Hard carbons derived from green phenolic resins for Na-ion batteries

Hard carbons have become recently one of the most promising classes of anode materials for sodium ion batteries (NIBs) owing to their high specific capacity and good cycling stability. Among the precursors used to prepare hard carbon, phenolic resins are of great interest due to their high carbon yield, however, their toxicity must be overcome. In this paper, we propose a green, simple and scalable procedure to obtain phenolic resins which by pyrolysis at high temperature (>1000 °C) result in eco-friendly hard carbons with low surface area, disordered structure and high carbon yield. The influence of several synthesis parameters (type of solvent, thermopolymerization/annealing temperature and gas flow) was studied to determine the impact on both phenolic resin and hard carbon characteristics. The synthesis time (12 h-3 days) was found to depend on the used solvent whereas the carbon yield (25–35%) on the cross-linking degree which could be controlled by adjusting both thermopolymerization temperature and atmosphere. The structure of the hard carbons mainly changed with the carbonization temperature (1100–1700 °C) while the texture of the material was sensitive to most of the studied parameters. Stable reversible capacity up to 270 mAhg−1 and 100% coulombic efficiency (CE) after few cycles are obtained, demonstrating the potential for Na-ion applications

Hard carbons derived from green phenolic resins for Na-ion batteries

Hard carbons have become recently one of the most promising classes of anode materials for sodium ion batteries (NIBs) owing to their high specific capacity and good cycling stability. Among the precursors used to prepare hard carbon, phenolic resins are of great interest due to their high carbon yield, however, their toxicity must be overcome. In this paper, we propose a green, simple and scalable procedure to obtain phenolic resins which by pyrolysis at high temperature (>1000 °C) result in eco-friendly hard carbons with low surface area, disordered structure and high carbon yield. The influence of several synthesis parameters (type of solvent, thermopolymerization/annealing temperature and gas flow) was studied to determine the impact on both phenolic resin and hard carbon characteristics. The synthesis time (12 h-3 days) was found to depend on the used solvent whereas the carbon yield (25–35%) on the cross-linking degree which could be controlled by adjusting both thermopolymerization temperature and atmosphere. The structure of the hard carbons mainly changed with the carbonization temperature (1100–1700 °C) while the texture of the material was sensitive to most of the studied parameters. Stable reversible capacity up to 270 mAhg−1 and 100% coulombic efficiency (CE) after few cycles are obtained, demonstrating the potential for Na-ion applications

Facile and sustainable synthesis of nitrogen-doped polymer and carbon porous spheres

International audienceThe development of green, sustainable and simple synthesis pathways for the design of polymer and carbonaceous materials with well controlled features is of great importance for many fields of applications. Herein, we report a green synthesis method for polymer and carbon particles with well-defined shape and size. This approach involves the use of green precursors, water as solvent, no templates 10 under ambient temperature and pressure conditions, simultaneously. Green polymer resins (phloroglucinol-glyoxylic acid) and a catalyst/nitrogen source (triethylenediamine) are dissolved in water at room temperature resulting in polymer particles which by subsequent thermal treatment transforms in carbon particles. Mainly spherical carbon particles with controlled size from 500 nm to 10 µm were obtained by simply adjusting the experimental conditions, i.e., the synthesis time and the molar ratio between the precursors or solvent. In some conditions, flower-like morphology was obtained as well. The synthesis mechanism from polymer resin spheres 15 formation to their conversion into carbon sphere was determined by several techniques, i.e., 13 C NMR spectroscopy, SEM, XPS and TPD-MS (temperature programmed desorption coupled by mass spectrometer). 2

Understanding ageing mechanisms of porous carbons in non-aqueous electrolytes for supercapacitors applications

