bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ultrafast InAs Quantum Dot Scintillation Detector
Authors: Dropiewski Katherine , Minns Allan , Yakimov Michael , Tokranov Vadim , Murat Pavel , Oktyabrsky Serge 
Published: February 2020

High-efficiency, picosecond scintillation detectors are critically needed for many applications, particularly in the fields of medical imaging, high energy physics and nuclear security. Recently, we proposed a design and considerations for a semiconductor scintillator composed of InAs Quantum Dots (QDs) acting as luminescence centers in a GaAs stopping matrix/waveguide, integrated with a photodetector grown epitaxially on top of the waveguide (WG) [1]. This material has appealing potential photonic properties including high light yield (~240,000 photons/MeV) due to the narrow semiconductor bandgap, fast capture of electrons in QDs (2-5ps) and high radiation hardness (>104 Gy). The high refractive index of GaAs (n=3.4) ensures light emitted by the QDs is waveguided within the GaAs matrix, which can then be collected by an integrated InGaAs p-i-n photodiode (PD).
A proof-of-concept integrated scintillation detector (Fig. 1) was grown using molecular beam epitaxy on a GaAs substrate. It has a 20 μm thick GaAs layer with embedded sheets of modulation p-type doped InAs QDs. A generic excitation source is shown interacting with the GaAs matrix, resulting in QD luminescence, which is then waveguided towards an InGaAs PD, grown on top of the WG and tuned to the QD luminescence band (~1150 nm). Employing QD structure engineering improves the internal efficiency of the QD luminescence to ~60% at room temperature and reduces overall waveguide attenuation to about 3-4 cm-1.
A sample, as shown in Fig. 1, was used to evaluate the timing characteristics of 5.5 MeV alpha particle responses. The source had a radioactivity of 1 µCi, suspended in air approximately 1 cm above the QD waveguide. The scintillation response (Fig. 2) had a decay time of 0.3 ns, corresponding to QD recombination time, and a noise-limited time resolution of 54 ps (Fig. 3). With a 2D waveguide and an integrated PD covering only 16% of the WG width, the collected charge averaged 1.5x105 electrons (Fig. 4), corresponding to a collection efficiency of about 14%. This can be estimated as 34,000 photoelectrons per 1 MeV of incident energy, given about 1 MeV of alpha particle energy loss in air. This data confirms the unique photonic properties of this scintillation detector, which has the potential to be much faster than any currently used inorganic scintillator.
Additionally, technologies for separating an epitaxial film from a substrate and bonding multiple waveguides using organic adhesives are tested and evaluated.
[1] S. Oktyabrsky, et al. "Integrated Semiconductor Quantum Dot Scintillation Detector: Ultimate Limit for Speed and Light Yield," IEEE TNS,
63, 656 (2016).

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Flexible, Stretchable and Healable Electronics
Authors: Cicoira Fabio 
Published: February 2020

Organic electronics, based on semiconducting and conducting polymers, have been extensively investigated in the past two decades and have found commercial applications in lighting panels, smartphone and TV screens using OLEDs (organic light emitting diodes) technology. Many other applications are foreseen to reach the commercial maturity in future in areas such as transistors, sensors and photovoltaics.
Organic electronic devices, apart from consumer applications, are paving the path for key applications at the interface between electronics and biology, such as in polymer electrodes for recording and stimulating neural activity in neurological diseases. In such applications, organic polymers are very attractive candidates due to their distinct property of mixed conduction: the ability to transport both electron/holes and ionic species. Additionally, conducting polymers offer the possibility to tune their surface properties (e.g., wettability or chemical reactivity) by changing their oxidation state, thus promoting or hindering the adhesion of biomolecules. This feature can be particularly useful for enhancing the biocompatibility of implantable electrodes.
My talk will deal with processing and characterization of conducting polymer films and devices for flexible, stretchable and healable electronics. I will particularly focus on micro-patterning of conducting polymer films for flexible and stretchable devices and on healing of conducting polymer films.
Low Temperature Synthesis of WS2 Using PECVD for Hydrogen Evolution Catalysis
Authors: Kanade Vinit Kaluram , Kim Hyeong-U , Kanade Chaitanya Kaluram , Shin Dongjoo , Lee Jae-Hyun , Kim Taesung 
Published: February 2020

