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This work reports the preparation of hydrogel nanocomposites based on copolymerization of methyl methacrylate using ammonium persulfate as the initiator, methylene bisacrylic amide as the crosslinker & various amounts of functionalized CNT for inter-hydrogel binding. Functionalization of CNTs was performed by its oxidation at room temperature using nitric acid as the oxidizing agent, then acylation of carboxylic acid agent in CNTs by SOCl2 addition and finally esterification of CNTs by the addition of ethylene glycol to acylchloride. The swelling rate of the obtained composites was checked in deionized water where the composite containing more CNTs percent in the hydrogel structure showed a higher swelling rate (>50%).Then, for increase of chemical activity, the obtained hydrogel nanocomposites were impregnated by solution of CuSO4 with different concentrations and the resultant hydrogels as the activity filler were analyzed by FTIR, XRD and SEM. [ABSTRACT FROM AUTHOR]

The decarbonization of energy to meet the low-carbon energy strategy set for 2050 has led to a continuous increase in the contribution of electricity generated from renewables to our growing energy demands, where their inherent intermittency of supply must be addressed by a step-change in energy storage. 10.3390/en14041139 2 Mirzaeian M., Abbas Q., Hunt M.R.C., Hall P. Pseudocapacitive Effect of Carbons Doped with Different Functional Groups as Electrode Materials for Electrochemical Capacitors. Additionally, the nonstop emerging demands of modern technologies still require the design of versatile energy-storage/power supply systems, ensuring a secure and continuous supply of energy on a large scale with wide ranges of power and energy densities commensurate with each application. [Extracted from the article]

Summary: Extensive use of carbon‐based materials has revolutionised the number of modern scientific areas such as transportation, electronic, material chemistry and electrochemical energy storage, mainly due to their outstanding characteristics such as excellent conductivity, mechanical strength, ease of availability and cost‐effectiveness. However, it is difficult to fine‐tune the physiochemical characteristics of naturally occurring carbonaceous materials according to desired applications. High purity carbon aerogels with control over porous structure prepared using synthetic chemistry techniques such as polymerisation can be a potential substitute carbon material due to their outstanding characteristics including superior conductivity, high level of porosity and chemical inertness. Designing tailored polymeric carbon materials according to their anticipated uses is advantageous and can be achieved by altering various synthesis parameters at the initial stages of preparation. This not only helps in fine tuning porous structure of carbon aerogels but can also assist in producing composite materials by introducing materials on the surface or within the bulk of produced carbons. [ABSTRACT FROM AUTHOR]

Polymeric carbon/activated carbon aerogels were synthesized through sol-gel polycondensation reaction followed by the carbonization at 800 °C under Argon (Ar) atmosphere and subsequent physical activation under CO 2 environment at different temperatures with different degrees of burn-off. Significant increase in BET specific surface area (SSA) from 537 to 1775 m2g−1 and pore volume from 0.24 to 0.94 cm3g−1 was observed after physical activation while the pore size remained constant (around 2 nm). Morphological characterization of the carbon and activated carbons was conducted using X-ray diffraction (XRD) and Raman spectroscopy. Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to investigate the effect of thermal treatment (surface cleaning) on the chemical composition of carbon samples. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to analyse the capacitive and resistive behaviour of non-activated/activated/and surface cleaned activated carbons employed as electroactive material in a two electrode symmetrical electrochemical capacitor (EC) cell with 6 M KOH solution used as the electrolyte. CV measurements showed improved specific capacitance (SC) of 197 Fg−1 for activated carbon as compared to the SC of 136 Fg−1 when non-activated carbon was used as electroactive material at a scan rate of 5 mVs−1. Reduction in SC from 197 Fg−1 to 163 Fg−1 was witnessed after surface cleaning at elevated temperatures due to the reduction of surface oxygen function groups. The result of EIS measurements showed low internal resistance for all carbon samples indicating that the polymeric carbons possess a highly conductive three dimensional crosslinked structure. Because of their preferred properties such as controlled porosity, exceptionally high specific surface area, high conductivity and desirable capacitive behaviour, these materials have shown potential to be adopted as electrode materials in electrochemical capacitors. • Polymeric carbon/activated carbon aerogels were synthesized through sol-gel polycondensation reaction. • Significant increase in BET SSA from 537 to 1775 m2g−1 was observed after physical activation using CO 2. • Improved SC of 197 Fg−1 was achieved after activation as compare to 136 Fg−1 for non-activated carbon aerogels. • Significant decrease in contact angle was observed when carbon substrate was substituted with activated carbon. [ABSTRACT FROM AUTHOR]

