bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Perovskite Oxide As High Performance Bifunctional Catalyst in Alkaline Solution
Authors: Yan Litao , Luo Hongmei
Published: February 2020

The global energy crisis coupling with the consumption of fossil fuels and the associated environmental issues, has stimulated extensive interest in searching for clean, efficient and sustainable energy storage and conversion systems. Producing oxygen through an OER process can be promising when effective catalysis of water oxidation into oxygen molecules could be achieved. Therefore, developing an efficient OER electrocatalyst is vital to the new generation of electrochemical storage and conversion devices such as electrolyzer, hydrogen production from water and metal-air batteries. However, there are still several challenges that have to be solved for the electrochemical water oxidation process to become economically attractive One of them is associated with the high overpotential and thereby energy losses at the electrode, where OER is taken place with four electron transfer, according to the following overall reaction:

2H2O (l) + 4 × 1.23 eV → O2 + 4H+ + 4e- (1)

Oxygen reduction reaction (ORR), reversible reaction of OER, also play an important role in electrochemical energy storage devices including fuel cell and metal air battery. Advanced ABO3 perovskite oxides with improved catalytic properties have been extensively developed and modified as bifunctional catalyst because of their high versatility in composition, crystalline and electronic structure. In this paper, (La0.8Sr0.2)1-xMn1-xIrxO3 (x=0, 0.05 and 0.1) nanoparticles with particle size of 20-50 nm were succesfully developed as the superior bifuctional catalyst in alkaline solution. The onset potential for ORR is around 0.92V, which is only 50 mv negative shift for state of art Pt/C catalyst while the onset potential for OER is around 1.55 V, which is comparabel with a state of art IrO2 catalyst.
Exploring Graphitic Carbon Nitride Based Nano-Heterogeneous Photocatalysts for Elimination of Wide Range of Contaminants and Water Splitting
Authors: Pawar Rajendra Charandeo , Kang Suhee , Lee Caroline Sunyong
Published: February 2020

Presently, contamination of waster with harmful and waste materials, leading to significant adverse effect on the environment and wildlife. Direct disposal of nonbiodegradable and undesirable chemical compounds into water makes it unsuitable for drinking and for other purposes. Hence, elimination of contaminants from wastewater has become an important issue, because of the adverse effects on human health and environment. Conventionally, various techniques including advanced oxidation, coagulation, adsorption, reverse osmosis, and ion exchange have been used to remove these hazardous pollutants from polluted water. Of these, photocatalysis purification based on heterostructures are one of the most prominent technologies in the direct use of solar energy for the degradation of wide range contaminants and production of H2; these are potentially the best promising green technologies that replace conventional energy resources. In order to achieve the desired efficiency, the photocatalysts should have an excellent light absorbance, rapid charge separation, and a high chemical stability. A great deal of effort has been devoted to enhancing the efficiency of the photocatalytic process and extending the light adsorption range of photocatalysts; these include formation of semiconductor nanoheterostructures, co-deposition of noble metals, and coupling with other technology. Among the various approaches, formation of nano-heterojunctions is a promising approach; it can induce band bending at the interface of junction resulting in a built-in field, which can drive the photogenerated electrons and holes to move in opposite directions.

In our laboratory, we fabricated and investigated different nano-heterogeneous photocatalysts based on graphitic carbon nitride (g-C3N4) and its hybrids with aligned ZnO/TiO2 nanorods, ZnTiO3 nanofibers, Au nanoparticles and CNTs, and graphene nanosheets via solvothermal methods. The fabricated have been tested to degrade organic pollutants such as methylene blue, and rhodamine B have degraded under visible irradiation. In addition, we measured H2 evolution from water splitting under visible irradiation. The photocatalytic activities of nano-heterogeneous photocatalysts was seen to be better over the pristine structure. Improved performance was aroused from broadened the optical window, short diffusion distance for excellent charge transport, and increase contact area with supporting electrodes for rapid interfacial charge separation and transportation. Therefore, the present ternary graphene aerogel based nano-heterogeneous photocatalysts could be applicable in hydrogen production and water purification technology.
Importance of Resonance Structure on Alkaline Stability
Authors: Maurya Sandip , Lee Kwan-Soo , Fujimoto Cy , Kim Yu Seung
Published: February 2020

Anion exchange membrane fuel cells (AEMFCs) have been a topic of extensive research from academia and industry as an alternative to proton exchange membrane fuel cells (PEMFCs). The AEMFCs offer benefits over PEMFCs such as facile fuel oxidation and enhanced oxygen reduction reaction catalysis1. However, the chemical stability of anion exchange membrane needs to be improved as most commonly used benzyltrimethyl ammonium cationic group undergoes direct nucleophilic substitution reaction, which results in loss of conductivity and fuel cell performance. One of the approaches to enhance the chemical stability is introducing electron conjugation into cationic functional group. Previous study demonstrated that the conjugated guanidinium possess better stability than non-conjugated guanidinium2.

Herein, we report the progress on resonance stabilization of the guanidinium functional group. The extended-resonance stabilized guanidinium functionalized poly(phenylene) (PP-TMG) AEM was synthesized from the Diels-Alder poly(phenylene) by acylation reaction followed by activated fluorophenyl-guanidine reaction3. The alkaline stability of PP-TMG was compared with benzyltrimethyl ammonium-poly(phenylene) (PP-BTMA) and hexamethylenetrimethyl ammonium-poly(phenylene) (PP-HTMA). Spectroscopic analysis with small molecules and cationic group tethered polymers will be also provided to discuss the resonance stabilization effect.

