bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) TMD Materials Challenges: Defects, Impurities, Passivation and Interfaces
Authors: Wallace Robert M 
Published: February 2020

Layered Transition Metal Dichalcogenides are under scrutiny for potential applications in electronics, catalysis, sensing, photonics, and other technologies. For many applications, superior control of the materials quality and the resultant interface is essential for practical, reliable device applications. This talk will describe our recent studies investigating TMD materials surfaces using in-situ and ex-situ analysis to establish the quality of both geological and synthesized TMDs, and the challenges associated with enabling useful device technologies.
This work was supported in part by the Center for Low Energy Systems Technology (LEAST), one of the six SRC STARnet Centers, sponsored by MARCO and DARPA, by the SWAN Center, a SRC center sponsored by the Nanoelectronics Research Initiative and NIST, and the US/Ireland R&D Partnership (UNITE) under the NSF award ECCS-1407765.
(Invited) Contacts to and Contact-Less Characterization of Transition Metal Dichalcogenides: Challenges Abound
Authors: Bartels Ludwig 
Published: February 2020

Transition metal dichalcogenides (TMD) such as MoS2 or WSe2 have often been billed as the semiconducting counterpart – or even successor - of graphene. While the semiconducting nature of the corresponding bulk materials is beyond doubt, the understanding of what semiconducting means for a 2 dimensional material is emerging only slowly. In this presentation I will talk about the formation of contacts to TMD materials and the associate shift of the Fermi level. Experimental techniques used to obtain the data includes X-ray photoelectron spectroscopy and transport measurements. The results shed light on fundamental challenges of transport and devices utilizing these materials. In addition, I will also talk about surface acoustic wave measurements that reveal photogenerated carrier concentrations in TMD materials. These measurements can be performed without the need for metal contacts and, thus, do conceptually not suffer from the limitations described above.
Development of Solid Oxide Fuel Cells at Versa Power Systems & FuelCell Energy
Authors: Torabi Alireza , Barton Joseph , Willman Carl , Ghezel-Ayagh Hossein , Tang Eric , Pastula Michael 
Published: February 2020

Fuel Cell Energy, inc (FCE) and its wholly-owned subsidiary Versa Power Systems (VPS) are advancing the current state of Solid Oxide Fuel Cell (SOFC) technology towards commercial deployment for efficient and nonpolluting generation of electric power from natural gas and other fuels such as coal.
SOFC technology represents an important opportunity to utilize fossil fuels in an efficient and environmentally-friendly manner. SOFCs are scalable, efficient (not subject to Carnot cycle limitations), and produce low emissions (e.g. nitrogen oxides) compared to combustion-based electrical power generation technologies (due to lower operating temperatures). SOFC power systems have the potential to achieve greater than 60 percent efficiency (based on higher heating value of fuel) and more than 97 percent carbon capture at a cost-of-electricity that is projected to be approximately 40 percent below that presently available through integrated gasification fuel cell (IGFC) systems with carbon capture. An attractive pathway to deployment of either IGFC or natural gas-fueled fuel cell (NGFC) systems is through near-term market opportunities in natural gas fueled distributed generation (DG) applications.
The recent advancements in the base technology include:

Reduced anode thickness from 1 mm to 0.6 mm

Demonstration of steady-state cell operation at 500 mA/cm2 for over 2 years with less than 0.35% per 1000 hour degradation rate

Demonstration of stable cell operation in high cathode gas humidity environment
The Fabrication of Garnet-Type Li7La3Zr2O12 Solid Electrolyte Materials
Authors: Zhang Xingxing , Fergus Jeff W. 
Published: February 2020

The use of solid electrolytes rather than currently used organic carbonate liquid solutions can improve battery safety. The implementation of solid electrolytes requires improvement in the lithium ion conductivity of the electrolyte materials. In this research, garnet-type Li7La3Zr2O12 (LLZO) is investigated. One of the challenges in the synthesis of LLZO is producing the desired cubic phase, because low-temperature processing can lead to formation of the tetragonal phase, while high-temperature processing can lead to loss of lithium. In this work, results on processing of garnet-type LLZO powders and ceramics are presented.
(Invited) Ion Conducting Oxides for Electrochemical Energy Conversion and Storage
Authors: Wachsman Eric D. 
Published: February 2020

