bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact of Nb Substitution on Crystal Structures and Electrode Reversibility of LiNiO2
Authors: Shimosugi Ryosuke , Yabuuchi Naoaki
Published: December 2020

Introduction

Lithium-ion batteries with high energy density have been currently used for transportation applications such as electric vehicles. As a positive electrode material, layered LiNiO2 shows high reversible capacity, good rate characteristics, and low material cost when compared to LiCoO2. However, a complicated phase transitions during charge and discharge proceed for LiNiO2, which influences long-term cyclability.[1] In this study, impact of Nb substitution on crystal structures and electrode reversibility of LiNiO2 is examined, and its origin of improved reversibility as electrode materials is discussed in detail.

Experimental

Nb-substituted LiNiO2 samples were synthesized from LiOH・H2O, Ni (OH)2, and Nb2O5 used as starting materials, and mixtures were calcined at 650 oC. Crystal structures of the samples were analyzed by synchrotron X-ray diffraction (XRD), and the particle morphology was observed by using a scanning electron microscope (SEM).

Results and Discussion

Synchrotron XRD data were collected for both LiNiO2 with or without Nb substitution. as shown in Figure 1. Although Nb substitution (5 mol% of Nb) for LiNiO2 clearly results in lowered crystallinity, successful synthesis of a rocksalt layered oxide, which is isostructural with LiNiO2, is noted from synchrotron XRD data.

Figure 2 shows results of electrochemical properties of LiNiO2 with or without Nb substitution. Although LiNiO2 without Nb ions delivers an initial discharge capacity of over 200 mA h g-1, the increase in polarization and reduction of reversible capacities are observed on continuous electrochemical cycles. On the other hand, the increase in polarization was effectively suppressed for the Nb-substituted sample, leading to good reversibility.

Based on these results, we will discuss factors affecting electrode reversibility of LiNiO2 and the possibility of cobalt-free high-capacity and long-cycle life positive electrode materials.

Reference

[1] U.-H.Kim et.al., and Y.-K.Sun, Energy Environ. Sci.,
11, 1271 (2018).

Figure 1
Mechanochemical Synthesis of Modified Li2ohbr to Improve Ionic Conductivity
Authors: Sugumar Manoj Krishna , Yamamoto Takayuki , Ikeda Kazutaka , Motoyama Munekazu , Iriyama Yasutoshi
Published: December 2020

All-solid-state lithium batteries have gained more attention as the next-generation batteries with high energy density, high safety and long life. Recently, cubic-phase lithium-rich anti-perovskite (LiRAP: Li3-x
OH
x
X (X = Cl, Br), including x = 0) compounds have been actively investigated due to their certain advantages to overcome the problems faced by other solid electrolytes [1]. In this work, we investigated the ionic conductivity of Li2OHBr by chemical doping.

Li2OHBr was mechanochemically synthesized using LiOH and LiBr [2]. Powder X-ray diffraction (PXRD) pattern of the synthesized sample well agreed with cubic Li2OHBr with a lattice constant of 4.046 Å and no impurities were observed as shown in Fig. 1(a). In the Nyquist plot of Au/Li2OHBr/Au symmetrical cell measured at 25 ºC, one semicircular arc was observed (Fig. 1(b)). The total ionic conductivity of Li2OHBr evaluated based on this semicircular arc was 1.1 × 10–6 S cm–1 at 25 ˚C. In an attempt to improve the ionic conductivity, Li2OHBr1-x
Cl
x
, Li1.8M0.1OHBr (M = Mg, Ca, Sr, Ba) and Li2+x
OH1-x
Br were synthesized by the same manner as Li2OHBr. The PXRD measurements revealed that most of the modified Li2OHBr formed cubic phase without impurities and the lattice constant slightly changed by chemical doping (Fig. 1(a)). The total ionic conductivity of Li2OHBr0.75Cl0.25, Li1.8Ca0.1OHBr and Li2.2OH0.8Br were 9.3 × 10–7, 4.9 × 10–7 and 3.6 × 10–6 S cm–1 at 25 ºC, respectively. It has been reported that grain-boundary resistance is generally larger than bulk resistance in LiRAPs[3] and also, the LiRAPs have a tendency to form Li vacancy around the grain boundary [4]. Thus, the reason why Li2.2OH0.8Br has larger ionic conductivity than Li2OHBr is because, the Li concentration around grain boundary is increased. So, it can be one of the strategies to improve ionic conductivity of LiRAPs.

Acknowledgement: This work was supported by JSPS KAKENHI Grant Number JP18K14318 and in part JP19H05813 (Grant-in-Aid for Scientific Research on Innovative Areas “Interface IONICS”). One of the authors Manoj Krishna Sugumar thankfully acknowledges the financial assistance from Yoshida Scholarship Foundation.

References:

[1] Y. Zhao, L. L. Daemen, J. Am. Chem. Soc. 134 (2012) 15042.

[2] M. K. Sugumar, T. Yamamoto, M. Motoyama, and Y. Iriyama, Solid State Ionics 349 (2020) 15298.

[3] J. A. Dawson, P. Canepa, T. Famprikis, C. Masquelier, and M. S. Islam, J. Am. Chem. Soc. 140 (2018) 362.

[4] K. Shen, Y. Wang, J. Zhang, Y. Zong, G. Li, C. Zhao, and H. Chen, Phys. Chem. Chem.
Phys. 22 (2020) 3030.

