bluuebunny/crossref_metadata_2025 huggingface dataset:
Minority Carrier Lifetime Extraction Methodology of SiC Epitaxial Layer
Authors: Sasaki Kyomin , Song Jinhan , Hoshii Takuya , Wakabayashi Hitoshi , Tsutsui Kazuo , Mizushima Ichiro , Yoda Takashi , Kakushima Kuniyuki
Published: February 2020

SiC has been focused as a strong candidate for high efficient power device semiconductors at high voltage regions1. Recent demonstrations of insulated gate bipolar transistors (IGBT) at a voltage over 15kV have proven the advantage of the use of SiC2. As the output characteristics are determined by the minority (hole) carrier lifetime (τp), measurement and control of the τp is utmost important. Optical methods are limited to measurements on separate wafers3, leading to differ from the real devices. In this presentation, we will propose an extraction methodology of minority carrier lifetime of an SiC epitaxial layer based on electrical measurement of pn diodes.

The methodology is based on current measurements on parallel pn diodes with a spacing of W
p under two different setups, shown in figure 1. The first one, named “single-setup”, is a setup measuring the center anode current while other anodes are kept open. The another one, named “multi-setup”, is a setup where all the anodes are grounded. The difference between the cathode voltage (V
C) under same current, defined as ΔV, reflects the difference in the resistance of the n-base region. Based on device simulations with a 20μm-thick SiC epitaxial layer (N
d=4.9×1015 /cm3) as an n-base region, one can find that ΔV is strongly dependent on the τp of the region (fig. 2(a) and (b)). Figure 3 shows the relationship between τp and ΔV at different W
p. With this relationship one can obtain a τp precisely once the ΔV is experimentally obtained.

In conclusions, we have proposed a methodology to extract the τp of an SiC epitaxial layer based on pn diodes with different setups. The proposed method allows us to estimate the τp with high precision.

[1] M. K. Das, Mat. Sci. Forum, 600-603, pp. 1183 (2009). [2] W. Sung, ISPSD, pp. 271 (2009). [3] P. B. Klien, J. Appl. Phys., 103, 033702 (2008).

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Investigation of Electrical Stability and Sensitivity of High Field Modulated Extended Gate FET Biosensors for miRNA Detection
Authors: Kuo Wen-Che , Wang Yu-Lin
Published: February 2020

miRNAs have been proven to be highly potential biomarkers for a variety of cancers and cardiovascular diseases. Typically miRNA detection method uses polymerase chain reaction (PCR) to amplify the miRNA concentration. This method has the disadvantage of being time-consuming and unable to directly detect the original concentration. Therefore, this study intends to design a FET biosensor to detect miRNA.

In order to design a stable and highly sensitive miRNA FET biosensor, this study used different metal deposition techniques to form sensing electrodes and observed sensor response in different temperatures and aqueous solutions to evaluate the fluctuation of the electrical signal, and found that the ions in the solution will follow the mechanism of Brownian motion. While the Brownian motion reduces, the stability of the electrical signal will be improved. Then we used different concentrations of ssDNA probe to functionalize the sensor chip to detect target miRNA concentration, to compare the dynamic range and sensitivity. The optimization can help us to make a miRNA FET biosensor with high sensitivity, high stability and large detection range.

Finally, the target detection experiments with the mismatch sequence demonstrate the high selectivity of the sensor. Comparison of ELISA based fluorescent signals with FET signals shows that FET biosensors have better detection limits. These data proved that the miRNA FET biosensor can directly measure the original concentration of miRNA without amplifying the concentration by PCR, which can effectively solve the problems faced by miRNA detection in the present time.

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Resonance-Frequency Modulation for Rapid, Point-of-Care Ebola-Glycoprotein Diagnosis with a Graphene-Based Field-Effect Biotransistor
Authors: Maity Arnab , Sui Xiaoyu , Jin Bing , Pu Haihui , Bottum Kai Justin , Huang Xingkang , Chang Jingbo , Zhou Guihua , Lu Ganhua , Chen Junhong
Published: February 2020

Recent outbreaks of Ebola-virus infections in several countries demand a rapid point-of-care (POC) detection strategy. Here we report an innovative pathway founded on electronic-resonance-frequency modulation to detect Ebola glycoprotein (GP), on the basis of a carrier-injection-trapping-release-transfer mechanism and the standard antibody-antigen interaction principle within a dielectric-gated reduced graphene oxide (rGO) field-effect transistor (GFET). The sensitivity of Ebola detection can be significantly enhanced by monitoring the device’s electronic-resonance frequency, such as its inflection frequency, where the phase angle reaches a maximum. In addition to an excellent selectivity, a sensitivity of ~36-160 % and ~17-40 % for 0.001-3.401 mg/L Ebola GP can be achieved at high and low inflection resonance frequencies, respectively, which are several orders of magnitude higher than those from other electronic parameters (e.g., resistance-based sensitivity). Using equivalent circuit modeling for contributions from channel and contact, analytical equations for resonance shifts have been generalized. When matching with the incoming ac-measurement signal, electronic resonance from the phase-angle spectrum evolves from various relaxation processes (e.g., trap and release of injected charges at surface-trap sites of the channel-gate oxide and channel-source or drain interfaces) that are associated with a characteristic emission frequency. Using charge relaxation dynamics, a high-performance bio-FET sensing platform for healthcare is realized through resonance shifting.

