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The intrinsically low electrical conductivity and the poor cycling stability are two major obstacles of manganese oxides to hamper their further application in high-performance supercapacitors. One effective way to enhance their electrochemical properties is construction of appropriate nanocomposite with different structures. Herein, we demonstrated the fabrication of a hierarchical MnO2 nanowires-Mn3O4 nanoparticles nanocomposite by an effective and innovative two-step synthesis strategy. Further, the Mn3O4 nanoparticles were exfoliated from the surface of α -MnO2 nanowires. And the optimum composition was calculated to be ~ 35% Mn3O4 and ~ 65% α -MnO2. The capacitance of the optimized MnO2–Mn3O4 nanocomposite electrode reaches 278.2 F g−1 at a current density of 20 A g−1, and the capacitance retained at 99.3% even after 5000 cycles. The asymmetric supercapacitor was also fabricated with optimized MnO2–Mn3O4 as the positive electrode and activated carbon as the negative electrode. It could deliver an excellent energy density of ~ 41.3 Wh kg−1 at a power density of ~ 1153W kg−1. And the superior cycling stability achieves as well. The excellent capacitance properties of the MnO2–Mn3O4 nanocomposite can be attributed to the hybrid structure, in which one-dimension α -MnO2 nanowires provide a super highway for electron and ion transfer and Mn3O4 nanoparticles attached offer the abundant pseudocapacitive sites for charge storage.
This work reports a facile metal-organic-framework based approach to synthesize Sn/C composite, in which ultrasmall Sn nanodots with typical size of 2–3nm are uniformly embedded in the nitrogen-doped porous carbon matrix (denoted as Sn@NPC). The effect of thermal treatment and nitrogen doping are also explored. Owing to the delicate size control and confined volume change within carbon matrix, the Sn@NPC composite can exhibit reversible capacities of 575mAhg−1 (Sn contribution: 1091mAhg−1) after 500 cycles at 0.2Ag−1 and 507mAhg−1 (Sn contribution: 1077mAhg−1) after 1500 cycles at 1Ag−1. The excellent long-life electrochemical stability of the Sn@NPC anode has been mainly attributed to the uniform distribution of ultrasmall Sn nanodots and the highly-conductive and flexible N-doped carbon matrix, which can effectively facilitate lithium ion/electron diffusion, buffer the large volume change and improve the structure stability of the electrode during repetitive cycling with lithium ions.
Activated carbons for supercapacitor electrodes are prepared from sugar cane bagasse using chemical activation with ZnCl2. The ZnCl2 activation of bagasse is studied using thermogravimetric analysis and the carbon pore structures are characterised using N2 and CO2 adsorption. In two-electrode, sandwich-type supercapacitor cells containing 1M H2SO4 the sugar cane bagasse carbons (SCCs) exhibit specific energy up to 10Whkg−1 and specific capacitance close to 300Fg−1. The electrochemical performance of the SCCs is attributed to their high specific surface area and the development of mesopores with ZnCl2 impregnation ratios of 1 or greater. By contrast, the pyrolysis of bagasse without ZnCl2 produces a carbon with low specific capacitance. The SCC prepared with a ZnCl2 ratio of 3.5 shows the most stable electrochemical performance at fast charge–discharge rates.
An interwoven hollow fiber structured mesoporous NiO catalyst doped with C, S was fabricated by the vacuum impregnation and thermal decomposition methods using eggshell membrane as template. The structure of the catalyst was characterized by X-ray diffraction, thermo-gravimetric analysis, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and specific surface area test. Under a high vacuum condition, the synthesized NiO material has a better interwoven fiber and mesoporous structure, which effectively increases the specific surface area of the material. C and S were doped into NiO via eggshell membrane pyrolysis, which then formed C–OH and SO42− species on the surface of the material. The electrocatalytic performance of the catalyst for the oxidation of methanol in alkaline solution was studied by cyclic voltammetry and chronoamperometry. The C, S doped mesoporous NiO material exhibits much higher catalytic efficiency and anti-poisoning ability than that of NiO nanoparticles due to the synergistic catalysis of NiO and doping C–OH and SO42− species.
