-EPOR system in cancer cells may down-regulate ABCG2 which excretes heme/ porphyrins, and several anti-cancer drugs. Moreover, if so, the excretion of both porphyrins and several anti-cancer chemo reagents should be inhibited to involve more effective PDT and chemotherapy.

Methods: To prove these possibilities, the authors carry out following experiments with gastric and colorectal cancer cells. The existence of EPOR, the amount of ABC transporters (B1, C5, G2) after the recombinant EPO (rEPO) exposure (dose dependency and time dependency) were analyzed by western blotting. Cytotoxicity of both PDT and anti-cancer drugs with or without rEPO was measured with the Cell Counting Kit-8.

Result: (1) EPOR existed in each cell line used in this study. (2) rEPO treatment involved down regulation of ABC transporters (B1, C5, G2) in dose dependently. (3) ABCG2 expression decreased until 24 hours after rEPO treatment. However, its expression re-increased 48 hours after treatment. (4) The 24 hours pretreatment of EPO significantly increased the effect of PDT, doxorubicin, paclitaxel, irrinotecan, cisplatin, 5-FU and oxaliplatin even in chemo-resistant cells.

Conclusions: rEPO accelerates the effect of PDT and anti-cancer drugs via the down regulation of ABC transporters.
Photophysics of Phosphorus Corroles and Application of the Compounds in Triplet-Triplet Annihilation Upconversion
Authors: Zhao Jianzhang
Published: February 2020

Triplet-triplet annihilation upconversion (TTA-UC) is in particular of interest, due to the strong absorption of the excitation light and the high upconversion quantum yields.[1,2] For TTA-UC, a proper triplet photosensitizer and a triplet acceptor are combined to perform the cascade photophysical processes to convert the photons with lower energy to photons with higher energy. Triplet photosensitizers are crucial for TTA-UC. The conventional triplet photosensitizers used for TTA-UC are transition metal complexes or organic compounds containing iodine or bromine atoms.[3] The rationales to use the heavy atoms are to employ the heavy atom effect to facilitate the ISC for triplet state formation upon photoexcitation. Heavy atom-free organic compounds were rarely used as triplet photosensitizers because the ISC is almost unpredictable without the heavy atom effect.[4]

Free base corrole is tetrapyrrolic macrocycle with one meso carbon less than porphyrins. Corrole compounds usually show strong absorption of visible light and high photo-stability, as well as efficient ISC. However, corroles were rarely used as triplet photosensitizers for TTA-UC. Herein we studied the photophysical properties of series of corroles with steady state and time-resolved spectroscopies. The corroles were used as triplet photosensitizers for TTA-UC, with perylenebisimide (PBI) as the triplet acceptor. Upon 589 nm cw-laser excitation, upconversion emission at 520 nm was observed. The upconversion quantum yield was determined as 1%.

References

[1] T. N. Singh-Rachford, F. N. Castellano, Coord. Chem. Rev.
2010, 254, 2560–2573.

[2] J. Zhao, S. Ji, H. Guo. RSC Adv., 2011, 1, 937–950.

[3] J. Zhao, S. Ji, W. Wu, W. Wu, et al. RSC Adv., 2012, 2, 1712–1728.

[4] J. Zhao, W. Wu, J. Sun and S. Guo. Chem. Soc. Rev., 2013, 42, 5323–5351.