Aqueous electrolyte

Zinc-ion capacitors (ZICs) have attracted significant attention as energy storage devices. Significant efforts have been devoted over the past decades to develop ZICs with improved performance, enhanced safety, and lower cost for practical application. Herein, free-standing, binder-free and electrochemical active expanded graphite (AEG) based paper-like cathodes were designed via a simple and cost-effective pyrolysis and mechanical pressing approach. Density-functional theory (DFT) calculations evaluated the absorption capacity of Zn and SO 4 at graphite surface, suggesting that the capacitive behavior could be enhanced through these interactions. The AEG cathode exhibits an approximately 25-fold increase in surface area, abundant surface dopants, and a porous structure, demonstrating its potential for application in ZICs. The AEG-ZICs delivered an areal capacity of ~ 4 mAh⋅cm-2 , an energy density ~ 3.3 mWh⋅cm-2 , and excellent cycling stability for over 750 h. Our work provides a promising approach for developing robust, cost-effective, and eco-friendly cathodes, contributing to the fundamental understanding of the charge storage mechanism in highly loaded electrodes, and emphasizing the potential for the commercialization of AEG-derived ZICs. ☆ This article is part of a special issue entitled: 'Electrochemical Energy' published in Chemical Engineering Journal.

This paper investigates the electrochemical performance of asymmetric supercapacitors in an environmentally friendly aqueous electrolyte (1.0 mol L -1 sodium sulfate solution). The asymmetric configuration is based on the use of a highly porous carbon xerogel as active material in both the positive and negative electrodes, but the carbon xerogel loading in each electrode has been substantially modified. This configuration leads to an increase in the operational voltage window up to values of 1.8 V and consequently to a higher specific capacitance (200 F g -1 ) and energy density (~ 25 Wh kg -1 ). Four different mass ratios were employed (1, 1.5, 2 and 3) and the electrochemical response of the cells was evaluated by means of cyclic voltammetry, galvanostatic charge-discharge and impedance spectroscopy. The results demonstrate that the optimal carbon mass ratio in the electrodes is higher than 2.0 because in these conditions the devices are able to operate with a maximum cell voltage of 1.8 V and with a high electrical efficiency.

This study employs a cost-efficient method to create a pliable BC/rGO-NiCo-LDH electrode film on a bacterial cellulose base. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, Xray photoelectron spectroscopy (XPS), and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) analyses verified the incorporation of reduced graphene oxide (rGO) and nickel-cobalt layered double hydroxide (NiCo-LDH) into the bacterial cellulose structure. The BC/rGO-NiCo-LDH composite material exhibited high-temperature stability and achieved a specific capacitance of 311 F g − 1 at a scan rate of 0.1 mV/s, surpassing that of earlier cellulose electrodes. The electrode film showed exceptional mechanical capabilities, displaying flexibility and load resistance without any structural damage. The film's flexibility and lightweight properties were improved due to the low density of 0.656 g cm − 3 , which is a result of the nanoporous structure and intrinsic low density of rGO and cellulose. A retention ratio of 0.40 for storage modulus at a glass transition temperature of around 90 • C demonstrated positive mechanical performance. This cost-effective and uncomplicated synthesis approach produced a BC/rGO-NiCo-LDH electrode with potential. The material possessed favourable mechanical and electrochemical characteristics, making it suitable for wearable electronics.