Nitrogen (N) is one of the most limiting nutrients for rice yield. There is mounting evidence that the endophytic fungus Phomopsis liquidambari B3 can establish a mutualistic symbiotic relationship with rice, enhancing N uptake and metabolism in rice (Oryza sativa L.). To examine the mechanism underlying the effect of B3 on nitrogen accumulation and metabolism in rice plants, a pot experiment was conducted to examine the N and phytohormone levels in response to endophyte infection at four whole growth durations during exposure to different N levels. Our results showed that the contents of auxin, cytokinin, and ethylene in rice were significantly enhanced by B3 under low N levels at different growth durations; B3 symbiosis increased N accumulation and rice yield and induced the expression of some genes related to N uptake and metabolism. To further verify that B3 symbiosis enhances N use in rice by regulating phytohormones, we performed a hydroponic experiment in which exogenous phytohormones and their specific inhibitors were applied. The results showed that the application of exogenous auxin, cytokinin, and ethylene increased the rice content of nitrogen, and their inhibitors decreased the amount of nitrogen absorbed in rice. As expected, B3 infection alleviated the negative effect caused by inhibitors slightly. In summary, we conclude that P. liquidambari symbiosis may regulate the content of auxin, cytokinin, and ethylene to improve N use in rice.
To overcome the volumetric expansion of Si used as an anode in lithium-ion batteries (LIBs), we propose 3D Si electrode structures formed on patterned Cu current collectors designed from metal molds fabricated using wire electrical discharge machining (WEDM). The line- and check-patterned Cu current collectors with microscale periods for LIBs are prepared using an imprinting technique with patterned metal molds fabricated using the WEDM process. The line- and check-patterned Si thin-film and powder-type electrodes as anodes are fabricated using radio frequency magnetron sputtering deposition method and conventional slurry casting process, respectively. The morphology of the Si electrodes before and after the cycling process is characterized using optical microscopy and scanning electron microscopy. The electrochemical properties of the Si electrodes are evaluated using a multi-channel battery tester and electrochemical impedance analyzer. In particular, the check-patterned Si electrodes exhibit relatively high-capacity and enhanced cycling performance due to the stress relief of the Si anode.
Lithium-ion batteries are now considered to be the technology of choice for future hybrid electric and full electric vehicles to address global warming. LiCoO2 has been the most widely used cathode material in commercial lithium-ion batteries. Since LiCoO2 has economic and environmental issues, intensive research has been directed towards the development of alternative low cost, environmentally friendly cathode materials as possible replacement of LiCoO2. Among them, spinel LiNi0.5Mn1.5O4 material is one of the promising and attractive cathode materials for next generation lithium-ion batteries because of its high voltage (4.7V), acceptable stability, and good cycling performance. Research advances in high voltage spinel LiNi0.5Mn1.5O4 are reviewed in this paper. Developments in synthesis, structural characterization, effect of doping, and effect of coating are presented. In addition to conventional synthesis methods, several alternative synthesis methods are also summarized. Apart from battery performance, the application of spinel LiNi0.5Mn1.5O4 material in asymmetric supercapacitors is also discussed.
The electroactive copolymer of diphenylamine (DPA) and 4,4′-diaminodiphenyl sulfone (DADPS) was synthesized electrochemically in 4M H2SO4 and ethanol medium. Both electrochemical synthesis and characterization of the copolymer deposited on a glassy carbon electrode (GCE) were carried out using cyclic voltammetry. The voltammograms exhibited different patterns of behavior with different feed concentrations of DPA. Equimolar concentrations of DPA and DADPS demonstrated very efficient growth of the copolymer film on the surface of the GCE. The copolymer exhibited high solubility in dimethyl sulfoxide (DMSO). The scan rate exerted little-effect on this GCE copolymer film, revealing the film's excellent electroactive adherent properties. The effect of pH on the copolymer film showed that the polymer was electrochemically active up to pH 7.0. Spectroelectrochemical analysis of the copolymer film, carried out on an indium tin oxide (ITO) plate, showed multicolor electrochromic behavior when the applied potential was changed. The copolymer was characterized by FTIR and 1H NMR spectral data. The surface morphology was studied using SEM analysis, the grain size of the copolymer was measured using XRD studies and was found to be 56nm. The electrical conductivity of the copolymer was 2.65×10−2 Scm−1, as determined using a four-probe conductivity meter.