Acknowledgement

This work is supported by the US Department of Energy, Energy Efficiency and Renewable Energy, Fuel Cell Technology Office (Program Manager Dr. David Peterson).

References:

(1) Varcoe, J. R.; Atanassov, P.; Dekel, D. R.; Herring, A. M.; Hickner, M. A.; Kohl, P. A.; Kucernak, A. R.; Mustain, W. E.; Nijmeijer, K.; Scott, K.; Xu, T.; Zhuang, L. Energy Environ. Sci.
2014, 7 (10), 3135–3191.

(2) Kim, D. S.; Fujimoto, C. H.; Hibbs, M. R.; Labouriau, A.; Choe, Y.-K.; Kim, Y. S. Macromolecules
2013, 46 (19), 7826–7833.

(3) Kim, D. S.; Labouriau, A.; Guiver, M. D.; Kim, Y. S. Chem. Mater.
2011, 23 (17), 3795–3797.
Efficient Dual-Site Carbon Monoxide Electro-Catalysts Via Interfacial Nano-Engineering
Authors: Huang Zhongyuan , Wang Zhe
Published: February 2020

Durable, highly efficient, and economic sound electrocatalysts for CO electrooxidation (COE) are the emerging key for wide variety of energy solutions, especially fuel cells and rechargeable metal−air batteries. Herein, we report the novel system of nickel−aluminum double layered hydroxide (NiAl-LDH) nanoplates on carbon nanotubes (CNTs) network. The formulation of such complexes system was to be induced through the assistance of gold nanoparticles in order to form dual-metal active sites so as to create a extended Au/NiO two phase zone. Bis(trifluoromethylsulfonyl)imide (NTf2) anion of ionic liquid electrolyte was selected to enhance the CO/O2 adsorption and to facilitate electro-catalyzed oxidation of Ni(OH)2 to NiOOH by increasing the electrophilicity of catalytic interface. The resulting neutral catalytic system exhibited ultra-high electrocatalytic activity and stability for CO electrooxidation than commercial and other reported precious metal catalysts. The turnover frequency (TOF) of the LDH-Au/CNTs COE catalyst was over 70 times higher than the previous reported other similar electrocatalysts, even close to the activity of solid-gas chemical catalysts at high temperature. Nonetheless, in the long-term durability testing, the negligible variation of current density remains exsisting after 1000 electrochemistry cycles.

Figure 1
Extracting Material Properties from Relaxation Experiments
Authors: Haile Sossina M
Published: February 2020

Redox active oxides, with mixed ionic and electronic conductivity (MIEC), are critical components in a wide range of energy technologies, serving as electrodes in fuel cells and batteries, and as reactive substrates in solar-driven thermochemical reactors. Accurate knowledge of the surface reaction rate constant, k
S, is essential for both optimal design of components using existing materials and rational discovery of new materials with enhanced catalytic activity. A variety of relaxation methods have been used extensively to determine k
S. Such approaches rely on the change in some measurable property, most commonly conductivity, upon application of a step change in gas-phase oxygen partial pressure. Under the appropriate experimental conditions, the rate at which the property changes in response to the change in gas-phase oxygen chemical potential provides a direct measure of the material kinetic parameters. Here, we present several considerations relevant to accurate extraction of these parameters, with particular focus on identifying relaxation occurring due to thermodynamic rather than material kinetic reasons. Furthermore, while the electrical conductivity relaxation (ECR) method is one of the most widely employed relaxation techniques because of the ease with which high precision conductivity measurements can be made using samples of almost arbitrary dimensions, ECR is impractical for the evaluation of a material in which the change in conductivity in response to change in oxygen partial pressure is extremely small. For such materials mass relaxation emerges as a viable alternative measurement approach. To this end, we describe a high temperature mass relaxation apparatus based on a gallium phosphate piezocrystal microbalance that enables measurements at temperatures as high 700 °C.
Mechanism of Enhanced Sulfur Tolerance on Sm-Doped CeO2: A Density Functional Study
Authors: Lim Dong-Hee , Yoon Sung Pil , Han Jonghee , Choi Sun Hee , Yoon Chang Won , Nam Suk Woo , Ham Hyung Chul
Published: February 2020

In this presentation, using first-principles calculation, the function of samarium (Sm) 4f states and Sm-perturbed O 2p states in enhancing the sulfur tolerance of Sm-doped CeO2 was elucidated. We find that the sulfur tolerance of Sm-doped CeO2 is closely related to the modification of O 2p states by the strong interaction between Sm 4f and O 2p states. In particular, the availability of unoccupied O 2p states near the Fermi level is responsible for enhancing the sulfur tolerance of Sm-doped CeO2 compared to the pure CeO2[1]. To better understand the importance of unoccupied O 2p states, the effect of various 4f shell dopants (Pr, Pm, and Eu) on the activity of surface lattice oxygen are also investigated. This work also hints on the importance of properly engineering the activity of oxygen ion in CeO2-based materials by adding dopant in order to develop sulfur-tolerant solid oxide fuel cell anode. [1] DH Lim, HS Kim, SP Yoon, J Han, CW Yoon, SH Choi, SW Nam, and HC Ham, Physical Chemistry Chemical Physics 16 (22), 10727-10733, (2014)
(Invited) Sulfur Poisoning of Ni-Based SOFC-Anodes – Short and Long Term Behavior
Authors: Weber André , Dierickx Sebastian , Russner Niklas , Ivers-Tiffée Ellen
Published: February 2020

