bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Manipulating Carrier Polarization in Semiconductor Nanocrystals
Authors: Zhang Chenwei , Yin Penghui , Radovanovic Pavle V
Published: December 2020

Degenerately-doped semiconductor nanocrystals exhibiting tunable localized surface plasmon resonance (LSPR) have attracted significant attention in recent years due to their unique optoelectronic properties. Unlike noble metal nanoparticles, colloidal plasmonic semiconductor nanocrystals have LSPR frequencies tunable in the infrared region, which makes them appealing for terahertz imaging, heat-responsive devices, and surface-enhanced infrared spectroscopic measurements. Besides expanding the LSPR frequency range, plasmonic semiconductor nanocrystals could potentially bring about numerous other opportunities related to single-phase plasmon-exciton interactions. However, non-resonant nature of the LSPR and exciton in semiconductors has been a major obstacle toward realizing such opportunities. In this talk I will discuss the results of our recent work on the structure and composition dependent plasmonic properties of colloidal semiconductor nanostructures. I will particularly focus on generating robust excitonic splitting in degenerately-doped transparent metal oxide nanocrystals, enabled by non-resonant plasmon-exciton coupling in an external magnetic field. This phenomenon allows for controlling carrier polarization in semiconductor nanocrystals using circularly polarized light. Furthermore, the ability to control carrier localization and nanocrystal morphology allows for further manipulation of the excitonic splitting pattern and quantum states in these non-magnetic semiconductor nanostructures. Possible applications of this emerging class of multifunctional materials for new electronic and quantum information technologies will also be discussed.
(Invited) Area-Selective Spatial ALD of SiO2 Interleaved with Etch-Back Supercycles: Quantification of Area Selectivity By Low Energy Ion Scattering
Authors: Mameli Alfredo , Brüner Philipp , Roozeboom Fred , Grehl Thomas , Poodt Paul
Published: December 2020

Area-selective ALD interleaved with etch-back steps in a supercycle fashion has recently been reported as very effective in achieving high selectivity. Such supercycles can result in lower defectivity on the non-growth area and thicker layers on the growth area, as compared to solely area-selective ALD.1, 2

Here, we use low energy ion scattering (LEIS) to probe the selectivity of the first supercycle, consisting of plasma-enhanced selective spatial-ALD of SiO2 and conventional CF4-based reactive ion etching (RIE). Given its extreme sensitivity to the top monolayer(s) of a thin film, LEIS can reliably quantify the selectivity/defectivity on the non-growth areas in terms of surface coverage and derived thickness.

A three-step approach was used for the area-selective spatial ALD of SiO2,3 which consisted of inhibitor, silicon precursor (BDEAS), and O2 plasma exposures. The process selectivity as a function of the number of cycles was probed using LEIS to monitor the SiO2 surface coverage on the non-growth area. After 20 spatial ALD cycles, no silicon was detected on the non-growth area (detection limit 2 % SiO2 surface coverage), implying excellent process selectivity. Increasing the number of ALD cycles resulted in a gradual loss of selectivity. Interestingly after 110 ALD cycles, the SiO2 coverage was 86%, indicating a not yet closed layer. At the same time, a SiO2 thickness of 11 nm was measured on the growth area, using spectroscopic ellipsometry. As the last step of the super-cycle, a 3 seconds RIE was sufficient to bring the SiO2 coverage back to zero on the non-growth area, while an 8 nm thick SiO2 layer was left on the growth area.

The data presented in this work demonstrate the effectiveness of combining area-selective spatial ALD + etch-back corrections to achieve extreme SiO2 selectivity while retaining high deposition rates. Finally, we have extended the plasma-enhanced area-selective spatial ALD of SiO2 to other oxides and metals non-growth areas.

REFERENCES

1. R. Vallat et al., JVSTA, 35, 01B104 (2017).

2. S. K. Song et al., Chem. Mater. 31 4793-4804 (2019).

3. A. Mameli et al., ACS Nano, 11, 9303-9311 (2017).

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(Invited) Intercalation Chemistry of Oxides
Authors: Manthiram Arumugam
Published: December 2020

The lithium-ion battery technology is based on intercalation chemistry phenomenon. The 2019 Chemistry Nobel Laurette Stanley Whittingham was the first to show in 1976 how the intercalation phenomenon can be utilized to realize a rechargeable lithium battery. He demonstrated the concept with a lithium-metal anode and a layered titanium sulfide cathode. Since then the field of intercalation chemistry for electrical energy storage has evolved during the past four decades, encompassing a variety of materials and intercalation working ions, such as monovalent lithium, sodium, and potassium, divalent magnesium, calcium, and zinc, and trivalent aluminum ions. Among the intercalation materials, oxides are at the forefront with rich fundamental structural chemistry and electrochemistry as well as with profound technological and societal impact. Accordingly, this presentation will focus on the richness and complexities of the intercalation chemistry of transition-metal oxides.

The scientific and technological impact of the intercalation chemistry of oxides is illustrated by the three families of cathodes for practical lithium-ion batteries: layered oxides, spinel oxides, and polyanion oxides. The presentation will first provide a comparison of these three families of oxides, pointing out the pros and cons with respect to employing them as electrodes in rechargeable batteries as well as their limiting features from a fundamental solid-state chemistry point of view. Particularly, the structural and chemical features that impact the charge-storage capacity, operating voltage, rate capability, and practical energy density will be discussed.

