3D Nano-heterostructure of ZnMn2O4@Graphene-Carbon Microtubes for High-Performance Li-Ion Capacitors.

Heterostructures show great potential in energy storage due to their multipurpose structures and function. Recently, two-dimensional (2D) graphene has been widely regarded as an excellent substrate for active materials due to its large specific surface area and superior electrical conductivity. However, it is prone to self-aggregation during charging and discharging, which limits its electrochemical performance. To address the graphene agglomeration problem, we interspersed polypyrrole carbon nanotubes between the graphene cavities and designed three-dimensional (3D)-heterostructures of ZnMn2O4@rGO-polypyrrole carbon nanotubes (ZMO@G-PNTs), which demonstrated a high rate and cyclic stability in lithium-ion capacitors (LICs). Furthermore, the 3D porous structure provided more surface capacity contribution than 2D graphene, ultimately resulting in a better stability (333 mAh g-1 after 1000 cycles at 1 A g-1) and high rate capacity (208 mAh g-1 at 5 A g-1). Also, the mechanism of performance difference between ZMO@G-PNTs and ZMO@G was investigated in detail. Moreover, LICs built from ZMO@G-PNTs as an anode and activated carbon as a cathode showed an energy density of 149.3 Wh kg-1 and a power density of 15 kW kg-1 and cycling stability with a capacity retention of 61.5% after 9000 cycles.

Pseudocapacitive Crystalline MnCo2O4.5 and Amorphous MnCo2S4 Core/Shell Heterostructure with Graphene for High-Performance K-Ion Hybrid Capacitors.

Potassium-ion capacitors (KICs) have received a surge of interest because of their higher reserves and lower costs of potassium than lithium. However, the cycle performance and capacity of potassium devices have been reported to be unsatisfactory. Herein, a unique crystalline MnCo2O4.5 and amorphous MnCo2S4 core/shell nanoscale flower structure grown on graphene (MCO@MCS@rGO) was synthesized by a two-step hydrothermal process and demonstrated in KICs. The MCO@MCS@rGO exhibits improved electrical conductivity and excellent structural integrity during the charging and discharging process. The reasons could be attributed to the cavity structure of MCO, the mechanical buffer and high electrolyte diffusion rate of MCS, and the auxiliary effect of graphene. The electrical conductivity of MCO@MCS shows a specific capacity of 272.3 mA h g-1 after 400 cycles at 1 A g-1 and a capacity of 125.6 mA h g-1 at 2 A g-1. Besides, the MCO@MCS@rGO and high-surface-area activated carbon in KICs exhibit a relative energy density of 85.3 W h kg-1 and a power density of 9000 W kg-1 and outstanding cycling stability with a capacity retention of 76.6% after 5000 cycles. Moreover, the reaction mechanism of MCO@MCS@rGO in the K-ion cell was investigated systematically using X-ray diffraction and transmission electron microscopy, providing guidance on the further development of pseudocapacitive materials.

Advanced non-noble materials in bifunctional catalysts for ORR and OER toward aqueous metal-air batteries.

The catalyst in the oxygen electrode is the core component of the aqueous metal-air battery, which plays a vital role in the determination of the open circuit potential, energy density, and cycle life of the battery. For rechargeable aqueous metal-air batteries, the catalyst should have both good oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalytic performance. Compared with precious metal catalysts, non-precious metal materials have more advantages in terms of abundant resource reserves and low prices. Over the past few years, great efforts have been made in the development of non-precious metal bifunctional catalysts. This review selectively evaluates the advantages, disadvantages and development status of recent advanced materials including pure carbon materials, carbon-based metal materials and carbon-free materials as bifunctional oxygen catalysts. Preliminary improvement strategies are formulated to make up for the deficiency of each material. The development prospects and challenges facing bifunctional catalysts in the future are also discussed.

A sponge-templated sandwich-like cobalt-embedded nitrogen-doped carbon polyhedron/graphene composite as a highly efficient catalyst for Zn-air batteries.