Solid Oxide Fuel Cells (SOFCs) enable a highly efficient, environmentally-friendly power generation. One major problem of SOFCs working under real conditions are the sulfur compounds contained in almost all available fuels as natural gas, diesel reformate or gas from hydrothermal gasification of biomass (1),(2). If the sulfur is not properly removed by an upstream desulfurization unit even small amounts of sulfur in the ppm range affect the performance of SOFCs. Previous studies showed that the initial performance loss observed after adding sulfur to the fuel is related to a poisoning of the Ni-electrocatalyst in the Ni/YSZ-cermet anode.

In this contribution the impact of sulfur on the short term and long term behavior of Ni-based cermet anodes will be discussed. Sulfur species are chemisorbed on the Ni-surface (3), blocking the adsorption sites and the surface diffusion of reactants and reaction products. By means of electrochemical impedance spectroscopy and a subsequent analysis of the spectra by the distribution of relaxation times (4) two poisoning mechanisms could be decoupled (i) a deactivation of the catalytic watergas-shift-reaction (WGS) at the nickel surfaces and (ii) the electro-oxidation of hydrogen at the three phase boundaries (5),(6). The time constant of these mechanisms depends on the available Ni-surface area and the amount of H2S supplied to the anode and is typically in the range of several hours. Furthermore a restructuring of the Ni-surfaces accompanied by an enhanced Ni agglomeration results in an enhanced aging in the longer term.

To improve the sulfur tolerance of SOFCs a cermet anode composed of Ni and ceria, a material combination well known as sulfur tolerant catalyst, can be applied. Impedance analysis of electrolyte supported cells exhibiting a Ni/ceria cermet anodes revealed a significantly improved sulfur tolerance. It will be shown that the impact of both poisoning mechanisms can be reduced. Cells with appropriate Ni/ceria anode layers showed the ability to convert carbon monoxide by a sufficiently fast WGS and electrooxidize hydrogen with a polarization resistance below 200 mΩ·cm².

References

(1) Y. Matsuzaki and I. Yasuda, Solid State Ionics, 132 (3-4), p. 261 (2000).

(2) K. Föger and K. Ahmed, Journal of Physical Chemistry B, 109 (6), p. 2149 (2005).

(3) C. H. Bartholomew, Applied Catalysis A: General, 212 (1), p. 17 (2001).

(4) H. Schichlein, A. C. Müller, M. Voigts, A. Krügel and E. Ivers-Tiffée, Journal of Applied Electrochemistry, 32 (8), p. 875 (2002).

(5) A. Kromp, S. Dierickx, A. Leonide, A. Weber and E. Ivers-Tiffée, J. Electrochem. Soc., 159 (5), p. B597 (2012).

(6) A. Weber, S. Dierickx, A. Kromp and E. Ivers-Tiffée, Fuel Cells, 13, p. 487 (2013).
(Invited) Integrating Theory and Experiment to Design and Develop Advanced Materials for the Production of Transportation Fuels Via Catalytic Fast Pyrolysis of Biomass: Transition Metal Carbides and Phosphides
Authors: Schaidle Joshua
Published: February 2020

As part of the DOE’s Energy Materials Network, the Chemical Catalysis for Bioenergy (ChemCatBio) Consortium seeks to overcome catalysis challenges for biomass conversion processes through the design and development of advanced catalytic materials. One such challenge being addressed by the consortium is for the catalytic fast pyrolysis (CFP) conversion process, in which biomass is heated to approximately 500°C at short contact times producing a vapor stream of over 300 different oxygenated organic compounds. This complex mixture is subsequently upgraded in the vapor phase over a heterogeneous catalyst to remove oxygen and improve the fuel properties of the condensed bio-oil. For this process, carbon efficiency has the greatest impact on the overall economics, and currently-available catalysts suffer from short lifetimes due to coke deposition and poor yields to the desired fuel-range products.

To address this challenge, the ChemCatBio consortium initiated a joint experimental and computational effort to design and develop advanced CFP catalysts based on transition metal carbide and phosphide formulations. This effort links catalyst evaluation at multiple scales, ranging from intrinsic kinetic measurements with model compounds at the mgcat scale to bio-oil production from a pine feedstock at the 100gcat scale, with computational modeling of the catalyst surface termination under reaction conditions, calculation of reaction energetics, and ultimately the integration of those energetics into a micro-kinetic model validated with experimental data. The results generated from this integrated approach are used to inform the synthesis of targeted catalyst formulations with desired properties. This presentation will provide an overview of this effort and, in the spirit of the ECS conference, will also briefly discuss the electrocatalytic properties of these transition meal carbide and phosphide materials.
(Invited) Design and Realization of New Thermochemically Active Materials
Authors: Garten Lauren , Dwaraknath Shyam , Whitehead Riley , Selvarasu Praneetha , Barcellos de Oliveira Debora R. , Chan Zamyla , Duan Chuancheng , Stone Kevin , Persson Kristin A , O'Hayre Ryan , Nocera Dan , Ginley David
Published: February 2020

