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

Insights on the synthesis mechanism of green phenolic resin derived porous carbons via a salt-soft templating approach

International audienceA combined salt-soft template approach to synthesize porous carbon materials is reported along with their synthesis mechanism. This consists in the evaporation induced self-assembly (EISA) of aqueous solutions containing green phenolic resins, a triblock copolymer template and a metallic salt, followed by thermal treatment and washing. The increase of pH up to 5 using NaOH, induces significant improvement in the carbon microporosity but in the detrimental of mesoporosity. As suggest by 13 C and 1 H NMR, the mesoporosity lost is caused by the decrease of H-bonding and self-assembly between the phenolic resin and the template due to the strong "salting-out" effect of eOH ions. For higher pH (pH-9), the porosity start to decrease and graphene-sheet like morphology is formed. The microporosity varies with the salt in the following order: KCl > NaCl > LiCl, while the mesoporosity in the opposite way. The structure changes as well from smooth turbostatic (KCl) to defective graphitic one (NaCl, LiCl). These textural and structural modifications are explained in terms of cation hydration enthalpy and cation-p binding energy and by the competition between the metal salt cations and the Na ions (used to regulate the pH) for water or phenolic resin aromatic ring sites

Catalyst-free soft-template synthesis of ordered mesoporous carbon tailored using phloroglucinol/ glyoxylic acid environmentally friendly precursors

International audienceCarbon porous materials with a periodically ordered pore structure, controlled pore size and geometry and high thermal stability are synthesized using self-assembly of environmentally friendly phloroglucinol/ glyoxylic acid precursors with an amphiphilic triblock copolymer template. Glyoxylic acid, a plant-derived compound, is used for the first time as a substituent of carcinogen formaldehyde usually employed in such a synthesis. Thanks to the double functionality, i.e., aldehyde and carboxylic acid, glyoxylic acid plays not only the role of a cross-linker for the formation of the resin but also the role of a catalyst by creation of H-bonding or specific reactions between the precursors. Hence, no extra catalyst such as strong acids (HCl) or bases (NaOH) is any longer required. Carbon films and powders were successfully prepared with high surface areas (up to 800 m2 g−1), high porous volume (up to 1 cm3 g−1), tunable pore size (0.6 nm to 7 nm) and various pore architectures (hexagonal, cubic, and ink-bottle) by tuning the precursor ratio and by applying different manufacturing engineering strategies. Insights on the synthesis mechanism of the phenolic resin and carbon mesostructures were obtained using several analysis techniques, i.e., nuclear magnetic resonance (13C NMR) and FTIR spectroscopy, temperature programmed desorption coupled with mass spectrometry (TPD-MS) and thermo-gravimetric analysis (TGA)

Insights on the Na+ ion storage mechanism in hard carbon: Discrimination between the porosity, surface functional groups and defects

Sodium ion batteries (SIBs) using hard carbon as negative electrode hold the promise of being low cost alternative to lithium ion batteries (LiBs). However, the Na+ storage mechanism in hard carbons is not fully understood yet and the attribution of Na storage in the sloping and plateau regions of the sodiation/desodiation curves remains still controversial. The current work employs N-2, Kr and CO2 gases to correctly assess the changes in hard carbon porosity induced by different pyrolysis temperature of cellulose. The sloping capacity was found to decrease with the decrease of the specific area of ultramicropores measurable only by CO2 adsorption, while the plateau capacity demonstrated an opposite behavior. The high temperature derived carbons (> 1400 degrees C) present no porosity which disqualifies the attribution of plateau region to the adsorption of Na+ in the nanopores but rather the insertion between the pseudo-graphitic domains. Temperature programmed desorption coupled with mass spectrometry (TPD-MS) was performed to determine the nature and the quantity of oxygen surface functional groups followed by oxygen chemisorptions to assess the amount of carbon edge defects expressed by active surface area (ASA) values. A decrease in the amount of oxygen groups and active surface area with the increase of the pyrolysis temperature was observed which is accompanied by a decrease of the sloping capacity. These results shed light in the storage mechanisms, the sloping region being ascribed mainly to the interaction of Na+ with carbon edge defects and adsorption in the microporosity while the plateau region assigned to the intercalation of Na+ in the pseudo-graphitic nanodomains

Direct synthesis of graphitic mesoporous carbon from green phenolic resins exposed to subsequent UV and IR laser irradiations

International audienc

Eco-Friendly Synthesis of Nitrogen-Doped Mesoporous Carbon for Supercapacitor Application

International audienc

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

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

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

The 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 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 formation to their conversion into carbon sphere was determined by several techniques, i.e., 13C NMR spectroscopy, SEM, XPS and TPD-MS (temperature programmed desorption coupled by mass spectrometer)