As we move forward, the layered oxide cathodes have become the prime candidates from an energy density consideration point of view, particularly for portable electronics and electric vehicles. However, bulk and surface instabilities during charge-discharge limit their practical energy density and cycle life, while the use of significant amounts of cobalt in them poses concerns on sustainability, cost, and supply-chain issues. Therefore, the presentation will then focus on layered oxide cathodes with high nickel contents and very low or no cobalt content to increase the energy density and lower the cost. Particularly, the role of modifications in chemical compositions through cationic substitutions on the cycle, thermal, and air instabilities will be discussed from a fundamental solid-state chemistry point of view. The use of advanced analytical techniques, such as in-situ x-ray diffraction, x-ray photoelectron spectroscopy, time of flight secondary ion mass spectrometry, scanning electron microscopy, high-resolution transmission electron microscopy, and differential scanning calorimetry in understanding the intricacies of the cathodes and mitigating the problems will be presented.
Welcome Remarks - D01: Semiconductors, Dielectrics, and Metals for Nanoelectronics and Plasma Nanosciences
Authors: Misra Durga
Published: December 2020

Welcome to D01: Semiconductors, Dielectrics, and Metals for Nanoelectronics and Plasma Nanosciences! Take a moment to listen to welcome remarks from the lead organizer, Durgamadhab Misra.
Enhancement of Thermal Transfer Efficiency on Electronic Equipment with Robust Copper Oxide Layer on Copper Substrate
Authors: Chung Wonsub , Park Junghyun
Published: December 2020

Electrodeposition and oxidation heat treatment were used for robust copper oxide layer on copper substrate to enhance the thermal transfer efficiency of electronic devices. The electrodeposition solution was modified to obtain rough and robust surface from copper ion concentration control compared to conventional electrodeposition solution. And oxidation heat treatment was optimized to formed dense copper oxide layer such as Cu2O and CuO. Fourier transform infrared spectroscopy (FT-IR) was used to measure the emissivity for thermal radiation performance at 50 ℃. Laser flash analysis (LFA) and Differential scanning calorimetry (DSC) were utilized to measure thermal diffusivity and specific heat capacity, respectively, thereby thermal conductivity of each specimen was calculated. Adhesion strength of deposited layer was evaluated by adhesion test and compared to general copper oxide layer which easily removed. In addition, the heat dissipation performance of specimen was evaluated with light emitting diode (LED) module. The electrodeposited copper substrate was attached to the LED module and directly estimated heat dissipation that applied actual devices. In conclusion, the modified electrodeposition and oxidation heat treatment surface on copper substrate shows a significant improvement of the thermal transfer performance due to enhanced thermal diffusivity and thermal radiation property.
Exploration of Photo and Electrochemical Studies with an Efficient Electrocatalyst on Fluorinated BiVO4 Photoelectrode for Photoelectrochemical Water Splitting
Authors: Kang Soon Hyung
Published: December 2020

Photoelectrochemical (PEC) water splitting to produce clean hydrogen provides a desirable approach to solve the global environmental and energy problems. Bismuth vanadate (BiVO4) has emerged as one of the most promising photoanode materials for oxidizing water due to its visiblelight activity and low cost. However, BiVO4 photocatalyst has suffered by the slow charge separation kinetics at solid/electrode interface that limits the photoelectrochemical performance. In order to minimize the poor properties, we modified the BiVO4 with an effective electrocatalysts, which was investigated experimentally under light illumination. The subsequent addition of electrocatalysts as an effective oxygen evolution catalyst subsequently reduces the large overpotential and generates the higher photocurrent. The charge transfer properties of the photoelectrodes can be effectively tuned by controlling the electrocatalysts loaded, thereby optimizing PEC performance. Electrochemical impedance spectroscopy (EIS) evidenced that the deposition of electrocatalysts can substantially lower the charge transfer resistance at the semiconductor interface. Furthermore, the advantages and drawbacks of catalyst deposition routesand the role of photoelectrochemical and advanced spectroscopic techniques for elucidation of the mechanism of the photo catalytic action will be discussed in detail.
Freestanding TaN Nanotubular Architecture Based Photoelectrochemical Behavior
Authors: Kang Soon Hyung
Published: December 2020

Nowadays, the exploration of new photoelectrode architectures to improve the light-harvesting and charge-collection properties of photoelectrochemical cells and related devices have been regarded as a challenging work. Here, we prepared the TaN nanotubular architecture for photoelectrochemical water splitting by RF sputtering and electrochemical anodization. Free-standing TaN nanotube electrode showed the great light harvesting in the visible light, showing the potential PEC performance.