Through combining predictive theory and experiment new functional materials for thermochemical cycles and reactions such as the oxygen evolution reaction. Many of these materials include metastable polymorphs of the groundstate materials and necessitate careful optimization of the inherent defect structure for that polymorph. The often exhibit multifunctional behavior. Barium nickelate, BaNiO3, and its sub-oxides have shown potential as oxygen evolution reaction catalysts. Initial results indicate performance comparable to precious metal catalysts. We have synthesized highly phase pure materials and evaluated it in a thermochemical redox cycle. In this work we examine the structural and phase changes that occur during the redox cycling of BaNiO3 at high temperature. Thermogravimetric analysis (TGA) on sol-gel synthesized powders under reducing and oxidizing conditions indicates a reversible cycling through multiple oxidation states. The structure of the BaNiO3powder as determined by synchrotron x-ray diffraction is measured prior to and after TGA analysis to track the phase changes associated with redox cycling. Transimission electron microscopy is used to track changes in the powder surface, crystal structure and morphology. The stability of this structure over a wide range of oxidation states gives this material applicability in a number of energy applications such as electrochemical water splitting, multiferroics, and solid oxide fuel cells, all of which are discussed.

This work was funded by the Center for the Next Generation of Materials by Design, an U.S. Department of Energy, Office of Science EFRC under Contract No. DE-AC36-08GO28308 to NREL.
(Invited) Exploring and Understanding Energy Conversion at Interfaces By Combining Simulations and X-Ray Spectroscopy
Authors: Prendergast David
Published: February 2020

The conversion of abundant but intermittent forms of energy, such as solar or wind, into more technologically accessible electrical or chemical energy, is typically driven by electron transfer processes at embedded material interfaces. To build optimal composite materials for energy conversion requires detailed understanding and exquisite control of the nanoscale details of these interfaces. The necessary guidance to drive such synthesis and fabrication efforts defines a challenge for direct characterization of these processes, as they happen, with techniques that are often best suited to open interfaces in the realm of surface science. For example, X-ray spectroscopy, which provides insight on local, element-specific chemistry and coordination, can be extremely surface sensitive, but has only recently advanced to reveal interfacial chemistry at the solid-liquid interface. Moreover, the interpretation of such measurements relies both on accurate modeling of condensed phase interfaces and of the associated observables. At the Molecular Foundry, we combine dynamical modeling of interfacial function with direct simulation of X-ray absorption and photoemission spectra. Our simulations provide nanoscale structural details of interfaces and can reveal unique spectral signatures of the interfacial phase or specific interfacial phenomena that may lie hidden in characterization measurements. The combination of such theoretical modeling with in situ characterization is vital to advance research on energy conversion and storage. Here we will discuss a range of recent applications in the areas of electrochemical energy storage, photoelectrochemistry, and gas storage via chemical conversion. Typically, we find that materials interfaces do present unique spectral signatures that are measurable indicators of nanoscale interfacial function, which can reveal intrinsic bottlenecks and paths to advancement.
(Invited) Hydrogen Storage Characterization and Optimization Research Effort, Hyscore
Authors: Gennett Thomas
Published: February 2020

The HySCORE collaboration is a DOE-FCTO funded initiative that brings together internationally recognized leaders in hydrogen storage materials characterization and development from NREL, LBNL, PNNL and NIST. This collaboration is predicated on a synergistic approach to further develop the key core-capabilities necessary for accurate evaluation of hydrogen storage materials capacity, kinetics, and sorption/desorption physio-chemical processes. Furthermore, these experts also conduct a parallel experimental-modeling collaborative approach to utilize the core-capabilities developed in order to rapidly define, model, synthesize and characterize the appropriate materials necessary for achieving the 2020 Hydrogen Storage goals set forth by DOE. The approach is multifaceted to mitigate risk and ensure success as we bridge the gap between physisorption and chemisorption to provide the basis for a new generation of hydrogen storage materials technologies. Our focus is to Develop and Enhance hydrogen storage core capabilities and to Validate claims, concepts, and theories of hydrogen storage materials. The overarching goal is to ascertain pathways and/or new materials that have the possibility to volumetric capacities of greater than 45 g/L and isosteric heats of hydrogen adsorption in the range of 15-20 kJ/mol with the additional caveats of acceptable gravimetric capacities and the ability to deliver on-demand H2 at an appropriate rate and pressure. In order to capture the benefits of reduced system cost and forecourt compression energetics, the maximum overpressure would be <100 bar of hydrogen, with a delivery temperature of greater than 150 K and as close to ambient temperature as possible. 

