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Two different carbon electrodes have been modified with 1,4,9,10-anthracenetetraone (AT) in order to produce composite electrodes combining the double layer capacitance of carbons and the redox capacity of the organic redox couple. Electrodes were prepared by impregnation of AT on both commercial high surface area functionalized carbon and on carbon black. Optimum loading amount, redox activity, and electrochemical potentials of AT were determined to be dependent on the substrate used, and the respective performances were characterized by cyclic voltammetry at different scan rates, and galvanostatic charge discharge experiments. Immobilized AT improves more than 50% of the total capacitances of both bare carbons, even after 1000 cycles at 200mAg−1. This increase is attributable to the use of AT, which can exchange up to four electrons, but is also surprisingly effective taking into account that no efforts were undergone to achieve covalent bonding. Although substantial loss of capacitance is observed for both modified carbons at higher rates, the results here discussed are a step forward to determine the contribution of covalent bond to carbon electrode performances and its benefits compared to loosely bound molecules, with the aim of optimizing supercapacitor electrodes based on this combination of materials.
A noise model for phototransistors in open base configuration is presented. The model was developed from the noise measurements on four different phototransistor designs. The extracted current gains from the noise model were verified by measured current gains from Gummel measurements. Furthermore the current noise spectral density was modeled and compared with the noise measurements. A difference of less than 12 % in the current gain was achieved. In addition to the extracted current gains also the most dominant shot noise terms including their values of each phototransistor are extracted.
To improve the electrochemical properties of LiNi1/3Co1/3Mn1/3O2 (NCM) under the high-voltage operating condition of 4.5 V, 0.5 wt.% of alumina (Al2O3) was introduced as a ceramic filler during NCM cathode preparation. Uniformly dispersed Al2O3 over the entire area of the NCM cathodes efficiently stabilized the oxidative decomposition of the liquid electrolyte up to 5.3 V. This behavior hindered the formation of a thick surface film on the NCM cathodes after high-voltage operation (4.5 V). The Al2O3-containing NCM cathodes (NCM/Al2O3) revealed much smaller total cell resistance compared to the bare NCM cathodes, resulting in improved cycle performance and rate capabilities, which were identified as a facilitated Li+ diffusion in presence of the Al2O3 particles. NCM/Al2O3 showed a 29.4% improvement over the bare NCM (79.3 and 112.3 mAhh g−1 for bare NCM and NCM/Al2O3, respectively, after the 100th cycle) at 3C (4.3 V cutoff, C/2 for charging and 3C for discharging processes) and a 53.5% improvement (35.0 and 75.3 mAhh g−1 for NCM/Al2O3 and bare NCM, respectively) at 5C (4.5 V cutoff).
Metal–organic frameworks (MOFs) are increasingly being explored for electrocatalytic oxygen evolution, which is half of the water splitting reaction. Here the authors show that, under reaction conditions, mixed metal oxyhydroxides form at the nodes of bimetallic MOFs, which are highly catalytically active.
Even though Cape Verde has high wind and solar energy resources, the conventional strategy for increasing access to electricity in isolated rural areas is by centralized microgrids with diesel generators. In this study, the design of 2 off-grid electrification projects based on hybrid wind–photovoltaic systems in Cape Verde is developed and analyzed. The design considers some significant novelty features in comparison with previous studies. First a detailed wind resource assessment is carried out combining meso-scale wind climate data and a specialized micro-scale wind flow model. Then a mathematical model is used for the design of off-grid projects considering a combination of individual systems and microgrids. In this study, locations far from the demand points are also considered as possible generation points. Various design configurations are analyzed and compared. The proposed configurations exploit the highest wind potential areas and are economically beneficial in comparison with diesel generator systems.