Research in functional materials has progressed from those materials exhibiting structural to electronic functionality. The study of ion conducting ceramics ushers in a new era of "chemically functional materials." This chemical functionality arises out of the defect equilibria of these materials, and results in the ability to transport chemical species and actively participate in chemical reactions at their surface. Moreover, this chemical functionality provides a promise for the future whereby the harnessing of our natural hydrocarbon energy resources can shift from inefficient and polluting combustion - mechanical methods to direct electrochemical conversion.
The unique properties of these materials and their applications will be described. The focus will be on the application of ion conducting ceramics to energy conversion and storage, chemical sensors, chemical separation and conversion, and life support systems. Results presented will include development of record high conductivity solid-state battery and fuel cell electrolytes, record high power density (3 kW/kg) solid oxide fuel cells, NOx/CO species selective solid-state sensors, high yield membrane reactors, and regenerative life support systems that reduce CO2 to O2 and solid C.
Effect of Co/Fe Ratio and Microstructural Design on the Structural and Electrical Properties of Mixed Conducting BaSrCo1-XFexO3-X
Authors: Fung Kuan-Zong , Tsai Shu-Yi , Ni Chung-Ta , Lo Shang-Yi , Chen Ta-Te 
Published: February 2020

Sr-doped LaMnO3, is commonly used as the cathode for SOFC applications due to its superior electronic conducting properties. With enhancement of ionic conduction, mixed conducting perovskites, such as BaSrCo1-xFexO3-x, may also be used as the SOFC cathode and ion transport membranes for gas separation.
However, the structural /electrical properties of BaSrCo1-xFexO3-x are not only highly dependent upon the Co/Fe ratio but also on the microstructural design.
In this study, Ba0.5Sr0.5Co1-xFexO3-x, is first fabricated by using carbonates/oxides as raw materials. Secondly, a BaSrCo1-xFexO3-x thin film is deposited on a porous BaSrCo1-xFexO3-x substrate by electrophoretic deposition technique. As a result, with high Co/Fe ratio, Ba0.5Sr0.5Co1-xFexO3-x exhibits hexagonal distortion of perovskite structure. With low Co/Fe ratio, Ba0.5Sr0.5Co1-xFexO3-x exhibits cubic perovskite structure. The structure evolution is rationalized based on XRD and XPS analysis in addition to the consideration of cationic valence and radii. The mixed conduction behaviors of Ba0.5Sr0.5Co1-xFexO3-x is rationalized based on the defect types and charge compensation mechanism. The sintering and densification of Ba0.5Sr0.5Co1-xFexO3-x is examined as a function of Co/Fe ratio. The microstructure of catalytic layers were also investigated. Finally, the enhancement of oxygen permeation through thin-film membrane is demonstrated as well.
La-Doped BaSnO3 As Anode Material for Low Temperature-Solid Oxide Fuel Cells
Authors: Abdul Jabbar Mohammed Hussain , Robinson Ian , Pan Ke-Ji , Wachsman Eric D 
Published: February 2020

Barium stannate doped with 2 at.% of lanthanum was synthesized and investigated as a potential anode material for low temperature solid oxide fuel cells (LT-SOFCs). Ba0.98 La0.02SnO3-δ ceramic was calcined at 1200-1300°C in air to obtain the cubic perovskite phase and then sintered at 1550°C for 12h. The sintered sample has shown approx. 7% shrinkage and 70% density. For the 30% porous sample, electrical conductivity values of 8.7 S/cm and 9.3 S/cm, respectively was achieved, at 600°C and 400°C, respectively in 10% H2/3%H2O/N2.The preliminary results has shown a decent redox stability, approx. 7 % loss in conductivity at 600°C when cycled 3 times between air and reducing conditions over a period of 60 h. Post-test XRD analysis on Ba0.98 La0.02SnO3-δ samples show structural stability by retaining the cubic perovskite phase. The material was also stable in dry and humidified H2. Interestingly, the material has shown semi-conductor like behavior in the presence of methane. The conductivity values of the materials in 97%CH4/3%H2O gas were 6.4 and 2.2 S/cm at 600 and 500°C, respectively. This material has promising performance for integration into an LT-SOFC anode, but processing challenges remain.
(Invited) Oxygen Evolution Catalysts for Water Electrolysis: Challenges and Progress with Extended Surface Ir-Based Catalysts
Authors: Alia Shaun M , Hurst Katherine , Neyerlin K.C. , Kocha Shyam S. , Ngo Chilan , Shulda Sarah , Pylypenko Svitlana , Pivovar Bryan S 
Published: February 2020