This talk will outline the advanced characterization techniques, standardized benchmarking/protocols and capabilities. We will also highlight several new materials sets, the impact of the new characterization tools and how this has acceleratd advances in hydrogen storage materials development.
(Invited) A Comprehensive Data Ecosystem to Accelerate Materials Research
Authors: Perkins John D. , White Robert R , Munch Kristin
Published: February 2020

In Materials-by-Design or Materials Genome Initiative (MGI) approaches to materials development, research (and researcher) friendly data tools are central to addressing the overarching challenge of creating new material science understanding from the vast amounts of data generated by both theory and experiments. At NREL, we have developed a comprehensive data ecosystem that includes automated data (and metadata) harvesting, expression of the aggregated data in an accessible database and the development of custom analysis tools as well as the deployment of public facing materials information resources. Using research examples taken from the Center for Next Generation Materials by Design EFRC and NREL’s internal development project on high-throughput x-ray diffraction analysis, we will present an overview of the complete NREL data ecosystem as it currently stands as well as a vision of how it might be integrated into multi-institute consortia such as the recently created DOE Energy Materials Networks. The public facing NREL MatDB database (materials.nrel.gov) contains the results of 200,000+ density functional theory calculations covering 30,000+ unique materials. Our recently established internal High-Throughput Experimental Materials database (HTEM-DB) currently contains data from more than 3300 combinatorial libraries representing roughly 86,000 different composition-processing synthesis combinations. Our data analytics use of HTEM-DB will be demonstrated by application to the rapid analysis of large x-ray diffraction datasets. HTEM-DB can be accessed via an API, direct SQL queries, a web interface and custom graphing-program based user tools to facilitate use by researchers. The overall result is a scientist-friendly extensible analysis environment with project specific machine learning and visualizations which is now both being put into use within Center for Next Generation Materials by Design and serving as the NREL access point for the NIST-led High-Throughput Experimental Materials Science Virtual Laboratory. A public facing version of the NREL HTEM-DB will be launched in 2017.
Electrochemical Nanoreactors of Mixed Metal-Oxide-Supported Noble- Metal-Nanoparticles for Efficient Oxidation of Dimethyl Ether and Ethanol
Authors: Rutkowska Iwona Agnieszka , Kulesza Pawel J
Published: February 2020

Noble metal-based (e.g. Pt, Pd, PtRu or PtSn) nanoparticles have been recognized as the most active catalytic systems towards oxidation of small organic molecules (ethanol, dimethyl ether) at low and moderate temperatures. Although all of them can be ideally oxidized to carbon dioxide, their actual electrooxidation mechanisms can significantly differ and may result in distinct electrocatalytic efficiencies and final reaction products. There is a need to develop functionalized electrocatalytic systems exhibiting specific reactivity and capability to induce the slow reaction steps at ambient conditions.

Platinum based nanoparticles are readily poisoned by the strongly adsorbed CO-type intermediate species requiring fairly high overpotentials for their removal. For example, to enhance activity of Pt-based catalysts toward the ethanol oxidation, additional metal or metal oxide nanostructures (rhodium, iridium, tin or molybdenum and tungsten oxides) will be intentionally introduced to the electrocatalytic interface. We are also going to demonstrate that catalytic activity of platinum-based nanoparticles can be significantly enhanced through their interfacial modification with ultra-thin monolayer-type films of mixed-metal-oxo-species of titanium, cerium, zirconium or molybdenum and tungsten in their simple and polyoxometallate forms Remarkable increases of electrocatalytic currents measured under voltammetric and chronoamperometric conditions have been observed. The most likely explanation takes into account possibility of specific interactions of noble metals with transition metal oxide species as well as existence of active hydroxyl groups in the vicinity of catalytic noble metal sites. It is noteworthy that certain metal and mixed-metal oxides can generate –OH groups at low potentials: they induce oxidation of passivating CO adsorbates (e.g. on Pt) or breaking C-H bonds (e.g. during oxidation of methanol or dimethyl ether). When combined with dispersed Rh or Ir, immobilized in the organized manner in the vicinity Pt sites, they tend to weaken C-C bonds during ethanol oxidation.

We will also demonstrate that deposition of Pt and bimetallic PtRu nanoparticles onto nanostructured zirconia support results in the enhancement of their catalytic activities toward electrooxidation of dimethyl ether, another possible alternate fuel. Once more, it is reasonable to expect that the abilities of zirconia to facilitate proton mobility and to donate active hydroxyl groups at the electrocatalytic interface in acid media are responsible for the observed enhanced catalytic effects. Specific interactions with platinum and ruthenium components are also postulated.
Modeling Standing Waves in a Thin Layer Sonoelectrochemical System
Authors: Landgren Jeffrey , Strohmer Gerhard , Leddy Johna
Published: February 2020

Recent experiments in thin layer (cell height 1 cm) sonoelectrochemistry demonstrate that sonication increases the rates of electrocatalysis. Heterogeneous electron transfer rates increase substantially upon ultrasound irradiation. A model is developed using Partial Differential Equations and the Galerkin Method (Finite Element Method) to understand catalytic effects observed when sound waves are applied in a thin layer electrochemical cell.

The cell consists of a hollow Teflon cylinder with a transducer. A three electrode system is used with the electrodes spaced equally apart and parallel to the cylinder base. The cylinder is filled with a redox probe and electrolyte solution such that a meniscus forms at the top. The transducer propagates sound waves through the solution (i.e., sonication). A comparison of cyclic voltammograms before, during, and after sonication reveals enhancement effects from the sound waves. For redox probes with slow kinetics, sonication simultaneously increases currents and appears to shift the reaction to more reversible. Data indicate that a combination of the height and shape of the meniscus play a vital role in this enhancement effect.