pour son accueil au début de ces trois années de thèse, puis à Pierre GROS qui a pris la relève en qualité de directeur adjoint. Je souhaiterai remercier le fameux professeur Théodore TZEDAKIS qui m'a fait le plaisir de présider ce jury de thèse, ainsi que Eric CHAINET et Virginie LAIR qui ont acceptés de juger ce travail. J'associe à ces remerciements Isabelle CRASSOUS ainsi que Jérôme ROCHE pour leur participation au jury. Je tiens à remercier chaleureusement celui qui à probablement perdu le plus de cheveux lors de ces trois dernières années, mon directeur de thèse Pierre CHAMELOT dit « Pedro ». Milles mercis pour ta bienveillance, ton soutien et ta bonne humeur qui m'ont poussé à m'accrocher même dans les moments difficiles de cette thèse. Tu m'as transmis tout le nécessaire pour franchir cette épreuve, des notions d'électrochimie, en passant par la fabrication de pièces à l'aide d'un tour ou à la réalisation de bons rhums arrangés (même si les miens font encore pale figure devant les tiens). Je tiens également à adresser un énorme merci à mon co-directeur de thèse, Mathieu GIBILARO. Merci pour ton écoute, tes nombreux conseils, ta grande disponibilité au quotidien et tes talents de « grammar nazi ». Merci de m'avoir fais découvrir le monde exotique des Sels Fondus lors de mon stage de L3. Je garderai de très bon souvenir des soirées au Botaniste ou au Black-lion. A ces remerciements j'aimerai associer Laurent MASSOT qui a grandement participé à l'encadrement de cette thèse. Merci pour toute l'aide que tu as apporté aussi bien scientifique que technique. Travailler avec toi c'est comme utiliser un « cheat-code » dans un jeu vidéo, tu trouves en un instant une solution à tous les problèmes sur lesquels on but sans cesse. Merci également d'avoir su trouver les bons mots quand ça n'aller plus et que le moral flanché, tu m'as permis de me remettre sur les rails et de ne rien lâcher. Merci infiniment à vous trois, je suis entré en thèse en étant en dépression mais j'en pars le coeur léger et avec le sourire. Si j'en suis là aujourd'hui c'est en grande partie grâce à vous trois. Un grand merci à Christelle, Pierre R., Patric et Sébastien qui m'ont assisté techniquement pour mettre en place des manips, usiner des pièces fragiles ou encore programmer le système pietzo. Je voudrais ensuite remercier l'ensemble des personnes avec qui j'ai pu partager convivialement le bureau lors de ces trois ans et notamment Julien membre du duo de choc Rox et Rouky ! Merci pour ta précieuse amitié et ton grand soutien ! Merci pour m'avoir fait l'immense plaisir de venir depuis Dijon pour assister à ma soutenance. Je garderai d'excellent souvenir de nos aventures que ce soit en Andorre, à Lombrive, à Cabrespine, au tranchoir ou même au Kraken ! De ta grande sagesse je retiendrai surtout comment écrire le prénom willem ouillem wouilhem m'orienter avec l'étoile polaire. Remerciements Merci également à Shérif et à Maarten qui m'ont accompagné sur la fin de la thèse et ont amené un peu de vie dans le bureau qui était devenu bien trop silencieux et morose. Bon courage pour vos thèses les gars ! Je remercie aussi l'ensemble des stagiaires (surtout Anaïs qui a dû supporter mon encadrement), des doctorants et post-doctorants avec qui j'ai pu partager de bons moments au quotidien. Merci notamment Cécilia, Lisa et Cholé pour les pauses thé, Mélissa pour ses cafés incroyables, ainsi que Nabil et Charaf pour nos fous rires et l'humour politiquement incorrect que nous partageons. Merci à l'ensemble des membres du laboratoire pour tous ces agréables moments d'échanges qu'ils soient scientifiques ou non. Merci à la famille F. sans qui je n'aurais probablement jamais repris mes études. Merci à tout mes amis qui m'ont soutenu lors de cette épreuve et m'ont fait le plaisir de venir ou de suivre la soutenance : Marc, Sylvain, Christophe, Agnès, Quentin, Nina, Catherine et son clone Caroline et bien d'autres. J'aimerai également remercier du fond du coeur des amis très chère qui suivent mon parcours depuis 10 ans maintenant : mes anciens camarades d'IUT : Elodie et Seb. Merci à toi Elodie de m'avoir fais l'honneur d'être ton témoin de mariage et merci Seb d'avoir fais le déplacement depuis Renne pour assister à la soutenance. Un immense merci à celles que je considère comme mes petites soeurs Solyane et Txori (et oui ce sont des vrais prénoms). Merci à vous deux pour votre soutien et votre présence, vous compter énormément pour moi. Un énorme merci à Thomas avec qui nous partageons de nombreux délire et activité depuis le collège. Merci d'avoir été là dans les bons et moins bons moments de la vie, merci de m'avoir soutenu, supporté et épaulé comme tu l'as fait durant tout ce temps. Milles merci également à mes parents qui m'ont toujours soutenu dans mes choix ainsi qu'à mon frère qui bien que peu présent est un complice incroyable. Enfin, merci à toi Tuire (encore un prénom chelou) pour ton soutient qui m'a grandement aidé à tenir

Most of plasmas created in laboratories for experiments in domains such as inertial confinement fusion are non-LTE plasmas. The modeling of the atomic kinetics of these plasmas is crucial to understand the radiative properties of these environments. There is a strong demand for experiments in which the plasma is characterized by independent X-ray spectroscopy diagnostics. Thus the development of new diagnostics for these experiments is also a major stake.

