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A new and low cost facile technique has been reported to fabricate coaxial nickel oxide/nickel (NiO/Ni) nanowire (NW) arrays as high performance electrodes for pseudocapacitors. The arrays are fabricated by direct electrochemical deposition of Ni inside nanoporous alumina template and the subsequent conversion of the outer shell into oxide by oxygen plasma annealing. This resulted in a unique core/shell, one-dimensional (1D) vertical nanostructure, which uses the inner Ni core as a conductor and robust support for a large effective surface area, and thereby provides reliable electrical connection to a thin redox-active NiO shell. The morphology, crystal structure, and shell thickness of NiO are found to be dependent on the annealing conditions (input power and plasma annealing time at a constant oxygen flow). The coaxial NiO/Ni NW arrays with the optimized redox-active NiO shell thickness displayed a high capacitance value of 0.36Fcm−2. Furthermore, the arrays show a rapid charge–discharge kinetics and stable long-term cycling performance (practically no drop in capacitance was observed even after 2000 cycles at high charging–discharging current of 5mAcm−2). Excellent cycling stability and faster charge–discharge kinetics are attributed to the unique core/shell (NiO/Ni) and vertically aligned nanoarchitecture that facilitates faster electron and ion transport during the charge–discharge reactions.
Despite recent progress in lithium-sulfur batteries (LSB), the chemically immobilizing mechanism for sulfur species hasn’t been understood totally. For the first time, we report on insight into the immobilizing nature for soluble lithium polysulfides (LPS) based on metal-organic frameworks (MOFs) derived porous TiO2-S cathodes for LSB. The LSB based on hierarchically porous TiO2-S cathode displays greatly enhanced rate capability with superior specific capacity and coulombic efficiency. Electrochemical impedance spectroscopy for fresh and cycled cells indicates that the charge transfer kinetics of the TiO2-S cathode can be obviously enhanced, and the diffusion coefficient of Li-ions greatly increases due to the Ti-S chemical bonding during charge/discharge process, almost 17 times higher than that of fresh TiO2-S hybrid cathode. The charge resistance and diffusion coefficient can be comparable to that of previously reported carbon/sulfur cathode. It is revealed that dissolution of lithium ploysulfides, deposition of Li2S/Li2S2 and shuttle effect can be greatly mitigated due to the chemical immobilization effect from Ti-S chemical bonding. Furthermore, the porous structures of MOFs-derived TiO2 effectively alleviate the volume change, shortens the diffusion path of Li+. The present work provides a hint to design rational cathodes for high performance LSB.
Co3O4 porous nanosheets were fabricated through two-step synthetic method: water bath stir process followed by annealing treatment. As an electrode for battery, the achieved sample exhibits excellent electrochemical performance. The cyclic voltammetry (CV) curve shows that the sample possesses two pairs of redox peaks, revealing good redox behavior of Co3O4. Both the two kinds of valence (Co2+ and Co3+) participated in Faradic reaction. The Co3O4 porous nanosheet reveals a high specific capacity of 583.1 C g−1 at a scan rate of 1 A g−1. With the obtained sample as positive electrode and commercial activated carbon (AC) as negative electrode, the Co3O4//AC asymmetric cell is able to achieve high voltage window of 0–1.7 V. The cycle capability of the as-made asymmetric device possesses 83.5% retention after 10,000 galvanostatic charge/discharge cycles. The energy density varies from 33 Wh kg−1 to 21 Wh kg−1 at a power density ranging from 798 W kg−1 to 18,900 W kg−1.
Here we propose a core-shell tubular nanostructure consisted of hollow carbon nanofiber and manganese oxide (MnO2) for the application of high capacitance electrochemical capacitors. Hollow nanostructured carbon nanofibers are prepared using an electrospinning technique with a dual nozzle. The hollow channel of carbon nanofibers enables the uptake of MnO2 precursor solution inside the hollow carbon nanofiber, leading to the formation of MnO2 layer on both the inner and outer surfaces of hollow carbon nanofiber. The utilization of both surfaces of hollow carbon nanofiber increases the effective reaction sites of electrode materials contacted with an electrolyte as well as maximizes the loading mass of MnO2 on the surface of hollow carbon nanofiber (94% compared to carbon contents), consequently enabling the fabrication of electrochemical capacitors with the increased specific capacitance of 237 F/g.
