bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Transmittance Limits and Their Effects on Light Extraction from Luminescent Materials
Authors: Piquette Alan , Mishra Kailash C. , Lenef Alan 
Published: February 2020

Light extraction from light emitting diodes and/or phosphors has been an increasingly studied topic over the last twenty plus years (see Figure 1). More recently, it has been shown that there is an absolute limit to the amount of electromagnetic radiation that can transmit from one medium to another across an interface defined by differing refractive indices.[1-4] This limit has been established using both thermodynamic arguments[1-3] and classical electromagnetic theory.[4] In this talk, we will briefly derive the limits of transmittance of light through an interface and discuss what implications there are for the overall extraction efficiency of a simple system.
Finite-difference time-domain (FDTD) simulations were performed to verify the transmittance limit. The results of the simulations will be presented for several different interface types, such as smooth, pseudo-random roughness, photonic crystal lattices, micro-sphere arrays, etc. It was found that regardless of the interface type, all of the simulations confirm the transmittance limit.
Finally, we will show that despite the relatively low transmittance limits, extraction efficiencies of 100% are theoretically possible, but only because of scattering and cavity effects, not through an increase of the so-called first-pass transmittance. We use a simple two-interface system and numerical simulations based on geometrical optics to demonstrate the effects of transmittance and other important factors on the overall forward extraction efficiency.
[1] J. Muschaweck and C. Wiesmann, Adv. Opt. Technol., 2, 291 (2013).
[2] A. Lenef, J. F. Kelso, and A. Piquette, Opt. Lett., 39, 3058 (2014).
[3] A. Lenef, A. Piquette, and J. Kelso, ECS J. Solid State Sci. Technol., 7, R3211 (2018).
[4] K. C. Mishra and A. Piquette, ECS J. Solid State Sci. Technol., 7, R3016 (2018).

Figure 1
Mechanistic Aspects on the Grafting By the Self-Decomposition of Aryldiazonium Salts: Effect of the Counterion
Authors: Morales-Martínez Daniel , Ramírez Vanessa , González Felipe J. 
Published: February 2020

The dipping of an electrode in a solution of aryldiazonium salts is an interesting reaction to form covalently grafted films on carbon and metallic surfaces [1]. However, although there are many evidences about the existence of the grafted film, the mechanism is unknown. In 1957, it was demonstrated that p-nitrofluorobenzene was got during the thermal decomposition of p-nitrophenyldiazonium tetrafluoroborate, putting in evidence the importance of the counterion during the decomposition of the aryldiazonium cation [2]. One way to explain the formation of this specie considers the decomposition of the aryldiazonium cation by a redox reaction that involves the transient passage by radicals as intermediates, which will be responsible of the spontaneous grafting of different electrode surfaces. Hence, the theoretical and experimental study for determine the mechanism of the spontaneous grafting is performed in this work. The results showed that there is an effect of the counterion in the rate of decomposition of the aryldiazonium salt. When the counterion is easier to be oxidized, the rate of decomposition is higher, which support the idea of a mechanism with a redox reaction involved and therefore, the existence of radicals as intermediates.

References

[1] Adenier, B. Barré, E. Cabet-Deliry, A. Chaussé, S. Griveau, F. Mercier, J. Pinson, C. Vautrin-Ul, Surface Science, 2006, 600, 4801-4812.
[2] G.B. Bachman, T. Hokama, J. Am. Chem. Soc. 1957, 79, 4370-4373.
Electrochemical Versatility of Soluble Redox Active Polymers
Authors: Montoto Elena C. , Rodriguez-Lopez Joaquin 
Published: February 2020

