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A simple procedure was developed to prepare a glassy carbon (GC) electrode modified with nickel oxide (NiOx) nanoparticles and water-soluble dyes. By immersing the GC/NiOx modified electrode into thionine (TH) or celestine blue (CB) solutions for a short period of time (5–120s), a thin film of the proposed molecules was immobilized onto the electrode surface. The modified electrodes showed stable and a well-defined redox couples at a wide pH range (2–12), with surface confined characteristics. In comparison to usual methods for the immobilization of dye molecules, such as electropolymerization or adsorption on the surface of preanodized electrodes, the electrochemical reversibility and stability of these modified electrodes have been improved. The surface coverage and heterogeneous electron transfer rate constants (k s) of thionin and celestin blue immobilized on a NiOx-GC electrode were approximately 3.5×10−10 molcm−2, 6.12s−1, 5.9×10−10 molcm−2 and 6.58s−1, respectively. The results clearly show the high loading ability of the NiOx nanoparticles and great facilitation of the electron transfer between the immobilized TH, CB and NiOx nanoparticles. The modified electrodes show excellent electrocatalytic activity toward hydrogen peroxide reduction at a reduced overpotential. The catalytic rate constants for hydrogen peroxide reduction at GC/NiOx/CB and GC/NiOx/TH were 7.96(±0.2)×103 M−1 s−1 and 5.5(±0.2)×103 M−1 s−1, respectively. The detection limit, sensitivity and linear concentration range for hydrogen peroxide detection were 1.67μM, 4.14nAμM−1 nAμM−1 and 5μM to 20mM, and 0.36μM, 7.62nAμM−1, and 1μM to 10mM for the GC/NiOx/TH and GC/NiOx/CB modified electrodes, respectively. Compared to other modified electrodes, these modified electrodes have many advantages, such as remarkable catalytic activity, good reproducibility, simple preparation procedures and long-term stabilities of signal responses during hydrogen peroxide reduction.
Biomass-derived carbons have been extensively researched as electrode material for energy storage and conversion recently. However, most of the previous works convert crude biomass directly into carbon and the electrochemical capacitances for the resultant carbons are quite often underestimated as well as large variations in capacitances exist in literatures due to the complex nature of biomass, which practically hinder their applications. In this work, polysaccharide nanofibers were extracted from an inexpensive natural fungus using a hydrothermal method and were converted to porous carbon nanofibers (CNFs) by potassium hydroxide activation. The porous carbons were assembled into symmetric supercapacitors using both potassium hydroxide and an ionic liquid (IL) as electrolytes. Solid state nuclear magnetic resonance characterization showed that the micropores of the as-prepared carbons are accessible to the IL electrolyte when uncharged and thus high capacitance is expected. It is found in both electrolytes the electrochemical capacitances of CNFs are significantly higher than those of the porous carbon derived directly from the crude fungus. Furthermore, the CNFs delivered an extraordinary energy density of 92.3 Wh kg−1 in the IL electrolyte, making it a promising candidate for electrode materials for supercapacitors.
A new method for the in operando analysis of evolving gases during cyclic aging of lithium ion batteries (LIBs) was developed to better assess safety concerning cell processes, especially those arising from the electrochemical degradation of the lithium hexafluorophosphate LiPF6/organic carbonate solvent based electrolyte. For electrochemical characterization at lab-scale, a cell in the shape of T-connector (“T-cell”) is usually used, offering connections to working, counter and reference electrode. To maintain comparability to this established system, an in operando X-shaped cell, i.e., a T-cell (“X-cell”), which varies only by an additional connector from the original setup, was designed. The new OEMS cell based on DEMS cell designs was linked to a modified GC–MS System and a potentiostat for in operando analysis of the evolving gases and the voltammetry experiments, respectively. This work comprises the evaluation of this new OEMS method in potentiostatic aging experiments of the conventional electrolyte 1M LiPF6 in EC:EMC (1:1, by wt.) in LiNi1/3Co1/3Mn1/3O2 (NCM)/Li half cells as a function of the applied cut-off potential. Mainly CO2 release at onset potentials >4.6V vs. Li/Li+ could be identified. At a potential of >5.4V vs. Li/Li+, the evolution of silicon tetrafluoride (SiF4) was observed mainly stemming from the HF induced degradation of the used glass fiber separator. Furthermore, triethyl phosphate (TEP) evolved from the LiPF6 decomposition at >5.5V vs. Li/Li+. Oxygen evolution either coming from the oxidative decomposition of the electrolyte or degradation of the NCM cathode material was not detected at even 5.5V vs. Li/Li+ and at 20°C.