Numerical analysis is used in conjunction with partial differential equations to develop the model. It takes into account the shape and height of the meniscus as well as the pressure, density, elasticity, mass, and surface tension of the fluid near the meniscus. The model then reveals the standing waves of the system. Standing waves occur in a stationary medium when waves are traveling in opposite directions and cause interference with one another. In general, if this scenario occurs with waves of approximately the same amplitude there is no net change in energy, another indication that the height of the meniscus is relevant.

To help quantify this phenomenon, four equations are used. Among them are two common equations used in fluid mechanics, a conservation of momentum equation (Compressible Euler Equation), a conservation of mass equation, a boundary motion equation, and an equation that describes the surface tension on the meniscus. The boundary motion equation includes a term that describes the position of the surface. The Galerkin Method is used to convert our continuous problem to a discrete one via the weak formulation with a proper basis. A reduction of the wave equation to an eigenvalue problem gives way to our standing waves. The wave interference taking place in the cell can be seen the provided picture.

This model is important for prediction of behavior of the sound waves before and after they contact the top boundary and the role of the meniscus convexity. The model proves that the sound waves contact the meniscus and are then reflected back down into solution. Lastly, the model provides all possible standing waves in the cell. This will lead to advances in understanding the experimental system for applications in electrocatalysis.

Figure 1
Rapid and Selective Determination of Acetaminophen in Surem Via Intermolecule Hydrogen Bonding with Arginineon Graphene
Authors: Zhang Yan , Huang Zhongyuan , Wang Zhe
Published: February 2020

An electrochemical sensor based on arginine (Arg) functionalized graphene (Arg-G) nanocomposite was fabricated for sensitive detection of acetaminophen. The nanocomposite was characterized by transmission electron microscopy (TEM), Raman spectra etc. The electrochemical behaviors of acetaminophen on Arg-G composite film modified glassy carbon electrode (GCE) were investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The experimental results indicated that the incorporation of arginine and graphene greatly enhanced the electrochemical response of acetaminophen. This fabricated sensor displayed excellent analytical performance for acetaminophen detection over a range from 0.1 to 100 μmol L−1 with a detection limit of 0.05 μmol L-1 (S/N=3). Moreover, the proposed electrochemical sensor also exhibited good reproducibility and stability, and has been used to detect acetaminophen in tablets and in mouse surem with satisfactory results.

Figure 1
Nano-Architected 3D Ultra Low-k Dielectrics
Authors: Lifson Max L. , Kim Min-Woo , Kim Bong-Joong , Greer Julia R
Published: February 2020

Low-k dielectric materials have become increasingly critical to the semiconductor industry as the interconnect delay becomes an overwhelming portion of the total device signal delay. Many attempts at lowering the dielectric constant involve using organic materials or introducing stochastic porosity; these solutions often lack the mechanical resilience that is necessary for devices to survive in-use operation and introduce challenges for integration within traditional semiconductor processing.

We demonstrate the fabrication of a 3-dimensional nano-architected low-k dielectric material that is comprised of hollow alumina tubes and contains 99% air. It has a stiffness of 30MPa and a dielectric constant well within the ultra low-k regime (below 2.0). We utilized two-photon lithography direct laser writing followed by atomic layer deposition to create these architectures. In addition to the low dielectric constant and high mechanical stiffness, these structural meta-materials exhibit exceptional energy absorption when uniaxially compressed and favorable electrical breakdown properties.
Characterization of Scaling in Ultra-Thin Poly-Si and Analysis of the Scaling Limit of Thin Film Thickness
Authors: Lee Hwan , Park Jin-Hong
Published: February 2020

Ultra-thin poly-Si channel has been widely studied and has already been adopted commercially by semiconductor manufacturers due to its short channel effect suppression and sub-threshold swing improvement. It is well known that the threshold voltage, VTH, increase as the poly-Si thickness, ts, is scaled below 10nm, due to quantum-mechanical (QM) effects. Although experiment results of VTH demonstrated identical behavior of increasing as ts was scaled, but the measured absolute VTH show significantly larger value than the expectation. The major problem of abrupt VTH increase is that it degenerate VTH distribution, which would cancel out merits of ultra-thin poly-Si device on high speed performance. Simulation results show the abrupt VTH increase is caused by a combined effect of bulk and front/back interface trap charges. As scaled down, yet the bulk trap density decrease, VTH is increased as it is overturned by front and back interface trap charge effects. Compared to front interface trap charges, back interface trap charges have larger influence on VTH. Since device with ts below 10nm is fully depleted before the gate voltage reaches VTH, the additional electric field formed across the poly-Si channel parallel shifts the band downwards. So the more parallel shifted the band is, the more additional portion of the front and back interface is filled with negative charge. As a result back interface charges increase VTH. The closer it gets to the channel, greater the influence become. It is quite clear why back interface trap charges contribute more to the VTH, compared with front interface trap charges. The simulation results considering bulk and front/back interface trap effects showed a good match experiment results. Considering the abrupt VTH increase and variation of poly-Si deposition process, the fundamental criterion of poly-Si thickness scaling limit should be no lower than 5nm.
Enhanced Thermal Durability with High Performance Lanthanum Nickelate Cathode Materials for Intermediate Temperature Solid Oxide Fuel Cells
Authors: Lee John In , Yang Jayoon , Kim Youdong , Park Jun-Young
Published: February 2020

Solid oxide fuel cells (SOFCs) have been regarded as a promising the energy conversion device from chemical energy of fuel, because of numerous advantages, such as high energy conversion efficiency, multi fuel capability, and no emission of pollutants [1]. Co-based perovskite oxides have spotlighted. For the cathode materials of SOFCs due to low over-potential for the oxygen reduction reaction (ORR), thus resulting in high performance of SOFCs [2]. However, the large dissimilarity of thermal expansion coefficient (TEC) between Co-based perovskites and typical yttria-stabilized zirconia (YSZ) and samarium-doped ceria (SDC) electrolytes result in degrading of long-term durability of SOFCs. The TECs’ of Co-based perovskite oxides are but the general electrolyte, such as YSZ’s TEC is and, indicating a huge difference between them [3].