Figure 1
Screen-Printed Three Electrode-Type Sticker Device with Long-Term Stable Liquid Junction-Type Reference Electrode
Authors: Miyazaki Kaishi , Hoshi Yoshinao , Watanabe Hikari , Shitanda Isao , Itagaki Masayuki
Published: December 2020

A three electrode system is widely used to evaluate the corrosiveness of metal. However, three electrode system normally requires various instruments such as a salt bridge, reference electrode, counter electrode and flask. Thus, the three-electrode-type corrosion test is often applied to lab tests rather than field work. To solve the problem, in this study, we developed a new concept of a three electrode system using a sticker device that enables the simple and accurate measurement just only stick the device on a test metal.

The three-electrode-type sticker device was fabricated by screen printing. Figure 1 (a) shows the model of the sticker device. A reference electrode with a liquid junction developed previously in our group1) used for the reference electrode part. A silver layer, a silver-silver chloride layer, a liquid junction layer, and a saturated KCl layer were also forms on the PET substrate by screen printing. A working electrode part of the sticker device has a 2 mm diameter hole. Electrochemical measurements can be performed by attaching this device to the measurement target. In this study, tin-plated copper and copper was used as a substrate.

At the reference electrode of the sticker device, a solution is penetrated from the liquid junction layer, and the saturated KCl layer absorbs the solution to form a saturated KCl aqueous solution, and functions as a reference electrode.

Figure 1 (b) shows the results of the open circuit potential measurement at the reference electrode of the sticker device. The open-circuit potential was stable at a solution concentration in the range of 10 ppm to 300 ppm after 60 seconds. Also, it was found that open-circuit potential was within ± 15 mV vs. SSE. It was confirmed that the potential after 300 seconds of immersion were almost constant in that each solution concentration, and that the device reference electrode had a stable with potential independent of the solution concentration.

Figure 1 (c) shows polarization curve of the tin-plated copper measured using the sticker device. When the working electrode potential was scanned to the noble side, the current drastically increase due to the occurrence of pitting corrosion between -0.2 V and 0.1 V, depending on the solution concentration. The pitting potential was confirmed to have a positive correlation with the chloride ion concentration.

Reference

1) M. Komoda, I. Shitanda, Y. Hoshi, and M. Itagaki, Electrochemistry, 87, 65 (2018).

Figure 1
Fastening Strategies to Prevent Galvanic Corrosion
Authors: Smith Cody Troy , Hihara Lloyd H.
Published: December 2020

In marine applications aluminum structures are commonly fastened together with stainless steel fasteners. This combination of dissimilar metals causes galvanic corrosion currents which degrade the aluminum structure. The purpose of this research is to develop fastening strategies that will reduce the degradation of the aluminum structure. The impetus for this research is specifically to increase reliability and availability of equipment installed on Navy range craft which operate in the support of training and test and evaluation (T&E) events. Direct fastener substitution would cause the least impact to the overall design of a system reducing alteration costs. Therefore, in this research different types of fasteners were tested to determine their effect on corrosion in the aluminum structure. Fastener types: 316 stainless steel (control), Titanium (Ti-6Al-4V), 316 stainless steel PVD coated with TiN, 316 stainless steel PVD coated with CrN, and 316 stainless steel coated with a Sol Gel. The efficacy of each fastener type was determined by several tests. Samples representing a bolted join in an aluminum structure were assembles using each type of fastener and deployed in a marine environment, after exposure weight loss data was collected. The fasteners were also subjected to cathodic potentiodynamic polarization to determine the kinetics of oxygen reduction and hydrogen evolution on the bare 316 SS, coated 316 SS, and bare Ti-6Al-4V. The cathodic polarization data of the fasteners were compared to that of the anodic polarization data of AA6061-T6. The potentiodynamic polarization data was used to gain an understanding of the galvanic corrosion mechanisms between the fasteners and AA 6061-T6. The results from the polarization experiments were compared to the actual corrosion damage of galvanic couples in the field.

Acknowledgements:

This material is based on research sponsored by the USAFA and University of Hawaii under agreement number FA7000-18-2-0004. The U.S. Government is authorized to reproduce and distribute reprints for Governmental purposes notwithstanding any copyright notation thereon.
Salt Adsorption Capacity of Hydrous and Anhydrous Ruthenium Oxides for Capacitive Deionization
Authors: Togashi Ryo , Takimoto Daisuke , Hideshima Sho , Sugimoto Wataru
Published: December 2020

Capacitive deionization (CDI) is a promising technology for desalination of seawater and recovery of mineral resources. By applying a voltage to a pair of electrodes within the potential of water electrolysis, ions such as Li+ and Na+ can be recovered by electrosorption. In order to increase the salt adsorption capacity (SAC) of the electrodes, various metal oxides have been proposed.1 For example, manganese oxide, titanium oxide and ruthenium oxide show higher SAC than activated carbon, owing to the contribution from both electric double-layer capacitance and pseudocapacitance. In particular, the SAC of ruthenium oxide electrodeposited on activated carbon was ~4 times higher than that of pristine activated carbon due to the additional pseudocapacitance.2 Since hydrous RuO2 shows higher pseudocapacitance compared with anhydrous RuO2,3 it is anticipated that hydrous RuO2 would show higher SAC compared to anhydrous RuO2. Here we evaluate and discuss the pseudocapacitance and SAC capability of hydrous and anhydrous RuO2-based electrode materials.