Non-noble metal materials are regarded as the most promising catalysts for the oxygen reduction reaction (ORR) to overcome the inherent defects of Pt-based catalysts, like high cost, limited availability and insufficient stability. Here, we fabricate sandwich-like Co encapsulated nitrogen doped carbon polyhedron/graphene (s-Co@NCP/rGO) via a facile and scalable strategy by loading Co-based zeolitic imidazolate framework (ZIF-67) and graphene oxide (GO) layers individually on a polyurethane (PU) sponge template. The 3D sandwich structure is maintained with the assistance of the sponge template, which promotes the uniform dispersion of ZIF-67-derived Co embedded nitrogen doped carbon polyhedra (Co@NCP) and prevents the graphene plates from agglomerating during the annealing process. The final product demonstrates considerable catalytic performance for the ORR with a half-wave potential of 0.85 V, preferable stability and increased poisoning tolerance by comparison to 20 wt% Pt/C, which stems from the 3D sandwich-like structure, N/Co-doping effect, large accessible surface area and hierarchical porous structures. The excellent ORR performance of the catalysts means that they can be utilised in a Zn-air battery as cathode catalysts. During such a demonstration, s-Co@NCP/rGO shows a high open-circuit voltage of 1.466 V, remarkable long-term durability and an outstanding peak power density of 186 mV cm-2, which shows its high potential as a prospective alternative for widespread practical application in the field of non-noble metal ORR catalysts.

Thermally Driven Structure and Performance Evolution of Atomically Dispersed FeN4 Sites for Oxygen Reduction.

FeN4 moieties embedded in partially graphitized carbon are the most efficient platinum group metal free active sites for the oxygen reduction reaction in acidic proton-exchange membrane fuel cells. However, their formation mechanisms have remained elusive for decades because the Fe-N bond formation process always convolutes with uncontrolled carbonization and nitrogen doping during high-temperature treatment. Here, we elucidate the FeN4 site formation mechanisms through hosting Fe ions into a nitrogen-doped carbon followed by a controlled thermal activation. Among the studied hosts, the ZIF-8-derived nitrogen-doped carbon is an ideal model with well-defined nitrogen doping and porosity. This approach is able to deconvolute Fe-N bond formation from complex carbonization and nitrogen doping, which correlates Fe-N bond properties with the activity and stability of FeN4 sites as a function of the thermal activation temperature.

Pseudocapacitance of TiO2-x /CNT Anodes for High-Performance Quasi-Solid-State Li-Ion and Na-Ion Capacitors.

It is challenging for flexible solid-state hybrid capacitors to achieve high-energy-high-power densities in both Li-ion and Na-ion systems, and the kinetics discrepancy between the sluggish faradaic anode and the rapid capacitive cathode is the most critical issue needs to be addressed. To improve Li-ion/Na-ion diffusion kinetics, flexible oxygen-deficient TiO2-x /CNT composite film with ultrafast electron/ion transport network is constructed as self-supported and light-weight anode for a quasi-solid-state hybrid capacitor. It is found that the designed porous yolk-shell structure endows large surface area and provides short diffusion length, the oxygen-deficient composite film can improve electrical conductivity, and enhance ion diffusion kinetic by introducing intercalation pseudocapacitance, therefore resulting in advance electrochemical properties. It exhibits high capacity, excellent rate performance, and long cycle life when utilized as self-supported anodes for Li-ion and Na-ion batteries. When assembled with activated carbon/carbon nanotube (AC/CNT) flexible cathode, using ion conducting gel polymer as the electrolyte, high energy densities of 104 and 109 Wh kg-1 are achieved at 250 W kg-1 in quasi-solid-state Li-ion and Na-ion capacitors (LICs and SICs), respectively. Still, energy densities of 32 and 36 Wh kg-1 can be maintained at high power densities of 5000 W kg-1 in LICs and SICs.

Functional Differentiation of Three Pores for Effective Sulfur Confinement in Li-S Battery.

Shuttle effect of the dissolved intermediates is regarded as the primary cause that leads to fast capacity degradation of Li-S battery. Herein, a microporous carbon-coated sulfur composite with novel rambutan shape (R-S@MPC) is synthesized from microporous carbon-coated rambutan-like zinc sulfide (R-ZnS@MPC), via an in situ oxidation process. The R-ZnS is employed as both template and sulfur precursor. The carbon frame of R-S@MPC composite possesses three kinds of pores that are distinctly separated from each other in space and are endowed with the exclusive functions. The central macropore serves as buffer pool to accommodate the dissolved lithium polysulfides (LPSs) and volumetric variation during cycling. The marginal straight-through mesoporous, connected with the central macropore, takes the responsibility of sulfur storage. The micropores, evenly distributed in the outer carbon shell of the as-synthesized R-S@MPC, enable the blockage of LPSs. These pores are expected to perform their respective single function, and collaborate synergistically to suppress the sulfur loss. Therefore, it delivers an outstanding cycling stability, decay rate of 0.013% cycle-1 after 500 cycles at 1 C, when the sulfur loading is kept at 4 mg cm-2 .