Hydrogen holds tremendous promise as one of many alternatives for clean energy generation with high energy density and zeroes environmental impact. Hydrogen can be easily produced by using Platinum-based catalyst to efficiently lowers the large potential of electrolysis, but confined due to scarce and expensiveness. Transition metal dichalcogenides (TMDCs) such as MX2 (M stands for Mo or W, Nb, Ta etc. and X= S, Se etc.) is essential materials which show promising catalytic activity. The bond between the metal and the chalcogen is a covalent bond, and the three layers themselves are held together by a weak van der Waals force. Tungsten Disulfide (WS2) is a representative transition metal dichalcogenide (TMDC), has been freshly pursued as one of the promising alternatives for hydrogen evolution reaction (HER). Tungsten Disulfide is one of the promising TMDC materials due to its various application in electronics, catalysis, optical and other fields. The WS2 elements were previously synthesized by different processes such as mechanical exfoliation, chemical exfoliation, chemical vapor deposition etc.
In this work, we report a strategy for synthesis few layers of WS2 at relatively low temperature (300 °C) using plasma enhanced chemical vapor deposition (PECVD) technique. The PECVD technology utilized to grow WS2 thin film directly on the 4-inch Si-SiO2 wafer. The quality of a synthesized WS2 was characterized by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), High-resolution transmission electron microscopy (HR-TEM), and energy dispersive spectrometry (EDS) mapping. The thickness of the synthesized WS2 film was found to be around a few nanometers and showed multilayered structure (~5-6 layers). The PECVD shows the advantage for the large area synthesis of WS2 thin film with high uniformity, purity, and reproducibility for the mass production. The PECVD technology utilized to directly grown on glassy carbon electrode (GCE) for analysis of HER performance without any transfer process. The catalysis shows overpotential (η) of 0.50 V and Tafel slope 122.0 mV/decade. The HER performance of synthesized films was similar or higher when compared with drop casting technique.

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Improved Components for High Temperature Alkaline Water Electrolysis
Authors: Patil Kailash , Sweet Andrew , McCatty Steve , Greene Winfield , Xu Hui 
Published: February 2020

Hydrogen production from water electrolysis is attractive due to its high efficiency, fast ramp rates, and high-pressure capability. However, current hydrogen production from electrolysis comprises only a small fraction of the global hydrogen market due to the high cost associated with expensive stack materials and electricity consumption. Currently commercial alkaline electrolyzers or proton exchange membrane electrolyzers operate at low temperatures. Intermediate or high temperature can effectively boost electrode kinetics and lower cell over-potential, thus improving the efficiency of water electrolysis. In this regards, Giner has developed a high-temperature alkaline water electrolysis (HTAWE), which employs lithium, sodium, or potassium hydroxides impregnated into a porous alumina or zirconia matrix [1]. The operating temperature can vary from 350 to 550 °C, depending on the category and ratio of binary or ternary electrolytes.
In this work, both aluminate and zirconia-based matrix metal oxides were used as the matrix support materials. Thin aluminate and zirconia based matrices were fabricated using the tape casting method. Precious or non-precious electrodes (e.g. Ir, Ni, Co-based) were optimized using a solvent-based slurry formulation process. Green sheet electrodes with a variety of thicknesses were developed using a doctor blade approach. Design of experimental techniques were applied to optimize the ceramic membrane properties and to select hydrogen evolution reaction (HER)/oxygen evolution reaction (OER) catalysts. The impact of various catalyst and electrode designs on the HTAWE will be evaluated. Polarization curves and long-term durability will be demonstrated at variety of temperatures. Hot-corrosion mitigation strategies will also be discussed to extend the lifetime of HTAWE cells in this work.

References

Hui Xu and Kailash Patil, “High Temperature Alkaline Water Electrolysis,” presented at the 2018 DOE Annual Merit Review and Peer Evaluation Meeting, Washington, DC, June 2018.