Supercapacitor electrodes from activated wood charcoal Aleksandrs Volperts , Galina Dobele, Aivars Zhurinsh, Zane Zalane, Jurijs Ozolinsh, Janis Kleperis, Darya Vervikishko, Evgeny Shkolnikov 1 Latvian State Institute of Wood Chemistry, Riga, Latvia 2 Riga Technical University, Faculty of Material Science and Applied Chemistry, Riga, Latvia 3 Latvian University Institute of Solid State Physics, 8 Kengaraga Street, Riga, LV-1063, Latvia 4 Scientific Association for High Temperatures, Russian Academy of Science, Moscow, Russia

Intermolecular forces and surface rheology of adsorbed surfactants can jointly influence the drainage and stability of foam films significantly, but have been separately considered in the literature. Here we use mixtures of sodium dodecyl sulphate and dodecanol to produce different surface shear viscosities and to elucidate the role of intermolecular forces and surface rheology in foam film drainage. The thickness of plane parallel foam films with very small radius versus time was obtained with an improved Scheludko cell setup used in conjunction with a high-speed video camera system operating at a frequency of 1000 frames per second. The surface tension and surface potential were measured by pendant bubble tensiometry and micro-electrophoresis, respectively. The surface shear viscosity was determined by a deep channel surface shear viscometer. The modelling considered surface tension gradient, surface shear viscosity and diffusion, and DLVO and non-DLVO intermolecular forces. Comparison between experimental data and theoretical models for foam film drainage shows that the film drainage is influenced by the Marangoni effect due to surface tension gradient, producing foam films with immobile interfaces. Intermolecular forces, in particular, non-DLVO hydrophobic attractive forces, have the most significant effect on the film drainage.

Cover: Schematic of a LIB battery, in which the electrolyte contains pseudo-delocalized anion. Four different anions based on this concept have been depicted. From top left MM26py (1methylpyridinium-2,6-dicarboxylate) & MM3411 (4-(dimethyl(3-sulfonatopropyl) ammonio)butane-1-sulfonate) and bottom row from left MM3311 (3,3'-(dimethylammonio) bis(propane-1-sulfonate)) & MM4411 4,4'-(dimethylammonio)bis(butane-1-sulfonate).

Intermolecular forces and surface rheology of adsorbed surfactants can jointly influence the drainage and stability of foam films significantly, but have been separately considered in the literature. Here we use mixtures of sodium dodecyl sulphate and dodecanol to produce different surface shear viscosities and to elucidate the role of intermolecular forces and surface rheology in foam film drainage. The thickness of plane parallel foam films with very small radius versus time was obtained with an improved Scheludko cell setup used in conjunction with a high-speed video camera system operating at a frequency of 1000 frames per second. The surface tension and surface potential were measured by pendant bubble tensiometry and micro-electrophoresis, respectively. The surface shear viscosity was determined by a deep channel surface shear viscometer. The modelling considered surface tension gradient, surface shear viscosity and diffusion, and DLVO and non-DLVO intermolecular forces. Comparison between experimental data and theoretical models for foam film drainage shows that the film drainage is influenced by the Marangoni effect due to surface tension gradient, producing foam films with immobile interfaces. Intermolecular forces, in particular, non-DLVO hydrophobic attractive forces, have the most significant effect on the film drainage.

Influence of the thermocatalytical synthesis on the formation of the porous structure and the properties of microporous carbon wood-based materials was shown. It was found that increase of activation temperature and addition ratio of alkali activator can be used to control not only total pore volume, but also micropore and mesopore proportion. The results of tests on the synthesized carbon materials as electrodes in supercapacitors are shown, as well as the influence of properties of the porous structure of carbon materials on working characteristics of electrodes. It was shown that the increase of activation temperature from 600 °C to 800 °C led to an increased proportion of mesopores in the porous structure; this negatively influencen the cell capacity of the supercapacitor. It was found that the most feasible way of production of activated cabons for the use as electrodes in supercapacitors with sulphuric acid-based electrolyte is low-temperature activation.