Clustered-Microcapsule-Shaped Microporous Carbon-Coated Sulfur Composite Synthesized via in Situ Oxidation.

Hollow materials as sulfur hosts have been intensively investigated to address the poor cycling stabilities of Li-S batteries. Herein, we report an enhanced hollow framework to improve the applicability of the sulfur confinement. A clustered-microcapsule-shaped microporous carbon coated sulfur (CM-S@MPC) composite is prepared from the clustered zinc sulfide precursor, through an in situ oxidation process. The high specific surface area and the in situ preparation guarantee the uniform distribution of sulfur inside the carbon microcapsule, even under a higher sulfur content of 83 wt %. In addition, the interconnected frame constructed by the stacking of carbon microcapsules also mitigates the lithium polysulfide loss by setting interlayered hurdles on their pathway along the outward diffusion. Hence, these enable a full demonstration of excellent cycling stability, compared to the control sample obtained via physical sulfur infiltration. The outstanding decay rate of 0.039% per cycle is achieved during 700 cycles at 1 C, even under high sulfur loading.

A comparison of the effects of midazolam, propofol and dexmedetomidine on the antioxidant system: A randomized trial.

Previous studies on the antioxidant activity of sedatives have predominantly been in vitro investigations that are lacking clinical data, resulting in conclusion without cogency. The aim of the present prospective, randomized study was to use single sedative drugs for anesthesia induction to compare their antioxidant properties. The effects on the antioxidant system of midazolam, propofol and dexmedetomidine were assessed using oxidative stress indicators and micronuclei (MN). Forty-nine patients undergoing esophageal cancer radical prostatectomy were selected. Midazolam, propofol and dexmedetomidine were used to induce anesthesia. Venous blood samples were obtained prior to and at 2 and at 24 h after surgery, and oxidative stress indicators were detected using the appropriate kits. The cytokinesis-block micronucleus cytome assay was executed and the frequencies of MN, nucleoplasmic bridges and nuclear buds were examined. It was found that the use of the three sedatives, respectively, led to a marked increase in the levels of free radical indicators at 2 h after surgery, which then decreased at 24 h after surgery. Furthermore, lower levels of oxidative stress were found following the use of propofol and dexmedetomidine compared with those following midazolam administration, and similar results were obtained regarding the level of MN. It is suggested that propofol and dexmedetomidine exhibit a superior antioxidant function to midazolam.

Carbon-riveted Pt catalyst supported on nanocapsule MWCNTs-Al2O3 with ultrahigh stability for high-temperature proton exchange membrane fuel cells.

Pt catalyst supported on nanocapsule MWCNTs-Al(2)O(3) (multi-walled carbon nanotubes, MWCNTs) catalyst has been prepared by microwave-assisted polyol process (MAPP). The results of electrochemical measurements show that the nanocapsule Pt/MWCNTs-Al(2)O(3) catalyst has higher activity due to more uniform dispersion and smaller size of Pt nanoparticles, and higher stability ascribed to the stronger metal-support interaction (SMSI) between Pt nanoparticles and nanocapsule support than in Pt/MWCNTs. Furthermore, the carbon-riveted nanocapsule Pt/MWCNTs-Al(2)O(3) catalyst has been designed and synthesized on the basis of in situ carbonization of glucose. The physical characteristics such as X-ray diffraction (XRD), energy dispersive analysis of X-ray (EDAX), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) have indicated that α-Al(2)O(3) indeed entered into the inside of the MWCNTs and formed a nanocapsule support of MWCNTs with α-Al(2)O(3) as stuffing. The accelerated potential cycling tests (APCT) show that carbon-riveted nanocapsule Pt/MWCNTs-Al(2)O(3) possesses 10 times the stability of Pt/C and has 4.5 times the life-span of carbon-riveted Pt/TiO(2)-C reported in our previous work. The significantly enhanced stability for carbon-riveted nanocapsule Pt/MWCNTs-Al(2)O(3) catalyst is attributed to the reasons as follows: the inherently excellent mechanical resistance and stability of α-Al(2)O(3) and MWCNTs in acidic and oxidative environments; SMSI between Pt nanoparticles and the nanocapsule support; the anchoring effect of the carbon layers formed during the carbon-riveting process (CRP); the increase of Pt(0) composition during CRP.