Li4Ti5O12/LiFePO4 cells are cycled under 4 different conditions of discharge profile (galvanostatic or driving-based) and cycling rates (C/8 or 1C) during 4–5 months. All the cells exhibit capacity fade whose extent is not correlated with the aging condition. In order to understand aging phenomena, cells are disassembled at the end of cycle life and the recovered electrodes are analyzed using electrochemistry, electron microscopy, XRD and MAS-NMR. Positive and negative electrodes show no loss in active material and no change in electrochemical activity, active material structure and composite electrode structure. This rules out any irreversible electrode degradation. Lithium stoichiometry estimated by both XRD and electrochemistry is unexpectedly low in the positive electrode when the aging is stopped at full discharge. That indicates a loss of cyclable lithium or electrons leading to cell balancing evolution. That loss may have been caused by parasitic reactions occurring at both electrodes, in accordance with their rich surface chemistry as evidenced by MAS-NMR.
Vanadium pentoxide is emerging as a low-cost and high-performance pseudo-capacitive electrode material but suffers from poor stability. Herein, we demonstrate that the electrochemical performance and stability of V2O5 nanowires can be significantly improved by coating a thin carbon layer as shell. Our study shows that the V2O5@C core shell nanowires achieve a remarkable areal capacitance of 128.5 F cm−2 at 10 mV s−1 with excellent rate capability. More than 94.4% of the initial capacitance is retained after 10,000 cycles for V2O5@C core shell nanowires, which is much higher than the pristine V2O5 nanowires (13.3%). This method could be extended to improve the stability and electrochemical properties of other electrode materials.
By means of a specially designed multi-step synthesis procedure involving steps of precipitation, controlled oxidation, selective etching and calcination, porous double-shelled Mn2O3 hollow microspheres are synthesized. Solid, hollow and yolk-structured Mn2O3 are also similarly synthesized for comparison. X-ray diffraction, scanning and transmission electron microscopies, IR spectroscopy, thermogravimetry, and Brunauer-Emmett-Teller measurements are employed to investigate their structures and compositions. Galvanostatic cell cycling and impedance spectroscopy are used to characterize the electrochemical properties of Mn2O3/Li cells. The results show that the hierarchical hollow structured (double-shelled, hollow and yolk-structured) Mn2O3 anode materials deliver higher reversible capacities and excellent cycling stabilities than the solid Mn2O3. Moreover, among the three hierarchical hollow structured samples, the double shelled sample possesses the best cycling performance, especially at a high current density.
Abstract E-textiles that integrate multifunctional materials into clothing hold great potential for the wearable electronics market. One of the ultimate objectives of wearable electronics is their integration with textiles and clothes so that device functions can be conducted along with the textile advantages such as comfort, breathability, soft fabrics, and high sustainability. Various components of electronic devices like textile circuits, light-emitting diodes, and a variety of sensors for pressure, temperature, and vital signs have been used in smart clothing. There are also some prototypes of flexible, textile-based, energy-storage devices such as batteries, supercapacitors, and direct-power generations that sustain these devices, which are integrated into clothing. These wearable technologies have potential applications in sportswear and could change athletes’ experience during sports considerably just like smartphones, tablets, and other gadgets have in the recent past.
Silicon nanowires of high purity and regular morphology are of prime importance to ensure high specific capacities of lithium-ion batteries and reproducible electrode assembly process. Using nickel formate as a metal catalyst precursor, straight silicon nanowires (65–150 nm in diameter) were directly prepared by electrolysis from the Ni/SiO2 porous pellets with 0.8 wt% nickel content in molten CaCl2 at 900 °C. Benefiting from their straight appearance and high purity, the silicon nanowires therefore offered an initial coulombic efficiency of 90.53% and specific capacity of 3377 mAh/g. In addition, the silicon nanowire/carbon composite exhibited excellent cycle performance, retaining 90.38% of the initial capacity after 100 cycles. Whilst further study on the charge storage performance is still ongoing, these preliminary results demonstrate that nickel formate is an efficient and effective metal catalyst precursor for catalytic preparation of high purity straight silicon nanowires via the molten salt electrolysis, which is suitable for large-scale production.