The stability performance of a solid-state polypyrrole-reduced graphene oxide (PPy-rGO) supercapacitor electrode after a series of charging-discharging cycles is investigated. The electrochemical performances show that the capacity retention, specific capacitance, equivalent series resistance, and charge transfer resistance all decrease after chargingdischarging cycles. Thermogravimetric analysis shows the degradation of electroactive materials, causing decreased electrochemical performance of PPy-rGO. The morphology changes reveal that the pore size is reduced by ∼12 μm at the 1000th charge-discharge cycle, which limits the diffusion of electrolyte ions into the electrode. The positive shifts in the binding energy of the N1s spectra at the 500th and 1000th charge-discharge cycles indicate the formation of a hydrogen-bridge bond, affecting the electron transfer in the PPy-rGO composite as observed through X-ray photoelectron spectroscopy. Moreover, the structural properties of rGO change from amorphous to graphitic after a series of charging-discharging processes, as shown by the Raman spectra. Furthermore, the peak of the NH bending vibration is red-shifted by approximately 108 cm−1, indicating the changes in the chemical environment after a series of charging-discharging cycles, as shown by Fourier transform infrared spectroscopy.

The paper considers the problem of increasing the information content of studies of electrochemical battery cells due to in-depth processing of the obtained experimental data. The necessity of developing software with a wider functionality compared to the standard software of battery testers and allowing the processing of experimental data obtained from different types of battery testers in a single interface is substantiated. The article describes the features of an experiment on cycling of electrochemical battery cells, the main parameters characterizing electrochemical battery cells-capacity, energy, charge and energy state, polarization resistance, self-discharge current. Algorithms for calculating and averaging parameters calculated in the program and used in the program data structures are presented. Keywords: experimental data processing, mathematical model, battery tester, mathematical methods, the study of complex systems and processes, Delphi. This is an open access article distributed under the terms of Creative Commons Attribution License (CC-BY 4.0)

Для моделирования характеристик литий-серных аккумуляторов на основе экспериментальной оценки электрохимических свойств электродных материалов разработано программное обеспечение «Battery Designer», входящее в состав программного пакета «ElChemLab». Описаны возможности программного обеспечения. Проведено сравнение удельной энергии литий-серных аккумуляторов при различной поверхностной ёмкости положительного электрода и при различном количестве электролита. Показано, что для создания литий-серных аккумуляторов с более высокими удельными характеристиками по сравнению с литий-ионными аккумуляторами ёмкость положительного электрода литий-серных аккумуляторов должна быть в диапазоне 4.5-15 мА•ч/см 2 , количество заложенного электролита-не более 3 мкл/мА•ч. Ключевые слова: моделирование, удельная энергия, литий-серный аккумулятор, литиевый аккумулятор, литий-ионный аккумулятор.

We report here a novel ex-situ synthesis of MWCNTs/NiS 2 nanocomposite on nickel foam as electrode material for supercapacitor applications. Nickel disulfide (NiS 2) nanoparticles were synthesized using a one-step solid-state method followed by the preparation of MWCNTs/NiS 2 nanocomposite using the ultra-sonication technique. The structural characterization was carried out using X-Ray diffraction (XRD), scanning electron microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDX) analysis. The capacitive properties were studied using cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) method in 2 M KOH solution. The MWCNTs/NiS 2 electrode with a 20% weight fraction of multiwalled carbon nanotubes (MWCNTs) showed the best electrochemical properties having a maximum specific capacitance of 2054.28Fg-1 at a 2Ag-1 current density and excellent cyclic stability. The electrode retained 99.99% specific capacitance even after 10,000 cycles. The enhanced electrochemical properties of the NiS 2 electrode can be attributed to fast diffusion paths provided by CNTs and enhanced redox reactions of NiS 2 nanoparticles due to high surface area, decreasing the overall resistance of electrode which is in agreement with the data obtained by electrochemical impedance spectroscopy (EIS).