Acknowledgement: The project is financially supported by the Department of Energy’s Fuel Cell Technology Office under the Grant DE-EE0007644
Structure-Activity Data Mining for Hydrogen Evolution Reaction at Organic Molecular Electrocatalysts
Authors: Yin Xi , Holby Edward F. , Zelenay Piotr 
Published: February 2020

Hydrogen evolution reaction (HER) is a fundamental process for many important energy applications such as hydrogen production through electrolysis and electrochemical hydrogen storage. Recently, we demonstrated a metal-free organic molecular electrocatalyst (OMEC) with high HER activity and durability in acidic polymer electrolyte, based on a small pyridine-based heterocyclic molecule.1, 2 Density functional theory (DFT) study of the HER mechanism at this molecule revealed that the atomic hydrogen adsorption energy at the pyridyl-N site is closely tied to the electrocatalytic activity.
In this talk, we will present a systematic study of the proton reduction step, also known as the Volmer step, at heterocyclic organic functional groups targeting rational design of the OMECs. DFT calculations have been performed to predict the reaction thermodynamics, reduction potentials, and the change of molecular electronic structures during the Volmer step. Several N-heterocycles, such as pyridine, pyridazine, pyrimidine, and pyrazine, and their derivatives involving electron-withdrawing/donating groups have been included in this study. Through data mining of the electronic and structural information from DFT calculation, we have developed descriptors for the structural-activity relationship among these heterocyclic molecules. The results set the foundation for rational design of OMECs for hydrogen evolution reaction.

References

X. Yin, L. Lin, H. T. Chung, U. Martinez, A.M. Baker, S. Maurya, P. Zelenay. Organic Molecular Catalyst for Hydrogen Evolution Reaction, ECS Meeting Abstracts, The Electrochemical Society, MA2017-02, 1659 (2017).

X. Yin, L. Lin, U. Martinez, H. T. Chung, P. Zelenay. Bifunctional Organic Molecular Electrocatalyst for Hydrogen Evolution Reaction and Hydrogen Peroxide Production, Meeting Abstracts, Cancun, Mexico, The Electrochemical Society, MA2018-02, 1609 (2018).

Acknowledgment

Financial support for this research by Los Alamos National Laboratory through LDRD-ER Program is gratefully acknowledged.
Performance of a Hybrid Regenerative Hydrogen-Vanadium Fuel Cell with Carbon Nanotube Electrode (CNT) Materials
Authors: Nguyen Trung Van , Li Yuanchao , Hammar Ryan 
Published: February 2020

The hybrid regenerative hydrogen-vanadium fuel cell [1,2] offers a feasible solution for storing electrical energy from the grid or intermittent renewable energy sources such as wind and solar. This system is an attractive alternative to the all-vanadium system due to the 50% reduction in the amount of vanadium solution required. This two-phase hybrid system also allows crossover species to be separated and reused. In this presentation, the performance of this system with carbon nanotube materials as electrodes for the vanadium reactions at the elevated temperatures (RT-50oC) will be discussed.
References:

Yufit, B. Hale, M. Matian, P. Mazur and N. Brandon, J. Electrochem. Soc., 160, A856 (2013).

Regis P. Dowd Jr., Vikram Lakhanpal, and Trung Van Nguyen, Electrochem. Soc., 164, F564 (2017).

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Analysis of Flow Field Scale-up, Design Tradeoffs, and Shunt Current in Redox Flow Battery Stacks
Authors: Houser Jacob , Aaron Douglas , Mench Matthew M. 
Published: February 2020