Organic redox-active materials offer advantages of material tunability while maintaining high performance for next-generation energy storage and conversion solutions. Macromolecular architectures such as polymers, colloids, and oligomers have recently gained interest for their size-exclusion capabilities. Redox Active Polymers (RAPs) have traditionally been electrochemically studied as films or composites [1], with few examples of solution-phase studies until recent years [2]. Soluble RAPs have begun emerging as viable active materials for energy storage solutions such as size-exclusion flow batteries [3-4]. Our laboratories have introduced several redox active motifs used as pendants on these soluble RAPs in recent years [3]. Their introduction into the field of energy storage as fluid energy carriers has elucidated some of their reactivity and applicability, yet detailed characterization of their complex charge transfer mechanisms and their interactions in solution and with catalytic and photocatalytic interfaces has not been fully addressed.
In this talk, I will highlight advances in characterizing the redox activity of these polymers and their behavior at electrode interfaces with the aim of using them as versatile redox fluids. I will also describe how their charge transfer mechanisms make them ideal for varied energy storage applications beyond size-exclusion redox flow batteries. The RAPs are evaluated using analytical techniques such as potential-controlled electrolysis, spectro-electrochemistry, and voltammetric methods including transient and steady-state methods. Additionally, comparisons to the small molecule counterparts of the RAP active units aid to understand the differences observed when redox active centers are tethered to a chain containing hundreds of pendants. I will discuss how this new type of soluble RAPs interact with energy conversion electrodes and how charge transfer and transport within RAP particles facilitates catalytic processes associated with energy storage.
[1] J. Am. Chem. Soc. 1978, 100, 4248.
[2] J. Am. Chem. Soc. 2018, 140, 2093.
[3] Acc. Chem. Res. 2016, 49, 2649.
[4] J. Am. Chem. Soc. 2014, 136, 16309.
Chromium Oxynitride Electrocatalysts for Electrochemical Synthesis of Ammonia Under Ambient Conditions
Authors: Yao Yao , Feng Qi , Li Jiadong , Zhu Shangqian , Yao Yuze , Wang Yajun , Wang Qi , Gu Meng , Wang Haijiang , Li Hui , Shao Minhua 
Published: February 2020

The electrochemical synthesis of ammonia via N2 reduction reaction (NRR) has received much attention in recent years due to its promising advantages of being more environmentally friendly and less energy consuming than conventional chemical synthesis. However, as the theoretical potentials of hydrogen evolution reaction (HER) and NRR are very close on most catalysts, H2 is the dominant product due to the much faster reaction kinetics of HER, leading to low NRR Faradaic efficiency and ammonia formation rate. The DFT calculation indicates that the transition metal nitrides, such as VN, CrN, and ZrN, are promising candidates for NRR electrocatalysts.1-2

In this study, chromium oxynitride (CrO0.66N0.56) was synthesized and its NRR performance was evaluated in a proton exchange membrane electrolyzer (PEMEL) under ambient conditions. The schematic illustration of the PEMEL employed in this study is shown in Figure 1a. The highest ammonia formation rate of 8.9×10-11 mol s-1 cm-2 and Faradic efficiency of 6.7% were achieved, shown in Figure 1b, which is so far the best result reported among the non-noble metal-based electrocatalysts under similar conditions. Its performance is even higher than that of Pt/C and Pd/C.
Figure 1. a) The schematic illustration of the PEMEL device for the electrochemical synthesis of ammonia. b) The ammonia production rate and faradaic efficiency of chromium oxynitride at various potentials in a PEMEL device with ammonia water pretreated under room conditions.

References

(1) Abghoui, Y.; Skulason, E., J. Phys. Chem. C
2017, 121, 6141-6151.
(2) Abghoui, Y.; Garden, A. L.; Hlynsson, V. F.; Björgvinsdóttir, S.; Ólafsdóttir, H.; Skúlason, E., Phys. Chem. Chem. Phys.
2015, 17, 4909-4918.

Figure 1
Twisty Pd-Au Nanowires for Highly Selective and Active CO2 electrochemical Reduction
Authors: Zhu Shangqian , Shao Minhua 
Published: February 2020

The continuous increase of CO­2 concentration in the atmosphere would potentially bring catastrophic global climate changes, which is one of the most urgent issues of the society. CO2 electrochemical reduction (CO2RR) is promising in simultaneously controlling the CO2 concentration and store renewable energy. However, selectively producing valuable chemicals and fuels with reasonable low overpotentials is quite difficult.
In this study, Pd and Pd-Au nanowires with a varied composition were synthesized. The nanowires have a twisty morphology with a lot of grain boundaries. For the first time, highly selective CO2-to-CO electrocatalytic conversion with low overpotentials was achieved on Pd-based nanocatalysts. All the synthesized nanowires exhibited significantly improved CO selectivity as compared to commercial Pd nanoparticles (Figure 1). At -0.6 V, a maximum faradaic efficiency over 94% can be obtained on Pd0.8Au nanowires. CO can also be detected with a faradaic efficiency of 8.5% at an overpotential of merely 90 mV. The Pd-Au nanowires have superior mass and specific activities, which are highly dependent on the composition. In situ infrared spectroscopic studies with an attenuated total reflection configuration (ATR-IR) was conducted to reveal the combined structure and composition impacts on the activity. It was found that *CO could be more easily generated at much lower overpotentials on nanowires as compared to that on particles. Additionally, the alloying between Pd and Au would generate more linearly-bonded *CO, which is more facile to desorb and results in an improved reaction rate.