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(Invited) Nanostructured Materials Based Sensors for Smart and Wearable Electronics
Authors: Lee Nae-Eung
Published: February 2020

Smart and wearable electronic systems are promising for personal healthcare in near future. For smart health technology, various sensor-integrated portable, mobile and wearable systems have been extensively developed. Recently many sensor devices are being integrated into smartphone, which enables analysis of biomarkers from various body fluids and monitoring of physiological parameters. And many wearable sensor-integrated systems including skin-attachable platform which can monitor physiological signs, detect biomarkers for disease diagnosis and monitor the patients with chronic diseases have been extensively investigated. Here, I will discuss imaging-based fluorescence biosensors for highly sensitive detection of biomolecules and pathogenic bacteria which can be integrated with smartphone or portable IOT systems. In addition, I will present our recent works on stretchable wearable physical sensors (strain, pressure, and temperature), chemical sensors (gas) and biosensors (metabolite, protein) based on low-dimensional nanoscale materials (0D, 1D and 2D), nanocomposites or their hierarchical nanohybrids in FET, resistor or electrochemical device structures. Finally, future prospects in the development of the sensors for smart healthcare will be discussed.
(Invited) Wearable Thermoelectric Generator and Refrigerator Integrated with Flexible Heat Sink
Authors: Kim Woochul
Published: February 2020

In this talk, we are going to present thermoelectric devices for wearable power generation and refrigeration purpose. We present two types of wearable thermoelectric devices based on bulk inorganic materials; one is bracelet type and the other is mat style. Utilizing high performance that can be extracted from the bulk inorganic materials, the devices based on the materials are bendable and flexible. Performance of the device attached on a human body is compared with theoretical analysis based on a simplified human thermoregulatory model we developed. In thermoelectric application, it is necessary for the device to be integrated with heat sink. Therefore, we also show our recent work on flexible heat sink to be integrated with the devices. The flexible heat sink we demonstrate can be categorized either ‘transient type’ or ‘steady-state type.’ Also, we also discuss the possibility of using the wearable thermoelectric refrigerator as ‘personal heating and/or refrigeration.’
Study of Stability and Reproducibility of Cardiac Troponin I Based on FET Sensor
Authors: Huang Shu-Wen
Published: February 2020

In recent years, our research team has successfully detected a variety of protein biomarkers for cardiovascular diseases (CVD). The most common type of ischemic heart disease is mainly caused by acute myocardial infarction (AMI, also known as heart attack) usually presented in an acute manner and requires immediate emergency treatment. One of the most important protein biomarkers for AMI in the blood is cardiac troponin I (cTnI). However, in order to develop a cTnI FET sensor that allows patients to track CVD for a long term and often, the instrument must have better sensitivity, stability and reproducibility.

In this study, the purpose is understanding the mechanisms contributing to reduce the disturbance in the system. Firstly, the better stability are obtained by adjusting the drain voltage and the gate voltage of the metal oxide semiconductor field effect transistor (MOSFET). It can also be a bias condition for future cTnI FET sensor operation. Although our research team has developed a handheld biomedical sensor, it can not monitor the electrical signal by setting different gate voltages simultaneously. Therefore, Agilent B1530/B1500A is used for measurement. In addition, the Protein detection of different anti-cTnI concentrations also have an great influence on the sensitivity and stability of biomedical sensors. The results of this study can be used as an important basis for optimizing hand-held biomedical sensors in the future.

Keyword: Troponin I、Bias condition、Sensitivity、Stability、Reproducibility
A Multicellular Structured Ionic Hybrid Pump for Ultrasensitive Mechanotransducer Skin
Authors: Chung Yoon Sun , Amoli Vipin , Kim Joo Sung , Kim So Young , Kim Do Hwan
Published: February 2020

Recently, many developments have focused on biomimetics for application in electronic skin, health monitoring devices, and smart prosthetics. However, close mimicry of human skin’s tactile sensing capability over wide pressure range is unexplored.