An asymmetric supercapacitor constructed using an electrochemical double-layer, active carbon positive electrode and a Bi2O3/porous carbon negative electrode in an alkaline solution is presented here. In this study, nanosized Bi2O3 was formed and highly dispersed into a porous active carbon material using a simple process. The characteristics of the Bi2O3 electrode as well as its electrochemical performance in the hybrid device were investigated. A highly reversible redox transit was observed in the cyclic voltammogram of the Bi2O3 loaded electrode. The transformations of Bi(III) to Bi(0) and Bi(0) to Bi(III) are clearly shown in the charge/discharge curve of Bi2O3, with potential plateaus at −0.6 and −0.5 V. The results of this experiment reveal that, with introduction of the Faradic reaction of Bi/Bi2O3, the overall specific capacity of the hybrid supercapacitor during discharge was significantly increased compared to that of a symmetric set-up.
Long-term electrochemical behaviors of hydrated MnO2 electrochemical capacitor (EC) electrode in alkali chloride (KCl(aq)) electrolyte have been studied by using potential cycling for thousands of cycles within different potential windows spanning from 0.8V (versus Ag/AgCl(aq)) to varied lower-end potentials below the open-circuit potential. Three potential ranges resulting in different cycling behaviors of the oxide EC have been identified. Range I: cycling above 0.2V results in no change in either microstructure or surface chemistry of the oxide electrode, and no capacitance reduction has been observed. Range II: cycling down to 0.0V leads to extensive morphological reconstruction and limited reduction of surface Mn ions, while the electrode capacitance remains stable. Range III: cycling with lower-potential end below 0.0V results in obvious capacitance reduction, along with different morphological reconstruction and Mn reduction from those in Range II. For each selected lower-end potential in Range III, the capacitance descends to a plateau within first thousand cycles, and the extent of the capacitance reduction increases as the lower-end potential decreases.
Positive Li–Co–O films for all-solid-state thin-film lithium batteries were prepared by electron cyclotron resonance (ECR) sputtering using Li x CoO2 targets (x =1.0, 1.2, 1.7 and 2.0). The Li–Co–O films prepared using the x =1.0, 1.2 and 1.7 targets contained a Co3O4 impurity phase with high-temperature phase LiCoO2. The film prepared using the x =2.0 target was found to contain only a pure LiCoO2 phase by Raman spectrometry and the inductively coupled plasma/atomic emission spectrometry (ICP/AES) method, and a thin-film battery using this film exhibited good electrochemical properties as a result of the improved utilization of the positive film.
The reversible oxidation/reduction of polypyrrole films coating a platinum electrode is studied here in NaCl aqueous solution by cyclic voltammetry at different scan rates. Reacting polypyrrole films are dense gels constituted by molecular (polymeric) electrochemical machines, ions and water, mimicking the intracellular matrix of living cells. Both, the extension of the reaction (the consumed charge) and the electrical energy consumed by the oxidation and reduction reactions change as a function of the scan rate or of the imposed frequency. That means that the reaction involving conformational, or allosteric, movements of the reacting polymeric chains senses the imposed working energetic conditions. A theoretical description of the attained empirical results is presented getting the sensing equations. An important energetic asymmetry exists for those reactions between oxidation and reduction consumed energies. Technological outlooks related to the efficiency of electrochemical energy transducers are presented. Results are translated to biological organs as muscles constituted by chemical molecular machines working under demand of higher energies by brain suggesting how the back signal informing the brain about the working energetic conditions can be generated.
In this work, high-performance LiFePO4/C materials are successfully prepared by a spray drying-carbothermal method. The effect of the carbon source (viz. inorganic, organic and their hybrid) is extensively investigated on the microstructure and electrochemical property of the composite materials. Vulcan XC-72, an inorganic carbon additive, can remarkably improve the electronic conductivity of the composite material; however, the resultant large crystallite size and low specific surface area limit the Li ion diffusion and thereby lower the electrochemical performance. As a typical organic carbon additive, glucose yields mesoporous LiFePO4/C particles with a much higher specific surface area and smaller crystallite size; however, the electronic conductivity of the pyrolyzed carbon is insufficiently high for the real applications. By using the dual hybrid carbon sources, the synthesized LiFePO4/C material features a high electronic conductivity, large specific surface area, small grain size, and the formation of mesopores. In line with these advantages, the composite yields the best electrochemical performance with the discharge capacity of 168.1 mAh g−1 at 0.1 C, which is approximate to the theoretical capacity. This material also performs well at high rates with discharge capacities of 122.0 and 93.0 mAh g−1 at 5.0 and 10.0 C, respectively.
