Double-Shelled Fe-Fe3C Nanoparticles Embedded on a Porous Carbon Framework for Superior Lithium-Ion Half/Full Batteries.

Cost-effective and environmentally friendly Fe-based active materials offer exceptionally high energy capacity in lithium-ion batteries (LIBs) due to their multiple electron redox reactions. However, challenges, such as morphology degradation during cycling, cell pulverization, and electrochemical stability, have hindered their widespread use. Herein, we demonstrated a simple salt-assisted freeze-drying method to design a double-shelled Fe/Fe3C core tightly anchored on a porous carbon framework (FEC). The shell consists of a thin Fe3O4 layer (≈2 nm) and a carbon layer (≈10 nm) on the outermost part. Benefiting from the complex nanostructuring (porous carbon support, core-shell nanoparticles, and Fe3C incorporation), the FEC anode delivered a high discharge capacity of 947 mAh g-1 at 50 mA g-1 and a fast-rate capability of 305 mAh g-1 at 10 A g-1. Notably, the FEC cell still showed 86% reversible capacity retention (794 mAh g-1 at 50 mA g-1) at a high cycling temperature of 80 °C, indicating superior structural integrity during cycling at extreme temperatures. Furthermore, we conducted a simple solid-state fluorination technique using the as-prepared FEC sample and excess NH4F to prepare iron fluoride-carbon composites (FeF2/C) as the positive electrode. The full cell configuration, consisting of the FEC anode and FeF2/C cathode, reached a remarkable capacity of 200 mAh g-1 at a 20 mA g-1 rate or an energy density of approximately 530 Wh kg-1. Thus, the straightforward and simple experimental design holds great potential as a revolutionary Fe-based cathodic-anodic pair candidate for high-energy LIBs.

Enhanced Energy Density in All-in-One Device Integrating Si Solar Cell and Supercapacitor Using [BMIm]Cl/PVA Gel Electrolyte.

All-in-one systems integrating solar cells and supercapacitors have recently received significant attention because of their high efficiency and portability. Unlike conventional solar photovoltaics, which require external wiring to connect to a battery for energy storage, integrated devices with solar cells and supercapacitors share one electrode, eliminating wiring resistance and facilitating charge transfer. In this work, we designed and fabricated all-in-one devices by combining a silicon solar cell and a supercapacitor with polymer gel electrolytes. Our all-in-one devices incorporating H3PO4/PVA and [BMIm]Cl/PVA exhibited areal capacitances of 452.5 and 550 mF·cm -2 at 0.1 mA·cm-2, respectively, following 100 s of photocharging. Notably, the [BMIm]Cl/PVA-based all-in-one device demonstrated significantly higher maximum energy density and power density compared to both the H3PO4/PVA-based all-in-one device and the values reported in literature. In addition, the cyclic photocharge/galvanostatic discharge process for the [BMIm]Cl/PVA-based all-in-one device represented consistent retention of areal capacitance, affirming its stability across charge-discharge cycles. After 100 s of photocharging, the [BMIm]Cl/PVA-based all-in-one device achieved a total energy efficiency of 1.85%, surpassing the 1.45% efficiency observed in the device using H3PO4/PVA. These results provide valuable insights for the design of self-charging all-in-one devices for portable and wearable applications.

Laser Synthesis of MOF-Derived Ni@Carbon for High-Performance Pseudocapacitors.

Although nanosizing of multiphase pseudocapacitive nanomaterials could dramatically improve their electrochemical properties, a proper way to simultaneously control both the size and the phase of the pseudocapacitive materials is still elusive. Herein, we employed a commercial CO2 laser engraver to do the transformation of a metal-organic framework (MOF-74(Ni)) into size-controlled Ni nanoparticles (4-12 nm) in porous carbon. The produced Ni@carbon hybrid showed the best specific capacitance of 925 F/g with excellent cycling stability when the particle size is 5.5 nm. We found that the highly redox-active α-Ni(OH)2 is more predominantly formed than the less redox-active ß-Ni(OH)2 as the particle size becomes smaller. Our results substantiate that various MOFs could be created into high-performance pseudocapacitive materials with the controlled size and phase. It is believed that the laser-based synthesis could also serve as a powerful tool for the discovery of new MOF-derived materials in the field of energy storage and catalysis.

Facile One-Pot Synthesis of Bimetallic Co/Mn-MOFs@Rice Husks, and its Carbonization for Supercapacitor Electrodes.