Electrolysis is near parity as an energy storage process when compared to the cost of competing technologies, including batteries, pumped hydro, and compressed air.[1] When coupled with renewable energy sources, such as wind and solar, electrochemical water splitting can also produce hydrogen using a nearly carbon free pathway.[1] Some overview content will be presented to provide justification for decreased capital costs in electrolyzers as well as focus on aspects of intermittent operation. An operational mode not used typically today in electrolysis, but one that will become of higher interest in the future with increasing renewable energy penetration and growing hydrogen markets.
Iridium nanoparticles are commonly used as electrocatalysts in acidic electrolyzers due to moderate stability and activity in the oxygen evolution reaction (OER). Baseline materials and protocols are still being developed to benchmark the current status of OER catalysts. The presentation will discuss results along these lines, as well as discuss mercury underpotential deposition as a method for determining surface area for iridium and/or iridium oxide.
Progress made at NREL on Ir based nanowires for OER that leverage off of previous experiences in the production of Pt based nanowires for oxygen reduction reaction [2] will also be presented.
References
[1] K. Harrison, M. Peters, in: U.S. Department of Energy (Ed.), http://www.hydrogen.energy.gov/pdfs/review13/pd031_harrison_2013_o.pdf, 2013.
[2] S.M. Alia, Y. Yan, B.S. Pivovar, “Galvanic Displacement as a Route to Highly Active and Durable, Extended Surface Electrocatalysts” Catalysis Science and Technology, 2014, 4 (10), 3589 - 3600.
Durable Membrane Electrode Assemblies (MEA) for Proton Exchange Membrane (PEM) Electrolyzer Systems Operating at High Current Densities
Authors: Lettenmeier Philipp , Wang Rainey , Abouatallah Rami , Gago Aldo Saul , Friedrich K. Andreas 
Published: February 2020

Hydrogen can be used as an energy vector for renewable energies such as solar or wind by using water electrolysis systems [1]. Commercially, it can be electrochemically produced by alkaline and proton exchange membrane (PEM) electrolysis, at which the investment cost of the later is presently almost three times higher than the alkaline technology [2]. However, the main advantage of PEM electrolysers is the possibility to operate at much higher current densities with a significant potential for cost reduction owing to the compact design [3]. An open question is still the life time of the membrane electrode assembly (MEA) of the PEM electrolyser operating at high performance. In this work rainbow stacks with MEAs from different suppliers are tested in a 20 kW PEM electrolyser (2.5 N m³ H2 h-1) operating constantly and dynamically up to 5 A cm-2. The 120 cm2 active area MEAs have membranes with the same thickness but different Ir-based catalyst loadings. Operating the electrolyser at low current densities has an impact in the H2 crossover. The most durable MEAs do not experience any lost in performance after more than 3000 h of operation under stationary and dynamic regimes. Post-mortem characterisation and water analysis are carried out to determine the degradation mechanism of the rest of the MEAs.
References
[1] A. Sternberg, A. Bardow, Energy Environ. Sci. (2015) 389.
[2] Fuel Cells and Hydrogen Joint Undertaking, Report: Commercialisation of Energy Storage in Europe, 2015.
[3] M. Carmo, D.L. Fritz, J. Mergel, D. Stolten, Int. J. Hydrogen Energy 38 (2013) 4901.
Self-Terminated Electrodeposition of Ultrathin Iridium Film Catalysts
Authors: Ahn Sang Hyun , Tan Haiyan , Liu Yihua , Bendersky Leonid A. , Moffat Thomas P. 
Published: February 2020

Self-terminated electrodeposition process is used to grow ultrathin catalytic iridium (Ir) films. With a simple potential pulsing method, semi-coherent Ir films are deposited on various substrates in K3IrCl6-Na2SO4 electrolytes at the temperature range between 40 °C and 70 °C. The electrochemical reduction of IrCl6-x·H2Ox
3-x to Ir is quenched at the onset potential of hydrogen evolution reaction, even though the deposition overpotentials exceed 1.0 V because the deposited Ir surfaces are immediately passivated by H adsorption which can prevent the further Ir deposition. However, the deposited Ir film surfaces are reactivated toward further electrochemical reduction of IrCl6-x·H2Ox
3-x to Ir when the potential is rapidly changed to positive value where the adsorbed H is oxidized. After 1 deposition pulse, the X-ray photoelectron spectroscopy (XPS) derived Ir thickness is 0.085 ± 0.028 nm based on uniform overlayer model which is mostly independent deposition time. With repeated potential pulses, the XPS derived Ir thickness is increased from 0.343 ± 0.012 nm (2 deposition pulses) to 3.143 ± 0.083 nm (10 deposition pulses). The Ir coverage determined by H under potential deposition (HUPD) approaches a monolayer coverage after 3 deposition pulses. The various combination of Ir-based ultrathin films prepared self-terminated electrodeposition demonstrate high activity for hydrogen catalysis in alkaline and oxygen catalysis in acid.
N-Doped Reduced Graphene Oxide Composites for Hydrogen Generation in Presence of Chloride Ion Impurities in Alkaline Medium
Authors: Halder Aditi , Bharadwaj Arpit , Kushwahab Himmat Singh , Saquib Mohammad 
Published: February 2020

