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The electrochemical behavior of composite electrodes obtained by mixing graphite (Timrex KS-15 by Timcall), partially oxidized by thermal treatment, with nanometric metal particles (Au, Ag, Ni, Cu, Al, Sn) at about 1% (w/o) is presented. The charge–discharge properties of the composite electrodes have been studied in the temperature range 20 to −30°C in 1M LiPF6 EC–DEC–DMC (1:1:1). The main effect is a general improvement of the cycling behavior at any temperature. In particular, at −30°C about 30% of the theoretical intercalation capacity is retained by electrodes containing Cu, Al and Sn. At the same temperature, the composites containing the above metals show evidences of lithium staging. This may indicate that certain metals affect the kinetics of phase transformation that, together with other effects including charge transfer resistance, lithium diffusion coefficient and polarization due to SEI and solvent conductivities, seems to be the main cause of the poor intercalation capacity of graphite anodes at low temperature.
In this study, an energy storage device using a three-electrode battery is fabricated. The charging process takes place during electrolysis of the alkaline electrolyte where hydrogen is stored at the palladium bifunctional electrode. Upon discharging, power is generated by operating the alkaline fuel cell using hydrogen which is accumulated in the palladium hydride bifunctional electrode during the charging process. The bifunctional palladium electrode is prepared by electrodeposition using a hydrogen bubble template followed by a galvanic displacement reaction of platinum in order to functionalize the electrode to work not only as a hydrogen storage material but also as an anode in a fuel cell. This bifunctional electrode has a sufficiently high surface area and the platinum catalyst populates at the surface of electrode to operate the fuel cell. The charging and discharging performance of the three-electrode battery are characterized. In addition, the cycle stability is investigated.
An environmentally benign vacuum pyrolysis (VP) approach is employed to recover Li and Co from spent LiCoO2-based lithium-ion batteries (LIBs). First, the electroactive materials were separated from the current collector by the VP method from 623 to 823 K with an attempt to choose an appropriate temperature. Then, the as-received cathode materials were mixed with different amounts of graphite from the anode to selectively convert LiCoO2 to Co or CoO and Li2CO3 by carbothermic reduction under vacuum and at 873 to 1273 K. After carbothermic reduction, the pyrolyzed powder was leached in water to separate Li2CO3 from Co/CoO. By alternating the C/LiCoO2 mass ratio and the pyrolysis temperature, a recovery rate reaches over 93% for Li and 99% for Co. Finally, the recovered CoO and Li2CO3 were used to regenerated LiCoO2 that delivered a specific capacity of 145 mAh g−1 at 1C and retaining 93% of the initial capacity after 100 cycles. Overall, a multi-vacuum-pyrolysis approach offers a closed-loop route for the management of spent LIBs without using any hazardous chemicals.
Nanostructured magnesium nickel oxide Mg0.6Ni0.4O and alumina Al2O3 were studied as additives to sulphur/polyaniline (S/PANI) composites via wet ball-milling of sulphur and polyaniline followed by heat treatment. Metal oxide nanoparticles, which have small particle size, porous structure and high specific surface area to volume ratio, are expected to be catalytic for chemical reactions, including electron transfer and are able to adsorb lithium polysulphides. The composites were characterized by SEM and electrochemical methods. Cyclic voltammetry studies suggest that the alumina additive acts differently to the Mg0.6Ni0.4O. The results suggest that although the alumina additive improves the S/PANI composite performance as a lithium–sulphur battery cathode, the use of Mg0.6Ni0.4O is more effective.
Polymethacrylontrile (PMAN)-based electrolytes were recently proposed as polymer matrix for ambient temperature applications. The living anionic polymerization of methacrylonitrile allowed PMAN–POE–PMAN triblock copolymers to be prepared from different starting PEGs. In order to appreciate the salt/polymer interactions, solvent-free polymer electrolytes were prepared by dissolution of lithium imide (LiTFSI) in PMAN homopolymer and copolymers. Despite the high T g of PMAN host polymer, conductivities as high as 10−4 S cm−1 were obtained around 90°C. Infra-red spectroscopy allowed the nitrile/salt interaction to be characterized. In particular, PMAN solvation number was determined from the homopolymer complexes. The investigation on the triblock copolymer complexes allowed the solvating competition between nitrile and ether functions to be highlighted.