Recently it has been demonstrated that operating conditions and applications have a significant impact on the effectiveness of different flow field designs commonly used in redox flow batteries (RFBs)1. Depending on the power and energy storage requirements, as well as the system operational capabilities, the optimal flow field design may vary between designs2. These results have only been presented concerning small laboratory scale designs, however. Due to the different transport mechanisms utilized by these various flow field designs, the mass transport performance and efficiency of each design will scale differently when the active area of the cell is increased to a size more representative of a commercial system. Additionally, the most common configuration of these cells in a commercial system is in an RFB stack where several cells are connected in series electronically and in parallel hydraulically. This further complicates the design tradeoffs seen in the smaller single cell design, while also introducing new design concerns in the form of shunt current, a self-discharge phenomenon only present when multiple cells are connected ionically through the liquid electrolyte.
Utilizing the energy and efficiency-based analysis previously published by our lab, we have conducted a thorough study of the differences between four flow fields when increasing the active area of the cell. CFD simulations using COMSOL Multiphysics provide quantitative data for electrolyte velocity and pressure drop, while experimental data provides depth of discharge and efficiency results. This analysis has also been extended to a small RFB stack to examine how these design tradeoffs are impacted by placing multiple cells electronically in series and sharing an electrolyte manifold. To quantify the shunt current in this stack, a novel in-situ shunt measurement technique was developed, allowing for real-time measurement of the shunt current present during all phases of stack operation.
The results of this study provide insights and guidelines for the future development of commercial RFB systems, specifically ways in which the fluid pathway can be optimized to improve system efficiency.

References:

Houser, J. Clement, A. Pezeshki, M. Mench. Influence of architecture and material properties on vanadium redox flow battery performance. J Power Sources. 2016;302:369-377.

Houser, J. Clement, A. Pezeshki, D. Aaron, M. Mench. Architecture for improved mass transport and system performance in redox flow batteries. J Power Sources. 2017;351:96-105.

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Microstructure Characterization of PGM-Free Catalyst Ink Using in-Situ Ultra Small Angle X-Ray Scattering
Authors: Park Jaehyung , Kariuki Nancy N. , Myers Deborah J. , Zhang Hanguang , Wu Gang 
Published: February 2020

Platinum-group metal (PGM)-free cathode catalysts have been widely studied to cut down a production cost of the fuel cell stack, which is one of main challenges to enable the widespread use of fuel cell vehicles. Transition metal-nitrogen-carbon (TM-N-C) such as Fe, Co, Mn or Ni catalysts are now regarded as the most promising PGM-free catalyst due to its stable ORR activity [1]. A high-performance atomic Fe catalyst derived from chemically Fe-doped zeolitic imidazolate framework (ZIF) has recently reported to be a wide range from 20 to 1000 nm after only one-step thermal activation [2]. The microstructure evolution of PGM-free catalysts and ionomer-catalyst interactions during the ink mixing and processing procedure have not yet been identified. This presentation will describe both PGM-free catalyst ink compositions and processing techniques for efficient preparation steps of the electrode while optimizing fuel cell performance and minimizing ink processing time and cost. The electron microscopy technique is widely used to identify the carbon particle size distribution, however, it may not represent the whole catalyst ink. This study uses the in situ measurement of ultra-small angle X-ray scattering (USAXS) combined with SAXS to examine the PGM-free catalyst agglomerate size distribution during ink mixing/processing. The sonicated catalyst ink is circulated through a thin-walled capillary tube situated in the beamline using a peristaltic pump. The ideal ink composition and processing method that facilitate the break-up of primary particle agglomerates with the minimum amount of sonication time are determined in different solvents, ionomer-carbon ratios, and sonication method/time. The microstructure characterization of PGM-free catalyst inks will also be correlated with the fuel cell performance.

Acknowledgements

This work was supported by the U.S. Department of Energy, Energy Efficiency and Renewable Energy, Fuel Cell Technologies Office under the auspices of the Electrocatalysis Consortium (ElectroCat). This research used the resources of the Advanced Photon Source (APS), a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. Argonne National Laboratory is managed for the U.S Department of Energy by the University of Chicago Argonne, LLC, also under contract DE-AC-02-06CH11357.