Efficient electrocatalyst is essential to develop water splitting technology for large-scale hydrogen production, especially using bifunctional earth-abundant alternative catalysts under alkaline and neutral conditions. NiFe-based oxides have promising activity towards the oxygen evolution (OER). However, they usually show unsatisfactory performance for the hydrogen evolution reaction (HER), due to their large particle size with limited active sites and poor conductivity. Herein, we report the synthesis of sulfur-incorporated NiFe2O4 nanosheets on nickel foam (S-NiFe2O4/NF), composed of ultra-small nanoparticles (~ 2nm), by a facile confined growth strategy with the assistance of thiourea. Due to the favorable 3D hierarchical structure, the self-supported electrocatalyst endows abundant active sites, high electrical conductivity and rapid mass transfer, thereby achieving remarkable catalytic performance for overall water splitting under alkaline and neutral conditions. Specifically, the optimal S-NiFe2O4/NF electrode requires only 1.65 and 1.95V to deliver a current density of 10mAcm−2 in 1.0M KOH and 1.0M PBS, respectively, outperforming that of the commercial Pt/C as well as its counterparts (i.e. S-NiO/NF, S-Fe3O4/NF and pure NiFe2O4/NF). In addition, the synthesis strategy developed here can be applied to other mixed transition metal oxides with similar morphology and structure for various applications, such as supercapacitors, metal-air batteries, and photocatalysis.
This paper reviews the present status of research, development and manufacturing for photovoltaics (PV) in Japan based on the Japanese New Sunshine Program conducted by the Ministry of International Trade and Industry (MITI) and the New Energy and Industrial Technology Development Organization (NEDO). In particular, the status of research and development on high-efficiency and low-cost crystalline silicon, thin-film silicon and Group II–VI compound solar cells and modules, and super high-efficiency Group III–V compound solar cells, is presented. In addition, Japanese government programs to promote solar houses, wherein 18,000 PV systems were installed on Japanese houses in 1999, are also demonstrated. Future prospects for PV technologies, such as silicon material, thin-film and module technologies, concentrator systems and new application fields, are discussed.
The nanostructured anatase titanium dioxide/activated carbon composite material for capacitive deionization electrode was prepared in a short time by a lower temperature two-step microwave-assisted ionothermal (sol–gel method in the presence of ionic liquid) synthesis method. This method includes a reaction and a crystallization step. In the crystallization step, the ionic liquid plays a hydrothermal analogy role in driving the surface anatase crystallization of amorphous titanium dioxide nanoparticles formed in the reaction step. The energy dispersive spectroscopic study of the composite indicates that the anatase titanium dioxide nanoparticles are evenly deposited in the matrix of activated carbon. The electrochemical property of the composite electrode was investigated. In comparison to the pristine activated carbon electrode, higher specific capacitance was observed for the nanostructured anatase titanium dioxide/activated carbon composite electrode, especially when the composite was prepared with a molar ratio of titanium tetraisopropoxide/H2O equal to 1:15. Its X-ray photoelectron spectroscopic result indicates that it has the highest amount of Ti-OH. The Ti-OH group can enhance the wetting ability and the specific capacitance of the composite electrode. The accompanying capacitive deionization result indicates that the decay of electrosorption capacity of this composite electrode is insignificant after five cycle tests. It means that the ion electrosorption–desorption becomes a reversible process.
Powders of spinel Li4Ti5−x V x O12 (0≤ x ≤0.3) were successfully synthesized by solid-state method. The structure and properties of Li4Ti5−x V x O12 (0≤ x ≤0.3) were examined by X-ray diffraction (XRD), Raman spectroscopy (RS), scanning electronic microscope (SEM), galvanostatic charge–discharge test and cyclic voltammetry (CV). XRD shows that the V5+ can partially replace Ti4+ and Li+ in the spinel and the doping V5+ ion does almost not affect the lattice parameter of Li4Ti5O12. Raman spectra indicate that the Raman bands corresponding to the Li–O and Ti–O vibrations have a blue shift due to the doping vanadium ions, respectively. SEM exhibits that Li4Ti5−x V x O12 (0.05≤ x ≤0.25) samples have a relative uniform morphology with narrow size distribution. Charge–discharge test reveals that Li4Ti4.95V0.05O12 has the highest initial discharge capacity and cycling performance among all samples cycled between 1.0 and 2.0V; Li4Ti4.9V0.1O12 has the highest initial discharge capacity and cycling performance among all samples cycled between 0.0 and 2.0V or between 0.5 and 2.0V. This excellent cycling capability is mainly due to the doping vanadium. CV reveals that electrolyte starts to decompose irreversibly below 1.0V, and SEI film of Li4Ti5O12 was formed at 0.7V in the first discharge process; the Li4Ti4.9V0.1O12 sample has a good reversibility and its structure is very advantageous for the transportation of lithium-ions.