In this study, a new DMF-derived ionic liquid electrolyte [EDMF]BF4 was prepared, characterized and applied as a high-capacitance electrolyte for electric double-layer capacitors (EDLCs). [EDMF]BF4 was measured to have very high ionic conductivity and low viscosity (24.8 mS cm−1 and 21.6 mPa s at 25 °C), as well as a comparable electrochemical window (4.4 V, on a GC electrode) with [EMIm]BF4, which is one of the most widely studied ionic liquid electrolytes with high performance. Therefore, [EDMF]BF4 was used as a non-volatile electrolyte for activated carbon-based EDLCs. The [EDMF]BF4-based EDLCs are capable to operate stably over a voltage of 2.7 V, and the specific capacitance of activated carbon was determined to be 165 F g−1 (100th cycle at 1 mA cm−2 and 30 °C), which is much larger than in the case of [EMIm]BF4 (126 F g−1). Besides, [EDMF]BF4 showed lower ohmic resistance and double layer resistance than [EMIm]BF4 in EDLCs. The high performance of [EDMF]BF4 electrolyte should be related to the quasi-linear [EDMF] cation of moderate size, which is presumably more suitable for enhanced ion mobility and compact electric double layer.
Lack of insight is frequent in schizophrenia and usually influences negatively both patient’s treatment and prognosis. This study aimed to investigate the relationship between insight, symptomatology and cognitive dysfunctions in schizophrenia using the PANSS five-factor model (modified from Gaag et al. in Schizophr Res 85:280–287, 2006). Forty patients diagnosed with chronic schizophrenia (DSM-IV) were evaluated with the scale to assess unawareness of mental disorder (SUMD), the PANSS and a neuropsychological battery. Spearman correlation and linear regression analyses were performed to investigate the relationship between clinical, neurocognitive and insight measures. The SUMD current and past awareness of symptoms score showed a correlation with WCST indices (correct answers and non-persevering errors). The negative and disorganization factor of the PANSS showed a positive correlation with current and past awareness of symptoms. However, when submitted to a linear regression model only the disorganization factor emerged as significant contributor for insight. Considering that the core items of the “disorganization factor” of the PANSS are related to cognition (e.g., poor attention, difficult in abstract thinking), insight is associated cognitive symptoms although no direct relationship between insight and neuropsychological tests was observed.
Recently, copper oxide (CuO) as promising anode material for lithium-ion batteries (LIBs) has received much interest. Hybridizing CuO with carbon is considered as a valid way to improve the conductivity and alleviate the volume effect of CuO, but how to achieve more optimized utilization rate of CuO-based anodes still remains a big challenge for us. In this work, activated tube-like carbon (ATC) is firstly prepared by pre-carbonization followed by alkali etching process using palm tree bark hair as initial carbon source, then the ATC is used as carbon matrix to load CuO by a modified phase-transfer approach. As a result, ultrafine CuO nanoparticles decorated ATC (ATC/CuO) can be obtained. For comparison, we also synthesize tube-like carbon (TC) by a direct pyrolysis process, and obtain TC/CuO hybrid by similar loading method. The morphology, structure, composition and surface property of the two carbon matrixes and the corresponding C/CuO hybrids are all systematically investigated. The results show that ATC/CuO hybrid possesses rich C O Cu bond and unique ultrafine CuO structure, which is attributed to the co-effect of abundant oxygen-containing groups, large specific surface area and special microporous property of ATC matrix. Consequently, the ATC/CuO electrode exhibited much enhanced cycling stability and rate capability when compared to sole CuO and TC/CuO electrodes. Obviously, our work provides a good guidance on the design and development of advanced carbon/metal oxide-based anodes for LIBs.