In this work, Al–Zn–Mg sacrificial anode was developed from recycled aluminum and zinc. Characterization of the alloy using XRD, TEM and optical microscopy was conducted. Also, the influence of precipitation hardening time on the performance of the sacrificial anodes in seawater was investigated. The results indicated that the formation of both stable and metastable MgZn2 phase during precipitation hardening process has a significant effect on the corrosion behavior of the alloy. The high anodic efficiency of the alloy was attributed to the formation of the stable MgZn2 (η-phase) within the aluminum matrix.
Low-grade inflammation leads to several metabolic disorders, and adherence to a Mediterranean diet (MedDiet), cardiorespiratory fitness (CRF), and muscular fitness (MF) has been considered important markers of metabolic healthy in youth. We investigated the combined association of adherence to Mediterranean diet, and muscular and cardiorespiratory fitness on high-sensitivity C-reactive protein (hs-CRP) in adolescents.
A mixture of cobalt phthalocyanine (CoPc) and graphene is thermally decomposed at 800°C to synthesize a novel catalyst. Scanning electron microscopy (SEM) and transmission electron microscope (TEM) show that the catalyst retains the lamellar structure of graphene. X-ray diffraction (XRD) reveals that the catalyst is no longer composed of CoPc and high-resolution TEM (HRTEM), X-ray photoelectron spectra (XPS) prove that Co and N elements have entered the graphene molecular structure, thus forming a Co-Nx-graphene (Co-Nx-G) catalyst composed of a CoN4-macrocyclic-like structure. This catalyst serves as an excellent catalyst of thionyl chloride (SOCl2) reduction. Cyclic voltammetry and battery discharge tests reveal that Co-Nx-G-800 substantially increases the discharge voltage and capacity of a Li/SOCl2 battery. Moreover, Co-Nx-G-800 exhibits stable catalytic activity during battery storage. Ultraviolet–visible spectroscopy shows that CoPc is soluble in a SOCl2 electrolyte solution, whereas Co-Nx-G-800 is not, this characteristic contributes to the stable catalytic property of Co-Nx-G.
This paper presents a two-dimensional computational model of micro-structured cathodic electrodes featuring nano-porous gas diffusion media that increase the surface to volume ratio of the deposited catalyst layer. A key objective of the modeling effort is to elucidate the Knudsen diffusion within the nano-porous electrode. In addition, the model is non-isothermal and resolves the natural convection in the ambient air directly above the cathode. A major component of the analysis is the identification of mass transport limitations introduced by the micro-structured electrode and the nano-porous gas diffusion layer. Furthermore, the potential for passive regulation of temperature and oxygen supply is investigated. This analysis of the natural convection is unique because it examines buoyancy effects above a horizontal plate with variation in thermal conductivity, segregated regions of porous media, and discrete heating locations. The results of this study indicate that this electrode configuration is feasible and does not suffer from insurmountable mass transfer limitations.
Cost efficient and long-term stable catalysts are in great demand for the oxygen evolution reaction (OER), a key process involved in water splitting cells and metal–air batteries. Here, we demonstrate that the ultrathin amorphous cobalt–vanadium hydr(oxy)oxide we synthesized is a highly promising electrocatalytic material for the OER with a low overpotential of 0.250 V (even lower down to 0.215 V when supported on Au foam) at 10 mA cm−2 and a long stable operation time (170 h) in alkaline media. In combination with in situ X-ray absorption spectral characterization and first-principles simulations, we reveal that the ultrathin, amorphous and alloyed structural characteristics have enabled its facile transformation to the desirable active phase, leading to a dramatically enhanced catalytic activity. Our finding highlights the remarkable advantages of the two-dimensional amorphous material and sheds new light on the design of high-performance electrocatalysts.