Herein, it is expected that an optimal TaN layer takes part in a role as a photoactive material. Furthermore, the materials combination should be considered to make a synergetic effect to overcome the original weak points of each material. Therefore, the electrocatalysts based on photoelectrode can be suggested using the visible-active TaN and Ag materials.
Facile Fabrication of Ir-Based Gas Diffusion Electrode for Proton Exchange Membrane Water Electrolyzer
Authors: Oh Jeong Hyun , Han Gyeong Ho , Ahn Sang Hyun
Published: December 2020

A production of clean energy is needed to to solve an environment problem and reduce our dependence on fossil fuels. Hydrogen (H2), recognized as one of the most promising clean energy has attracted considerable attention. H2 is generated by a water splitting. Specifically, H2 and oxygen (O2) are electrochemically created from cathodic hydrogen evolution reaction (HER) and anodic oxygen evolution reaction (OER) through the water splitting, respectively. The efficiency of water splitting is dependent on anodic OER required to high overpotential (η) due to slow kinetics of OER. An effective strategy to reduce the high η is critical to develop efficient catalysts reducing high η required toward OER. The operation of the Proton Exchange Membrane Water Electrolyzer (PEMWE) has been challenged by low stability and activity of the catalyst for OER in an acidic environment. Herein, a strategy controlling of iridium (Ir) valency through various oxidation methods is proposed that OER catalysts exhibit specific high performance and excellent durability in acid electrolytes. Metallic Ir is made by galvanic displacement caused by the difference of chemical reduction potential. From the metallic Ir, electrochemical (EC) and thermochemical (TC) IrOx are created by applying repeated Cyclic voltammetry (CV) in specific potential range and by heat-treating at 400 °C in air atmosphere, respectively. Metallic Ir, EC and TC IrOx exhibited the overpotential as 261, 270 and 284 mV at 10 mA/cm2, respectively. Especially, metallic Ir and TC IrOx have been maintained the initial performance for 60 h in step-by-step durability tests at 10, 50, 100 mA/cm2. We demonstrated that the performance toward OER is directly affected Ir valency ratio with Ir3+ and Ir4+ related to intrinsic activity and durability, respectively. Thus, a strategy to control the suitable Ir valency to be promising OER catalyst has critical to achieve a balanced activity and stability.
Electrochemical Fabrication of MoOx@NiMo Heterostructure Catalysts for Hydrogen Evolution Reaction
Authors: Park Juhae , Kim Hyunki , Han Gyeong Ho , Ahn Sang Hyun
Published: December 2020

In spite of environmental contamination due to the indiscriminate fossil fuel use, energy demand is rapidly increasing globally. The world is focusing on research on clean and renewable energy resources that do not emit pollutants. Among them, hydrogen has been referred to as a rising energy resource because its large energy density and zero carbon footprint. Water electrolysis is considered to be one of the most efficient methods of producing hydrogen in high purity. The water electrolysis is composed of the cathode where hydrogen evolution reaction (HER) occurs and the anode where oxygen evolution reaction (OER) occurs. Pt is well known as a catalyst for good performance in cathode, but there are problems of shortage and high cost. Therefore, there are many studies on non-noble metal, especially about transition metal. In addition, researches on catalysts with heterostructure that have good performance in HER have been conducted. However, some catalysts with heterostructure have the disadvantage of being manufactured over a long period of time at high temperature and high pressure. There is an electrodeposition method to solve this problem. Electrodeposition method has the advantage of adjusting morphology, structure and composition variously by easily controlling variables such as concentration of precursor in deposition bath, deposition time, and voltage, using only a small amount of time and energy.

In this study, we fabricated heterostructure MoOx@NiMo catalysts by electrodeposition method. First, NiMo with various ratios was electrodeposited by varying Ni concentration in deposition bath. Secondly, surface of NiMo was etched by applying constant potential. In this way, excess Ni on surface removed and Mo was oxidized to MoOx which plays a crucial role on HER catalytic activity, and heterostructure of core and shell was manufactured easily. The heterostructure of catalyst was confirmed by transmission electron microscopy (TEM). Through X-ray photoelectron spectroscopy depth profile (XPS), core composition was determined. And the effect of the core composition on the intrinsic activity was investigated. After leaching, the Mo oxidation state and crystal structure generated on the surface were scrutinized through TEM. In addition, using XPS, we identified the ratio of Mo oxidation state on the surface and confirmed how the ratio of MoOx affects performance. Consequently, catalyst with Ni/Mo ratio of 2.6 in core showed the highest intrinsic activity, and when more MoO2 is formed on surface, the catalyst showed higher intrinsic activity. Also, HER activity and stability of all catalysts were evaluated in acidic media.
(Invited) Dendritic Lithium Electrodeposition: A New Mechanistic Perspective Investigating Li+ Transport Limitations Imposed By the SEI
Authors: Maraschky Adam , Akolkar Rohan
Published: December 2020