Meanwhile, lanthanum nickelate, Lan+1NinO3n+1, may have high thermal stability than Co-based perovskites, because the TEC of Lan+1NinO3n+1 is , similar to the YSZ electrolyte [4]. In this work, hence anode-supported cells are fabricated with SDC electrolytes, Ni-cermet anode, and lanthanum nickelate cathode. To investigate the performance and durability of cathode materials, I-V measurements and load cycling testing methods are used to check the performance and durability of cells. The electrochemical impedance spectroscopy measurements are also performed for the electrochemical analysis. In addition, various physicochemical analysis tools are used, such as SEM, TEM, and XRD as the postmortem analysis [5].

References

[1] K.T. Lee, E.D. Wachsman, Science 334 (2011) 935.

[2] E. Boehm, J.-C. Grenier, Solid State Sciences 5 (2003) 973.

[3] S. Pang, X. Xi, J. Power Sources 326 (2016) 176.

[4] R.K. Sharma, E. Djurado, J. Power Sources 325 (2016) 337.

[5] T.H Lee, J.-Y. Park. J. Power Sources 331 (2016) 495

Keywords : Solid oxide fuel cells; Lanthanum nickelate; Thermal Expansion Coefficient; Durability

* Corresponding authors: jyoung@sejong.ac.kr (J.-Y. Park)
A Molecular Dynamics Study of Interfacial Structure and Ion Transport of Mixed Carbonate/LiPF6 Electrolytes Near Graphite Electrode Surfaces
Authors: Boyer Mathew J , Hwang Gyeong S
Published: February 2020

Electrolyte and electrode materials utilized within lithium ion batteries have been extensively studied as separate segments, however the structural and dynamical properties of the electrode/electrolyte interface remain relatively undefined their immense role in dictating cell performance. By utilizing molecular dynamics simulations, we examine the structural reorganization of solvent molecules (cyclic ethylene carbonate: linear dimethyl carbonate 1:1 and 1:3 molar ratio doped with 1M LiPF6) upon the immersion of a graphite anode at various charge states. The interfacial structure was found to be sensitive to the molecular geometry and polarity of each solvent molecule as well as the surface structure and charge distribution of the negative electrode. An in depth analysis of the rearrangement of molecules at the anode/electrolyte interface elucidates structural influence on ion transport of both Li+ and fully or partially decomposed solvent molecules in order to better understand transient electrochemical processes which occur at this interface during the early stages of the SEI formation. The coupling of enhanced sampling techniques, such as metadynamics, with equilibrium structural data provides a computational framework for studying these processes at their onse,t which may further assist in efforts to engineer the anode/electrolyte interface leading to an optimal SEI layer.
A Group Additivity Based-Thermodynamic Analysis of a Conceptual Glycerol/Ferric Redox Flow Battery
Authors: Akrasi James , Kalu Egwu Eric , Yeboah Yaw D.
Published: February 2020

The electrochemical oxidation of glycerol has been studied and known to be a source of several chemicals of premium industrial value and has also been utilized in the concept of direct glycerol fuel cells to produce electrical energy additionally[1]. In the current study however, this concept is extended to cover both electrochemical oxidation and reduction of glycerol as a substitute for the hydrogen ion in redox flow battery with a Fe2+/Fe3+ couple as cathode [2]. A predictive thermodynamic analysis has been developed and applied to the study and proof of this conceptual glycerol redox flow battery. Reactions toward electrochemical formation of several partial oxidation and reduction products of glycerol in acidic media under discharge and charging conditions of the proposed glycerol flow battery are presented. Free energy values of the reaction species as estimated by the Group Additivity Value (GAV) method were used to determine the feasibility of these proposed reaction towards cogeneration of electricity and commodity chemicals. The equilibrium voltages representing the maximum electrical work under these conditions are also computed. Experimental validation of this theoretical concept has also been investigated using electrochemical methods to study the electro-catalytic activity of electrolessly deposited NiCuSnP supported on carbon towards glycerol oxidation in acidic medium as anode in a proton exchange membrane-glycerol redox flow battery.