Anxiety disorders are common in children and severely impair their functioning. Because a hallmark symptom of anxiety is somatic complaints, anxious youth often seek help from their school nurse. Thus, school nurses are in an ideal position to identify anxious children and intervene early. This study assessed the feasibility of a brief nurse-administered intervention (CALM—Child Anxiety Learning Modules) based on cognitive behavioral strategies to reduce anxiety symptoms and improve academic functioning. Nine elementary school nurses completed a one-day training and administered the CALM intervention to 11 children with elevated symptoms of anxiety (M age: 8.09; range 5–11; 54% male; 91% White). Feasibility of the intervention was assessed using several indicators (e.g., training satisfaction, intervention satisfaction/helpfulness). Pre-post intervention child outcomes were collected from evaluators, parents, children, and teachers. Results indicated that the majority of nurses were highly satisfied with the training and reported the intervention was feasible. Paired t tests on pre-post outcome measures revealed significant reductions in anxiety, somatic symptoms, and concentration problems. Nurses (70%), parents (81%), and children (50%) reported that the intervention was either somewhat or very helpful. Preliminary results identified barriers to implementation but also suggest that the intervention is feasible and helpful. A sufficiently powered randomized controlled trial is needed to assess the intervention’s efficacy.
In this paper, we present a first principles high throughput screening system to search for new water-splitting photocatalysts. We use the approach to screen through nitrides and oxynitrides. Most of the known photocatalytic materials in the screened chemical space are reproduced. In addition, sixteen new materials are suggested by the screening approach as promising photocatalysts, including three binary nitrides, two ternary oxynitrides and eleven quaternary oxynitrides.
The application of Microsoft Excel Solver routines to analyze data from a thermal-probe placed in a number of samples is described. The successful application of the Solver routine to the thermal-probe temperature time data requires the selection of an appropriate time-interval. The various critical times are discussed and a method proposed for selecting the appropriate Solver routine and the time-interval over which the experimental data must be analyzed. Values of the sample thermal conductivity, the thermal diffusivity and the probe to sample conductance are reported for a stainless-steel probe in unused mineral oil, and paraffin wax and for a copper probe in Magna904 and PTFE. The results for a commercial probe in agar agree with accepted data for water and the results for a clay–straw mixture demonstrates the method applied to a good insulator.
LiNiO2 with Ni defects in the 3b sites (named “Ni defected” LiNiO2) was prepared and characterized using electrochemical calorimetry. Different from conventionally prepared “Standard” LiNiO2, “Ni defected” LiNiO2 exhibited high reversibility. The 1st coulombic efficiency was recorded to be 101% due to minimization from the Ni ion substitution at the Li 3a sites. The reversible capacity was 212 mAh g−1 in the 1st cycle with 87% capacity retention after 80 cycles because Li+ ordering and Jahn-Teller distortion during the charge and discharge cycle were suppressed by introducing the Ni defect 3b sites. The proposed simple defect design concept introduced the development of a high capacity and highly reversible LiNiO2 material without metal substitutions and without increasing the charge cut-off voltage.
EC–DMC–DEC solutions comprising LiPF3(CF2CF3)3 (LiFAP), LiPF6 and LiN(SO2CF2CF3)2 (LiBETI) were tested with graphite and LiMn2O4 electrodes. Cyclic voltammetry (CV, fast and slow scan rates), chronopotentiometry, impedance spectroscopy, surface sensitive FTIR and XPS were used for this study. It was found that the new salt LiFAP is a promising candidate for use in rechargeable Li-ion batteries. The thermal behavior of these electrolyte solutions was also studied using accelerating rate calorimetry (ARC). It was found that LiFAP solutions are more stable than LiPF6 solutions while LiBETI solutions have the highest thermal stability.
Genotoxicity testing is an important part of preclinical safety assessment of new drugs and is required prior to Phase I/II clinical trials. It is designed to detect genetic damage such as gene mutations and chromosomal aberration, which may be reflected in tumorigenic or heritable mutation potential of the drug. Botanical new drugs in the U.S. are entitled to a waiver for preclinical pharmacology/toxicology studies, including genotoxicity testing, in support of an initial clinical trial under IND, contingent on previous human experience. Recently, ethical concerns have been raised over conducting Phase I/II clinical trials of new drugs with positive genotoxicity findings in healthy volunteers. Although the relevance of this issue to patients, as opposed to healthy volunteers, depends on the drug’s indication, duration of treatment, and specific findings related to the assays, the regulatory view is to avoid exposing patients to genotoxic compounds unnecessarily in clinical trials. This philosophy may impact on herbal supplement marketing and botanical drug development, in that genotoxicity data are often lacking while consumers are exposed to the herbal supplement, or healthy volunteers are tested in an initial Phase I/II clinical trial on the botanical drug. This paper presents results of a survey conducted on genotoxicity data in botanical INDs submitted to the Agency and discusses the significance of this information. The information presented indicates that the sponsors of botanical INDs have increasingly recognized the importance of genotoxicity information and may have prioritized its acquisition in their strategic drug development programs.