High-energy density batteries are essential for powering future electric vehicles and electric aircraft. The Li-metal anode offers the highest theoretical specific capacity among practically available anode materials. One major obstacle in the development of secondary Li-metal batteries is the dendritic electrodeposition of Li during the battery charging process. In this contribution, we report on our investigations of the onset time of dendritic growth during galvanostatic electrodeposition of Li metal. Using a combination of electrochemical and optical microscopy techniques, we observe that Li dendrites initiate at a time when the surface overpotential during galvanostatic electrodeposition reaches a maximum value. The dendrite onset time (τonset) is shown to increase with increasing temperature and decrease with increasing current density and initial solid electrolyte interphase (SEI) thickness. These observations guide the development of an analytical transport model wherein the Li+ concentration available for plating decreases gradually within the SEI as it becomes thicker during electrodeposition. At t = τonset, the mobile Li+ concentration at the Li–SEI interface approaches zero. Due to this Li+ concentration depletion, surface roughness on the Li electrode amplifies, eventually producing dendrites. Once dendrites form, they rupture the SEI, lowering the surface resistance for Li plating. Model predictions of how τonset varies with current density, initial SEI thickness, and temperature are found to be in qualitative agreement with experimental observations. The analytical model explains mechanistically how transport limitations within the SEI control the onset time of dendrites during Li electrodeposition. Our results highlight the critical need for SEI materials that suppress or eliminate solid-state Li+ concentration gradients, which are responsible for dendrite initiation during Li-metal battery charging.
Core-Shell-Type Carbon-Coated Lithium Titanium Oxide Composites Derived from Ti-Based Metal Organic Framework As Anode Materials for Lithium Secondary Batteries
Authors: Kim Tae Woo , Yoon Chang Sick , Jang Bo-yun , Kim Hyunuk
Published: December 2020

Lithium titanium oxide, Li4Ti5O12 (LTO), is one of the most promising anode materials for Li secondary batteries. Although it has a lower specific capacity of approximately 175 mAh/g than does graphite (372 mAh/g), this material shows the unique property of the negligible lattice change in the Li-ion insertion/desertion process, providing excellent high-rate cycling stability. The biggest obstacles of limiting the application of LTO material electrode are poor electrical conductivity and low lithium-ion diffusion coefficient. To overcome these problems, in this work carbon-coated LTO (LTO/C) composites with core-shell-type structure are synthesized and it is derived from Ti-based metal organic framework (Ti-MOF). For the synthesis of the LTO/C composites, Ti-MOF was chemically lithiated by n-BuLi and heated at different temperature (500-800 oC) in an inert atmosphere. According to powder X-ray diffraction analysis, the as-lithiated sample shows an amorphous structure, and the LTO structure is generated after heat-treatment of above 600 oC. Transmission electron microscopy clearly shows core-shell-type LTO particles surrounded by carbon layers with a thickness of 3-5 nm. The electrochemical measurements clearly demonstrate the promising functionality of the present LTO/C composite as anode for lithium secondary batteries. The LTO/C composite obtained by heating at 700 oC show the largest discharge capacity (cal. 152 mAh/g) with good cyclability. The present experimental findings underscore the validity of the use of MOF as a useful platform for new synthetic strategies of carbon coated LTO materials and also for the improvement of their functionality.
A Simple and Facile Strategy for Fe-Coating on Rare-Earth Permanent Magnet: Exchange-Coupled Magnet Preparation
Authors: Lee Jimin , Yoo Bongyoung , Choa Yong-Ho
Published: December 2020

In modern permanent magnet research, implementation of an exchange-coupling interaction in spring magnets that are composed of more than two kinds of magnetic materials (e.g., Sm-Co@Fe) with core-shell architecture is a major direction to afford an enhanced magnetic performance far beyond those of the single-phased counterparts. Many efforts have been made to synthesize exchange-spring nanomagnets with conventional physical techniques such as electroless deposition, however, an ideal realization of the exchange-coupling effect has been hampered by a variety of restrictions. Moreover, even the use of a strong acidic/basic solution for electroless coatings causes fast oxidation of the metallic magnets and at worst, phase decomposition into a non-magnetic phase because metal magnets are vulnerable to harsh process conditions. Therefore, the great challenge remains hitherto to prepare binary-phased spring magnets possessing an ideal exchange-coupling interaction. Herein, we report a streamlined spring magnet preparation based on NH4F-assisted direct displacement. By turning a byproduct (i.e., CaO) obtained during Sm-Co preparation process into an initiator for Fe-coating under neutral solution condition, uniformly nanoscale Fe layer was successfully deposited onto the surface of a Sm-Co magnet, while Ca-based byproduct was selectively rinsed out by NH4F, which is employed as Ca2+ scavenger. This is the first report about the direct Fe-plating process on rare-earth magnet, which enabled it without a use of catalysts or such strong acidic/basic solution.

Figure 1
Fabrication of Expanded Layered Double Hydroxide for Toxic Anion Elimination
Authors: Song Yoseb , Yoo Su-been , Park Ji Young , Choa Yong-Ho
Published: December 2020

Layered double hydroxide (LDH), known as a toxic ion absorber, is layered structured material composed by metal hydroxide cation layer and anion layer. As followed process, LDH can selectively absorb cations or anions such as As5+, Cl-, NO3
- , and so on. This absorption materials have been highlighted as a critical factor to treat of wastewater.

In this research, we suggest new structure of LDH which is called expanded LDH for enhancing anion absorption efficiency. The expanded LDH is synthesized by heat treatment at relatively low temperature than calcined LDH. At heat treatment temperature, water of crystallization and part of anions are eliminated as gases. The cation layer of expanded LDH is partially anchored by remained anions. Because of anchored region, cationic layer is not able to move away freely from another cationic layer. The unique structure of expanded LDH cause recovery to initial LDH structure through anion absorption as refolding process.

Fabricated expanded LDH is characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffractometer, thermogravimetry-mass spectroscopy and Fourier transmission infrared analysis.