The electrochemical properties of La0.9Sm0.1Ni(5.0−x)Co x (x=2.0, 2.5, 3.0) hydride electrode alloys with and without magnetization treatment, including the electrochemical capacity C max, the charge–discharge life cycle and the high-rate dischargeability (HRD), are investigated in detail. The results show that, the effect of magnetization treatment on the electrochemical properties of the alloys studied is marked, and this effect varies with the alloy composition. After being magnetized, the electrochemical capacity of the alloys increases, the capacity decay rate decreases and the HRD improves. According to the linear polarization and anodic polarization measurements, the exchange current density I 0 and the limiting current density I L of the alloys before and after being magnetized are both found increased.
Recent studies on all-vanadium redox flow batteries (VRFBs) have focused on carbon-based materials for cost-effective electrocatalysts to commercialize them in grid-scale energy storage markets. We report an environmentally friendly and safe method to produce carbon-based catalysts by corn protein self-assembly. This new method allows carbon black (CB) nanoparticles to be coated with nitrogen-doped graphitic layers with oxygen-rich functionalities (N-CB). We observed increased catalytic activity of this catalyst toward both V2+/V3+ and VO2+/VO2+ ions, showing a 24% increased mass transfer process and ca. 50 mV higher reduction onset potential compared to CB catalyst. It is believed that the abundant oxygen active sites and nitrogen defects in the N-CB catalyst are beneficial to the vanadium redox reaction by improving the electron transfer rate and giving faster vanadium ion transfer kinetics.
In this work, three different morphologies of CuCo2S4 materials have been prepared by a facile hydrothermal synthesis route by controlling the species of solvent and molar concentration of precursors. The effects of reaction conditions on the physical characteristics (including microstructure, morphology, specific surface area and pore structure) and electrochemical behaviors of the products were systematically investigated. The experimental results reveal that as-obtained highly uniform micro-/nanostructure CuCo2S4 particles prepared by mixed solvent (H2O/ethylene glycol(EG)) and low molar concentration of precursors manifest the best electrochemical performances. The specific capacity is up to 90.6mAhg−1 at a current density of 2Ag−1, and 47.9% of capacity retention rate can be retained when the current density varies from 2 to 50Ag−1. Furthermore, a superior cycling stability with 95.6% of initial capacity retention rate can be maintained at 3Ag−1 after 5000 consecutive charge-discharge cycles. The enhanced electrochemical performances can be mainly attributed to the highly uniform micro-/nanostructure with relatively larger specific surface area and total pore volume. Therefore, the results above demonstrate that the as-prepared highly uniform micro-/nanostructure CuCo2S4 particles might be promising candidate battery electrode materials for energy storage.
The use of fuzzy multiple criteria analysis (MCA) in solid waste management has the advantage of rendering subjective and implicit decision making more objective and analytical, with its ability to accommodate both quantitative and qualitative data. In this paper a modified fuzzy TOPSIS methodology is proposed for the selection of appropriate disposal method and site for municipal solid waste (MSW). Our method is superior to existing methods since it has capability of representing vague qualitative data and presenting all possible results with different degrees of membership. In the first stage of the proposed methodology, a set of criteria of cost, reliability, feasibility, pollution and emission levels, waste and energy recovery is optimized to determine the best MSW disposal method. Landfilling, composting, conventional incineration, and refuse-derived fuel (RDF) combustion are the alternatives considered. The weights of the selection criteria are determined by fuzzy pairwise comparison matrices of Analytic Hierarchy Process (AHP). It is found that RDF combustion is the best disposal method alternative for Istanbul. In the second stage, the same methodology is used to determine the optimum RDF combustion plant location using adjacent land use, climate, road access and cost as the criteria. The results of this study illustrate the importance of the weights on the various factors in deciding the optimized location, with the best site located in Çatalca. A sensitivity analysis is also conducted to monitor how sensitive our model is to changes in the various criteria weights.
Zinc deposition from alkaline zincate solution in single flow zinc/nickel battery has been investigated. The effect of different substrates such as copper, cadmium and lead were examined by using cyclic voltammetry and cathodic polarization technique. It was found that the cadmium substrate is better than the others. Zinc deposition was carried out by using galvanostatic technique, and the deposits were examined by SEM. The results demonstrated that there is no zinc dendrite on the cadmium substrate in flowing electrolyte. Coulombic and voltage efficiencies of 98 and 88%, respectively, are obtained in a small laboratory cell.