Figure 1. Faradaic efficiency of CO measured on Pd/C, synthesized Pd and Pd0.8Au nanowires.

Figure 1
Enhancement of Electrocatalytic Reduction of Carbon Dioxide at Electrodes Modified with Highly-Acidic Mixed-Metal-Oxide Films
Authors: Rutkowska Iwona Agnieszka , Kulesza Pawel J. 
Published: February 2020

Electroreduction of carbon dioxide to simple organic fuels and chemicals is a topic of growing scientific and technological interest. The reaction provides means for both reducing emissions of CO2 into atmosphere and storing renewable energy. The presentation will address low-temperature CO2-conversion processes based on electrocatalytic and photoelectrochemical approaches. Among important issues are choice of the catalytic or semiconducting materials, their morphology and operating conditions including temperature, solvent, electrolyte, pH etc. There is a need to improve the reaction dynamics and selectivity toward specific products. In practical electrolysis cells, the CO2-reduction (at cathode) is accompanied by water oxidation (at anode or photoanode).
Given the fact that the CO2 molecule is very stable, its electroreduction processes are characterized by large overpotentials. It is often postulated that, during electroreduction, the rate limiting step is the protonation of the adsorbed CO product to form the CHO adsorbate. In this respect, the proton availability and its mobility at the photo(electro)chemical interface has to be addressed. On the other hand, competition between such parallel processes as hydrogen evolution and carbon dioxide reduction has also to be considered.
Recently, mixed oxide systems stabilized through Zr-O-W bonds have been demonstrated to be very attractive acid catalysts exhibiting high catalytic activities and good stabilities in many demanding industrial reactions. The mixed WO3/ZrO2 systems are characterized by fast charge (electron, proton) propagation during the system’s redox transitions. By dispersing metallic Cu electrocatalytic nanoparticles over, under or within, such active WO3/ZrO2 matrices, the electrocatalytic activities of the respective systems toward the reduction of carbon dioxide have been significantly enhanced even at decreased loadings in acid media. The enhancement effects should be attributed to features of the mixed metal oxide support such as porosity and high population of hydroxyl groups (due to presence of ZrO2), high Broensted acidity of sites formed on mixed WO3/ZrO2, fast electron transfers coupled to unimpeded proton displacements (e.g. in HxWO3), as well as strong metal-support interactions between nanosized metals (Cu) and the metal (W,Zr) oxo species.
Application of the hybrid system composed of both above-mentioned oxides resulted in high current densities originating from electroreduction of carbon dioxide mostly to methanol (CH3OH) as demonstrated upon identification of final products.
Kinetic Monte Carlo Simulation of CO2 Electroreduction Cascade
Authors: Chavan Kanchan Suklal , Matanovic Ivana , Calabrese Barton Scott 
Published: February 2020

Capture of CO2 and conversion into useful chemicals can alleviate atmospheric buildup and provide an alternative source of chemical building blocks. CO2 can be reduced electrochemically to small chain carbon molecules (C1-C3) like CO, ethylene, formic acid, methane and alcohols.1 Integrating multiple catalytic sites on an electrode surface enables further reduction to higher value hydrocarbons.
In this work, we describe kinetic Monte Carlo (kMC) simulations of CO2 reduction to ethane on an integrated catalytic electrode surface. Electrode surface incorporates two catalyst sites, which may include molecular catalytic structures or tethered metal complexes.2 The catalytic mechanism at each active site, as well as adsorption and transport of intermediates between sites, is considered in the overall model. Monte Carlo simulation allows inclusion of both kinetic and transport events whose time scales span multiple orders of magnitude.3 Channeling of intermediate transport between active sites via Van Der Waals, electrostatic, and ligand-exchange interactions is considered. We predict the effect of catalyst loading and composition on overall cascade efficiency, a defined by ethane yield.
References

R. J. Lim, M. Xie, M. A. Sk, J.-M. Lee, A. Fisher, X. Wang, and K. H. Lim, Catal. Today, 233, 169–180 (2014) doi:10.1016/J.CATTOD.2013.11.037.