Figure 1
Environmental-Friendly Anti-Corrosion Behavior of Cafe Layered Double Hydroxide for the Durability of Concrete Steel Structure
Authors: Park Ji Young , Cho Hong-baek , Choa Yong-Ho
Published: December 2020

The concrete is deteriorated due to corrosion of the reinforcement steel, which is a major problem in field of construction resulting in a huge economic loss and serious safety disasters frequently. The main destruction factor of reinforced concrete durability is chloride penetration, whose penetration into reinforced concrete accelerates corrosion of rebars leading to degradation of the structure. In this study, we fabricate calcium-iron layered double hydroxides (CaFe-LDHs) via facile one-pot synthesis by utilizing a modified co-precipitation method under room temperature and investigate the effect of corrosion protection on rebar from chloride ion. The maximum uptake capacity over 800 mg/g (Cl-/LDH) for chloride ion was obtained by an LDHs, heat-treated at 700℃ of LDHs (C-700 LDHs) which was over 10 times of pristine LDHs. Moreover, when the C-700 LDHs was applied for rebar corrosion, noticeable inhibition efficieny of 98.87% was obtained which was comparing with rebar without LDHs. The mechanism for the enhanced removal performance of chloride ion and anti-corrosion effect is elucidated drawing on the structural transformation of CaFe-LDHs. These observations make the structure modulated CaFe-LDHs as an new outstanding corrosion protection material as an additive or as a coating material in concrete structure in the construction field.
(Invited) Three-dimensional Free-standing Assemblies of Electrodeposited Nanowires for Photoelectrochemical and Catalytical Applications
Authors: Li Mohan , Ulrich Nils , Maimaitituerxunjiang Abudukade , Wagner Michael , Toimil Molares Maria Eugenia
Published: December 2020

The implementation of metal and semiconductor nanostructures in devices for catalysis, sensing, and energy conversion requires an excellent control on geometry, crystallinity and composition of the individual nanostructures, as well as its successful assembly into 2-D and 3-D architectures. In particular, nanowire ensembles offer important advantages compared to planar films including e.g. larger surface area and surface to volume ratio, and better crystalline quality.

Ion-track nanotechnology is a powerful technique to create templates for the controlled synthesis of such 3-D nanowire architectures. Etched ion-track membranes are fabricated in two separate process steps: (i) sequential irradiation of polymer foils from one or various directions with swift heavy ions resulting in the creation of tracks; (ii) converting the ion tracks into nanochannels by selective chemical etching. Channel density and orientation, as well as diameter and geometry are adjusted by the irradiation and etching conditions, respectively. Afterwards, by electrodeposition in the nanochannels and subsequent removal of the polymer template 3-D assemblies of nanowires are synthesized. Since the nanowires adopt the exact shape of the host channel, their diameter can be adjusted between ~15 nm and a few µm, and their length between ~1 and several tens of µm.

In this talk, we will discuss the electrochemical deposition of Au1-xAgx, Cu, and Cu2O in interconnected nanochannel networks, the characterization of the resulting 3-D nanowire assemblies, and the investigation of their photoelectrochemical and catalytical properties.
Characterization of Electrodeposited Cu Interfaces Via Shell-Isolated Nanoparticle Enhanced Raman Spectroscopy
Authors: Raciti David , Moffat Thomas , Hight Walker Angela R.
Published: December 2020

The advent of SERS created a new avenue for investigating interfacial phenomena by coupling the localized surface plasmon resonance (LSPR) of metal nanostructures to the inelastic scattering properties of molecules. Seeing a 104-fold enhancement in Raman signals, SERS scattering events were used to identify adsorbed molecules and substrate-surface structural conformations. But, even with the advent of SERs, Raman spectroscopy was still confined to LSPR active materials with roughened surfaces. However, recent technical modifications to SERS, such as shell-isolation and localized probe modes, have shown potential for the operando investigation of flat non-plasmon active single-crystal surfaces. Shell-isolated Nanoparticle Enhanced Raman Spectroscopy(SHINERS) provides two parallel paths for electric field enhancement of non-plasmon active surfaces while minimizing chemical perturbations by encasing reporters in a chemically inert shell (Figure 1). This technique can be used to perform measurements before, during, and after electrodeposition to gain an understanding for changes at metal-solution interfaces under an applied bias. SHINERS serves as a great utility to not only understand surface adsorbates, but to also characterize how dynamic surfaces respond to surface adsorbates. The precarious nature of metastable surfaces (e.g. metallic Cu) make capturing surface information challenging, preventing accurate structure-activity assignments necessary to fully understand the system. The lack of techniques (operando, especially) capable of evaluating functional interfaces, vs model systems, has further inhibited understanding of surface phenomena. Breaking these limits, will enable novel findings that afford new understanding and strategies to develop refined interfaces and processes. Herein, we report the synthesis of Au@SiO2 core-shell nanoparticles and their application to track the state of interfacial phenomena on electrodeposited Cu surfaces (Figure 1).

Figure 1. Electron microscopy images of Au-SiO2 nanoparticles (a) dispersed on Cu Trenches (b) for shell-isolated nanoparticle enhanced Raman spectroscopy (c) measurements to probe for surface adsorbates, which shows enhancement relative to the bare Cu surface (d).