We report the development of redox-active conjugated polymers that have potential applications in electrochemical energy storage. Side chain engineering enables processing of the polymer electrodes from solution, stability in aqueous electrolytes and efficient transport of ionic and electronic charge carriers. We synthesized a 3,3′-dialkoxybithiophene homo-polymer (p-type polymer) with glycol side chains and prepared naphthalene-1,4,5,8-tetracarboxylic-diimide-dialkoxybithiophene (NDI-gT2) copolymers (n-type polymer) with either a glycol or zwitterionic side chain on the NDI unit. For the latter, we developed a post-functionalization synthesis to attach the polar zwitterion side chains to the polymer backbone to avoid challenges of purifying polar intermediates. We demonstrate fast and reversible charging of solution processed electrodes for both the p- and n-type polymers in aqueous electrolytes, without using additives or porous scaffolds and for films up to micrometers thick. We apply spectroelectrochemistry as an in operando technique to probe the state of charge of the electrodes. This reveals that thin films of the p-type polymer and zwitterion n-type polymer can be charged reversibly with up to two electronic charges per repeat unit (bipolaron formation). We combine thin films of these polymers in a two-electrode cell and demonstrate output voltages of up to 1.4 V with high redox-stability. Our findings demonstrate the potential of functionalizing conjugated polymers with appropriate polar side chains to improve the accessible capacity, and to improve reversibility and rate capabilities of polymer electrodes in aqueous electrolytes.
Bilirubin oxidase was immobilised on ITO electrodes: bare or covered by ITO nanoparticulate film. The latter material was obtained by immersion and withdrawal of the substrate into ITO nanoparticles suspension. Formation of a protein deposit was confirmed by scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. The electrode surface is covered by a protein film in the form of globular aggregates and it exhibits mediatorless electrocatalytic activity towards dioxygen reduction to water at pH 4.8. Modification of the electrode with ITO particles increases its catalytic activity about ten times up to 110μAcm−2 seen for electrodes prepared by twelve immersion and withdrawal steps into ITO nanoparticle suspension. The catalytic activity is almost unaffected by addition of mediator to solution. The stability of the electrodes is increased by cross-linking of the enzyme with bovine serum albumin and glutaraldehyde. This electrode was applied as biocathode in a zinc–dioxygen battery operating in 0.1moldm−3 McIlvaine buffer (pH 4.8).
This work reports the development of a facile, one-step microwave heating method for the synthesis of graphene-supported Pd1Pt3 (Pd core/Pt shell) electrocatalysts. The structure and composition of the synthesized nanocomposites were characterized via transmission electron microscopy and atomic force microscopy as well as energy-dispersive X-ray, X-ray powder diffraction, FTIR, and Raman spectroscopies. Using voltammetry, the electrocatalytic characteristics of the graphene-supported Pd1Pt3 nanostructures were evaluated for the oxidation of methanol as a model reaction. The results show that the introduction of graphene increases the electrochemically active surface area of the Pd1Pt3 nanostructures. As compared to the unsupported Pd1Pt3 electrocatalyst, the graphene-supported Pd1Pt3 electrocatalyst exhibited 80% enhancement of the electrocatalytic specific mass current for the oxidation of methanol. This method may serve as a general, facile approach for the synthesis of graphene-supported bimetallic PtM electrocatalysts with increased utilization of the Pt metal, which is expected to have promising applications in fuel cells.
Herein, a unique nanostructure of TiO2@SnO2@3DC composite composed of three-dimensionally tussocky carbon coating porous TiO2/SnO2 quasi-nanospheres has been fabricated by a well-engineered strategy based on improvement of SnO2-based material lithium storage via constructing reasonable synergistic effect of structures and components. Thus feasible synergistic effect of TiO2/SnO2 quasi-nanospheres and tussocky carbon coating provides a robust guarantee for structural stability and electrochemical properties of TiO2@SnO2@3DC composite, resulting in improved electrochemical lithium storage performance. Moreover, this work may pave the way to fabricate non-smooth three-dimensional carbon coating for versatile SnO2/C-based composites.