chlorides with Pluronic F127 were used as a soft-salt template for tuning the textural and structural properties of carbon. Highly conductive metal hydroxide solutions, where the cations are the same as those in the salt template, have been used as electrolytes. By increasing the size of the cation in the template, the textural properties of carbon, such as the specific surface area, micropore volume, and pore size, were remarkably enhanced. It directly translates to an increase in the specific capacitance of the electrode material. For a constant current charge/ discharge at 0.1 A g −1 , the electrode composed of LiCl-T and operating with 1 mol L −1 LiOH demonstrates the capacitance of 124 F g −1 , whereas CsCl-T with the same electrolyte has a capacitance of 216 F g −1. Moreover, the materials show the highest capacitance retention (up to 75%) vs. the current regime applied when the cation used during synthesis matches the cation present in the electrolyte (i.e., LiCl-T with LiOH). Interestingly, capacitance normalized by specific surface area has been found to be the highest when LiOH solution is applied as an electrolyte. Thus, for this metric, the size of ions seems to be a crucial parameter. The importance of mesoporosity is highlighted as well by using materials with a similar fraction of micropores and with or without mesopores. Briefly, the presence of mesopore fraction proved to be essential for improved capacity retention (69% vs. 30%). Besides textural properties, the graphitization degree impacts the electrochemical performance as well. It increases among the samples, in accordance with cation-π binding energy, e.g., LiCl-T is the most "graphitic-like" material and CsCl-T is the most disordered. Thus, the more graphitic-like materials demonstrate higher rate capability and cycle stability.

chlorides with Pluronic F127 were used as a soft-salt template for tuning the textural and structural properties of carbon. Highly conductive metal hydroxide solutions, where the cations are the same as those in the salt template, have been used as electrolytes. By increasing the size of the cation in the template, the textural properties of carbon, such as the specific surface area, micropore volume, and pore size, were remarkably enhanced. It directly translates to an increase in the specific capacitance of the electrode material. For a constant current charge/ discharge at 0.1 A g −1 , the electrode composed of LiCl-T and operating with 1 mol L −1 LiOH demonstrates the capacitance of 124 F g −1 , whereas CsCl-T with the same electrolyte has a capacitance of 216 F g −1. Moreover, the materials show the highest capacitance retention (up to 75%) vs. the current regime applied when the cation used during synthesis matches the cation present in the electrolyte (i.e., LiCl-T with LiOH). Interestingly, capacitance normalized by specific surface area has been found to be the highest when LiOH solution is applied as an electrolyte. Thus, for this metric, the size of ions seems to be a crucial parameter. The importance of mesoporosity is highlighted as well by using materials with a similar fraction of micropores and with or without mesopores. Briefly, the presence of mesopore fraction proved to be essential for improved capacity retention (69% vs. 30%). Besides textural properties, the graphitization degree impacts the electrochemical performance as well. It increases among the samples, in accordance with cation-π binding energy, e.g., LiCl-T is the most "graphitic-like" material and CsCl-T is the most disordered. Thus, the more graphitic-like materials demonstrate higher rate capability and cycle stability.

We report here a novel ex-situ synthesis of MWCNTs/NiS 2 nanocomposite on nickel foam as electrode material for supercapacitor applications. Nickel disulfide (NiS 2) nanoparticles were synthesized using a one-step solid-state method followed by the preparation of MWCNTs/NiS 2 nanocomposite using the ultra-sonication technique. The structural characterization was carried out using X-Ray diffraction (XRD), scanning electron microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDX) analysis. The capacitive properties were studied using cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) method in 2 M KOH solution. The MWCNTs/NiS 2 electrode with a 20% weight fraction of multiwalled carbon nanotubes (MWCNTs) showed the best electrochemical properties having a maximum specific capacitance of 2054.28Fg-1 at a 2Ag-1 current density and excellent cyclic stability. The electrode retained 99.99% specific capacitance even after 10,000 cycles. The enhanced electrochemical properties of the NiS 2 electrode can be attributed to fast diffusion paths provided by CNTs and enhanced redox reactions of NiS 2 nanoparticles due to high surface area, decreasing the overall resistance of electrode which is in agreement with the data obtained by electrochemical impedance spectroscopy (EIS).

h i g h l i g h t s Generalized 3D computational model of an electric double layer supercapacitor. 3D microstructural aspects do not have a significant impact on the performance. Specific capacitance, ionic conductivity, and tortuosity are critical. State-of-the-art numerical methods provide accurate and robust solutions.