Figure 1
Conductivity Enhancement of Aerosol Jet Printed Components By Electrodeposition
Authors: Tsui Lok-kun , Kayser Ste-ven Chase , Lavin Judith Maria
Published: December 2020

Additive manufacturing (AM) is an attractive technique in the production of electronic components at lower cost compared to traditional circuit fabrication techniques. Aerosol jet printing (AJP), a direct write technique (Figure 1(a)), uses an atomized mist of gas directed through a nozzle to achieve high resolution (< 10 μm) linewidth prints.[1] A wide variety of inks can be printed including conducting, magnetic, and insulating materials. The standoff distance of 1-5 mm allows for both planar and conformal printing with the aerosol jet. However, the films produced by aerosol jet printing are less conductive than bulk films due to the necessity to sinter nanoparticle inks. Building thick layers to achieve the necessary conductivity is possible, but it is both time consuming and reduces the achievable resolution of the printed part. An alternative approach is to use the aerosol jet printed structure as a seed layer for the deposition of a high conductivity film by electrodeposition.

Aerosol jet printed components were made by printing 20 vol% UTDots Ag40X nanoparticle ink in 60 vol% xylenes and 20 vol% terpineol. Samples were modified by electrodeposition in a Microfab SC Cu bath (17 g/L Cu2+) with a Cu anode. Plating was performed in a 2-electrode configuration. Voltages between -0.4 and -0.5V were applied to the cell. Components modified included a transformer coil (Figure 1(b)) printed on a cylindrical ceramic bobbin. Here, modification of a 1.8 m long conductive coil reduced the resistance from 1.4 kΩ to 10 Ω. Similarly, Cu deposited on Ag traces over a 500 μm step decreased the resistance from 20-400 Ω to < 1 Ω. This technique represents a novel method to achieve both the high conductivity afforded by electrodeposition and the high resolution, low cost patterning of aerosol jet printing.

References: [1] N.J. Wilkinson, M.A.A. Smith, R.W. Kay, R.A. Harris, Int. J. Adv. Manuf. Technol. (2019), 11, 4599-4619. https://doi.org/10.1007/s00170-019-03438-2

Figure 1. (a) Simplified schematic of an aerosol jet printer. (b) Optical microscopy of transformer windings modified by electrodeposition of Cu.

SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.
SAND2020-3906 A

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In-Situ Electrochemical Dilatometry Study for Understanding Volume Changes of the Graphite Electrodes for Lithium-Ion Battery
Authors: Park You Kyung , Park Hyeong-Il , Choi Seong Hoon , Youn Donghan , Kim Hansu
Published: December 2020

In-situ electrochemical dilatometry is applied as an analytical technique to investigate the effect of both solid electrolyte interface (SEI) formation and the microstructure of the electrode on the dilation behavior of the graphite electrodes during lithium ion intercalation at the same time. It was found that the dilation and contraction behavior of the graphite electrode was dependent on the microstructure of the graphite electrode. The relationship between the microstructure, such as preferred orientation of graphite particles and the pore structure, and the volume changes of the graphite electrode were investigated by half-cell type in-situ electrochemical dilatometer during cycling. Dilation behavior of graphite electrodes monitored by in-situ dilatometer clearly showed the volume changes of the graphite electrodes induced by Li ion intercalation/de-intercalation as well as the SEI layer formation, and how the microstructure of the electrodes affects their volume expansion upon lithium ion intercalation. It was also found that differential dilation plots of the graphite electrodes upon lithiation and delithiation gave us more detailed information of dilation and contraction behaviors with respect to the amount of Li ion intercalated into graphite.
Understanding the Performance of Flow-Electrodes for Capacitive Deionization through Hydrodynamic Voltammetry
Authors: Carmona Orbezo Aranzazu , Dryfe Robert AW
Published: December 2020

Flow-electrode capacitive deionization is a promising approach to scale up this desalination technology, because of its ability to regenerate the electrodes outside the main cell, and thereby remove a higher amount of salt from the feed water using carbon slurries as flowable electrodes. Previous works have focused on improving the performance by changing the flow-electrode composition or by proposing different cell designs, using a wide range of volumetric flow rates for the electrode, as well as performing mathematical and experimental modelling considering the slurries as Newtonian fluids. In this work, hydrodynamic voltammetry is used to understand the electrochemical behaviour of the carbon slurries, to develop an optimization method that will give an improved electrochemical performance of the slurries. Results show that the apparent viscosity of the slurries must be considered to explain the behaviour of the slurry within the cell, as well as the effect of shear thinning on the migration of activated carbon particles inside the slurry. A dimensionless number is proposed to define a threshold that will ensure a capacitive behaviour of the flow-electrode.

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Mechanism and Kinetics for the Electrochemical Hydrogenation and Hydrogenolysis of Furfural in Acidic Media over Copper
Authors: May Andrew , Biddinger Elizabeth
Published: December 2020

The use of electrochemical methods provides opportunities for processes that are more sustainable then their non-electrochemical counterparts. Electrochemical processes can operate in modular format and be used to store intermittent energy in the form of produced liquid fuel. One example of a process that can be done electrochemically is the hydrogenation and hydrogenolysis (ECH) of furfural. Furfural is derived from biomass, and through hydrogenation and hydrogenolysis it can be transformed to furfuryl alcohol and 2-methylfuran which are used as a binder and a fuel, respectively. In order for processes such as furfural ECH to move towards use outside of lab research, the kinetics and mechanism must be understood to allow for efficient design of new catalysts and ECH reactors. In this work we provide insights into the kinetics of the process in acidic media and proposed potential mechanisms.