The depletion in fossil fuel reserve leads to the search for a clean, alternate fuel which can replenish the energy demand without causing greater harm to the environment. Hydrogen is one such kind of promising sustainable energy fuel which can be produced from very cheap resources like water. The major hurdle behind the efficient and economical production of hydrogen through electrochemical conversion of water is the large thermodynamic overpotential related to it. Enormous volume of researches has been carried out towards the development of catalysts, improving support materials efficiency and electrochemical environment related to hydrogen evolution reaction (HER).
In this work we are going to present a catalyst which shows appreciable enhancement in the electrochemical activity towards HER in alkanine medium and can withstand very high chloride ion impurities in operating conditions. Often, the performance and durability of a fuel cell are greatly influenced by the presence of impurities present in the feed stock, air stream or other components of fuel cell. Among the different contaminants chloride (Cl-) ion is one of the serious impurities which can diffuse through the gas diffusion system and can poison the electrocatalysts and membrane and ultimately leads to the decrease performance of the fuel cell system. Hence it is important to develop a robust catalyst which will have dual functionalities. Along with enhanced performance, it also should be able to withstand the extreme poisoning effect during hydrogen evolution reaction.
In comparison to un-doped reduced graphene oxide (RGO)–Pt composites and commercial Pt /C catalysts, the nitrogen-doped graphene oxide (NGO)-Pt composites show low overall potential towards HER both in acidic and alkaline environment. Electro-catalytic performance of the prepared cathodes has been investigated by hydrogen evolution reaction in 0.1M perchloric acid, 0.5 M sulfuric acid and 0.1molar KOH solution. The controlled exposure of chloride ion impurities shows under similar condition NGO-Pt shows better stability and less reduction of electrochemical surface area (ESA) and hence less susceptible towards chloride poisoning under identical conditions. The loss of electrochemical surface area (ESA), before and after chloride poisoning, is much less in case of NGO-Pt . Figure 1 shows the comparison between the RGO-Pt,commercial-Pt and NGO-Pt for loss of ESA.

Figure 1
(Invited) Computational Design of Coatings, Interfaces, and Nano-Structures for Si Based Electrodes
Authors: Qi Yue , Kim Sung-Yup , Kim Kwang Jin 
Published: February 2020

The chemical composition and mechanical properties change of coating materials, interfaces, and Si itself during lithiation and delithiation process imposed a grand challenge to design coating/Si nanostructure as an integrated electrode system. In our work, reactive force field (ReaxFF) parameters for Li-Si-Al-O-F were developed along with a new algorithm to simulate lithiation and delithation processes with different rates. With the reactive dynamics simulations, we were able to simultaneously track and correlate the lithiation-delithiation rate, compositional change, mechanical property evolution, stress distributions, and fracture. Interesting insights were obtained from these studies. For example, it was found that the lithiation rate during the initial mixing stage increases exponentially with vacancy concentrations in Si; and it was discovered the self-accelerating Li diffusion in Al2O3 coating forms a well-defined Li concentration gradient, leading to an elastic modulus gradient, which effectively avoids local stress concentration and mitigates crack propagation. A new mechanics model based on these varying properties was developed to determine how to stabilize the coating with a critical size ratio.
A Multiphysics Study of Chemical Potential Distributions As Drivers for Solid Oxide Cell Mechanical Degradation
Authors: Nelson George J. , van Zandt Zachary 
Published: February 2020