In the present work, Mesoporous Rhombohedral β-NiS (Nickel Sulphide) was synthesized by a solvothermal route using thiourea as Sulphur source. Rietveld refinement confirms the single phase formation of Rhombohedral β-NiS. Reaction temperature affects the electro-catalytic, optical and morphology of the synthesized β-NiS nanoparticles. 1-D nano-rods and cluster beans like structures are observed in FESEM images. At lower temperature, energy band gap of the synthesized β-NiS nanoparticles is found to be 2.75 eV. Carbonaceous free electrodes were used for electrocatalytic studies in 1 M aqueous LiOH electrolyte. Electrocatalytic activity of β-NiS nanoparticles were studied by cyclic voltammetry technique and electrochemical impedance spectroscopy. During the analysis of cyclic voltammetry technique it was found that the synthesized β-NiS electrode showed maximum areal capacitance 12.02 F cm À 2 with 83% cyclic stability over 1000 cyclic voltammetry cycles.

В экспериментах использовались аккумуляторы фирмы «SAFT» стационарного применения длительного режима разряда. Разряд аккумуляторов выполнялся до напряжения 1 В при постоянных токах разряда от 0,1C n (C n-номинальная емкость аккумулятора) до токов разряда, при которых отдаваемая аккумулятором емкость была близка к нулю. Заряд аккумуляторов выполнялся в соответствии с инструкцией по их эксплуатации. Было доказано, что для аккумуляторов фирмы SAFT стационарного применения длительного режима разряда эмпирические уравнения КоровинаСкундина, обобщенное уравнение Пейкерта, уравнение пористого электрода и интеграл вероятности описывают изменение емкости аккумуляторов при различных тока разряда при одних и тех же параметрах независимо от емкости исследуемых аккумуляторов. В то время как уравнения Пейкерта и Агуфа справедливы только от точки перегиба экспериментальной кривой С(i) и до бесконечности. Уравнение Либенова не может быть использовано для вычисления емкости щелочных аккумуляторов.

Permeability of partially molten bimineral aggregate with differing grain sizes and grain forms is numerically modeled. It is assumed that melt appears only at edges of contacting grains of different compositions. Every grain is supposed to consist of a number of identical square (2D case) or cubic (3D case) elements. Belonging of an element to one of the compositions is defined randomly. In this case it is assumed that the elements with the same composition, which share a side combine to form a grain without internal boundaries. Therefore the grains of each of «minerals» may have a complicated form and different sizes. It is demonstrated that formation of an infinite cluster of melt inclusions requires melting at the edges of more than about 15 % of grains. The latter value may be adopted as a perme-ability threshold. Therefore, if the modal content of the first consumed mineral phase is too low to overcome the connectivity threshold, an infinitesimal melting is not accompanied by ...

Supercapacitor electrodes from activated wood charcoal Aleksandrs Volperts , Galina Dobele, Aivars Zhurinsh, Zane Zalane, Jurijs Ozolinsh, Janis Kleperis, Darya Vervikishko, Evgeny Shkolnikov 1 Latvian State Institute of Wood Chemistry, Riga, Latvia 2 Riga Technical University, Faculty of Material Science and Applied Chemistry, Riga, Latvia 3 Latvian University Institute of Solid State Physics, 8 Kengaraga Street, Riga, LV-1063, Latvia 4 Scientific Association for High Temperatures, Russian Academy of Science, Moscow, Russia

On the basis of two models of lightning currents spreading on carbon plastic, the criteria of material destruction are determined. One of the models – the anisotropic conductive medium model from the Laplace equation with specified Neumann boundary conditions – makes it possible to obtain an exact solution in the form of Bessel functions for longitudinal and transverse current densities and to consider the material destruction zones by the radius and the depth. The model adequately describes the experiment with different arrangement of electrodes simulating the passage of lightning currents on constructions made of conductive composite and metal. The second – the model of composite layered structure – is constructed using the diagram of carbon plastic substitution and makes it possible to find the distribution of currents by a numerical method. The results of the calculations for both models are well consistent. The dynamics analysis of carbon plastic destruction revealed the criter...