RuO2·0.5H2O or RuO2 were prepared by heating of RuO2·xH2O at 200°C or 450°C, respectively.3 The slurry, prepared by mixing RuO2·0.5H2O or RuO2, polyvinylidene fluoride and N, N-dimethylformamide, was pasted on a Ti plate and dried at 120oC to prepare electrodes (10-11 mg cm-2) for batch-mode CDI experiments. Activated carbon (MSP-20) electrode was prepared as a control sample. The CDI experiment was carried out with a voltage of 1.2 or 0 V, by circulating 100 mL NaCl feed solution (initial concentration: 5 mM NaCl) at a flow rate of 9.8 mL min-1 per electrode. The SAC was determined by measuring the change in the conductivity on the negative electrode side, using a calibration curve of conductivity and concentration of NaCl solution.

The specific capacitance of RuO2·0.5H2O and RuO2 were 172 F g-1 and 13 F g-1, while the SAC was 7.4 mg g-1 and 4.0 mg g-1, respectively. This means that RuO2·0.5H2O shows 13.2 times higher capacitance and twice higher SAC. The results suggest that the increase in the specific capacitance by applying RuO2·0.5H2O might be attributed to the increase in the SAC value. On the other hand, the specific capacitance of RuO2·0.5H2O was higher than that of activated carbon, while the SAC of RuO2·0.5H2O was lower than that of activated carbon. There seems to be a difference in the effect of pseudocapacitance and electric double layer capacitance on the SAC value.

This work was supported in part by the Japan Society for the Promotion of Science (JSPS) Grant-in-Aid for Challenging Research (Exploratory) Grant Number 17K19174.

References

K. Singh, S. Porada, H. D. de Gier, P. M. Biesheuvel and L. C. P. M. de Smet, Desalination, 455, 115 (2019).

X. Ma, Y. Chen, K. Zhou, P. Wu and C. Hou, Electrochim. Acta, 295, 769 (2019).

W. Sugimoto, H. Iwata, K. Yokoshima, Y. Murakami and Y. Takasu, J. Phys. Chem. B, 109, 7330 (2005).

Figure 1
Effect of Bath Temperature and Current Density on Higher Deposition Rate for Copper-Molybdenum Alloy Plated Film with High Molybdenum Content
Authors: Kamiyama Shota
Published: December 2020

Recently, miniaturizing electronic devices, such as handy phone, have been strongly requested. Number of mounted electronic components has been abruptly increased. Therefore, the high density of the component is mounted, the need for heat dissipation is increased. A heat radiation substrate is one of the most promising candidates to suppress increasing temperature of electronic devices. The heat radiation substrates need both high thermal conductivity and low coefficient of thermal expansion. A semiconductor has low coefficient of thermal expansion. A copper-molybdenum alloy has both high thermal conductivity and low coefficient of thermal expansion. An electroplated Cu-Mo alloy film has been investigated. However, deposition rate was decreased with high molybdenum content in the alloy. High molybdenum content is necessary to obtain low coefficient of thermal expansion. The low deposition rate is serious issue to put into industrial usage. The purpose of this study is to produce a film with high molybdenum content by high deposition rate. The chemicals used in bath preparation were CuSO4・5H2O 0.13 mol/L, Na2MoO4・2H2O 0.53 mol/L, C6H5Na3O7・2H2O 0.91 mol/L. The bath was adjusted to pH 9.0 and then electroplated. Nickel plate is used as the substrate and platinum plate is used as the anode. In this study, both bath temperature and current density have been investigated. Higher bath temperature makes deposition rate lower as shown in Fig.1. Higher current density makes deposition rate higher, but the current density dependence of the deposition rate is different on the bath temperature as shown in Fig.2. Lower dependence is observed in the case of higher bath temperature and effect of bath temperature on molybdenum content is different in the case of each current density. In the case of high current density, the molybdenum content increased with increasing bath temperature as shown in Fig.3. Therefore, when both bath temperature and current density are high, the films with high molybdenum content are plated by relatively high deposition rate as shown in Fig.4. The three micrometers thick copper-molybdenum alloy film with 23.9 at% molybdenum content film are plated for 1 hour under the condition of 50℃ bath temperature and 10 mA/cm2 current density. This deposition time to obtain 3 micrometers is one twentieth to obtain previously studied film with 17.9 at% molybdenum content.

Figure 1
A Study of the Correlation between Word-Line Resistance, Gamma Ratio and Write Failure in SRAM
Authors: Yang Tae Kyu , SHIN Changhwan
Published: December 2020

Based on the technical needs of customers and users, semiconductor devices have been advanced for the last a few decades. Most of customers and users prefer to have a faster speed and a longer usage time for their electronic devices (e.g., smartphone, tablet PC, and wearable devices). Those needs must have been the de-facto driving force for scaling down the physical dimension of transistors in integrated circuit (IC). When it comes to develop advanced transistors with faster speed but lower power consumption, there should exist conflicting electrical characteristics. For example, as the feature size of transistors in IC chip has been aggressively scaled down, the metal line resistance in IC has become a key knob in determining the aforementioned conflicting electrical characteristics, when the metal lines are designed to be densely placed and structured in a very limited chip area. If the metal line structure is less immune to heat dissipation from transistors, the performance of transistors should be degraded. Since a high speed operation for application processor (AP) is demanded by chip designers, the performance of static random access memory (SRAM) has become more critical. This is because the total volume of SRAM in AP has gradually been increasing. In this thesis, it turned out that the degraded gamma ratio (i.e., the ratio of the on-state drive current of pass-gate transistor to the on-state drive current of pull-up transistor) of failed bit-cells in SRAM array was the main reason for write failure. In addition, it was observed that the Word Line (W/L) sheet resistance of the failed cell is higher than that of good cells. We found that the gamma ratio become smaller when the W/L resistance is high (which is originated from a thinner metal line by metal etch test). We have set up an in-house failure model, in which a high-W/L-resistance-induced W/L enables a signal delay, and thereby, the write margin of SRAM is degraded. Therefore, the performance of pass-gate transistor with a higher WL resistance has become slower than that of normal transistor. To enhance the gamma ratio, we have developed a metal etch recipe. This can tune for reducing the deviation in the distribution of gamma ratio, and therefore, raise up the mean value of gamma ratio by optimizing the PMOS performance. As a result, the gamma ratio was improved from 1.1 to 1.2, and we can completely secure the strong stability of bit-cell without any write failure. And we have used a new index to manage the SRAM write failure, i.e., a Gamma of RWL Index. This would be useful for predicting the write failure of SRAM in real time in FAB. In industry, the index is standardized internally, and we are expecting that this newly-developed index would become significant in managing various FAB parameters.