Li W., Xin L., Zhang Z., Wang Z.,. (2012) Simultaneous Generation of Mesoxalic Acid and Electricity from Glycerol on a Gold Anode Catalyst in Anion-Exchange Membrane Fuel Cells ChemCatChem Vol 4 1105-1114

Khalid Fatih K, Wilkinson D., Moraw F., Ilicic A and Girarda F Advancements in the Direct Hydrogen Redox Fuel Cell Electrochemical and Solid-State Letters, 11 2 B11-B15 (2008)

Figure 1
Degradation Mechanisms of a Cermet Anode for Aluminum Production
Authors: Meyer Pauline , Gibilaro Mathieu , Chamelot Pierre , Massot Laurent
Published: February 2020

Aluminum production is made by alumina electrolysis (Al2O3) in a molten mixture of cryolite (Na3AlF6-AlF3-CaF2-Al2O3) at high temperature (960°C), between a liquid aluminum cathode and a carbon reactive anode:

2Al2O3(cry) + 3C(s) → 4Al(l) + 3CO2(g)

As the production of one ton of aluminum causes emission of 1.2 tons of CO2 [1], an inert anode is under development to form O2.

Anodes made of iron and nickel mixed spinel oxides have been studied since the 80's. As spinel oxides have no sufficient electrical conductivity, addition of a metallic phase was proposed in the 80's, creating the so-called CERMET (CERamic – METal), with a metallic phase (Ni, Cu and Fe) and a conductive oxide phase (NixFe3-xO4 & Ni1-xFexO). In the spinel structure, tetrahedral and octahedral sites are occupied by ions of different valences (eg: Fe2+/Fe3+), creating an electrical conduction thanks to an electron hopping phenomenon.

CERMET anodes were tested at 0.8A/cm² for different durations (from 30min to 8h) and analyzed by SEM, coupled with the energy-dispersive x-ray spectroscopy (EDX). First experiments revealed both chemical and electrochemical degradation: dissolution of the oxide phase and oxidation of the metallic phase.

To investigate this complex system, experiments without polarization were firstly performed. Results showed that the dissolution of oxide phase is due to a significant substitution phenomenon between Al3+ in the electrolyte and Fe3+ in the spinel phase [2], leading the formation of a soluble aluminate NixFe3-x-yAlyO4. To study the Al3+ impact on the aluminate formation, LiF-CaF2 solvent was selected and Al3+ ions were added as a solute at different concentrations. It was demonstrated that the degradation rate of the oxide phase increases with the Al3+content and was estimated by measuring the amount of dissolved oxide phase (Optical Microscopy) vs the immersion duration in the electrolyte.

Then, studies under galvanostatic electrolysis were carried out and new phases were identified: FeF2, Cu2O and Ni1-x-yFexCuyO monoxide.

Thanks to these observations and thermodynamic calculations, a global degradation mechanism of the anode was proposed.

[1] K.C. Grjotheim, C. Krohn, M. Malinovsky, K. Matiasovsky, J. Thonstad, "Aluminium electrolysis: the chemistry of the Hall-Heroult process", Aluminium Verlag, Düsseldorf, 1977.

[2] B. Gillot, A. Rousset, "On the limit of Aluminum substitution in Fe3O4 and γ-Fe2O3", Phys. Stat. Sol, 1990.
Macroporous Carbon Nanotube (CNT) Foams As Lithium Air Battery Cathodes
Authors: Shen Chao , Liu Teng , Zhang Mei , Zheng Jim P. , Hendrickson Mary A. , Plichta Edward J.
Published: February 2020

In recent years Lithium air (Li-air) battery has attracted considerable attention mainly due to its extreme high specific energy1,2. The theoretical specific energy is estimated up to 3,000 Wh kg-1, which is approximately one order of magnitude higher than that of conventional Li-ion battery3. The cathode of Li-air battery is chosen as porous carbon material in most studies, which plays a significant role of Li2O2 storage and electron transfer. Good electronic conductivity, fast oxygen diffusion, stable mechanical integrity and sufficient surface area and porosity are required for Li-air battery cathode4.

In this study, a simple and scalable method for manufacturing three-dimensional carbon nanotube (CNT) foams as the Li-air battery cathode was being reported. CNT foams were synthesized using poly(methyl methacrylate) (PMMA) microspheres as a template and Polyacrylonitrile (PAN) as a precursor to create crosslinks among CNTs5,6. The tunable porosity and major pore size afford the opportunity to estimate the influence of cathode pore structure with controlled configuration and properties. A series of CNT foams with high porosity and desired major pore size were tested as cathodes in Li-air cells for single galvanostatic discharge performance. As shown in Fig. 1, the cathode with major pore size of 6 μm achieved a specific capacity over 10,000 mAh g-1 at a current density of 0.13 mA cm-2. Meanwhile, a direct inverse correlation between cathode major pore size and cell discharge specific capacity was observed. The electrochemical performance was combined with microscopy, porosimetry and modeling for further discussion. The results revealed that discharge product of Li2O2 were mainly deposited in micro-size pores and the reduced pore size favored the discharge reaction due to the increased volume specific surface area.

1. N. Akhtar and W. Akhtar, Int. J. Energy Res., 39, 303–316 (2015).

2. N. Imanishi and O. Yamamoto, Mater. Today, 17, 24–30 (2014).

3. J. P. Zheng, R. Y. Liang, M. Hendrickson, and E. J. Plichta, J. Electrochem. Soc., 155, A432-A437.

4. J. Lu, L. Li, J. Park, Y. Sun, F. Wu and K. Amine, Chem. Rev., 114, 5611–5640 (2014).

5. Y. Cui and M. Zhang, ACS Appl. Mater. Interfaces, 5, 8173–8178 (2013).

6. Y. Cui and M. Zhang, J. Mater. Chem. A, 1, 13984-13988 (2013).

Figure 1