Here, we present ultralow-powered, ultrasensitive, visco-poroelastic mechanotransducer skin sensors based on a multicellular structured ionic hybrid pump composed of ionic liquids, thermoplastic polyurethane (TPU) elastomer, and silica particles as a tactile sensing matrix. Local confinement of ion pairs onto the surface of silica dispersed in the TPU closely emulates the structural and functional features of living cell. Structure-derived confinement of ions in the silica without pressure and subsequent mechanical stimulus driven squeezing-out of ions generated an electric double layer (EDL), which allowed high sensitivity over 40 kPa-1 over a wide spectrum of pressure (0-100 kPa). Finally, we open a new avenue towards other parctical applications decribing a patch-type drone microcontroller capable of controlling drone’s height, speed, and revolution speed.
(Invited) 3D Conformal Additive Printing of Semiconducting Nanocrystals for Energy Harvesting and Biosensing
Authors: Zhang Yanliang
Published: February 2020

Semiconducting nanocrystals have been widely studied in the past two decades with unique and superior energy conversion and sensing properties compared to their bulk form. However, there is still a prominent need to transform the nanocrystals into functional devices in a scalable and low-cost manufacturing process and translate their unique properties from nanoscale to meso- or macro- scale.

This work explores a novel 3D conformal aerosol jet printing approach to convert a wide range of nanocrystals into flexible and functional devices for energy harvesting and biosensing. Solution-processed chalcogenide nanoplate inks have been synthesized and printed into flexible thermoelectric energy harvesters, which yield competitive figure of merit ZT values comparable with their rigid bulk counterparts fabricated by conventional method. A flexible thermoelectric device is demonstrated with high power density of 19 mW/cm2 and 1 mW/cm2 with 80 K and 20 K temperature difference respectively.

In addition, we have utilized biocompatible 2D nanomaterial inks and printed complex device patterns on 3D curved substrates and soft materials (e.g. hydrogel) for biosensing. The printed sensors can be used as bioelectrodes, temperature sensing, strain sensing, etc. The printed energy harvester and bio-sensors can be integrated into a self-powered wireless sensor system, which can completely eliminate the need of external power supply and greatly facilitate the implementation of these sensors.

The 3D conformal aerosol jet printing of colloidal nanoparticle inks demonstrated here opens up exciting opportunities to transform semiconducting nanocrystals into functional and flexible devices for broad energy harvesting and sensing applications.
(Invited) heterostructured “Binary Materials” for Photodetection from Mid-Infrared, Visible, to X-Ray
Authors: Wu Tom
Published: February 2020

Light-matter interaction is a long-lasting theme in condensed matter physics and optoelectronics. Light detection in different wavelength regimes is the foundation of a wide range of sensing, imaging, medical and surveillance technologies. In this talk I will discuss the use of transition-metal oxides, hybrid organo-metal perovskites and other nanomaterials in "binary" mixed-dimensional heterostructures with proper bandgaps and architectures to detect photons with different wavelengths. First, for visible light detection, we demonstrate that combining 3D hybrid perovskites with high-mobility 1D carbon nanotubes or 2D two-dimensional metal dichalcogenides significantly enhances charge transport and device performance. Second, we report a mid-infrared (up to 10 um) hybrid graphene photodetector enabled via coupling graphene with a narrow bandgap semiconductor Ti2O3. Finally, using epitaxial ferroelectric/semiconductor oxide junctions with a current-perpendicular-to-plane geometry, we achieve a new X-ray detector with colossal persistent X-ray-induced photoconductivity.
Ultrafast InAs Quantum Dot Scintillation Detector
Authors: Dropiewski Katherine , Minns Allan , Yakimov Michael , Tokranov Vadim , Murat Pavel , Oktyabrsky Serge
Published: February 2020

High-efficiency, picosecond scintillation detectors are critically needed for many applications, particularly in the fields of medical imaging, high energy physics and nuclear security. Recently, we proposed a design and considerations for a semiconductor scintillator composed of InAs Quantum Dots (QDs) acting as luminescence centers in a GaAs stopping matrix/waveguide, integrated with a photodetector grown epitaxially on top of the waveguide (WG) [1]. This material has appealing potential photonic properties including high light yield (~240,000 photons/MeV) due to the narrow semiconductor bandgap, fast capture of electrons in QDs (2-5ps) and high radiation hardness (>104 Gy). The high refractive index of GaAs (n=3.4) ensures light emitted by the QDs is waveguided within the GaAs matrix, which can then be collected by an integrated InGaAs p-i-n photodiode (PD).