Solid oxide cells are promising energy conversion devices that enable the generation of power from diverse fuel sources in fuel cell operation and the production of hydrogen and syngas fuels when operating as electrolyzers. Accelerated degradation has been observed for electrolytic operation in comparison to fuel cell operation. Of particular note, oxygen electrode delamination has been observed for solid oxide electrolyzers. It has been proposed that this mechanical failure mode arises from adverse gradients in the oxygen chemical potential across the electrode-electrolyte interface. A multiphysics model of solid oxide cell operation has been developed for mass and charge transport in the presence of a distributed electrochemical reactions. Both 1D and 2D transport within the cross-section of a planar positive electrode-electrolyte-negative electrode (PEN) unit cell are addressed. Mass transport in the porous composite electrodes is treated using the dusty-gas model. Charge transport is cast in terms of ion and electron electrochemical potentials, a feature that facilitates analysis of mixed ion and electron conduction. The present work focuses on analyzing oxygen chemical potential gradients within the solid electrolyte and the porous composite electrodes, with an emphasis on gradients near interfaces between the PEN components. Two general modeling cases are compared: one neglecting electronic conduction within the solid electrolyte and one accounting for small yet present electronic conduction. Electrochemical potential distributions are assessed across the cell structure over a range of electrolytic and galvanic operating conditions. These distributions are used to assess the likelihood of adverse oxygen chemical potential gradients within the cell. The effects of interconnect geometry for planar cells are also considered. It is found that variations in electrochemical potential arise within the PEN structure, a phenomenon that may drive mechanical failure. These gradients may increase the likelihood of electrolyzer failure for certain combinations of electrode and interconnect geometry. The use of device scale geometric design is discussed as a means of mitigating these gradients and reducing the likelihood of cell mechanical failure from adverse distributions of reactant chemical potentials.
Hydrostatic Stress - Temperature Diagrams for Electronic Charge Carriers in SrTiO3
Authors: Youssef Mostafa , Van Vliet Krystyn J. , Yildiz Bilge 
Published: February 2020

The electronic conductivity and the redox activity of metal oxides depend on the extent of the wave function spread of the electronic charge carriers. Delocalized (free) electrons and holes lead to large electronic conductivity, whereas self-trapped (small polaron) electrons and holes provide active centers for charge transfer and redox reactions. It is possible to control the state of the electronic charge carriers in metal oxides, free vs. self-trapped, by utilizing mechanical stress and strain. Tensile stresses tend to favor trapping, and the critical tensile stress above which trapping occurs also depends strongly on temperature. Here we adopt SrTiO3 as a model system and computationally predict regimes of trapping or delocalization for electrons and holes as a function of hydrostatic stress and temperature. SrTiO3 is a representative of the perovskite family of metal oxides, and itself is a widely used crystal for electronic studies. Starting from density functional theory (DFT), we parametrized on-site Hubbard terms (+U) for Ti 3d states and O 2p states that adhere to the generalized Koopman’s theorem. This adherence qualifies DFT equipped with the selected U to accurately describe trapped electrons and holes. Using this DFT+U approach we found that in SrTiO3 at zero temperature and zero stress, trapped holes on oxygen ions are favored by 170 meV, whereas free electrons are favored by 110 meV. Using the quasiharmonic approximation we extend these results to finite temperature and finite hydrostatic stress. In particular we calculate the Gibbs free energy of formation of electrons and holes in both trapped and free states. Based on these free energies, we build a stress-temperature diagram for the predominant electronic defect state. The analysis we present here for SrTiO3 is broadly applicable to other semiconducting metal oxides, and illustrates how strain (or stress) can serve as a modulator of electronic charge carriers.
(Invited) Multi-Modality X-Ray Imaging at a 10 Nanometer Resolution
Authors: Chu Yong S , Yan Hanfei , Huang Xiaojing , Kalbfleisch Sebastian , Ge Mingyuan , Lauer Kenneth , Nazaretski Evgeny 
Published: February 2020

The Hard X-ray Nanoprobe (HXN) beamline at the NSLS-II is constructed to explore new frontiers of the x-ray microscopy, by enabling an unprecedented spatial resolution of ~10 nm in the hard x-ray regime. The beamline offers simultaneous multi-modality imaging capabilities including x-ray fluorescence, x-ray diffraction, x-ray absorption, x-ray scattering, phase-contrast imaging, spectroscopy, and ptychography. These suite of imaging tools open up new scientific opportunities to visualize complex nanostructures with unprecedented sensitivity to material composition, morphology, crystalline phases/strain, and chemical state. Use of hard x-rays allows accurate quantification of buried nanostructure with straightforward analyses. Presentation will describe the present and near-future scientific capabilities of this new imaging facility with the recent results.