Efficacy of waste recycling is one of the key determinants of environmental sustainability of a city. Like other pro-environmental activities, waste recycling cannot be successfully accomplished by just one or two people, but only by a concerted effort of the community. The collective-action dilemma creates a common underlying difficulty in formulating workable solutions to many environmental problems. With a view to the non-excludability of the outcome, rationality drives people to free-ride efforts of others in waste recycling. To solve this free-rider problem, some scholars suggest the use of economic incentive. This article attempts to study the impacts of reward schemes on waste recycling behaviour of residents in 122 private housing estates in Hong Kong. The study is differentiable from the others as the latter mainly focus on domestic waste recycling in low-rise low-density housing while this one looks into the same in a high-rise high-density residential setting. According to the results of analyses on a set of aggregate data, reward schemes are found to have a significant positive relationship with the per-household weight of recyclables collected, keeping other things constant. The research findings suggest that economic incentives do work in promoting waste recycling in Hong Kong. Practical and policy implications follow.
Three-dimensional (3D) nanoarchitectures have demonstrated substantial advantages in capturing the performance of traditional electrode materials. In this regard, novel Cu@SnS core–shell nanowire array is fabricated via a rational electrochemical assembly strategy. Meanwhile it is also discovered that striking structural and compositional evolution from Cu@SnS core–shell nanowires to hybrid CuS/SnS nanotubes can be achieved by a simple tuning of reaction conditions. As a proof of concept, long-term cycling stability and remarkable rate capability are exhibited by Cu@SnS nanoelectrode in the study of its Li+ storage properties (e.g., it delivers a capacity of ∼347 mAh g−1 at 3.33C even after 80 rate-varying cycles), which verifies the effectiveness of the designed 3D configuration in tackling possible electrical/mechanical failures of the electrode during repeated Li+ uptake/release process. Moreover, because of their potential for achieving high power and energy densities on a small footprint area, the designed metal sulfide nanoelectrodes may be promisingly applied in microenergy storage devices.
Unitized regenerative fuel cells (URFC) convert electrical energy to and from chemical bonds in hydrogen. URFCs have the potential to provide economical means for efficient long-term, seasonal, energy storage and on-demand conversion back to electrical energy. We first optimize the catalyst layer for discrete electrolyzer and fuel cell and then configure the URFC. The goal is to identify a cost competitive configuration for URFCs, and demonstrate it in terms of upper limit of round trip efficiencies (RTEs). Two possible configurations of URFCs are compared via experiments and techno-economic analysis (TEA), which emphasize the advantages of the unconventional constant-electrode (CE) URFC over the traditional constant-gas (CG) configuration. We also study the stability via accelerated stress tests (ASTs) and demonstrate steady state operation in a daily cycle for day to night energy shifting. From the investigations, the optimum composition of the URFC anode catalyst layer is 90 at% Ir-black balanced by Pt-black for both CE and CG configurations. At 80 °C and 1 A cm−2, the optimized CE URFC achieves 57% and 60% RTE with air and O2 as the reductant gases, respectively. We then evaluated the differences in durability using an AST over 10k charge–discharge cycles; the results reveal that the wider potential window at the anode in CE (0.05–1.55 V) has minimal effect on catalyst layer stability compared to CG (0.55–1.55 V). Furthermore, there was no degradation up to the range of 2k–5k cycles; beyond that the fuel cell (discharge) performance degraded while the electrolyzer (charge) performance was still stable. The observations here indicate substantial potential to employ URFCs as efficient and cost-effective bidirectional energy-conversion devices within energy storage and utilization systems after appropriate technological and operational optimizations.
Estimating the total sleep time in home recording devices is necessary to avoid underestimation of the indices reflecting sleep apnea and hypopnea syndrome severity, e.g., the apnea–hypopnea index (AHI). A new method to distinguish sleep from wake using jaw movement signal processing is assessed.