A. S. Varela, N. Ranjbar Sahraie, J. Steinberg, W. Ju, H.-S. Oh, and P. Strasser, Angew. Chemie Int. Ed., 54, 10758–10762 (2015) doi:10.1002/anie.201502099.

M. Stamatakis and D. G. Vlachos, ACS Catal., 2, 2648–2663 (2012) doi:10.1021/cs3005709.
Electrodeposition of Graded Metal Coatings on Spherical Mandrels
Authors: Peters Vanessa N. , Horwood Corie , Bhandarkar Neal , Stadermann Michael , Bunn Thomas 
Published: February 2020

Inertial confinement fusion energy research at the National Ignition Facility (NIF) requires the fabrication of hollow metal spherical capsules for the laser-driven fusion reaction. These sub-millimeter diameter capsules must have perfect coating uniformity and a specific gradient density, achieved by plating two metal elements with graded composition. We are investigating electrodeposition to produce hollow metal spheres as opposed to other deposition techniques (i.e. physical vapor deposition, film casting, etc.), because electrodeposition coats faster, more smoothly, with good thickness uniformity, and better grain size control.
Electroplating metals on spheres presents its own specific challenges; the spherical samples must make contact with the electrified cathode, but must also remain in motion during plating to ensure an even coating. Additionally, electroplating on hollow spheres also involves the challenge of keeping the sphere submerged in the electrolyte. These issues were mitigated by enclosing the mandrel in an electrified cage which the electrolyte is flown through, resulting in intermittent contact of the mandrel with the cathode and a continuous flow of fresh electrolyte to the mandrel surface while plating.
We have developed several approaches for electroplating alloys[1] and density gradients on metal spherical mandrels. We will present results from a parametric study that improved coating uniformity, obtained desired thickness, and achieved the required density gradients during electrodeposition.
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. IM Release Number: LLNL-ABS-748349
[1] C. Horwood, M. Stadermann, T.L. Bunn, Metal Alloy ICF Capsules Created by Electrodeposition, Fusion Sci. Technol. 73 (2018) 335–343. doi:10.1080/15361055.2017.1387458.
Electrochemical Deposition of Alkaline-Earth Elements (Sr and Ba) into Liquid Metals in Molten LiCl-KCl-SrCl2-BaCl2 salt
Authors: Kim Hojong , Lichtenstein Timothy , Smith Nathan 
Published: February 2020