Invasive vagus nerve stimulation has been demonstrated to be an effective treatment in major depressive episodes. Recently, a novel non-invasive method of stimulating the vagus nerve on the outer canal of the ear has been proposed. In healthy subjects, a prominent fMRI BOLD signal deactivation in the limbic system was found. The present pilot study investigates the effects of this novel technique of auricular transcutaneous electric nerve stimulation in depressed patients for the first time. A total of 37 patients suffering from major depression were included in two randomized sham controlled add-on studies. Patients were stimulated five times a week on a daily basis for the duration of 2 weeks. On days 0 and 14, the Hamilton Depression Rating Scale (HAMD) and the Beck Depression Inventory (BDI) were assessed. In contrast to sham-treated patients, electrically stimulated persons showed a significantly better outcome in the BDI. Mean decrease in the active treatment group was 12.6 (SD 6.0) points compared to 4.4 (SD 9.9) points in the sham group. HAMD score did not change significantly in the two groups. An antidepressant effect of a new transcutaneous auricular nerve stimulation technique has been shown for the first time in this controlled pilot study. Regarding the limitations of psychometric testing, the risk of unblinding for technical reasons, and the small sample size, further studies are necessary to confirm the present results and verify the practicability of tVNS in clinical fields.
The solar still is gaining popularity among the scientific community for the production of distillate and fluoride free water due to its low cost and simple working principle. Continuous efforts have been made by various researchers to increase its productivity. Various techniques and configurations have been attempted in the literature to enhance the efficiency of the solar still. Many researchers have also studied different parameters influencing the performance of solar stills. Thermodynamic analysis, such as, energy balance and losses by using the second law of thermodynamics have also been reported in the literature. However, optimum combinations of the operating parameters in addition to thermodynamic optimization for high distillate yield as well as the efficiency have not been thoroughly studied in the literature. In the present work, an emphasis has been given to review the effects of various operating and geometric parameters, and thermodynamic optimization on the performance of a solar still.
The low noise emission of battery electric vehicles (BEVs) has led to discussions about how to address potential safety issues for other road users. Legislative actions have already been undertaken to implement artificial sounds. In previous research, BEV drivers reported that due to low noise emission they paid particular attention to pedestrians and bicyclists. For the current research, we developed a hazard detection task to test whether drivers with BEV experience respond faster to incidents, which arise due to the low noise emission, than inexperienced drivers. The first study (N =65) revealed that BEV experience only played a minor role in drivers’ response to hazards resulting from low BEV noise. The tendency to respond, reaction times and hazard evaluations were similar among experienced and inexperienced BEV drivers; only small trends in the assumed direction were observed. Still, both groups clearly differentiated between critical and non-critical scenarios and responded accordingly. In the second study (N =58), we investigated additionally if sensitization to low noise emission of BEVs had an effect on hazard perception in incidents where the noise difference is crucial. Again, participants in all groups differentiated between critical and non-critical scenarios. Even though trends in response rates and latencies occurred, experience and sensitization to low noise seemed to only play a minor role in detecting hazards due to low BEV noise. An additional global evaluation of BEV noise further suggests that even after a short test drive, the lack of noise is perceived more as a comfort feature than a safety threat.
