Core-shell structured Co@CN nanocomposites as highly efficient dual function catalysts for reduction of toxic contaminants and hydrogen evolution reaction.

In this study, we have reported nitrogen-doped graphite C coated Co nanocomposite (Co@CN) catalysts synthesized by one-step arc discharge method. The surface compositions, morphologies and the catalytic properties of the Co@CN nanocomposites were studied minutely. The results reveal that the prepared Co@CN nanocomposites have typical core-shell structure and show highly efficient catalytic performance in a reduction of 4-nitrophenol (4-NP), rhodamine and methylene blue. Their rate constant (Kapp) is 0.074 s-1 in a reduction of 4-NP, which is much higher than that of reported transition metal-based catalysts. Moreover, the overpotential of Co@CN is only 96 mV at a current density of 10 mA cm-2 in alkaline solution, showing high electrocatalytic activities in the hydrogen evolution reaction. The excellent synergistic effect between nitrogen-doped graphite C shell and magnetic Co core enables the Co@CN nanocomposites catalysts to hold abundant active sites and to transmit rapidly electron ability, resulting in Co@CN nanocomposite catalysts having a highly efficient catalytic nature.

Effectiveness of Surgical Treatments for Basal Ganglia Hemorrhage and Imaging Factors Affecting Hematoma Evacuation Rate by Neuroendoscopic Surgery.

BACKGROUND: Basal ganglia hemorrhage (BGH) is a devastating neurologic disease with high morbidity and mortality, and its management is still controversial. We evaluated the effectiveness of surgical treatments for BGH and investigated computed tomography (CT) imaging features affecting the hematoma evacuation rate (ER) in patients treated with neuroendoscopic surgery. MATERIALS AND METHODS: A total of 104 BGH patients who underwent craniotomy, burr-hole drainage, or neuroendoscopic surgery were analyzed retrospectively. Clinical characteristics, imaging features, and postoperative complications were compared. Univariate and multivariate regression analyses were applied to identify imaging factors associated with ER. RESULTS: A significant difference in ER was observed: 78.4% in patients treated with neuroendoscopic surgery, 33.6% in patients treated with burr-hole drainage, and 82.5% in patients treated with craniotomy (p < 0.001). Similar results were observed for operative time (p < 0.001). Five cases (12.5%) of rebleeding were found in patients treated with burr-hole drainage (p = 0.020). No significant difference was found for pneumonia, intracranial infection, gastrointestinal bleeding, hospital mortality, hospital stay, expenses, 3-day Glasgow Coma Scale (GCS) scores after surgery, or GCS at discharge. The CT imaging feature, the island sign (p = 0.004), was observed as an independent factor correlated with lower ER for neuroendoscopic surgery. CONCLUSIONS: The benefits and drawbacks of surgical treatments confirmed they have their own indications, and neuroendoscopic surgery may be relatively beneficial for BGH treatment. The island sign was an independent factor affecting ER for neuroendoscopic surgery. Therefore, comprehensive assessment of clinical data, especially the island sign, should be performed preoperatively in BGH patients.

Amorphous/Nanocrystalline Carbonized Hydrochars with Isomeric Heterogeneous Interfacial Polarizations for High-performance Microwave Absorption.

Carbon allotropes and their derivatives have exhibited superior performances for microwave absorption ascribed to their dielectric attenuation capacity raised from the multiple dipolar configurations. Such characteristics could be achieved by constructing diverse micro/nanoscale architectures, incorporating vacancies and heteroatoms, and composing with heterogeneous components. Alternatively, we herein present a facile approach for the synthesis of carbonized hydrochars, which are composed of dispersed ultrafine nanocrystallines graphite and amorphous matrix. Such a isomeric construction has a high-density interfaces, accompanied with significant interfacial polarizations, leading to the improvement of microwave absorbing capabilities. For carbonized hydrochars, the RLmin value can reach -40.36 dB, and corresponding effective bandwidth is 2 GHz. This work provides a concept for designing microwave absorption materials based on isomeric heterogeneous interfacial polarizations in single-element systems.

Percarbonate promoted antibiotic decomposition in dielectric barrier discharge plasma.

A coupling technique introducing sodium percarbonate (SPC) into a dielectric barrier discharge (DBD) plasma was investigated to enhance the degradation of antibiotic tetracycline (TC) in aqueous. The dominant effects of SPC addition amount and discharge voltage were evaluated firstly. The experiments indicated that the moderate SPC dosages in the DBD presented an obvious synergistic effect, improving the TC decomposition efficiency and kinetics. Elevating the voltage was conducive for the promotion of antibiotic abatement. After 5 min treatment, the removal reached 94.3% at the SPC of 52.0 µmol/L and voltage of 4.8 kV for 20 mg/L TC. Especially the defined synergy factors were greater than one since the SPC being added, and the energy yield was increased by 155%. Besides, the function mechanism was explained by the hydrogen peroxide and ozone quantitative determinations and radical scavenger test, and the results confirmed that the collaborative method could increase the generation of reactive species, and the produced hydroxyl and superoxide radicals both played the significant roles for the TC elimination. Furthermore, the decomposition and mineralization of the synergism were verified by UV-vis spectroscopy, TOC and COD analyses, and the degradation byproducts and transformation pathways were identified based on the analysis of HPLC-MS finally.