This kinetic analysis was done in acidic media of pH 0 (0.5M H2SO4) over copper flags. The kinetics of the ECH of furfural was investigated by varying the substrate concentration between 10 and 120 mM and potential between -500 and -800 mV vs RHE. The temperature was varied between 15°C to 45°C to develop Arrhenius plots and extract the activation energies of the parallel reactions.

Three mechanisms were derived and compared to the data for the ECH of furfural: non-competitive Langmuir-Hinshelwood, competitive Langmuir-Hinshelwood, and Eley-Rideal, all with the assumption that furfuryl alcohol is not an intermediate species in the formation of 2-methylfuran.
A Tutorial on the Use of Indirect Impedance to Measure Corrosion Activity in Reinforced Structural Components
Authors: Alexander Christopher Lewis
Published: December 2020

Traditional methods capable of measuring the corrosion rate of reinforcing steel in concrete require electrical contact to the steel and are therefore destructive in cases where contact is only accessible through drilled holes into the concrete cover. Studies have shown that the application of an electric field to the surface of an electrolytic medium can indirectly polarize a metal within the solution.1 Based on this concept, an indirect impedance measurement may be used to assess the properties of steel reinforcement within concrete without an electrical contact.2,3 A four-electrode array is placed on the concrete surface and the perturbation signal is applied between the outer two electrodes while the response is measured between the inner two electrodes. As shown in the figure provided, the electrode configuration results in a nonuniform current distribution in which a portion of the injected current goes through the concrete and another portion goes through the steel. The result is an impedance response that while capable of sensing corrosion properties of the steel, is also confounded by the properties of the concrete. Therefore, challenges arise in relating the measured impedance of the system to the impedance of the steel-concrete interface. One of the challenges is establishing the sensing location and polarized surface area of the steel. Another challenge lies in determining the appropriate contribution of the concrete to the measured impedance.

This tutorial will provide a detailed description of the indirect impedance method including experimental design considerations, measurement approaches, analysis methods, and potential complications. A calibration method will be presented to relate the apparent polarization resistance to the actual polarization resistance and therefore circumvent the challenge of quantifying the steel sensing area. The necessary assumptions of the calibration procedure will be described.

C. Andrade, I. Martinez, and M. Castellote. "Feasibility of determining corrosion rates by means of stray current-induced polarisation." Journal of applied electrochemistry 38, no. 10 (2008): 1467-1476.

J. Monteiro, H. Morrison, Non-destructive method of determining the position and condition of reinforcing steel in concrete, 1999. US Patent 5,855,721.

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Figure 1
Lithium Plating Detection Methods in Lithium-Ion Batteries
Authors: Viswanathan Umamaheswari , Garrick Taylor R. , Fortier Mary E
Published: December 2020

Lithium-ion batteries provide a low-cost, long cycle-life and high energy density solution to the expediting energy requirement of the automotive industry. There is a growing need of fast charging batteries for commercial application. However, large charging currents may cause Lithium plating which describes the deposition of metallic Lithium at the anode surface. It takes place at conditions of high currents and/or low temperatures because of kinetic limitations. The main reason behind plating is the slow solid-state diffusion of Lithium ions inside the active material. If the anode surface potential falls below 0 V versus Li/Li+, the formation of metallic Lithium is thermodynamically feasible. To avoid or reduce the amount Lithium plating, it is essential to detect its onset during a charging event.

Determination of accurate Lithium plating curve is crucial in estimating the boundary conditions for battery operation without compromising life and safety. There are various data analysis methods involved in deriving the Lithium plating curve: anode potential using a three-electrode cell, variation of relaxation voltage after charging (dV/dt), variation of accumulated charge with voltage (dQ/dV) and coulombic efficiency of charge/discharge with %SOC (state of charge) are more commonly employed techniques. In addition to these methods, estimation of its occurrence is typically underpinned by electrochemical models where the negative (anode) electrode potential is expressed by a set of partial differential equations based on the electrochemical and physical properties of the battery components such as the electrodes and electrolyte. The present paper reviews the common test methods and analysis that are currently utilized in Lithium plating determination. Knowledge gaps are identified, and recommendations are made for the future development in the determination and verification of Lithium plating curve in terms of modelling and analysis.
Understanding the Lithiation Pathways of Tetrel Clathrates with Synchrotron X-Ray Characterization
Authors: Dopilka Andrew , Childs Amanda , Ovchinnikov Alexander , Bobev Svilen , Chan Candace K.
Published: December 2020

Tetrel clathrates are materials composed of cage-like frameworks of covalently bonded Group IV (Si, Ge, Sn) elements containing guest atoms in the center of each cage. Our group has been investigating the electrochemical properties of Si and Ge clathrates for potential applications as Li-ion battery anodes. Our studies have found that in some cases the Li-alloying pathways are distinctly different in clathrates compared to those seen in the diamond cubic analogs. For example, the Ba8Al16Si30 Type I clathrate does not undergo a Li-alloying reaction [1] while the Ba8Ge43 clathrate does [2]. In the case of Ba8Ge43, the reaction pathway appears to follow an amorphous phase transformation, in contrast to diamond cubic Ge, which undergoes several phase transformations to form crystalline Li-Ge phases [3].