Figure 1
Gallium Doped Zinc Oxide Work Function Extraction Using Transparent Gate MOSFET Devices
Authors: Saikumar Ashwin Kumar , Phelps Justin , Nehate Shraddha Dhanraj , Abdolvand Reza , Sundaram Kalpathy B.
Published: December 2020

Recent commercialization has peaked interest in transparent conducting oxides being implemented in transparent applications. Gallium doped zinc oxide (GZO) films exhibit excellent transmission characteristics in the visible spectrum while maintaining high electrical conductivity. In majority applications the work function of the material used has an impact on the device performance as it affects the energy barrier height at the hetero-junction interface. Hence, the work function identification is of critical importance.

In this article, we discuss work function extraction of GZO from a Metal Oxide Semiconductor Field Effect Transistor (MOSFET) device for the first time. Four level mask sets were used to fabricate two MOSFET devices following exact same conditions. Source and drain contacts were made using aluminum metal for both MOSFETs. One of the MOSFET was fabricated with aluminum as gate contact and the other MOSFET with transparent conducting GZO as its gate contact. GZO used in this research were RF sputtered. From the threshold voltage equation of both the fabricated MOSFETs, work function of GZO was extracted. The electrical and optical transmission studies were also performed on the sputtered GZO thin films and are reported in this study.
Effect of Mesopores of Marimo Nano Carbon Anode Material on Power Generation Performance of Direct Glucose Fuel Cell
Authors: Akiyama Shingo , Nakagawa Kiyoharu
Published: December 2020

Direct Glucose Fuel Cell (DGFC) is attracting attention as a clean and sustainable energy source because glucose is the most organic substance in nature. In this study, the effect of the mesopores of marimo nano carbon (MNC) on power generation performance for anode material of direct glucose fuel cell was investigated. Three types of MNC with different mesopore distributions were used for the catalyst support material, Pt was used as the supported metal. Also, Vulcan XC-72 which is carbon black of microporous material was used as a comparative material. In the glucose fuel cell performance test, MNC having many pores of about 35 nm showed the highest maximum output density of 0.72 mW cm-2 at 5 wt% metal loading and 0.3 M Glucose. Vulcan XC-72, which was a microporous material had low power generation performance. MNC showed higher power generation performance than that of Vulcan XC-72. The pores of about 35 nm probably promoted ion diffusion and rapid mass transport of reactants and products. These results indicated that MNC was an effective material as anode material for DGFC.

Figure 1
Novel Nitric Oxide Releasing Films Based on Inducible Nitric Oxide Synthase and Their Biomedical Applications
Authors: Maher Shaimaa , Kalil Haitham , Bayachou Mekki
Published: December 2020

Although a tremendous number of biomaterials are labeled as biocompatible for blood-contacting medical devices, such as vascular grafts, stents, heart valves, and catheters, the thrombogenic nature of these materials can cause serious complications in patients, and eventually functional failure. There are two major limiting factors to clinical application of these materials: 1) platelet activation and thrombus formation, and 2) infection. Nitric oxide (NO) has been known to exert anti-thrombotic, anti-proliferative, and anti-inflammatory effects in the vasculature. Several polymers incorporate NO-generating substances in order to improve biocompatibility of blood-contacting medical devices. However, an important drawback for these NO-release materials is the finite stoichiometric amount of embedded NO that they contain, which could impact their function for long-term or semi-permanent types of implants. In addition, controlling the release rates of NO flux that can be emitted at the polymer/blood interface proved to be challenging, and often requires the addition of other components to the polymer. Therefore, we hypothesized that incorporating the enzyme nitric oxide synthase into polymeric films as functional catalytic units that generate NO would result its antithrombotic coatings with potentially unlimited amounts of NO released.

In this project, we use layer-by-layer thin film building strategy to form layers of polyethyleneimine (PEI) and recombinant NOS enzymes as NO-releasing coatings. Charge-based layer-by-layer electrostatic adsorption allows for assembly of multi-component protein/PEI films with defined thickness and catalytic properties. When surfaces coated with PEI/NOS multilayered films are exposed to substrate arginine, a source of reducing equivalents, and other ingredients of the NOS reaction, nitric oxide is formed and released. In this work, we characterize the PEI/NOS thin films in terms of structure of NOS within the films as well as the amount of active NOS. Fourier transform infrared (FTIR) spectroscopic analysis was used to characterize structure-activity relationships of these NOS-containing thin films. We used cyclic voltammetry to determine the active enzyme concentration on the modified surfaces. We also examined how this activity relates to enzymatic activity in terms of NO released fluxes from the thin films. Finally, we assessed the functional performance of these films in terms of the extent to which they counteract platelet adhesion on the coated surfaces. To this end, we used platelet adhesion assays to determine how the number of platelets adsorbed on the PEI/NOS films is affected by the amount of NO released from the PEI/NOS thin films.
Oscillatory Reaction Rates in the Electro-Oxidation of Formaldehyde on Palladium
Authors: Melle Baptista Gabriel , Varela Hamilton
Published: December 2020