In the last two decades, several effective virtual reality-based interventions for anxiety disorders have been developed. Virtual reality interventions can also be used to build resilience to psychopathology for populations at risk of exposure to traumatic experiences and developing mental disorders as a result, such as for people working in vulnerable professions. Despite the interest among mental health professionals and researchers in applying new technology-supported interventions for pre-trauma mental resilience training, there is a lack of recommendations about what constitutes potentially effective technology-supported resilience training. This article analyses the role of technology in the field of stress-resilience training. It presents lessons learned from technology developers currently working in the area, and it identifies some key clinical requirements for the supported resilience interventions. Two processes made up this research: 1) developers of technology-assisted resilience programs were interviewed regarding human-computer interaction and system development; 2) discussions with clinicians were prompted using technology-centered concept storyboards to elicit feedback, and to refine, validate and extend the initial concepts. A qualitative analysis of the interviews produced a set of development guidelines that engineers should follow and a list of intervention requirements that the technology should fulfill. These recommendations can help bridge the gap between engineers and clinicians when generating novel resilience interventions for people in vulnerable professions.
Recently, with the stringent environmental regulations and shortage fossil-fuel reserve, power generation based on renewable energy sources is seen as a promising solution for future generation systems. A combination of these sources with an optimized configuration can face the climate change obstacles, permit better reliability, and reduce the cost of the generated energy. This paper presents a proposed particle swarm optimization (PSO) algorithm for an optimized design of grid-dependent hybrid photovoltaic-wind energy systems. This algorithm uses the actual hourly data of wind speeds, solar radiation, temperature, and electricity demand in a certain location. The PSO algorithm is employed to obtain the minimum cost of the generated energy while matching the electricity supply with the local demand with particular reliability index. The algorithm has been tested by considering a real case study used the actual situation to supply the electricity demand from utility grid at electricity market prices to estimate how significant are the cost saving compared to the actual situation costs. Results showed that the proposed algorithm responds well to changes in the system parameters and variables while providing a reliable sizing solution.
Even though the use of solid-state electrolytes for all-solid-state lithium battery applications has been a topic of great interest, an optimal material for this purpose has not been found. On the basis of the fact that ionic liquids are solidified at oxide particle surfaces and become quasi-solid materials, we previously fabricated a new lithium-ion-conducting solid electrolyte material comprising silica nano-particles and an ionic liquid that exhibited high ion conductivity comparable to the bulk ionic liquid. In the current study, this electrolyte was applied in the fabrication of an all-solid-state lithium secondary battery cell, by using three-dimensional structural cathode mixing the solid electrolyte and a cathode material (LiCoO2). The most important feature of the newly developed cell is that it was fabricated using thick films. There are no prior reports of all-solid-state secondary batteries employing thick films that exhibit high capacity. In this design, all of the cathode active materials could make contact with the electrolyte and the electron-conducting material despite the all-solid-state nature of the device. As a result, we have succeeded in the fabrication of an all-solid-state lithium secondary battery exhibiting high capacity of 126mAhg−1, nearly equal to theoretical capacity 138mAhg−1, despite the use of a micrometer order thick-film device. This study paves the way for the application of a new approach to the all-solid-state lithium secondary battery design.
To determine whether systemic medical factors, such as vascular risk factors, metabolic and inflammatory markers contribute to cognitive decline in Parkinson’s disease (PD); if confirmed to determine whether a clinically applicable risk factor model can predict the conversion from normal cognition (NC) to mild cognitive impairment (MCI). 58 patients who met the UK Brain Bank Criteria for PD underwent clinical and laboratory assessment at study entry; 47 patients were re-assessed after 2 years. Medical history, vascular risk (QRISK2), blood metabolic and inflammatory factors, brain vessel examinations, activity of daily living, and neuropsychological testing were performed. Forty patients had NC and 18 patients had MCI at baseline. Patients with MCI had higher level of interleukin 6, folic acid below normal range and higher l-dopa equivalent dose compared to cognitive normal patients at baseline. Patients with NC at baseline were classified into two groups: patients who remained cognitively normal (non-converters, n = 23) and patients who progressed to MCI (converters, n = 11). MCI converters were older at baseline and had higher QRISK2 than the non-converters. Patients with higher QRISK2, lower uric acid level and lower activity of daily living scale at baseline had a higher risk of converting from NC to MCI with a sensitivity of 72.2%, a specificity of 87%, and an overall accuracy of 82.4%. Systemic medical factors are associated with cognitive impairment in PD both cross-sectionally and longitudinally. A risk factor model predicting the decline from NC to MCI could be constructed.