In this work, we employ synchrotron X-ray pair-distribution function (PDF) analysis, X-ray diffraction (XRD), and in
situ heating experiments to elucidate the electrochemically induced structural changes in Ge and Sn clathrates and how they differ from those in the elemental analogs. The Type I Ba8Ge43
and Type VIII Ba8Ga16Sn30 clathrates are chosen and compared to diamond cubic Ge and beta-Sn. The PDF method allows us to probe the local structure of the amorphous phases that form after lithiation, while in situ heating experiments enable us to observe structural changes to the amorphous phases upon moderate heating. The insights learned from the structural characterizations are then used to explain the differences in the electrochemistry between the Tetrel clathrates and their elemental analogs.

The results suggest that the amorphous phases that are part of the final lithiated state of Ba8Ge43 have local structures similar to the Li-Ge crystalline phases. We conclude that the Ba atoms prevent the bulk nucleation of Li-Ge crystalline phases and restrict the Li-Ge ordering to the scale of 10-15 Å, resulting in a solid solution mechanism and a lower reaction voltage compared to cubic-Ge. Similar analysis of the Type VIII Ga-Sn clathrate (Ba8Ga16Sn30) results in a similar lithiation path showing a solely amorphous phase transformation. These results give insight to the fundamentals of how the initial structure of group IV materials affect their Li-alloying properties and structures.

Figure 1 (a) Unit cell of Ba8Ge43, purple atoms are Ge and green atoms are Ba. (b) PDFs of the lithiation of Ba8Ge43 at different states of lithiation. (c) PDFs of cubic-Ge at different states of lithiation.

[1] R. Zhao. ACS Appl. Mater. Interfaces. 9 (2017) 41246–41257.

[2] A. Dopilka. ACS Appl. Mater. Interfaces. 10 (2018) 37981–37993.

[3] H. Jung. Chem. Mater. 27 (2015) 1031–1041.

Figure 1
Zinc and Nickel Based Oxides Anchored Onto Nitrogen-Doped Carbon Nanotubes As Bifunctional Catalysts for Zinc-Air Batteries
Authors: McDougall Alexandra , Assen Drew , Ivey Douglas G
Published: December 2020

Rechargeable zinc-air batteries are a promising battery technology as they are safe, environmentally friendly, low cost, and have a high theoretical energy density. However, there are several challenges with zinc-air batteries which occur mainly at the air electrode. The main challenge is the slow reaction kinetics for the oxygen evolution and reduction reactions (OER/ORR). To improve the OER and ORR precious metal catalysts have typically been added to the air electrode. However, using precious metals as catalyst materials inhibits large scale applications due to the high material cost and material scarcity. Transition metal oxides are an effective lower cost alternative. Combining transition metal oxides with nanocarbon structures can further increase OER and ORR rates and improve electrochemical stability. [1], [2]

In this study, a combination of nitrogen-doped nanotubes (N-CNTs) and transition metal oxides is impregnated into a gas diffusion layer (GDL) made from porous carbon paper. This synthesis process ensures that the catalyst is present throughout the GDL, improving the reaction kinetics [2]. Zinc- and nickel-based tri-metallic and tetra-metallic oxides are investigated. Nickel-based oxides have demonstrated potential for high electrochemical activity but have not been fully studied [3]. Zinc is chosen, in part, because it appears to be incorporated into the transition metal oxide catalysts during battery cycling, so its effect on battery behavior is worth further study. The metal oxide combinations are determined from previous bi-metallic and initial tri-metallic oxide results. For each combination, different ratios are tested, since the amount of each transition metal affects the OER and ORR kinetics. Each combination is examined through various electrochemical and microstructural characterization techniques; e.g., linear sweep voltammetry, electrochemical impedance spectroscopy, electron microscopy and energy-dispersive X-ray spectroscopy. A Design of Experiments approach is used to determine the best metal ratios for each combination. The overall goal of this work is to find a catalyst that increases the efficiency, lowers the voltage gap, and improves the cyclability of zinc-air batteries.

[1] N. Xu et al., “Self-Assembly formation of Bi-functional Co 3 O 4 /MnO 2-CNTs hybrid catalysts for achieving both high energy/power density and cyclic ability of rechargeable zinc-Air battery,” Sci. Rep., vol. 6, no. September, pp. 1–10, 2016.

[2] D. Aasen, M. Clark, and D. G. Ivey, “ A Gas Diffusion Layer Impregnated with Mn 3 O 4 ‐Decorated N‐Doped Carbon Nanotubes for the Oxygen Reduction Reaction in Zinc‐Air Batteries ,” Batter. Supercaps, vol. 2, no. 10, pp. 882–893, 2019.

[3] J. Yi et al., “Non-noble Iron Group (Fe, Co, Ni)-Based Oxide Electrocatalysts for Aqueous Zinc-Air Batteries: Recent Progress, Challenges, and Perspectives,” Organometallics, vol. 38, no. 6, pp. 1186–1199, 2019.