A proof-of-concept integrated scintillation detector (Fig. 1) was grown using molecular beam epitaxy on a GaAs substrate. It has a 20 μm thick GaAs layer with embedded sheets of modulation p-type doped InAs QDs. A generic excitation source is shown interacting with the GaAs matrix, resulting in QD luminescence, which is then waveguided towards an InGaAs PD, grown on top of the WG and tuned to the QD luminescence band (~1150 nm). Employing QD structure engineering improves the internal efficiency of the QD luminescence to ~60% at room temperature and reduces overall waveguide attenuation to about 3-4 cm-1.

A sample, as shown in Fig. 1, was used to evaluate the timing characteristics of 5.5 MeV alpha particle responses. The source had a radioactivity of 1 µCi, suspended in air approximately 1 cm above the QD waveguide. The scintillation response (Fig. 2) had a decay time of 0.3 ns, corresponding to QD recombination time, and a noise-limited time resolution of 54 ps (Fig. 3). With a 2D waveguide and an integrated PD covering only 16% of the WG width, the collected charge averaged 1.5x105 electrons (Fig. 4), corresponding to a collection efficiency of about 14%. This can be estimated as 34,000 photoelectrons per 1 MeV of incident energy, given about 1 MeV of alpha particle energy loss in air. This data confirms the unique photonic properties of this scintillation detector, which has the potential to be much faster than any currently used inorganic scintillator.

Additionally, technologies for separating an epitaxial film from a substrate and bonding multiple waveguides using organic adhesives are tested and evaluated.

[1] S. Oktyabrsky, et al. "Integrated Semiconductor Quantum Dot Scintillation Detector: Ultimate Limit for Speed and Light Yield," IEEE TNS,
63, 656 (2016).

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(Invited) Self-Powered Textiles for Healthcare Applications
Authors: Lin Zong-Hong
Published: February 2020

Pathogenic bacteria that give rise to infection have posed major health concerns over the past several decades. In this paper, we propose a self-powered active disinfection system controlled by human motions. The system is mainly composed of a multilayered triboelectric nanogenerator (m-TENG) for the harvesting of biomechanical energy and conductive fabrics as electrodes for the wearable disinfection system. The working principle of the system is based on hybrid effects of H2O2 production and electroporation, which provide good disinfection performance toward gram-negative Escherichia coli (E. coli) and gram-positive Staphylococcus aureus (S. aureus). In addition, we also demonstrate that the presence of gold-coated tellurium nanowires (Au-Te NWs) on the fabrics increased the strength of local electric field and enhanced the system’s disinfection performance. With the help of Au-Te NWs, the disinfection activities of the system reach values of more than 87% and 96% against S. aureus and E. coli, respectively, when the m-TENG was operated at a frequency of 1 Hz for 60 minutes. Furthermore, the disinfection activity can be strengthened by increasing the operation frequency or electric output of the m-TENG. Alternatively, the generated electricity can be stored in a capacitor to achieve rapid disinfection via an instantaneous discharging process. Because of the fiber-based structure in the disinfection device and the shoe-embedded design of the m-TENG, our proposed self-powered active disinfection system can be easily integrated into commercial textiles to fabricate smart clothes to combat pathogenic bacteria.
Flexible, Stretchable and Healable Electronics
Authors: Cicoira Fabio
Published: February 2020

Organic electronics, based on semiconducting and conducting polymers, have been extensively investigated in the past two decades and have found commercial applications in lighting panels, smartphone and TV screens using OLEDs (organic light emitting diodes) technology. Many other applications are foreseen to reach the commercial maturity in future in areas such as transistors, sensors and photovoltaics.

Organic electronic devices, apart from consumer applications, are paving the path for key applications at the interface between electronics and biology, such as in polymer electrodes for recording and stimulating neural activity in neurological diseases. In such applications, organic polymers are very attractive candidates due to their distinct property of mixed conduction: the ability to transport both electron/holes and ionic species. Additionally, conducting polymers offer the possibility to tune their surface properties (e.g., wettability or chemical reactivity) by changing their oxidation state, thus promoting or hindering the adhesion of biomolecules. This feature can be particularly useful for enhancing the biocompatibility of implantable electrodes.

My talk will deal with processing and characterization of conducting polymer films and devices for flexible, stretchable and healable electronics. I will particularly focus on micro-patterning of conducting polymer films for flexible and stretchable devices and on healing of conducting polymer films.
Low Temperature Synthesis of WS2 Using PECVD for Hydrogen Evolution Catalysis
Authors: Kanade Vinit Kaluram , Kim Hyeong-U , Kanade Chaitanya Kaluram , Shin Dongjoo , Lee Jae-Hyun , Kim Taesung
Published: February 2020

Hydrogen holds tremendous promise as one of many alternatives for clean energy generation with high energy density and zeroes environmental impact. Hydrogen can be easily produced by using Platinum-based catalyst to efficiently lowers the large potential of electrolysis, but confined due to scarce and expensiveness. Transition metal dichalcogenides (TMDCs) such as MX2 (M stands for Mo or W, Nb, Ta etc. and X= S, Se etc.) is essential materials which show promising catalytic activity. The bond between the metal and the chalcogen is a covalent bond, and the three layers themselves are held together by a weak van der Waals force. Tungsten Disulfide (WS2) is a representative transition metal dichalcogenide (TMDC), has been freshly pursued as one of the promising alternatives for hydrogen evolution reaction (HER). Tungsten Disulfide is one of the promising TMDC materials due to its various application in electronics, catalysis, optical and other fields. The WS2 elements were previously synthesized by different processes such as mechanical exfoliation, chemical exfoliation, chemical vapor deposition etc.