Formaldehyde has been used as a model system to investigate the electro-oxidation of small organic molecules, mainly on platinum[1]. This reaction is extremely dependent on the control conditions (potential and current) and it is also known to display self-organized oscillations on platinum[2]. In the present work we report a study of the oscillating reaction rates in the electro-oxidation of formaldehyde on polycrystalline palladium and in aqueous sulfuric acid media. The mapping of the existence region of potential oscillations was obtained by a slow current scan. Galvanodynamic oscillations were observed to range from 0.50 to 0.85 V. Further analysis was performed by galvanostatic measurements. The amplitude of potential oscillations increases in time. The potential-increase part of the cycle is formed by a rapid increase to about 0.60 V and then a slow one to 0.85 V, followed by an abrupt drop, with an average oscillation frequency of 0.15 Hz. Both the morphology and the frequency of oscillations differ from that observed for the electro-oxidation of formaldehyde on platinum, where the electrode potential varies from 0.40 to 0.90 V, and the it increases slowly until reaching 0.60 V followed by a rapid potential increase of up to 0.90 V, and then it decreases abruptly. Oscillations on platinum under comparable conditions were also about three times faster [3]. Overall, our results suggest the surface chemistry underlying the dynamics of formaldehyde elector-oxidation on palladium and platinum is considerably different, particularly under oscillatory regime. Some mechanistic aspects of the, far less studied, palladium system will be discussed.

References

[1] E.A. Batista, T. Iwasita, Adsorbed Intermediates of Formaldehyde Oxidation and Their Role in the Reaction Mechanism, Langmuir. 22 (2006) 7912–7916. doi:10.1021/la061182z.

[2] M.T.M. Koper, M. Hachkar, B. Beden, Investigation of the oscillatory electro-oxidation of formaldehyde on Pt and Rh electrodes by cyclic voltammetry, impedance spectroscopy and the electrochemical quartz crystal microbalance, J. Chem. Soc. Faraday Trans. 92 (1996) 3975. doi:10.1039/ft9969203975.

[3] G. Samjeské, A. Miki, M. Osawa, Electrocatalytic Oxidation of Formaldehyde on Platinum under Galvanostatic and Potential Sweep Conditions Studied by Time-Resolved Surface-Enhanced Infrared Spectroscopy, J. Phys. Chem. C. 111 (2007) 15074–15083. doi:10.1021/jp0743020.

Figure 1
(Invited) Advanced Battery Electrode Architectures Enabled By Additive Manufacturing Techniques
Authors: Fu Kun
Published: December 2020

Thick electrode with high-areal-capacity and high power is a practical and promising strategy to increase the energy density of batteries, but development towards thick electrode is limited by the electrochemical performance, mechanical properties, and manufacturing approaches. Additive manufacturing (AM) offers a new opportunity to create electrodes with desirable and optimal design to meet battery requirements in terms of high energy, high power, and mechanical strength. In this talk, I will discuss our recent work about how to use lab-developed 3D printer and printing principles and procedures to tailor electrode structures from nano-scale to microscale to achieve property-controlled battery electrodes.
Fabrication of Hollow Carbon Sphere@Au By Pyrolyzing Polystyrene@Polydopamine@Au As a Highly Efficient Electrocatalyst for Biosensing Application
Authors: Sun Bo-Yao , Chou Shih-Cheng , Fan Tzu-Ling , Wu Pu-Wei
Published: December 2020

We demonstrate a facile approach to fabricate an electrocatalyst consisting of Au encapsulating a hollow carbon microsphere (HCMS@Au) for the detection of uric acid (UA), dopamine (DA), and ascorbic acid (AA). The HCMS@Au is obtained by the pyrolysis of polystyrene@polydopamine@Au (PS@PDA@Au) microspheres. Electrochemical methods including potentiostatic mode and pulse voltammetric scans are employed to identify relevant redox signals for UA, DA, and AA. The HCMS@Au reveals a lower detection limit for DA in the ambiance of AA and UA. We attribute the Au nanoparticles with high electric conductivity and uniform size that are distributed conformally on the hollow carbon microspheres for the enhanced detection sensitivity. The morphology and composition of HCMS@Au are analyzed by scanning electron microscope, transmission electron microscope, and energy dispersive spectroscope.
Investigating SERS of Electrogenic Bacteria Via Charge Transfer Enhancement By Graphene Quantum Dots (GQDs)
Authors: Keisham Bijentimala , Cotts Sheldon , Berry Vikas
Published: December 2020

We report on the enhancement of the phononic excitation in electrogenic bacteria due to the electron transfer to interfaced graphene quantum dots (GQDs). This phenomenon enables GQDs to detect otherwise unobservable bacterial Raman peaks by chemeo-phononic amplification by a factor of ten. We show confirmation of the charge transfer ability of the electrogenic bacteria into GQD and provides a platform for chemical enhancement phenomena for biological sensing at the cellular level. This study also reports on the electrogenic bacteria’s phonon-polarization directly related to the chemical enhancement from the GQDs.
Hitting Two Molecules with One Photon; Photooxidation of C60 By Self-Sensitized Singlet Oxygen
Authors: Kalkan Kaan , Zhang Linqi
Published: December 2020