The usage of three-phase induction generators for energy production in non-conventional energy systems covers a dynamic research area. When single-phase consumers are predominant, besides the use of a single-phase generator, a three-phase induction machine with a proper balancing circuit represents a reliable alternative. Over the last 25 years, efforts have been made to enhance the balanced operation of a three-phase induction generator in single-phase mode. This paper presents a survey of the existing literature, focusing on several significant aspects such as phase balancing methods, excitation requirements, steady-state and dynamic analysis, and maximum available power in single-phase mode of operation.
The electrochemical behavior of composite anodes prepared either by mixing partially oxidized graphite and Cu powders or by coating the pristine partially oxidized graphite electrodes with few-nanometer-thick Cu layers has been studied by slow-scan-rate cyclic voltammetry (SSCV) and galvanostatic charge/discharge cycles over the temperature range of −30°C to 20°C. The interfacial intercalation/deintercalation kinetics has also been investigated using electrochemical impedance spectroscopy (EIS). The role of the Cu in improving low-temperature performances and kinetics of graphite electrodes is discussed.
Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) bifunctional electrocatalysts are essential for rechargeable zinc-air batteries. Here, a novel design strategy is demonstrated for developing highly dispersed Fe2Ni2N/Co trimetallic nitride nanocrystals strongly coupled with N-doped carbon nanotubes (Fe2Ni2N/Co@NCNT). This unique hybrid catalyst exhibits superior electrocatalytic activity and stability toward both ORR and OER over most reported non-noble metal catalysts. The resulting zinc-air battery shows an impressively small charge–discharge voltage gap of 83 mV at 20 mA cm−2, as well as ultra-long cycling stability even exceeding 850 cycles (850 h) at 5 mA cm−2. Notably, we followed the changes of interatomic distance and local coordination of FeFe and FeN bonds, using in situ XAFS to investigate the origins of the excellent structural stabilities of the Fe2Ni2N/Co@NCNT catalysts during electrocatalysis.
The Ni0.5TiOPO4/C composite Li-ion battery anode material has been prepared by a sol–gel method with a subsequent pyrolysis step for the formation of C-coating. The resulting sub-micronsized particles displayed a narrow particle size distribution and a corresponding high electrochemical activity which, in turn, facilitates in-depth analysis of the electrochemical behavior of the material. It is shown that by limiting the degree of lithiation in the material, the redox potential in subsequent cycles is substantially affected. Ex-situ XRD reveals a gradual evolution of the structure during cycling of the material, with lower crystallinity after the first discharge cycle. By correlating the electrochemical properties with the structural studies, new insights into the electrochemical behavior of the Ni0.5TiOPO4/C anode material are achieved, suggesting a combination of intercalation and conversion reactions.
Electrochemical double-layer capacitors are promising energy storage devices with high power density, moderate energy density, rapid charging rates, and high cycle life. In order to maximize energy density, highly porous carbon materials are often incorporated in the electrodes. The structure of the porous carbon network is critical to ensure high power delivery and charging rate. In this study, two types of oil sands petroleum cokes, from either batch or continuous industrial coking, were used to prepare porous carbon samples. The two activated petroleum coke samples have similar chemical compositions, specific surface areas, and pore size distributions, but due to the different industrial coking methods, the two samples have differing macrostructures and porous networks. Using mercury intrusion porosimetry and scanning electron microscopy, the meso-structure, macrostructure, and pore connectivity of the two samples were characterized and compared to the capacitance performance of the activated coke samples. The results show that, in order to ensure high rate performance, especially in ion depleted electrolyte scenarios, the porous carbon samples must have an interconnected network of pores between 10 and 1000 nm in diameter. These pore sizes are shown to improve the rate of ion diffusion, and allow greater capacitance values to be achieved at rapid charging rates.
High-quality Prussian blue crystals with a small number of vacancies and a low water content are obtained by employing Na4Fe(CN)6 as the single iron-source precursor. The high-quality Prussian blue shows high specific capacity and remarkable cycling stability as the cathode material for Na-ion batteries because of its excellent ion storage capability and impressive structure stability.