In this work, we report a strategy for synthesis few layers of WS2 at relatively low temperature (300 °C) using plasma enhanced chemical vapor deposition (PECVD) technique. The PECVD technology utilized to grow WS2 thin film directly on the 4-inch Si-SiO2 wafer. The quality of a synthesized WS2 was characterized by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), High-resolution transmission electron microscopy (HR-TEM), and energy dispersive spectrometry (EDS) mapping. The thickness of the synthesized WS2 film was found to be around a few nanometers and showed multilayered structure (~5-6 layers). The PECVD shows the advantage for the large area synthesis of WS2 thin film with high uniformity, purity, and reproducibility for the mass production. The PECVD technology utilized to directly grown on glassy carbon electrode (GCE) for analysis of HER performance without any transfer process. The catalysis shows overpotential (η) of 0.50 V and Tafel slope 122.0 mV/decade. The HER performance of synthesized films was similar or higher when compared with drop casting technique.

Figure 1
Universal Mechanism and Rate Equation for Hydrogen Oxidation Reaction
Authors: Zeleke Tamene Simachew , Tsai Meng-Che , Su Wei-Nien , Hwang Bing-Joe
Published: February 2020

Scientific communities haven’t common consensus on the mechanism of hydrogen oxidation reaction in alkaline medium to date. Herein, we propose a new universal equation and plausible mechanism for hydrogen oxidation reaction via the help of In-situ Raman technique for the first time. In all HOR cyclic voltammetry applied potentials, the OH- species on Pt electrode surface have been found as adsorbed species and the amounts of adsorbed OH-(OHadd) are increased with potentials. The rate equation and universal mechanism of hydrogen oxidation reaction, which proposed on Pt/C electrode in 0.1 M KOH solution show that both adsorbed hydroxyl (OHadd) and adsorbed hydrogen (Hadd) have an effect on rate of reactions.
(Invited) Nickel Based Electrocatalysts for Water Electrolysis Under Large Current
Authors: Chen Shuo
Published: February 2020

Water electrolysis is a promising approach to produce pure hydrogen and oxygen without releasing greenhouse gases. For practical applications, electrolyzers working at large current density (on the order of A cm-2) are desired. Consequently, highly efficient, stable, and low cost electrocatalysts to expedite anodic oxygen evolution reaction (OER) and cathodic hydrogen evolution reaction (HER) are necessary. In this presentation, I will introduce our recent progress on nickel based electrocatalysts, including Ni2(1-x)Mo2xP, NiFe layered double hydroxide, and Fe-Ni-P for water electrolysis at a current density of 1 A cm-2. The electrocatalysts were prepared by high temperature reaction of precursors with nickel foams, which ensure high electrical and robust mechanical connections. After IR correction in 1 M KOH, our typical overpotential at 1 A cm-2 for HER is ~300 mV, and that for OER is also less than 300 mV. Interestingly, NiFe layered double hydroxide and Fe-Ni-P can effectively catalyze both HER and OER, which may benefit fabrications of electrolyzers. I will also present theoretical understandings on catalyzing HER by density functional theory (DFT) calculations.
Improved Components for High Temperature Alkaline Water Electrolysis
Authors: Patil Kailash , Sweet Andrew , McCatty Steve , Greene Winfield , Xu Hui
Published: February 2020

Hydrogen production from water electrolysis is attractive due to its high efficiency, fast ramp rates, and high-pressure capability. However, current hydrogen production from electrolysis comprises only a small fraction of the global hydrogen market due to the high cost associated with expensive stack materials and electricity consumption. Currently commercial alkaline electrolyzers or proton exchange membrane electrolyzers operate at low temperatures. Intermediate or high temperature can effectively boost electrode kinetics and lower cell over-potential, thus improving the efficiency of water electrolysis. In this regards, Giner has developed a high-temperature alkaline water electrolysis (HTAWE), which employs lithium, sodium, or potassium hydroxides impregnated into a porous alumina or zirconia matrix [1]. The operating temperature can vary from 350 to 550 °C, depending on the category and ratio of binary or ternary electrolytes.