Self-assembled films from SnO2 and polyallylamine (PAH) were deposited on gold via ionic attraction by the layer-by-layer (LbL) method. The modified electrodes were immersed into a H2PtCl6 solution, a current of 100μA was applied, and different electrodeposition times were used. The SnO2/PAH layers served as templates to yield metallic platinum with different particle sizes. The scanning tunnel microscopy images show that the particle size increases as a function of electrodeposition time. The potentiodynamic profile of the electrodes changes as a function of the electrodeposition time in 0.5molL−1 H2SO4, at a sweeping rate of 50mVs−1. Oxygen-like species are formed at less positive potentials for the Pt–SnO2/PAH film in the case of the smallest platinum particles. Electrochemical impedance spectroscopy measurements in acid medium at 0.7V show that the charge transfer resistance normalized by the exposed platinum area is 750 times greater for platinum electrode (300kΩcm2) compared with the Pt–SnO2/PAH film with 1min of electrodeposition (0.4kΩcm2). According to the Langmuir–Hinshelwood bifunctional mechanism, the high degree of coverage with oxygen-like species on the platinum nanoparticles is responsible for the electrocatalytic activity of the Pt–SnO2/PAH concerning ethanol electrooxidation. With these features, this Pt–SnO2/PAH film may be grown on a proton exchange membrane (PEM) in direct ethanol fuel cells (DEFC).
This work provides a two-dimensional thermal model for cylinder Ni/MH battery. Thermal model is developed to analyze the thermal behavior of the battery when charged and overcharged. Quantity of heat and heat generation rate of the battery during charge and overcharge period are studied by quartz frequency microcalorimeter. Heat generation curve is fitted into a function, and heat transport equation is solved. Analysis with the model and experiment show that temperature rise is about 3°C and difference between the model and the experiment is no more than 0.1°C.
Porous LiNi1/3Co1/3Mn1/3O2 microspheres were synthesized by a co-precipitation approach combined with high-temperature calcination. To improve the electrochemical performances, phosphate coating was formed on the surfaces of porous LiNi1/3Co1/3Mn1/3O2 microspheres by H3PO4 etching and subsequent annealing treatment. As anticipated, phosphate-coated LiNi1/3Co1/3Mn1/3O2 microspheres (2mol.% H3PO4) delivered discharge capacity of 100. 1mAhg−1 at 5°C, which was higher than that of pristine LiNi1/3Co1/3Mn1/3O2 microspheres (64.8mAhg−1). The improvement of rate capability and cycle stability of LiNi1/3Co1/3Mn1/3O2 microspheres could be attributed to the phosphate coating, which suppressed the side reaction between cathode and electrolyte. The phosphate surface modification has a promising application in improving the performance of layered oxide cathode materials for lithium ion batteries.
In the past decades, nickel and cobalt oxide/hydroxide materials have been investigated intensively for supercapacitor applications. Some works report very high specific capacitance values, up to 3152Fg−1, for these materials. By contrast, some other works report quite modest capacitance values, up to 380Fg−1 for the same materials prepared using same strategy. It is found that most works reporting very high capacitance value applied nickel foam as current collector. In this paper, surface chemistry and electrochemical properties of nickel foam are investigated by XPS analysis, cyclic voltammetry and galvanostatic charge–discharge measurement. The results show that using nickel foam as current collector can bring about substantial errors to the specific capacitance values of electrode materials, especially when small amount of electrode active material is used in the measurement. It is suggested that an electrochemically inert current collector such as Ti or Pt film should be used for testing electrochemical properties of nickel and cobalt oxide/hydroxide positive electrode materials.