Novel hybrid nanomaterials comprising metal-organic framework compounds carbonised in the presence of biomass material derived from rice husk have been investigated as a new class of sustainable supercapacitor materials for electrochemical energy storage. Specifically, two synthetic routes were employed to grow Co/Mn metal-organic framework compounds in the channels of rice husks, which had been activated previously by heat treatment in air at 400 °C to produce a highly porous network. Pyrolysis of these hybrid materials under nitrogen at 700 °C for 6 h produced metal-containing phases within the nanocarbon, comprising intimate mixtures of Co, MnO and CoMn2O4. The materials thus produced are characterized in detail using a range of physical methods including XRD, electron microscopy and X-ray photoelectron spectroscopy. The synthetic pathway to the metal-organic framework compound is shown to influence significantly the physical properties of the resulting material. Electrochemical evaluation of the materials fabricated revealed that higher specific capacitances were obtained when smaller crystallite sized bimetallic Co/Mn-MOFs were grown inside the rice husks channels compared to larger crystallite sizes. This was in-part due to increased metal oxide loading into the rice husk owing to the smaller crystallite size as well as the increased pseudocapacitance exhibited by the smaller crystallite sizes and increased porosity.

Effective CO2 and CO Separation Using [M2(DOBDC)] (M = Mg, Co, Ni) with Unsaturated Metal Sites and Excavation of Their Adsorption Sites.

Isostructural [M2(DOBDC)(EG)2] (M = Mg, Co, Ni) frameworks are first synthesized by controlling the pH* in the reaction medium. Coordinated ethylene glycols form a hexagonal OH cluster, which works as a template to grow single crystals with high crystallinity. After the liberation of solvated molecules, [M2(DOBDC)] shows notably higher surface areas than the reported values and completely different CO2 and CO separation properties depending on the kinds of unsaturated metal. Therefore, breakthrough experiments using a CO2/CO mixed gas show that Mg-MOF has a longer breakthrough time for CO2 than for CO, whereas Co/Ni-MOFs have longer breakthrough times for CO than for CO2. Apart from CO2 and CO, other gases such as CH4, H2, and N2 were almost not adsorbed at all in these materials at 298 K. To reveal the role of unsaturated metal sites, CO2 and CO adsorption sites are unequivocally determined by single-crystal X-ray diffraction analysis. One of very interesting discoveries is that there are two CO2 and CO adsorption positions (sites A and B) in the hexagonal channels. Site A is the unsaturated metal center working as Lewis acidic sites, and site B is the secondary adsorption site located between two A sites. A close inspection of crystal structures reveals that unsaturated Co(II) and Ni(II) sites adsorb both CO2 and CO, whereas the unsaturated Mg(II) sites strongly capture only CO2, not CO. Density functional theory calculations elucidate the discrepancy in CO affinity: Co(II) and Ni(II) form strong π-back-donating bonds with CO via electron transfer from the d orbitals of the transition metals to the antibonding molecular orbitals of CO, whereas Mg(II) does not participate in electron transfer or orbital overlap with CO. This observation provides new insight into the synthesis of novel functional materials with high CO2/CO separation performance.

Cellulose-Derived Supercapacitors from the Carbonisation of Filter Paper.

Advanced carbon materials are important for the next-generation of energy storage apparatus, such as electrochemical capacitors. Here, the physical and electrochemical properties of carbonised filter paper (FP) were investigated. FP is comprised of pure cellulose and is a standardised material. After carbonisation at temperatures ranging from 600 to 1700 °C, FP was contaminant-free, containing only carbon and some oxygenated species, and its primary fibre structure was retained (diameter ≈20-40 µm). The observed enhancement in conductivity of the carbonised FP was correlated with the carbonisation temperature. Electrochemical capacitance in the range of ≈1.8-117 F g(-1) was achieved, with FP carbonised at 1500 °C showing the best performance. This high capacitance was stable with >87 % retained after 3000 charge-discharge cycles. These results show that carbonised FP, without the addition of composite materials, exhibits good supercapacitance performance, which competes well with existing electrodes made of carbon-based materials. Furthermore, given the lower cost and renewable source, cellulose-based materials are the more eco-friendly option for energy storage applications.

[Measuring workload of home visit care activities using relative values].

OBJECTIVES: The purpose of this study was to measure the workload of home visit care activities and their relative values. This study examined also factors that affect the workload of home visit care activities. METHODS: The participants of this study were 126 home-helpers of 50 home visit care agencies at the 2nd Longterm Care Insurance Demonstration Project. The workload of home visit care activities was divided into total work and four dimensions; physical efforts, mental efforts, stress and time. Home visit care activities consisted of four categories with 24 items. We used magnitude estimation method to measure their relative values of the four dimensions. The participants answered the relative values of each activities based on the reference service. We used the activity for supporting their elderly's evacuation as the reference service. RESULTS: Most of the respondents were over 40 years old female. They consumed most their time supporting elderly's going out. They consumed their highest physical, mental efforts, and stress for activities of coping with emergency situation. The Pearson correlation coefficients showed significant relationships between workload and each dimensions. This study showed that all four dimensions are statistically significant predictors of workload of home visit care activities. Also, we found that the home-helper's career affects the workload of home visit care activities. CONCLUSIONS: The workload of home visit care activities could be explained by physical efforts, mental efforts, stress and time.