In this work, both aluminate and zirconia-based matrix metal oxides were used as the matrix support materials. Thin aluminate and zirconia based matrices were fabricated using the tape casting method. Precious or non-precious electrodes (e.g. Ir, Ni, Co-based) were optimized using a solvent-based slurry formulation process. Green sheet electrodes with a variety of thicknesses were developed using a doctor blade approach. Design of experimental techniques were applied to optimize the ceramic membrane properties and to select hydrogen evolution reaction (HER)/oxygen evolution reaction (OER) catalysts. The impact of various catalyst and electrode designs on the HTAWE will be evaluated. Polarization curves and long-term durability will be demonstrated at variety of temperatures. Hot-corrosion mitigation strategies will also be discussed to extend the lifetime of HTAWE cells in this work.

References

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

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

Hydrogen evolution reaction (HER) is a fundamental process for many important energy applications such as hydrogen production through electrolysis and electrochemical hydrogen storage. Recently, we demonstrated a metal-free organic molecular electrocatalyst (OMEC) with high HER activity and durability in acidic polymer electrolyte, based on a small pyridine-based heterocyclic molecule.1, 2 Density functional theory (DFT) study of the HER mechanism at this molecule revealed that the atomic hydrogen adsorption energy at the pyridyl-N site is closely tied to the electrocatalytic activity.

In this talk, we will present a systematic study of the proton reduction step, also known as the Volmer step, at heterocyclic organic functional groups targeting rational design of the OMECs. DFT calculations have been performed to predict the reaction thermodynamics, reduction potentials, and the change of molecular electronic structures during the Volmer step. Several N-heterocycles, such as pyridine, pyridazine, pyrimidine, and pyrazine, and their derivatives involving electron-withdrawing/donating groups have been included in this study. Through data mining of the electronic and structural information from DFT calculation, we have developed descriptors for the structural-activity relationship among these heterocyclic molecules. The results set the foundation for rational design of OMECs for hydrogen evolution reaction.

References

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

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

Acknowledgment

Financial support for this research by Los Alamos National Laboratory through LDRD-ER Program is gratefully acknowledged.
Plasma-Treated Niau Nanosponge As an Efficient Electrocatalyst for Hydrogen Evolution Reaction
Authors: Nguyen Ngoc-Anh , Nguyen Van-Toan , Ali Yousuf , Choi Ho-Suk
Published: February 2020

We report a simple method to prepare plasma-treated NiAu nanosponge as an electrocatalyst for hydrogen evolution reaction (HER) in water electrolysis. First, an as-prepared NiAu nanosponge sample was synthesized by using NaBH4 as a reducing agent without using any surfactant. Second, the as-prepared NiAu nanosponge sample was treated by using argon plasma under atmospheric pressure with a treatment time of 15 min to obtain the final plasma-treated NiAu nanosponge sample. The plasma-treated NiAu nanosponge sample was performed as an electrocatalyst for HER. As a result, plasma-treated NiAu nanosponge sample exhibited an enhanced-performance in HER activity as well as stability because of the exposure of more active sites and the appearance of many defects. In more details, the overpotential at a current density of 10 mA.cm-2 of the plasma-treated NiAu nanosponge sample (88 mV) is lower than that of the as-prepared NiAu nanosponge (134 mV), and this is due to the plasma treatment process. In addition, plasma-treated NiAu nanosponge sample also showed an excellent durable ability of HER activity for 80,000 seconds.
Performance of a Hybrid Regenerative Hydrogen-Vanadium Fuel Cell with Carbon Nanotube Electrode (CNT) Materials
Authors: Nguyen Trung Van , Li Yuanchao , Hammar Ryan
Published: February 2020

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

References:

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

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

Figure 1
Analysis of Flow Field Scale-up, Design Tradeoffs, and Shunt Current in Redox Flow Battery Stacks
Authors: Houser Jacob , Aaron Douglas , Mench Matthew M.
Published: February 2020

Recently it has been demonstrated that operating conditions and applications have a significant impact on the effectiveness of different flow field designs commonly used in redox flow batteries (RFBs)1. Depending on the power and energy storage requirements, as well as the system operational capabilities, the optimal flow field design may vary between designs2. These results have only been presented concerning small laboratory scale designs, however. Due to the different transport mechanisms utilized by these various flow field designs, the mass transport performance and efficiency of each design will scale differently when the active area of the cell is increased to a size more representative of a commercial system. Additionally, the most common configuration of these cells in a commercial system is in an RFB stack where several cells are connected in series electronically and in parallel hydraulically. This further complicates the design tradeoffs seen in the smaller single cell design, while also introducing new design concerns in the form of shunt current, a self-discharge phenomenon only present when multiple cells are connected ionically through the liquid electrolyte.