Orthorhombic V2O5 has been considered as one of the most promising cathode materials for new lithium ion batteries (LIBs) due to its high specific capacity, easy synthesis and good safety. However, the poor rate and cycling performance of V2O5 electrodes significantly impede their applications in high-power and long-life LIBs. The present work reports facile synthesis of self-doped V4+–V2O5 nanoflakes through combusting the NH4V4O10 and VO2 (B) mixture in the presence of 2-ethylimidazole. The resulting V4+–V2O5 exhibited superior rate capability (a reversible capacity of 293, 268, 234, 214, 196 and 139mAhg−1 at 100, 300, 600, 1000, 2000 and 4000mAg−1, respectively) and remarkable cycling performance (95% capacity retention after 100 discharge/charge cycles at 2000mAg−1). The outstanding performance is derived from the uniform nanoflake structure, which offers more surface area and reaction sites for lithium ion intercalation, and the presence of tetravalent vanadium ions accompanied with oxygen vacancies, which might promote and catalyze the electrochemical reactions at the surface, in addition to improve the intrinsic electrical conductivity and Li ion diffusion coefficient, as reflected by the smaller polarization and more reversible and easier phase transitions than those of V2O5 without detectable V4+ and oxygen vacancies.
The use of ionic liquid (IL) electrolytes is a promising strategy to enhance the performance of supercapacitors above room temperature. In this paper we present the results of a study on optimization of electrode materials for IL-based supercapacitors featuring a hybrid configuration with carbon negative electrode and poly(3-methylthiophene) (pMeT) as positive operating at 60°C with the ILs N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14TFSI) and 1-ethyl-3-methyl-imidazolium bis(trifluoromethanesulfonyl)imide (EMITFSI). As it concerns the carbon electrode two routes have been pursued: (i) surface modification of commercial activated carbon and (ii) synthesis of mesoporous cryo- and xerogel carbons. Pore size distribution and electrochemical characterization data are related and suggest that the second route should be the most promising for carbons of high specific capacitance and low time constant in IL. For the polymer electrode the nature of the galvanostatic polymerization bath plays a crucial role to provide pMeT of high specific capacitance and the best results may be obtained when pMeT is electropolymerized in the same IL used for the capacitance tests. The strategy of using the acid additive trifluoromethanesulfonimide in IL-based polymerization baths is also described in some detail. This strategy that provides pMeT featuring more than 200Fg−1 in IL is a clean procedure which prevents consumption of the ionic liquid with great advantage in terms of costs.
The arithmetical performance of typically achieving 5- to 7-year-olds (N =29) was measured at four 6-month intervals. The same seven tasks were used at each time point: exact calculation, story problems, approximate arithmetic, place value, calculation principles, forced retrieval, and written problems. Although group analysis showed mostly linear growth over the 18-month period, analysis of individual differences revealed a much more complex picture. Some children exhibited marked variation in performance across the seven tasks, including evidence of difficulty in some cases. Individual growth patterns also showed differences in developmental trajectories between children on each task and within children across tasks. The findings support the idea of the componential nature of arithmetical ability and underscore the need for further longitudinal research on typically achieving children and of careful consideration of individual differences.
One of the earliest attempts to estimate the heat production rate in an electrochemical cell is that of Sherfrey and Brunner [1]. Their methodology and the developments that followed generated models of greater or lesser sophistication that are difficult to apply because of notation problems. In many cases, the modeling equations are referenced in subsequent papers but the cell's thermal response continues to be determined experimentally. A computationally simpler approach is developed and evaluated. This methodology follows essentially the original methodology but begins at a more fundamental level, i.e., the energy conservation law. By doing this, the critical parameters are easily addressed in a more systematic way and produce quantitative results suitable for more extended modeling and simulation exercises. These quantitative parameters include (1) the heat generation rate in multi-cell batteries, (2) the heat generation rate during cell venting, (3) the thermal response as a measure of the state of health of a battery, (4) an estimator of the heat generation rate that does not require a temperature measurement and (5) a first order differential equation that models the dynamic thermal response as a function of the power input (or output) of the battery.
As outlined in the introductory article “The Neverending Story—Using the Narrative as a Fundamental Approach to Teaching Biology and Beyond,” historical storytelling has the potential to add understanding and synthesis to learning that is usually restricted to memorization and skills-based application. The following stories were written in an attempt to reconcile mandated microbiology topics, such as biochemistry and the properties of DNA, with an overarching evolutionary framework that is applicable regardless of the scale of observation. These stories were designed with secondary school biology teachers and students in mind, particularly at the senior-grade level. In an effort to preserve narrative flow, internal referencing has been sacrificed, but a complete set of source material is cited at the end of the compilation.