Thermodynamic properties of micellization of Sulfobetaine-type Zwitterionic Gemini Surfactants in aqueous solutions--a free energy perturbation study.

In this article, the validity and accuracy of the free energy perturbation (FEP) model used in a previous article for ionic liquid-type Gemini imidazolium surfactants (ILGISs) is further evaluated by using it to model the Enthalpy-entropy compensation of Sulfobetaine-type Zwitterionic Gemini Surfactants (SZGSs), with different carbon atoms of the hydrophobic group or the spacer chain length, in aqueous solutions. In the FEP model, the Gibbs free energy contributions to the driving force for micelle formation are computed using hydration data obtained from molecular dynamics simulations. According to the pseudo-phase separation model, the thermodynamic properties of micellization in aqueous solutions for SZGS were discussed. The results show that the micellization of SZGS in aqueous solutions is a spontaneous and entropy-driven process. It is linearly Enthalpy-entropy compensated and different from the micelle formation of ILGIS but similar to anionic surfactants. The compensation temperature was found to be (302±3)K which was lower than ILGIS. As the temperature rises, the micellization is easy initially but then becomes difficult with the unusual changes of enthalpy values from positive to negative. The contribution of entropy change to the micellization tends to decrease but the contribution of enthalpy change tends to increase. In particular, as the number carbon atoms in the alkyl chains and spacer chains are increased, the thermodynamic favorability and stability of the micelles both increase.

Enthalpy-entropy compensation of ionic liquid-type Gemini imidazolium surfactants in aqueous solutions: a free energy perturbation study.

Molecular dynamics simulations and free energy perturbation (FEP) were performed for studying the enthalpy-entropy compensation with a series of ionic liquid-type Gemini imidazolium surfactants (ILGIS), with different carbon atoms of the hydrophobic group or the spacer chain length, in aqueous solutions. According to the law of mass action, the thermodynamic properties of micellization in aqueous solutions for ILGIS were discussed. The results show that the solvation free energy changes calculated from the free energy perturbation are close to the Gibbs free energy calculated from the surface tension method and can be used to discriminate the tendency for micellization and predict the thermodynamic properties of ILGIS. The micellization of ILGIS in aqueous solutions is a spontaneous and entropy-driven process. It is enthalpy-entropy compensated, and the enthalpy-entropy compensation plots exhibit an excellent linearity. The compensation temperature was found to be (307±2) K. As the number carbon atoms in the alkyl chains is increased, the tendency and stability of micellization both increase. At spacer length S≤6, with the spacer chain length increasing, the thermodynamic favorability and stability of the micelles decrease. However, if S>6, thermodynamic favorability and stability increase with raising the spacer chain length.

Carbon riveted Pt/C catalyst with high stability prepared by in situ carbonized glucose.

Carbon riveted Pt/C catalyst was designed and prepared by in situ carbonized glucose in this paper. Characterization results show that carbon riveted Pt/C prevents Pt nanoparticles from coalescence. Its stability is markedly enhanced due to the anchoring effect of the carbon layers formed during the carbon riveting process.

[A study of clinical effects on treatment of 225 cracked-teeth].

PURPOSE: To analyse the clinical effects of cracked-teeth after filling or full crown restoration. METHODS: 225 cracked-teeth were divided into two groups: the early 77 cracked-teeth and the late 144 cracked-teeth according to their clinical features and diagnosis, and then different interventions were applied, the clinical effects were recordered and analysed. RESULTS: There was a significant difference after the early 77 cracked-teeth being treated by filling or full crown rehabilitation after 3 years follow up. The treatment to the late 144 cracked-teeth was excellent after 3 years' observation with root canal therapy or pulp mummification, and finally full crown restoration. CONCLUSIONS: By diving cracked-teeth into different stages and giving corresponding treatment, the cracked-teeth can be preserved successfully.

Modeling of residual chlorine in water distribution system.

Water quality within water distribution system may vary with both location and time. Water quality models are used to predict the spatial and temporal variation of water quality throughout water system. A model of residual chlorine decay in water pipe has been developed, given the consumption of chlorine in reactions with chemicals in bulk water, bio-films on pipe wall, in corrosion process, and the mass transport of chlorine from bulk water to pipe wall. Analytical methods of the flow path from water sources to the observed point and the water age of every observed node were proposed. Model is used to predict the decay of residual chlorine in an actual distribution system. Good agreement between calculated and measured values was obtained.