Utilizing the energy and efficiency-based analysis previously published by our lab, we have conducted a thorough study of the differences between four flow fields when increasing the active area of the cell. CFD simulations using COMSOL Multiphysics provide quantitative data for electrolyte velocity and pressure drop, while experimental data provides depth of discharge and efficiency results. This analysis has also been extended to a small RFB stack to examine how these design tradeoffs are impacted by placing multiple cells electronically in series and sharing an electrolyte manifold. To quantify the shunt current in this stack, a novel in-situ shunt measurement technique was developed, allowing for real-time measurement of the shunt current present during all phases of stack operation.

The results of this study provide insights and guidelines for the future development of commercial RFB systems, specifically ways in which the fluid pathway can be optimized to improve system efficiency.

References:

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

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

Figure 1
Fluorenone Based Anolyte for an Aqueous Organic Redox-Flow Battery
Authors: Rodriguez Jaime , Niemet Claire , Pozzo Lilo D
Published: February 2020

As renewable energy sources (e.g. solar, wind) are increasingly incorporated into our electrical grid, adequate large-scale energy storage is necessary to smooth out the intermittency of these renewable sources. Redox-flow batteries (RFBs) are an attractive energy storage solution with several attributes, most notably their decoupling of power and energy. Recently, organic RFBs have gained widespread attention over their inorganic counterparts due to the ability to synthetically tune and tailor the molecular structure of the active material for improved performance. Here, we present the first aqueous organic RFB utilizing a fluorenone based negative electrolyte (anolyte). With the addition of a carboxylic acid functional group, solubility of the fluorenone anolyte is enabled under alkaline conditions with a maximum solubility of 1M. Paired with a ferro/ferricyanide redox couple in the positive electrolyte (catholyte), this RFB can achieve an open circuit potential of 1.18V which rivals many other aqueous organic RFB chemistries that have previously been reported. Galvanostatic charge/discharge cycling has shown coulombic efficiencies in excess of 90% with energy and voltaic efficiencies above 80%. Moreover, the cost of this material has been quoted to be as low as $2/kg compared with the current state-of-the-art inorganic vanadium RFBs at greater than $80/kg. This work will show the potential for fluorenone based anolytes as promising candidates to further promote widespread commercialization of RFBs.
Microstructure Characterization of PGM-Free Catalyst Ink Using in-Situ Ultra Small Angle X-Ray Scattering
Authors: Park Jaehyung , Kariuki Nancy N. , Myers Deborah J. , Zhang Hanguang , Wu Gang
Published: February 2020

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

Acknowledgements

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

References

[1] S.T. Thompson, A.R. Wilson, P. Zelenay, D.J. Myers, K.L. More, K.C. Neyerlin, and D. Papageorgopoulos, Solid State Ionics, 319 (2018) 68-76.

[2] H. Zhang, S. Hwang, M. Wang, Z. Feng, S. Karakalos, L. Luo, Z. Qiao, X. Xie, C. Wang, D. Su, Y. Shao, Gang Wu, J. Am. Chem. Soc., 139 (2017) 14143-14149.
(Allen J. Bard Award Address in Electrochemical Science) Energy Conversion and Storage: Novel Materials and Operando Methodsbard
Authors: Abruña Héctor D.
Published: February 2020

This presentation will deal with the development of new materials and operando methods for energy conversion and storage with emphasis on fuel cells and battery materials and technologies. The presentation will begin with a brief overview of the methods employed. Particular emphasis will be placed on the use of X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS) X-ray microscopy and tomography and transmission electron microscopy (TEM) under active potential control. The utility of these methods will be illustrated by selected examples including electrocatalysts for the oxygen reduction reaction (ORR), hydrogen oxidation reaction (HOR) and spectroscopic studies of Li/S batteries and Li metal deposition and dendritic growth. The presentation will conclude with an assessment of future directions.
Electrode Layer Development and in Situ Diagnostic Characterization in Low Temperature Fuel Cells
Authors: Neyerlin K.C. , Van Cleve Timothy , Wang Guanxiong , Star Andrew G. , Kabir Sadia , Osmieri Luigi , Khandavalli Sunilkumar , Wang Min , Ulsh Michael , Mauger Scott A , Medina Samantha , Pylypenko Svitlana
Published: February 2020

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

Ink formulation and electrode design optimization is often an iterative process, in which conclusions from in situ performance/ diagnostics as well as ex situ characterization (e.g. microscopy and tomography) are relayed to a model. The model then identifies fundamental limiting phenomena which are to be improved in the next loop. This process may often take several iterations to ensure an optimal combination of ionic and gas phase accessibility to the active site.