Influence of the thermocatalytical synthesis on the formation of the porous structure and the properties of microporous carbon wood-based materials was shown. It was found that increase of activation temperature and addition ratio of alkali activator can be used to control not only total pore volume, but also micropore and mesopore proportion. The results of tests on the synthesized carbon materials as electrodes in supercapacitors are shown, as well as the influence of properties of the porous structure of carbon materials on working characteristics of electrodes. It was shown that the increase of activation temperature from 600 °C to 800 °C led to an increased proportion of mesopores in the porous structure; this negatively influencen the cell capacity of the supercapacitor. It was found that the most feasible way of production of activated cabons for the use as electrodes in supercapacitors with sulphuric acid-based electrolyte is low-temperature activation.

the goal of our work is to model and study the transfer of heat, mass and load in a fuel cell with exchanging membrane of proton supplied with hydrogen. This enables us to know the phenomenon taking place inside the membrane, thus we can better envisage his behaviour under various conditions. We thus established the equations of transfer of mass, heat and transport of load of a porous membrane of type Nafion 117. For the transfer of heat, we consider the effect of convection, conduction as well as the Joule effect Thomson of the heating of the membrane at the time of the passage of an electrical current. For the mass transfer the diffusion of fick was considered with the effect of the electro osmotic force, and finally for the transport of the species we employed an equation of the Darcy type for an isotropic porous membrane. We pose thus two partial derivative equations of parabolic type which we solved while discretizing by the differences finished for space and burlisch-stoer for...

The topic of this thesis is about experimental study of phenomena which are associated with light propagation in nonlinear dielectric media. In the first part of this work, we study experimentally the snake instability of the bright soliton stripe of the (2+1)-dimensional hyperbolic nonlinear Schrodinger equation. The instability is observed, through spectral measurements, on spatially extended femtosecond pulses propagating in a normally dispersive self-defocusing semiconductor planar waveguide. The second part of this thesis is about light propagation in nonlinear periodic media. We experimentally observe a stationary spatial gap (or Bragg) soliton in a periodic semiconductor planar waveguide. Based on the interference pattern of the soliton beam, we measure the power parameter of the soliton which is related to the position of the spatial spectrum in the linear band gap. Cette these de doctorat a pour sujet l’etude experimentale de phenomenes associes a la propagation de la lumie...

The synthesis and characterization of electrochemically deposited polyaniline-grafted graphene oxide was successfully carried out. Excellent electrochemical stability, thermal consistency, reversibility and lower internal resistance were noted at various current densities when graphene oxide was electrochemically deposited on the surface of conducting polyaniline at + 0.75 V. Electrochemical deposition of graphene oxide on the polyaniline was confirmed by scanning electron microscopy, Fourier transformed infrared spectroscopy, Raman scattering and UV/Vis spectroscopy measurements. The electrochemically deposited polyaniline-grafted graphene oxide is confirmed in various characterization techniques employed and has promising electrochemical features due to its good transparency and stability and hence can find various applications in the manufacture of electronic materials and in the construction of electrochemical sensors that are cheap, simple and environmental friendly.

In the present work, two different phases of nickel sulphide (β-NiS and NiS 2) were successfully synthesized via facile hydrothermal route. The physical and chemical characterizations such as X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy confirms formation of β-NiS and NiS 2. Mesoporous caterpillar and cabbage-like nanostructures were observed in FESEM image with enlarged specific area 247.22 m 2 /g and 251.47 m 2 /g, respectively. Due to large surface area of the synthesized β-NiS and NiS 2 nanoparticles, bandgap was found to be reduced as 0.98 eV and 0.74 eV, respectively, than the bulk NiS. Charge transfer characteristics were examined by electrochemical impedance spectroscopy (EIS) technique; caterpillar-like nanostructures (β-NiS) has lowest charge transfer resistance 2.91 Ω, due to its unique structure. Cyclic Voltammetry (CV) analysis reveals that the synthesized β-NiS and NiS 2 nanoparticles show that the charge storage mechanism is non-Faradaic. Cabbage-like β-NiS nanoparticles show maximum areal capacitance 14.24 F cm −2 in 1 M LiOH electrolyte and show 89% cyclic stability over 1000 cycles. The electrocatalytic performance, such as high areal capacitance and lower charge transfer resistance indicate that the synthesized β-NiS and NiS 2 nanoparticles facilitate fast ion diffusion during redox processes.