Thanks to its unique properties, C60 has remarkably impacted nanoscience in the past two decades. Specifically, it is the most efficient singlet oxygen (1O2) photosensitizer ever known. Yet, there has been no reported evidence of 1O2 reacting with its original C60 photosensitizer, which we refer to as ‘oxidation with self-sensitized 1O2’. The literature suggests both oxygen and C60 must be at excited states to undergo reaction, implying a 2-photon process: first, oxygen is photosensitized in the C60 and O2 complex (1C60·1O2); second, 1C60* is photogenerated (1C60*·1O2). However, this scheme is unlikely to occur in a solvent, where 1O2 would be rapidly quenched by solvent molecules before the second photon is absorbed by C60. Here, we substantiate a single-photon oxidation mechanism via self-sensitized 1O2 in solvents above a photon energy of 3.7 eV. Using phosphorescence (1270 nm) excitation spectroscopy and kinetics measurements, we identify the transition, 1Ag → 21Hu, as the driver of photooxidation. Subsequently, intersystem crossing generates the higher energy triplet transient, 3C60**·3O2, which then converts to 1C60*·1O2. Both excited by the same photon, at the same place and same time, C60 and O2 readily react. Such triplet-triplet annihilation, yielding two simultaneously-excited singlets, is unique. This scheme is stimulating for the conception of novel efficient photochemical processes, implemented with C60 or other photosensitizers. Additionally, rate constants derived from this study allow us to predict a C60 half-life of about a minute in the atmosphere, possibly explaining the scarceness of C60 in the environment.
Thermal Annealing of Polycatecholamine Coated Carbon Nanotube: A New Path for Copper-Carbon Nanotube Composites Fabrication
Authors: Duhain Antoine , Guillot Jérôme , Lamblin Guillaume , Lenoble Damien
Published: December 2020

In present days, the continuous miniaturization of electronic devices comes along with a problematic reduction of their life-time. This is due to the underlying current density being operated increasingly close to the maximum current-carrying capacity (ampacity) of the materials (copper, gold...) used in the conduction channels of micro-circuitry. In this respect, there is a growing attention for new materials with higher ampacity, and copper-carbon nanotube (CNT) composites could constitute a promising alternative. The interest of such copper-carbon composites relies on the combination of the complementary properties of both materials: the high conductivity of copper and the high ampacity of CNT.

However, the fabrication of an efficient Cu-CNT composite still remains a huge challenge and, up to now, the metal filling of a CNT hydrophobic matrix using electrochemical methods systematically requires an organic solvent based solution, which is not industrially and ecologically friendly. This constitutes an important drawback of those types of fabrication paths.

A new promising way to fabricate such a composite by electrochemistry is shown in our work (see figure 1). It is based on a copper doped polycatecholamine coating of CNT. The coated CNT are deposited to form a matrix and the interstices between CNT are then filled with metallic copper by using an electrochemical step in aqueous solution.

In this context, it is relevant to study how the coating impacts the CNT surface conductivity. In this respect, we characterize the CNT coating resistance before and after thermal annealing using C-AFM. Combined SEM and STEM images show the apparition of well dispersed nanoparticles on the CNT surface after thermal annealing. The change of nuclei density and their size distribution is also characterized in function of the annealing temperature. Finally, we use XPS and DSC to show that annealing of copper doped polycatecholamine coated CNT is, in fact, able to promote the reduction of Cu(II) into Cu(I) and Cu(0).

Figure 1
Electrophoretically Deposited Graphene-Based Composite Coatings for Spacecraft Charging Mitigation
Authors: Liu Danny X. , Wang Dan , Boman Joshua , Lyle Matthew , Hall Timothy , Dennison JR , Inman Maria
Published: December 2020

Spacecraft charging has been recognized as an important consideration for spacecraft design, and occurs due to interaction between hazardous space plasmas and spacecraft surface. Spacecraft can experience charging throughout operation due to high flux of incident electrons (ex. during geomagnetic sub-storm). As a result, different materials/components may experience a range of potentials which may lead to plasma-induced arcs, damaging spacecraft components. Graphene are emerging two-dimensional (2D) carbon materials with excellent physical and chemical properties, such as high conductivity, high tensile strength, high transparency, and high carrier mobility. These excellent properties make graphene potentially useful for applications in energy storage, aerospace, coatings and polymer markets and thermal protection. Substrates constituted by graphene harness the thermal and mechanical properties to create novel coatings with superior performance, hence broadening the graphene application spectrum. Of particular interest is the potential capability of graphene-based materials to provide increased protection against spacecraft charging in the space plasma environments. Furthermore, the work function of graphene can be tuned by either metal doping or functionalization, thereby facilitating autonomous or passive electron emission and increasing the electron yields and enhancing the possibility of emission through negative electron affinity. By enabling charge dissipation between the various components at modest potential differences, discharge arcing may be prevented

Within this context, Faraday Technology is developing a graphene-based composite coating with high electron yields over a wide range of incident electron energies. This approach utilizes electrophoretic deposition to deposit graphene-based coatings onto test substrates, which may maintain integrity of spacecraft by autonomous electron emission in relevant environments. Next, an electrochemical process is used to decorate the graphene surface with various low work function metals (alkali, alkaline earth, transition). This approach offered significant improvements in the electron yield (290% increase over the undecorated coating) and substantially extended the range (~9 times) of incident electron energies between crossover points as shown in Figure 1/Table 1.