Solid oxide fuel cells (SOFCs) show considerable promise for meeting the current ever-increasing energy demand and environmental sustainability requirements because of their high efficiency, low environmental impact, and distinct fuel diversity. In the past few decades, extensive R&D efforts have been focused on lowering operational temperatures in order to decrease the system (stack and balance-of-plant) cost and improve the longevity of operationally useful devices of commercial relevance. Nanomaterials and related nanotechnologies have the potential to improve SOFC performance because of their advantageous functionalities, namely, their enlarged surface area and unique surface and interface properties compared to their microscale analogs. Recently, the use of nanomaterials has increased rapidly, as reflected by the exponential growth in the number of publications since 2002. In this work, we present a comprehensive summary of nanoparticles, nano-thin films and nanocomposites with different crystal phases, morphologies, microstructures, electronic properties, and electrochemical performances for low temperature SOFCs (LT-SOFCs), with focus on efforts to enhance electrical efficiency, to induce novel fundamental properties that are inaccessible in microcrystalline materials, and to promote the commercialization of LT-SOFCs. Recent progress in the applications of many classically or newly chemical and physical nanomaterials and nanofabrication techniques, such as thin film vacuum deposition, impregnation, electrospinning, spark plasma sintering, hard- and soft-template methods, and in-situ nanoparticle surface exsolution are also thoroughly described. The technological and scientific advantages and limitations related to the use of nanomaterials and nanotechnologies are highlighted, along with our expectations for future research within this emerging field.
Fuel cells are attractive devices that convert chemical energy into electricity through the direct electrochemical reaction of hydrogen and oxygen. Intermediate temperature fuel cells operated at 200–300 °C can simplify water and thermal managements, enable the use of non-precious or low-loading precious metal catalysts and provide insensitivity toward fuel and air impurities such as carbon monoxide. However, the performance of current intermediate temperature fuel cells is poor due to a lack of highly-conductive membrane electrolytes and optimal electrodes designed for these fuel cells. Here, we demonstrate high-performing intermediate temperature fuel cells that use SnP2O7–polymer composite membranes and a quaternary ammonium-biphosphate ion-pair coordinated polymer electrolyte in the electrodes. The peak power density of the fuel cell under H2 and O2 reached 870 mW cm−2 at 240 °C with minimal performance loss under exposure to 25% carbon monoxide.
Mg-substituted Li(Ni,Co,Al)O2 have been prepared by a co-precipitation method and examined by XRD, neutron diffraction, X-ray absorption, magnetization and electrochemical measurements. Neutron diffraction measurement indicated that the Mg ions were mostly substituted for Ni ions located in transition metal layers in LiNi0.75Co0.15Al0.05Mg0.05O2. Although a tiny amount of Ni ions in lithium layers in LiNi0.8Co0.15Al0.05O2 was detected by magnetization measurements, such Ni ions decreased by Mg-substitution. The Mg-substitution for Ni in LiNi0.75Co0.15Al0.05Mg0.05O2 was also confirmed by X-ray absorption measurements. The 500mAh-type cylindrical lithium-ion cells of LiNi0.8−x Co0.15Al0.05Mg x O2 (x =0, 0.05) with graphite negative-electrode were prepared and their battery performances were evaluated by cycling test at 2C charge/discharge rate at 60°C. A lithium-ion cell of LiNi0.75Co0.15Al0.05Mg0.05O2 exhibited better capacity retention and smaller battery resistance than that of LiNi0.8Co0.15Al0.05O2 after 500 cycles. Electrochemical impedance spectroscopy revealed that the Mg-substitution suppressed the increase in charge-transfer resistance upon cycling. The effects of Mg-substitution in LiNi0.8Co0.15Al0.05O2 were discussed in terms of crystal structure and battery performance.