Here, the development and utilization of in situ diagnostics designed to probe specific phenomena (e.g. catalyst/ionomer interactions, molecular and Knudsen diffusion, electrochemical active site accessibility and catalyst layer proton resistance) will be utilized to contrast the ink, processing and fabrication methods necessary to achieve high performance PGM (e.g. Pt/C and Pt alloy/C) and PGM-free (e.g. FeNx/C based) electrocatalysts based electrodes.

References

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

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

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

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

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

With a deepening electrification of society, electrochemical conversion from one chemical to another will be essential for the chemical plants of the future. While there is intense focus on reduction reactions (i.e. CO2, water, N2), partial oxidation reactions have been relatively underinvestigated. This talk will discuss our recent work on electrochemical partial oxidation of propene. With propene having both a double bond and an allylic carbon, this is an optimal test molecule to create a broad spectrum of products following a variety of mechanisms.

By using a Pd catalyst, we were able to produce acrolein, acrylic acid, allyl alcohol, propylene glycol, acetone with only small amounts of CO2 formation. Variations is oxidation potential allowed us to see changes in product distribution, which we then used to theorize potential reaction mechanisms. With acrolein being one of our largest products, this meant the allylic carbon was oxidized rather the double bond. DFT calculations showed that the acrolein mechanism was feasible, provided surface coverage of other species (oxygen species and flat lying propene) dominated the surface coverage, thus allowing for a small amount of allylic carbon to bind to the surface due to steric advantages. Electrochemical Sniffer Chip technology (1) was then used to measure submonolayer gas absorption/desorption as a function of electrochemical potential, which provided supporting evidence to the aforementioned mechanism. The talk will show our process in analyzing this reaction and mechanisms as well as how these discoveries are applicable to the broader field of partial oxidation reactions.

(1) Trimarco, D. et. al, Review of Scientific Instruments 86, 075006 (2015)

Figure 1
PEM Electrolyzer Characterization and Limitations When Using Carbon-Based Hardware and Material Sets
Authors: Young James L. , Ganci Fabrizio , Madachy Steven , Fischer Stefanie , Carmo Marcelo , Bender Guido
Published: February 2020

In contradiction to the more established research field of proton exchange membrane fuel cells (PEMFCs), the research and development field for proton exchange membrane water electrolysis (PEMWE) is an upcoming and growing area. Over the past decades, a specific fuel cell research hardware configuration has been widely accepted for material development work that requires typical performance and durability tests on subscale cells. This hardware consists of thick endplates often made of aluminum, gold plated copper current collectors that are insulated with a sheet material from the endplate and graphite flow-fields that contain the flow channel structure. The latter may be machined in many designs ranging from single to multiple serpentine or parallel flow patterns.

In contrast to the fuel cell field, the electrolysis research field does not yet have established material sets. Operating conditions are harsher than in a fuel cell system, since the potentials required for the oxygen evolution reaction are significantly higher. In commercial water electrolysis systems this is compensated by typically using titanium material sets that are often protected against oxidation through coating processes. Such material choices make small scale research hardware and porous transport layers expensive and very difficult to source.

In this work, we show that the stability of traditional carbon-based fuel cell materials is sufficient for electrolyzer initial performance characterization procedures such as cell conditioning, a limited number of polarization curve measurements, and electrochemical impedance spectroscopy. We identify and quantify the onset of carbon degradation and define a strategy that allows the utilization of standard fuel cell hardware for specific PEMWE experiments. With knowledge that existing fuel cell materials can be applied in electrolyzer research by acknowledging the associated limitations, fuel cell research hardware and experience can be more readily transferred to the younger and rapidly growing electrolyzer research field.
(Invited) Synthesis of Porous Bi Electrocatalysts for Selective Production of Formate from CO2 and Their Applications
Authors: Park Hyunwoong
Published: February 2020

Electrocatalytic CO2 reduction reaction is receiving growing attention as an efficient and viable process for the production of value-added carbon chemicals. Among CO2 conversion products, formate and CO are the most cost-effective while the former is easier to be stored and transported. Various metals (Cd, In, Sn, Pb, Hg, and Bi) are known to be suitable for the selective conversion of CO2 to formate. Among them, Bi is favored over others due to low toxicity. Herein we present a facile synthesis of 3D-porous Bi catalysts on conducting substrates via an electrodeposition. Although as-synthesized Bi suffers from a rapid surface oxidation, the as-formed oxides are electrochemically removed. The Bi electocatalysts show a high Faradaic efficiency for the formate production (>95%) in various aqueous media and outstanding durability. The experimental results and the applications of Bi electrocatalysts will be discussed in detail. This research was supported by the Basic Science Research Program (2016R1A2B4007366 and 2018R1A6A1A03024962) through the National Research Foundation, Korea.