The growth of orthorhombic vanadium pentoxide nanostructures was accomplished using an aerosol-assisted chemical vapor deposition process. These materials showed excellent electrochemical performance for magnesium-ion storage in an aqueous electrolyte; showing specific discharge capacities of up to 427 mAh g−1 with a capacity retention of 82% after 2000 scans under a high specific current of 5.9 A g−1. The high rate capability suggested good structural stability and high reversibility. We believe the development of low-cost and large-area coating methods, such as the technique used herein, will be essential for the upscalable fabrication of next-generation rechargeable battery technologies.

Development of electrode materials and electrolytes with low overpotentials during oxygen reduction reaction (discharging) and oxygen evolution reaction (charging) is essential for achieving high efficiency in aqueous Li-air batteries. α-MnO2 was hydrothermally synthesized and used as an electrode to investigate its possible application in an aqueous Li-air battery. The electrolyte was modified by the addition of trace amounts of halide anions and alkali metal cations. Fluoride anions and potassium cations are most effective in reducing the overpotential of oxygen reduction and evolution reactions. Electrochemical studies and XPS analysis support the fact that the specific adsorption of F inside the double layer changes the oxidation state from Mn(IV) to Mn(III), resulting in an increase in catalytic activity for oxygen reduction/evolution reactions.

Operating temperature greatly influences the performance of supercapacitors. In order to achieve a very consistent performance at various working temperatures, we develop a low-cost and high performance supercapacitor utilizing graphene-based electrodes and Li 2 SO 4-based aqueous electrolyte. The fabricated supercapacitor shows excellent charge storage characteristics from À 20 1C to 45 1C. Specific capacitance of the electrode obtained from chargedischarge measurements, which are carried on two electrode cells, is 91 F/g at room temperature and there is no significant change observed when tested at various environments in a large temperature range (e.g. 74 F/g and 99 F/g at À 20 1C and 45 1C, respectively). This supercapacitor also exhibits an outstanding capacitance retention and cycleability during its operation at different temperatures. Impedance measurements reveal the exceptionally low equivalent series resistance (ESR) and charge transfer resistance of the supercapacitor electrodes. Study of the relationship between charge storage and temperature by employing Arrhenius-type equation shows very low activation energy for the charge storage process. The remarkable electrochemical performances obtained here elucidate the great potential of the graphene-based supercapacitor for the efficient energy storage at various environmental temperatures.

Проведено компьютерное моделирование структуры и способов функционирования активных слоев (активированный углерод, водный раствор электролита) двойнослойного конденсатора (ДСК). Изучен процесс заряда ДСК, проведены расчеты основных габаритных характеристик ДСК-времени заряжения, удельной емкости, запасенной энергии. Сформулирована центральная проблема расчета ДСК с реальной, не монопористой структурой. Предложена идеальная структура пористого электрода с тремя типами пор: микро-, мезо-и макропор. Показано, что в пористом электроде с идеальной структурой можно работать с толстыми активными слоями (до 1 см) и получать на квадратный сантиметр видимой поверхности удельную емкость C=2450 Ф/см 2 и удельную энергию W=1200 Дж/см 2. Ключевые слова: компьютерное моделирование, двойнослойный суперконденсатор, идеальная структура пористого электрода, активированный углерод, водный электролит, гальваностатический и потенциостатический режимы заряда.

Utilization of plant-based bioresources toward the exploration and development of novel nano materials for long-term sustainable energy storage could enhance cost competitiveness in terms of energy supply markets and reduction of environmental impacts, and meet the urgent need for green and sustainable development strategies. The latest research trend in energy storage is to focus on storage devices including supercapacitors (SC), lithium-ion batteries, fuel cells, and leadacid batteries. SCs are attractive due to their superior performance in power and energy densities along with prolonged life cycle and easy operating conditions in applications such as electric vehicles, portable electronics as well as stationary electric grids. Since SCs are constructed by non-renewable and fossil resources, urgent alternative effective materials are the need of the hour. Multidimensional high porosity nanostructured carbon from renewable biomass sources could be a promising greener alternative as electrode materials for SC. In SCs, porous nanocarbon derived from biomass acts as conductive layer on the electrode surface. Electrical conductivity, accessibility of electrolyte, pore structure and shape, pore size distribution, along with high surface area play major roles on the specific capacitance of the SC. This review comprises the latest research platforms on biomass-derived multidimensional nano carbon electrode materials for energy storage devices specifically for SCs and their future outlook.