Acknowledgements: The financial support of DOD Air Force Contract No.: FA9453-19-P-0573 is acknowledged.

Figure 1
Carbon Aerogels Electrodes for Energy Storage Applications
Authors: Parra-Puerto Andres , Rubio-Garcia Javier , Markiewicz Matthew , Zheng Zhuo , Kucernak Anthony
Published: December 2020

Resorcinol – Formaldehyde Carbon Aerogels (CAGs) with different microstructure properties are very interesting materials for energy storage applications [1]. By changing the molar ratio between resorcinol and catalyst, and varying the resorcinol concentration, it is possible to change the density, mesoporosity and microporosity of the aerogels [2]. In this work we synthesize a number of materials with different properties and test their performance in an all Vanadium RFB.

The BET analysis showed a total surface area between 643 to 931 m2 g-1 and a variation of deposition morphology. The best performing material did not have the highest surface area, but instead had a good balance between microporous and external surface area (about 50:50), and on the macroscopic scale had sufficiently large pores to allow efficient electrolyte permeation. In contrast although the poorest electrodes had the highest surface areas, they had poor macroscopic porosity leading to large mass transport loss. The best performing electrode achieved a power density of 706 mW cm-2 at 1 V. This electrode was cycled at two different current densities for 20 cycles, achieving a battery efficiency between 75 to 80 % [3].

References

[1] J. Biener et al., “Advanced carbon aerogels for energy applications,” Energy Environ. Sci., vol. 4, no. 3, p. 656, Mar. 2011, doi: 10.1039/c0ee00627k.

[2] A. M. Elkhatat and S. A. Al-Muhtaseb, “Advances in tailoring resorcinol-formaldehyde organic and carbon gels,” Adv. Mater., vol. 23, no. 26, pp. 2887–2903, 2011, doi: 10.1002/adma.201100283.

[3] A. Parra-Puerto, J. Rubio-Garcia, M. Markiewicz, Z. Zheng, and A. Kucernak, “Factors Leading to Optimum Carbon Aerogel Based Electrodes for Redox Flow Batteries.” In Preparation

Figure 1
Operando Small-Angle Scattering Investigation of the Lithium/Sulfur Battery - Are Structural Features of the Nanocarbons Important?
Authors: Hark Eneli , Risse Sebastian , Kent Ben , Müller Rafael , Ballauff Matthias , Lu Yan
Published: December 2020

Great deal of studies have been focused on the energy conversion and storage devices [1,2]. Among them, lithium/sulfur battery (Li/S) with the high gravimetric energy density (~730.0 Wh/kg) and affordability (sulfur is an earth-abundant element) [1]. Targeted research could promote the commercialization of Li-S batteries in a more efficient way and keep up with challenges for building continual batteries in terms of performance and energy density, which are greatly influenced by the multi-phase interfacial reactions, polysulfide equilibria and shuttling as well as by the electrolyte decomposition under the operating conditions [1,2].

In presentation, we will present recent work on Li/S batteries in two parts: First part is related to studies of the carbonaceous materials used as cathodes in these systems. The well-tailored carbons as the sulfur hosts in Li/S batteries could be used to prevent low sulfur utilization, therefore the model-free analysis by small-angle x-ray scattering in order to obtain reliable data on the internal surface area and the average pore size will be discussed [3].

The morphological and porous features of carbons can be extremely modified when they are processed in real electrochemical conditions. Thus, in a second part we will present the simultaneous performance of several independent techniques: small-angle neutron scattering (SANS) (heatmap of the Li/S during the galvanostatic cycling), electrochemical impedance spectroscopy (EIS), galvanostatic/potentsiostatic cycling of the Li/S test cell [4]. A nanoporous and binder-free carbon electrode was applied as a model electrode for further in situ/operando analysis, which is deemed of great importance for mechanism study of batteries.

The structural characterization of the nanocarbons is a crucial step towards better understanding the elucidation of structure-property-relationships which in turn will shed light on the processes occurring in complex in Li/S battery systems and helps to design cost-effective, safe batteries with preferably high capacities and longer lifetime over many cycles. A key structural features of nanocarbons and operando Li/S analysis will be the subjects of a presentation. Results obtained by in situ/operando SAS techniques are scientifically interesting and technologically very relevant for electrochemical applications.

[1] G. Li, Z. Chen, J. Lu, Chem 4, 2018, 3–7.

[2] A. El Kharbachi, O. Zavorotynska, M. Latroche, F. Cuevas, V. Yartys, M. Fichtner, Journal of Alloys and Compounds 817 (2020) 153261.

[3] E. Härk, A. Petzold, G. Goerigk, S. Risse, I. Tallo, R. Härmas, E. Lust, M. Ballauff. Carbon 146 (2019) 284-292.

[4] S. Risse, E. Härk, B. Kent, M. Ballauff, ACS Nano 13 (9) (2019) 10233-10241.