The use of phosphoranimines (PAs), a class of linear, monomeric phosphazenes, as electrolytes for Li-ion battery applications has been investigated as a route to improve safety and stability for Li-ion batteries. Of the potential PAs for use in battery applications, this work focuses on the initial synthetic preparation and analysis of N-trimethylsilyl-P,P-bis((2-methoxyethoxy)ethoxy)-P-ethylphosphoranimine (PA-5). PA-5 has high LiPF6 solubility in excess of 2M, high thermal stability with a melting point below −80°C and high thermal stability as a neat compound to at least 250°C. As part of electrolyte blends, the inclusion of PA-5 shifts the onset of thermal degradation by close to 40°C at 35% loading and by 20°C at a 10% loading, improves the low temperature performance of the electrolyte, and when used as a primary solvent leads to increases in the flash point (by 20°C) when compared to more traditional EC:EMC blends. Cycling capabilities of full-coin cells with graphite negative electrodes and Li1+w[Ni0.5Mn0.3Co0.2]1-wO2 positive electrodes using PA-5:EC:EMC electrolyte blends are comparable with the performance seen for traditional EC:EMC blends. Analysis of the impact of the use of additives such as vinylene carbonate in PA-5:EC:EMC blended electrolyte results in enhanced capacity retention and improved coulombic efficiency.
A new approach has been developed to rapidly synthesize nanostructured LiMn2O4 thin films by flame spray deposition (FSD) and in situ annealing. A precursor solution of lithium acetylacetonate and manganese acetylacetonate in an organic solution was supplied through a flame spray pyrolysis (FSP) reactor. The liquid solution spray was ignited and stabilized by a premixed methane/oxygen flame ring surrounding the FSP nozzle. Thus, LiMn2O4 nanoparticles were formed by combustion and deposited onto a current collector followed by in situ annealing. Two different types of current collectors, i.e. stainless steel and aluminum coated with carbon-based primer were tested. The prepared thin films were characterized by X-ray diffraction and field-emission scanning electron microscopy. The electrochemical properties of the thin films were evaluated by cyclic voltammetry and galvanostatic cycling. The LiMn2O4 films exhibited good cyclability. Films that underwent sintering and crystal growth during in situ annealing developed more robust film structures on the current collector surface and exhibited better electrochemical performance than poorly adhered films.
Alkali metal thermal electric converter (AMTEC) technology offers several advantages over conventional forms of electric generation. Some of these advantages are high efficiency, high density, reliability, absence of moving parts, and competitive manufacturing costs. These and other advantages make AMTECs ideally suited for several space, aerospace, military and domestic applications. Current AMTEC designs suffer from some drawbacks that need to be rectified if the full potential of the technology is to be realized. These are current cell efficiencies that are still at values below the theoretically possible, and the adverse power–time characteristic of the cell. The PX-3A AMTEC cell, for instance, shows decreasing values of the maximum power output with time. Maximum power decreases from 2.54W at the end of 172h to 1.27W at 18,000h of cell operation. This latter problem, called power degradation, in particular, will preclude the use of the cell for applications that require operation of the cell for long periods of time. This paper discusses in detail the advantages of AMTEC technology and the problems with current designs. In particular, the problem of power degradation is dealt with in some detail and some measures are suggested that will help arrest this loss of power with time.
Facile and sustainable route is developed to convert biomass into hierarchically porous carbon matrix cooperating with highly conductive graphene. By tailoring the porosity of the carbon matrix to promote fast mass transfer and cooperating highly conductive interconnected graphene frameworks to accelerate the electron transport, the carbon sulfur cathodes simultaneously achieve high areal and gravimetric sulfur loading/content (6 mg cm−2/67 wt%) and deliver outstanding electrochemical performance. After 100 cyclic discharge-charge test at the current density of 0.2 C, the reversible capacity maintains at 707 mA h g−1.
Here, we isolated a NAC transcription factor PtoVNS11 fromPopulus tomentosaCarr. Molecular characterization showed that PtoVNS11 was involved in the regulation of secondary cell wall formation in poplar.
