bluuebunny/crossref_metadata_2025_split 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
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
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.
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
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