The synthesis of nickel hydroxide occurs by many stages. When the precipitating reagent is NH4OH solution, the precipitation of nickel hydroxide occurs between pH 8.0 and 8.6. For pH between 8.6 and 10.0, a soluble complex such as [Ni(NH3)6]2+ is formed. The precipitation of nickel hydroxide happens again after the pH equals 10.0. Finally, there occurs the ageing of α-Ni(OH)2. A mixture of α-Ni(OH)2 and β-Ni(OH)2 phases is formed when the solid state reaction is not totally completed. One adsorbed layer becomes very hard with the exit of the water intercalated in the α-Ni(OH)2. In presence of KOH solution occurs the formation and the ageing of α-Ni(OH)2. Synthesis was characterized by the following techniques: X-ray diffraction, Fourier transform infrared spectroscopy (FT-IR), differential thermal analysis (DTA) and gravimetric thermal analysis (GTA), and specific surface area and UV–vis spectroscopy.
The present guideline (S2k) on allergen-specific immunotherapy (AIT) was established by the German, Austrian and Swiss professional associations for allergy in consensus with the scientific specialist societies and professional associations in the fields of otolaryngology, dermatology and venereology, pediatric and adolescent medicine, pneumology as well as a German patient organization (German Allergy and Asthma Association; Deutscher Allergie- und Asthmabund, DAAB) according to the criteria of the Association of the Scientific Medical Societies in Germany (Arbeitsgemeinschaft der Wissenschaftlichen Medizinischen Fachgesellschaften, AWMF).
The combination of high conductivity and good stability against Li is not easy to achieve for solid electrolytes, hindering the development of high energy solid-state batteries. In this study, doped electrolytes of Li3P1-x Sb x S4-2.5x O2.5x are successfully prepared via the high energy ball milling and subsequent heat treatment. Plenty of techniques like XRD, Raman, SEM, EDS and TEM are utilized to characterize the crystal structures, particle sizes, and morphologies of the glass-ceramic electrolytes. Among them, the Li3P0.98Sb0.02S3.95O0.05 (x = 0.02) exhibits the highest ionic conductivity (∼1.08 mS cm−1) at room temperature with an excellent stability against lithium. In addition, all-solid-state lithium batteries are assembled with LiCoO2 as cathode, Li10GeP2S12/Li3P0.98Sb0.02S3.95O0.05 as the bi-layer electrolyte, and lithium as anode. The constructed solid-state batteries delivers a high initial discharge capacity of 133 mAh g−1 at 0.1C in the range of 3.0–4.3 V vs. Li/Li+ at room temperature, and shows a capacity retention of 78.6% after 50 cycles. Most importantly, the all-solid-state lithium batteries with the Li10GeP2S12/Li3P0.98Sb0.02S3.95O0.05 electrolyte can be workable even at −10 °C. This study provides a promising electrolyte with the improved conductivity and stability against Li for the application of all-solid-state lithium batteries.
The charge/discharge characteristics of lithium ion batteries at low temperature (LT = −20 °C) are enhanced by using ethylene carbonate (EC)-based electrolytes with the help of assistant solvents of nitriles. Conventional liquid electrolytes (e.g. a mixture of EC and dimethyl carbonate (DMC), abbreviated as LED) cannot support a satisfactory capacity at low temperature as well as at high rates even if electric vehicles require low-temperature operation. Introducing propionitrile or butyronitrile (Pn or Bn) into LED (resulting in LEDPn or LEDBn) as a co-solvent increases significantly the high-rate capacities at −20 °C. For example, LEDPn delivers 62% of the available capacity at 1 C and 46% at 3 C with a 2.7 V cut-off while the control LED provides just 6% and 4% at the same rates. Successful operation at −20 °C with nitrile-assistant electrolytes results from high ionic conductivity, low viscosity and freezing point depression caused by the eutectic behavior of the carbonates (EC/DMC) and Pn. Based on the phase diagram of Pn with EC/DMC, we expect a meaningful battery operation up to −110 °C, probably lower, at the eutectic composition.