Drawing conclusions from the literature regarding the moral development of people with intellectual disabilities (IDs) is difficult because of the use of unstandardised and idiosyncratic measures. In order to address this short-coming, a moral reasoning production measure (the Socio-Moral Reflection Measure – Short Form; SRM-SF) and a recognition measure (the Moral Theme Inventory; MTI) were presented to men with and without IDs who had no known history of engaging in illegal behaviour. The instruments were completed on two occasions, separated by a two-week interval, in order to investigate their basic psychometric properties. The results indicated that there was a strong relationship between the MTI and the SRM-SF, suggesting that the MTI has convergent validity. The internal consistency of the MTI and the SRM-SF ranged from moderate to substantial for both men with and without IDs. However, the test–retest reliability of the MTI was poor for men with IDs, while it was good for men without IDs. The test–retest reliability of the SRM-SF was good for both men with and without IDs. Comparison of the moral reasoning abilities of men with and without IDs suggested that many of the differences between the two groups could be accounted for by general intellectual functioning. The exception was overall score on the SRM-SF and moral reasoning in relation to the law, where men with IDs scored at stage 2(1), when intelligence was controlled. The results were interpreted by suggesting that the relationship between moral reasoning and illegal behaviour may take an inverted U curve shape, moderated by intelligence.
The development of practical lithium oxygen batteries with high specific energy needs to move towards the use of thick positive electrodes. However, a specific textural design of thick electrodes is required to enhance O2 diffusion which represents a significant limiting factor of the cell capacity. In this work we investigate, through a continuum modeling approach, the feasibility of using a bi-porous cathode to improve electrochemical cell response. This electrode contains mesopores providing active surface area towards the Oxygen Reduction Reaction (ORR) and macropores acting as an oxygen reservoir and diffusion medium. Results of this work highlight the complex interplays between the formulation, thickness and texture of the electrode as well as their impacts on the electrochemical performance.
Volume swelling is a typical mode of battery failures, which happens not only in the operation but also during the storage of rechargeable batteries as a result of electrolyte degradation, particularly the chemical oxidation of electrolyte solvents by the active oxygen released in phase transition of the layered cathode materials. Aiming to remove the active oxygen, we herein propose Pyrite FeS2 powder as an in-situ oxygen remover based on the fact that FeS2 can be ultimately oxidized to Fe2O3 and Li2SO4 by the active oxygen, and the redox reaction depletes considerable amount of oxygen. By mixing FeS2 powder into a conventional LiNi0.80Mn0.10Co0.10O2 (NMC811) cathode, it is found that under normal cycling conditions of the Li/NMC811 cells, FeS2 is electrochemically stable while being capable of reacting with active oxygen and hence stabilizing the cell's capacity retention. The concept proposed in this work provides a practically viable and cost-effective approach for preventing volume swelling of the rechargeable batteries based on the layered cathode materials.
Ultrastructural changes induced by heavy metals (cadmium, zinc, and copper) and polyphosphate metabolism were studied in Chlamydomonas acidophila. Transmission electron microscopy indicated that cadmium led to the most drastic morphometric changes. An increase in number and volume of starch grains and vacuoles as well as the presence of electron dense deposits in vacuole and membrane whorls were observed. Energy-dispersive X-ray analysis revealed that vacuolar deposits inside cells treated with cadmium contained phosphate and cadmium. These ultrastructural changes were accompanied by a change in the intracellular polyphosphate level, as shown by in vivo 31P-nuclear magnetic resonance. It was also observed that cadmium treatment caused polyphosphate degradation and increased vacuolar short-chains and orthophosphates.
Many people with epilepsy experience cognitive problems as a consequence of their epilepsy and its treatment. However, relatively few longitudinal studies have been conducted to investigate how these problems progress during the course of the disorder, particularly in those who are newly diagnosed. Fifty patients with newly diagnosed epilepsy were assessed using a comprehensive neuropsychological test battery before they started antiepileptic treatment and after a mean of 5years. At the 5-year follow-up, the majority of cognitive measures remained stable, although significant (but subtle) declines were noted for memory and psychomotor speed domains in 38% of people with epilepsy.