Electrochemical deposition of Sr and Ba into liquid metals (Bi and Sb) was investigated in LiCl-KCl-SrCl2-BaCl2 electrolytes at 500–650 °C as a means to separate stable alkaline-earth ions from the molten salts (eutectic LiCl-KCl) utilized for recycling used nuclear fuel. Considering the higher stability of Sr and Ba ions relative to the Li and K ions in the chloride system, it would seem impractical to deposit Sr and Ba from the molten chloride solutions by electrochemical means; however, this work will present that the deposition of Sr and Ba into liquid metal electrodes becomes thermodynamically feasible by leveraging the strong chemical interactions between alkali/alkaline-earth metals and liquid metals.
The thermodynamic properties of four binary alkaline earth-liquid metal alloys, (Sr, Ba)-(Bi, Sb), were determined by electromotive force (emf) measurements using solid-state electrolytes to examine the degree of chemical interactions (activity) between alkaline-earth metals and liquid metals. Using a pure alkaline-earth metal A (A = Sr or Ba) as the reference electrode and binary A-B alloys (B = Bi or Sb) as working electrodes in solid-state binary CaF2-AF2 electrolyte, emf measurements were conducted over a temperature range of 450–850 °C in 25 °C increments. Reproducible emf values were obtained within ±5 mV accuracy during cooling-heating cycle at alloy mole fractions up to x
A(in B) = 0.40. Based on the experimentally determined emf values of alkaline-earths in liquid Bi and Sb electrodes, the electrode reactions involving Sr and Ba elements were found to be thermodynamically feasible due to substantially larger emf values of Sr and Ba in Bi, compared to those of Li and K in Bi. Namely, the chemical interactions of liquid metals (Bi and Sb) were stronger for alkaline-earths (Sr and Ba) than for alkali (Li and K) metals.
Based on thermodynamic measurements, the liquid metal electrodes were subjected to cathodic discharge at a constant current density of 50 mA cm–2 in eutectic LiCl-KCl with the addition of 5–10 mol% of SrCl2 and/or BaCl2. As shown in Figure 1, the use of liquid metals (Bi and Sb) resulted in the deposition of Ba in LiCl-KCl-10mol%BaCl2 electrolyte. Further study in LiCl-KCl-SrCl2-BaCl2 electrolytes also indicated that the use of strongly interacting liquid metal electrodes could result in the co-deposition of Sr and Ba in addition to Li. The results of this work show that alkaline-earth fission products (Sr2+ and Ba2+) accumulated in molten salts can be recovered into liquid metals by electrochemical separation, which could be employed as a critical step for recycling the process salt (LiCl-KCl) in order to minimize the generation of additional nuclear wastes.
Figure 1. Cross-section analyses of Bi (discharged at 510 °C) and Sb (discharged at 650 °C) electrodes under constant current density at 50 mA cm–
2 in LiCl-KCl-10mol%BaCl2 electrolyte, using SEM and elemental X-ray mapping.

Figure 1
Electrochemical Synthesis of Chromium Borides in Halide-Oxide Melts
Authors: Ashinova Oksana , Kushkhov Hasbi , Ligidova Marina , Shogenova Madina 
Published: February 2020

The work is devoted to investigation of electrochemical synthesis of chromium borides from halide-oxide melts. In this paper results of synthesis of chromium borides from halide-oxide melts is presented. Cyclic voltammetry and potentiostatic electrolysis were chosen by method of investigation of chromium and boron-ions electroreduction processes. Electrochemical synthesis of chromium borids by joint electroreductioon of chromium and a boron ions in halide –oxidie melts NaCl-KCl-K2Cr2O7-KBF4 melt is carried out.
Investigation of a mechanism of bichromate ions electroreduction in NaCl-KCl-K2Cr2O7 melt have been conducted by method of a cyclic voltamperometriya at different concentration of potassium bichromate. The optimal parameters of electrolysis process is established: electrolysis potential, temperature of process, duration of electrolysis. Syntheses powders of chromium borides were identified by X-Ray methods.
Investigating Processes Occurring in Acoustically Levitated Ionic Liquid Droplets
Authors: Duranty Edward R. , Jacoby Seth A. , Davis James H. 
Published: February 2020

Chemical processes that occur in small volume containers have many benefits that have only recently become apparent. Containers such as thin films, compartments within microfluidic systems, and droplets require small amounts of solvent and therefore provide an inherently green alternative to reactions that take place in typical laboratory containers. Additionally, reactions that take place in small volumes seem to improve the rates of processes ranging from simple syntheses to protein folding. This increase in rate is attributed to increased surface area availability, rapid reagent mixing times, and increased heat transport properties as compared to the bulk. Acoustic levitation is a popular technique for the suspension of small volumes, most commonly droplets, in a “contact-free” container that preserves the large droplet surface area, a leading contributor to increased chemical activity.
In our laboratory we are coupling acoustic levitation and droplet chemistry with ionic liquids which are rapidly becoming the solvent of choice for many systems. This increased popularity is primarily due to their unique “tunability” and their low vapor pressures. Thus far we have reproducibly levitated 10μL droplets of deionized water, aqueous calcium hydroxide, toluene, and most interestingly the ionic liquid 1-butyl-1methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BMP-BTI) using an acoustic levitation device reported in the literature as a “TinyLev.” We have currently measured droplet lifetimes for aqueous solutions near 30 minutes, 15 minutes for toluene, and approximately 2 weeks for BMP-BTI. These preliminary results suggest that ionic liquids may be suitable acoustically-levitated droplets and we are currently working to develop a technique for probing the interactions and structure of solutes within an ionic liquid solvent via laser light scattering.

Figure 1