A unique approach for improving the thermal stability of delithiated LiCoO2 cathodes has been presented, which is based on the encapsulation of LiCoO2 by a new cyano-substituted polyvinylalcohol (cPVA)-based gel polymer electrolyte. In a bid to maximize the effect of encapsulation, the cPVA-based gel polymer electrolyte was applied to the LiCoO2 cathode with a predetermined degree of porosity. Through this new process, the gel polymer electrolyte is expected to locate preferentially onto the LiCoO2 at well-controlled thickness, with the overall porous structure of the modified cathode being little influenced. Due to the presence of cyano (CN) groups, the cPVA shows high dielectric constant (ɛ =15 at 1kHz at 20°C), which is thus expected to enhance the Li-salt dissociation, leading to the excellent ionic conductivity (around 7mScm at 25°C). Under the assumption that the LiCoO2 could be fully covered with the cPVA, the encapsulated thickness is calculated around 10nm, which was further evidenced by the FE-SEM results. Meanwhile, compared to the pristine LiCoO2 cathode (ΔH =413Jg−1), the modified LiCoO2 cathode exhibited the superior thermal stability (ΔH =31Jg−1) and also presented the satisfactory C-rate performances and cyclability. Such a remarkable enhancement in the thermal stability and the electrochemical performances has been discussed on the basis of the morphology of the modified LiCoO2 cathode and the electrochemical properties of the cPVA-based gel polymer electrolytes.
The MESSIER, a measure of social and communication skills and the Vineland Social Maturity Scale were administered to 618 severe and profoundly mentally retarded adults. The goal of the study was to establish the potential utility of the MESSIER for classifying level of intellectual disability in this group. Comparing MESSIER scores to previously established DSM-IV-TR diagnosis, 86% of the severe and 80% of the profoundly mentally retarded persons were correctly classified. The implications of these data in using the MESSIER for classification and treatment planning are discussed.
We report the failure mechanism of a Ni-rich layered cathode material (LiNi0.8Co0.1Mn0.1O2) in Li-ion full cells. Laminated pouch-type full cells were cycled 300 times, after which the cells exhibited 16.3% capacity fading. After 1, 100, 200, and 300cycles, each full cell was disassembled and the cathode was investigated via a half-cell test, X-ray diffraction (XRD), and field emission scanning electron microscopy (FE-SEM). XRD analysis showed loss of the active lithium source in the cathode, and FE-SEM observation exhibited traces of mechanical failure in the Ni-rich secondary particles. Particle strength measurements on the cathode materials by applying compressive force demonstrated that the mechanical strength of particles significantly weakened after full-cell cycling. Thus, the capacity of the Ni-rich cathode may deteriorate during full-cell cycling because of decreases in compressive particle strength. This issue should be considered in materials preparation processes.
The electrochemical properties of layered Li-rich oxide Li1.2Ni0.13Co0.13Mn0.54O2 (LLO) can be enhanced by a facile NaF surface modification. We have clarified by XPS, HR-TEM and HAADF-STEM analyses that the mechanism is the formations of a gradient coating layer Na1-xLixF and a gradient LLO surface Li1.2-xNaxNi0.13Co0.13Mn0.54O2 via a Li+/Na+ exchange reaction. The exchange reaction occurs at the Li-slabs of LLO down to a depth of less than 15 nm. After such a double gradient surface modification, the LLO displays markedly improved cycle life and rate capability as well as suppressed voltage decay. It exhibits a capacity retention of 85% beyond 1000 cycles at 10 C and a voltage decay of only 0.0021 V per cycle at 0.5 C, revealing great application prospects in energy storage materials.