References

[1] S.T. Thompson, A.R. Wilson, P. Zelenay, D.J. Myers, K.L. More, K.C. Neyerlin, and D. Papageorgopoulos, Solid State Ionics, 319 (2018) 68-76.
[2] H. Zhang, S. Hwang, M. Wang, Z. Feng, S. Karakalos, L. Luo, Z. Qiao, X. Xie, C. Wang, D. Su, Y. Shao, Gang Wu, J. Am. Chem. Soc., 139 (2017) 14143-14149.
Electrode Layer Development and in Situ Diagnostic Characterization in Low Temperature Fuel Cells
Authors: Neyerlin K.C. , Van Cleve Timothy , Wang Guanxiong , Star Andrew G. , Kabir Sadia , Osmieri Luigi , Khandavalli Sunilkumar , Wang Min , Ulsh Michael , Mauger Scott A , Medina Samantha , Pylypenko Svitlana 
Published: February 2020

Proper integration of materials to enable high performing low temperature fuel cell operation has never been more crucial to realizing the isolated (e.g. half-cell or ex-situ) improvements of advanced electrocatalysts, supports and ionomers. Variables such as ink formulation (i.e. solvents and solvent ratios), processing method, ionomer chemistry, carbon morphology/porosity and even the presence or absence of Pt, can impact the ink level interactions of the materials set and subsequently alter the final electrode morphology. The resulting electrode structure can in turn influence active site accessibility and ORR activity as well as oxygen transport resistance and electrode proton conductivity.1–5

Ink formulation and electrode design optimization is often an iterative process, in which conclusions from in situ performance/ diagnostics as well as ex situ characterization (e.g. microscopy and tomography) are relayed to a model. The model then identifies fundamental limiting phenomena which are to be improved in the next loop. This process may often take several iterations to ensure an optimal combination of ionic and gas phase accessibility to the active site.
Here, the development and utilization of in situ diagnostics designed to probe specific phenomena (e.g. catalyst/ionomer interactions, molecular and Knudsen diffusion, electrochemical active site accessibility and catalyst layer proton resistance) will be utilized to contrast the ink, processing and fabrication methods necessary to achieve high performance PGM (e.g. Pt/C and Pt alloy/C) and PGM-free (e.g. FeNx/C based) electrocatalysts based electrodes.
References

A. Orfanidi, P. J. Rheinländer, N. Schulte, and H. A. Gasteiger, J. Electrochem. Soc., 165, F1254–F1263 (2018).

S. Khandavalli et al., ACS Appl. Mater. Interfaces, 10, 43610–43622 (2018).

D. Myers, https://www.hydrogen.energy.gov/pdfs/review15/fc106_myers_2015_o.pdf.

F. Xu et al., Langmuir, 26, 19199–19208 (2010).

D. A. Cullen et al., J. Electrochem. Soc., 161, F1111–F1117 (2014).
Electrochemical Partial Oxidation of Alkenes: Understanding Selectivity and Reaction Mechanisms
Authors: Seger Brian , Winiwarter Anna , Scott Søren B. , Chorkendorff Ib , Silvioli Luca , Rossmeisl Jan 
Published: February 2020

With a deepening electrification of society, electrochemical conversion from one chemical to another will be essential for the chemical plants of the future. While there is intense focus on reduction reactions (i.e. CO2, water, N2), partial oxidation reactions have been relatively underinvestigated. This talk will discuss our recent work on electrochemical partial oxidation of propene. With propene having both a double bond and an allylic carbon, this is an optimal test molecule to create a broad spectrum of products following a variety of mechanisms.
By using a Pd catalyst, we were able to produce acrolein, acrylic acid, allyl alcohol, propylene glycol, acetone with only small amounts of CO2 formation. Variations is oxidation potential allowed us to see changes in product distribution, which we then used to theorize potential reaction mechanisms. With acrolein being one of our largest products, this meant the allylic carbon was oxidized rather the double bond. DFT calculations showed that the acrolein mechanism was feasible, provided surface coverage of other species (oxygen species and flat lying propene) dominated the surface coverage, thus allowing for a small amount of allylic carbon to bind to the surface due to steric advantages. Electrochemical Sniffer Chip technology (1) was then used to measure submonolayer gas absorption/desorption as a function of electrochemical potential, which provided supporting evidence to the aforementioned mechanism. The talk will show our process in analyzing this reaction and mechanisms as well as how these discoveries are applicable to the broader field of partial oxidation reactions.
(1) Trimarco, D. et. al, Review of Scientific Instruments 86, 075006 (2015)

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