Figure 1
Corrosion Resistance of Electrochemically Exfoliated Doped-Graphene Nanostructures
Authors: Lopez Pablos Maria , Roberts Edward P.L.
Published: December 2020

Graphene with its high conductivity and accessible surface area makes it an ideal material applicable as an adsorbent that can be electrochemically regenerated and reused over several cycles. However, it has been reported that corrosion causes degradation, weight loss and lifetime reduction of these adsorbents [1]. Most studies on corrosion mechanism in carbon materials has focused on highly porous and disordered materials used as catalyst supports for fuel cell electrodes. However, little work has been done to identify the corrosion mechanism in doped-graphene materials. The current study analyzes the corrosion resistance by using an accelerated corrosion protocol on electrochemically synthesized graphene samples with different doped heteroatoms including nitrogen and phosphorus. The accelerated corrosion protocol consisted of a potential steps whereby graphene was exposed to high potential for a few seconds for carbon corrosion to occur [2]. The corrosion mechanism and the degree of oxidation of the doped-graphene materials were characterized using cyclic voltammetry (CV), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Electroactive groups, changes in the double layer capacitance, and morphological changes were identified using these techniques. The stability of samples was determined for different samples using the accelerated corrosion test. Interestingly, the peaks associated with electroactive oxygen-containing surface groups were present and showed the extent of corrosion for both graphene samples before and after the test. A higher degree of corrosion was observed from the phosphorus doped-graphene as compared to the nitrogen-doped graphene. This was further confirmed from the corrosion current and percentage change in gravimetric capacitance. The implication of these findings suggest that the large distortion caused by the additional P-doping in the carbon lattice allows open edge sites and produces wrinkles [3]; thus providing more defective sites and facilitating corrosion. Further materials analyses are ongoing to fully elucidate this process in detail and support the results obtained from the electrochemical tests.

References

[1] F. Sharif, L. R. Gagnon, S. Mulmi, and E. P. L. Roberts, “Electrochemical regeneration of a reduced graphene oxide / magnetite composite adsorbent loaded with methylene blue,” Water Res., vol. 114, pp. 237–245, 2017.

[2] F. Forouzandeh, X. Li, D. W. Banham, F. Feng, S. Ye, and V. Birss, “Understanding the Corrosion Resistance of Meso- and Micro-Porous Carbons for Application in PEM Fuel Cells,” J. Electrochem. Soc., vol. 165, no. 6, pp. F3230–F3240, 2018.

[3] C. H. Choi, S. H. Park, and S. I. Woo, “Binary and ternary doping of nitrogen, boron, and phosphorus into carbon for enhancing electrochemical oxygen reduction activity,” ACS Nano, vol. 6, no. 8, pp. 7084–7091, 2012.

Figure 1
Green Synthesis of Nickel Borides Supported over Multiwall Carbon Nanotube As a Novel Catalyst for Hydrogen Evolution
Authors: Quach Qui , Phillips Erin , Biehler Erik , Abdel-Fattah Tarek M
Published: December 2020

The use of non-renewable fuels such as coal, oil, and natural gas significantly affects ecological system and human health. A substantial effort has been spending to find an eco-friendly and efficient energy source. Hydrogen appears as a green energy source which emits water as its byproduct during the combustion. The primary concern of hydrogen fuel is its dependence on fossil fuels in the production. Hydrogen feedstock material like Sodium borohydride (NaBH4) becomes potential, alternative source for manufacturing hydrogen fuel. However, the reaction between NaBH4 and water was slow and required a durable catalyst 1,2,3. The synthesis method of some catalysts is often expensive and require the use of various toxic chemicals4. The purpose of this study was to discover a green method of synthesizing nickel borides composite (NiB@MWCNT) and to utilize it in enhancing hydrogen generation reaction. The composite was synthesized from supported nickel metal organic framework (Ni-MOF-5) in the presence of Multiwalled Carbon Nanotube (MWCNT). The structure and composition of NiB@MWCNT was determined by Powder X-Ray Diffraction (PXRD), Scanning Electron Mircroscopy (SEM, Figure 1), Energy Dispersive X-Ray Spectroscopy (EDS), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), and Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). The catalytic efficiency of NiB@MWCNT was tested at temperatures of 281K, 295K, and 303K. The temperature trials indicated the activation energy was 43 kJ mol-1. NiB@MWCNT also showed a steady hydrogen generation of 44.4 ml through the reusable test.

References:

T. Dushatinski, C. Huff, and T. Abdel-Fattah, Applied Surface Science, 385, 282 (2016).

C. Huff, J. M. Long, A. Heyman, and T. Abdel-Fattah. Applied Energy Materials, 9, 4635-4640 (2018)

C. Huff, J. M. Long, A. Aboulatta, A. Heyman, and T. Abdel-Fattah, ECS Journal of Solid State Science and Technology, 10, M115-M118 (2017)

Y. Huang, Y. Wang, R. Zhao, P. Shen, and Z. Wei. International Journal of Hydrogen Energy. 23. 7110-7115 (2008).

Figure 1. SEM imaging of NiB@CNT at 50 micrometer scale

Figure 1
Coral-like Metal Oxide/C Hybrid Microspheres Comprising a Porous Yolk and a Hollow Thin-Shell for Anodes in Li Ion Batteries
Authors: Cho Jung Sang
Published: December 2020

Nowadays, innovative anodes are in demand owing to the requirement for improvement in the performance of Li ion batteries (LIBs). Although yolk–shell structured transitional metal oxides (TMOs) with various compositions have been studied as anodes for LIBs thus far, their long-term cycle properties are unsatisfactory in practical implementation. In order to solve this problem, hybrids of TMOs and C could be a effective strategy, but with the traditional synthetic process for the yolk–shell structure, it is difficult to prepare the yolk-shell structured TMO/C hybrid. In this study, we introduce a novel synthetic strategy for the yolk-shell structured TMO/C hybrids. The yolk shows a coral-like structure with interconnected mesopores. The synergetic effects of the coral-like yolk-shell structure with well-defined interconnected mesopores and a highly conductive C content result in advanced anodes with excellent Li+ ion storage properties. The detailed formation mechanism of the structure and its electrochemical properties as anodes for LIBs were investigated, in detail.