Two activated porous carbon powders with different surface functional groups content have been electrochemically polarized in tetraethylammonium tetrafluoborate (Et4NBF4) in acetonitrile electrolyte to study their ageing mechanism as supercapacitor electrodes. Temperature-programmed desorption coupled with mass spectrometry technique (TPD-MS) is used to track the change of carbon surface chemistry – surface functional groups and/or adsorption of degradation products occurring upon polarizations. A potentiostatic study of the carbons in a two-compartment cell unveil the catalytic role of water in the ageing mechanism. Combining these results with our previous work, we propose different scenarios to depict the ageing mechanisms of the two carbons. For carbon A, hydrolysis of BF4− at the positive electrode leads to carbon oxidation together with soluble poly-acetonitrile oligomer occurred from reaction between BF4• radicals and acetonitrile. Ageing mechanism is also assumed to set off with the hydrolysis of BF4− for carbon B; but, in here the formed oligomers react with acid functional groups present at the carbon surface to form a protective, passive-like layer at both positive and negative electrodes which hampers a further electrode ageing

Стратегия хирургического лечения местнораспространенных опухолей малого таза с применением эвисцераций. Сообщение1. Синдромы кишечной непроходимости, кровотечения и сдавления мочевых путей

Представлен обзор и анализ методов хирургической коррекции синдромов кишечной непроходимости, кровотечения и сдавления мочевых путей при местнораспространенных опухолях малого таза. Обобщен 10−летний опыт хирургического лечения данной патологии в Институте общей и неотложной хирургии. Приведена классификация основных методов оперативных пособий, направленных на достижение гемостаза и деривации мочи и кала.The methods of surgical correction of syndromes of intestinal obstruction, hemorrhage and urinary tract compression at local tumors of the small pelvis are reviewed and analyzed. The 10−year experience of surgical treatment for this pathology at Institute for General and Urgent Surgery is generalized. Main methods of operative treatment aimed at achievement of hemostasis and urine and feces derivation are presented

Relationship between the carbon nano-onions (CNOs) surface chemistry/defects and their capacitance in aqueous and organic electrolytes

The effect of surface functionalities on the supercapacitors performances has been highlighted often in many works. However, studies devoted to the influence of carbon defects did not gain particular attention due to the difficulty to quantify such parameter. In this context, carbon nano-onions were used as model material in order to understand the influence of the surface chemistry (nature and amount of oxygen groups) and structural defects (active surface area, ASA) on the capacitance. Different types of thermal treatments in oxidizing or reducing atmospheres allowed to finely tune the surface chemistry and the ASA as demonstrated by temperature programmed desorption coupled with mass spectrometry (TPD-MS). For the first time, the presice control of these characteristics independently one of each other allowed to highlight an important influence of the carbon defects on the capacitance in organic and aqueous electrolytes which outbalance the oxygen functional group effect

Experimental Challenges in Studying Hydrogen Absorption in Ultrasmall Metal Nanoparticles

International audienc

Synthesis and stability of Pd–Rh nanoalloys with fully tunable particle size and composition

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Alkaline hydrogel electrolyte from biosourced chitosan to enhance the rate capability and energy density of carbon-based supercapacitors

International audienceThis paper reports the development of a safe carbon-based supercapacitor, which is based on a green biodegradable hydrogel electrolyte that is prepared from chitosan biopolymer and KOH as the electrolyte source. The impact of electrolyte solution ageing time on electrolyte gel formation is investigated. A critical time of 2 days is necessary to obtain gel electrolytes mechanically exploitable. This is associated with the gel structural modification, as observed by FTIR and 1H/13C NMR. Between 2 and 4 days, the capacitance increases from 76 to 95 F g−1 and remains stable up to 21 days. Good rate handling is achieved (62%) with a capacitance of 59 F g−1 at 10 A g−1. Remarkably, the developed gel exhibits good stability when the cell voltage is increased from 0.8 V to 1.3 V. The voltage window extension allows to obtain for the C–C device, a high energy density (5.1 W h kg−1) at a power density of 32.5 W kg−1, which is almost 3 times higher than that delivered by liquid 2 M KOH at 0.8 V. The gel electrolyte could be used with pseudocapacitive materials, C/Co3O4 and voltage window extension is achieved along with significant increase in energy density from 1.66 to 6.31 W h kg−1. Better capacitance retention is obtained by the chitosan–KOH gel electrolyte than by liquid KOH. Advantageously, the gel electrolyte prevents the electrode degradation and positive current collector from undergoing corrosion