Facile synthesis of magnetic Co3O4/BFO nanocomposite for effective reduction of nitrophenol isomers.

Co3O4/BiFeO3 nanocomposite catalysts were synthesized by a facile hydrothermal method following the impregnation process. The nanocomposite was successfully characterized by powder X-ray diffraction(XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), nitrogen adsorption desorption isotherms and X-ray photoelectron spectroscopic (XPS) analysis. The as-synthesized Co3O4/BiFeO3 nanocomposites were tested as a catalyst in the reduction of nitrophenol isomers with NaBH4 at room temperature. The results indicate that the as-prepared Co3O4/BiFeO3 nanocomposites are an efficient recyclable catalyst for the reduction of nitrophenol isomers. The reduction kinetics for all the reactions follows the pseudo-first order. The rate reduction of nitrophenols followed the order 3NP > 2NP > 4NP.

A coordination polymer-derived Co3O4/Co-N@NMC composite material as a Zn-air battery cathode electrocatalyst and microwave absorber.

Zn-air batteries, promising energy storage equipment with high energy density, light weight and a compact structure, are a perfect power source for electric vehicles. For a Zn-air battery, the activity of the air cathode electrocatalyst plays an important role in its performance. Here, employing a coordination polymer as a precursor, a composite material built from Co3O4 and Co-N active centres with nitrogen-doped mesoporous carbon as a matrix has been synthesized successfully. This composite material possesses outstanding activity and stability in the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) processes. It possesses a small half-wave potential (ORR1/2 = 0.786 V) and low overpotential (OER10 = 1.575 V) for the ORR and OER, respectively. With this composite material as an air cathode electrocatalyst, a rechargeable Zn-air battery was assembled successfully. During the discharge process, the maximum power density of this Zn-air battery is 122 mW cm-2 at 0.76 V. The specific capacity of this battery is 505 mA h g-1 at 25 mA cm-2. The voltage gap between the charge and discharge processes is only 0.744 V at 10 mA cm-2 and 1.308 V at 100 mA cm-2. This rechargeable battery also shows promising stability after long-term charge-discharge experiments. Furthermore, the composite material also exhibits outstanding microwave adsorption properties. Its maximum reflection loss (RL) arrives at -13.9 dB with a thickness of only 1.0 mm. Thus, we find that coordination polymers are an ideal precursor for Zn-air battery cathode electrocatalysts and microwave absorbers.

Decomposition of MOFs for the preparation of nanoporous Co3O4 fibres and sheets with excellent microwave absorption and photocatalytic properties.

Unique nanoporous Co3O4 fibres and sheets were successfully fabricated via a facile hydrothermal route (150 °C) and subsequent annealing process at 500 °C in air. The excellent microwave absorption of the nanoporous Co3O4 materials originates not only from the dielectric loss and impedance matching, but also from geometrical effects. Herein, the photocatalytic behavior of the as-prepared Co3O4 has also been reported based on the degradation of methylene blue (MB) dye in an aqueous medium under simulated solar light.

Graphene oxide coated coordination polymer nanobelt composite material: a new type of visible light active and highly efficient photocatalyst for Cr(VI) reduction.

A visible light active photocatalyst was synthesized successfully by coating graphene oxide (GO) on a coordination polymer nanobelt (CPNB) using a simple colloidal blending process. Compared with neat CPNB, the resulting graphene oxide coated coordination polymer nanobelt composite material (GO/CPNB) exhibits excellent photocatalytic efficiency in the reduction of K2Cr2O7 under visible light irradiation. In the composite material, GO performs two functions. Firstly, it cuts down the band gap (E(g)) of the photocatalyst and extends its photoresponse region from the ultraviolet to visible light region. Secondly, GO exhibits excellent electron transportation ability that impedes its recombination with holes, and this can enhance photocatalytic efficiency. For GO, on its surface, the number of functional groups has a great influence on the photocatalytic performance of the resulting GO/CPNB composite material and an ideal GO"coater" to obtain a highly efficient GO/CPNB photocatalyst has been obtained. As a photocatalyst that may be used in the treatment of Cr(VI) in wastewater, GO/CPNB exhibited outstanding stability during the reduction of this pollutant.