Abstract Nitrogen doped resorcinol/formaldehyde carbon aerogels with controlled nitrogen content are synthesized by controlling the resorcinol/melamine molar ratio (R/M) during the synthesis of aerogel precursors. The carbons were used as electrode materials in an electrochemical capacitor using 6 M KOH solution as electrolyte. All samples exhibited amorphous structure with low degree of graphitization. The maximum specific capacitance of 208 Fg-1 was observed after doping of the carbon with nitrogen at R/M = 80. Drop in solution and charge transfer resistances from 0.57Ω to 0.15Ω and 0.05Ω–0.04Ω was also observed respectively, with the drop in contact angles from 123° to 103° for the carbon doped with nitrogen at R/M = 80. BET results showed that the pore volume and surface area of carbon increase after N-doping, with a BET surface area of 841 m2 g−1 at R/M = 80. This R/M ratio is an optimum ratio at which incorporation of nitrogen into the carbon matrix improves the capacitive performance of cell as a result of improved porosity/wettability/conductivity/active sites of the electrode. Doping at higher nitrogen concentrations (R/M < 80) decreased the specific capacitance of the cell significantly due to decreased conductivity of carbon and suppression of the hopping rate of dopant. Graphical abstract Image 1078 Highlights • Nitrogen doped resorcinol/formaldehyde carbon aerogels with controlled nitrogen content are synthesized. • The contact angle of carbon and 6 M KOH solution dropped significantly from 123° to 103° after nitrogen doping. • The best specific capacitance of 208 Fg-1 is obtained for the carbon doped with nitrogen at an R/M ratio of 80. • The solution resistance dropped significantly from 0.57Ω to 0.15Ω after N- doping at an R/M ratio of 80. • R/M ratio of 80 is the optimum R/M ratio at which nitrogen doping results in superior performance of the cell. [ABSTRACT FROM AUTHOR]

Among different electric energy storage technologies electrochemical capacitors are used for energy storage applications when high power delivery or uptake is needed. Their energy and power densities, durability and efficiency are influenced by electrode and electrolyte materials however due to a high cost/performance ratio; their widespread use in energy storage systems has not been attained yet. Thanks to their properties such as high surface area, controllable pore size, low electrical resistance, good polarizability and inertness; activated carbons derived from polymeric precursors are the most used electrode materials in electrochemical capacitors at present. Other electrode materials such as shaped nano-carbons or metal oxides are also investigated as electrode materials in electrochemical capacitors, but only as useful research tools. Most commercially used electrochemical capacitors employ organic electrolytes when offering concomitant high energy and high power densities. The use of aqueous based electrolytes in electrochemical capacitor applications is mainly limited to research purposes as a result of their narrow operating voltage. Recent studies on room temperature ionic liquids to be employed as electrolyte for electrochemical capacitor applications are focused on fine tuning their physical and transport properties in order to bring the energy density of the device closer to that of batteries without compromising the power densities. In this paper a performance analysis, recent progress and the direction of future developments of various types of materials used in the fabrication of electrodes for electrochemical capacitors are presented. The influence of different types of electrolytes on the performance of electrochemical capacitors such as their output voltage and energy/power densities is also discussed. [ABSTRACT FROM AUTHOR]

Controlled porosity carbons aerogels were synthesized by sol–gel polycondensation of resorcinol (R) and formaldehyde (F) using sodium-carbonate as the catalyst (C). The Effect of variation of R/C ratio and carbonization temperature on the porous structure of resultant gels and carbons was investigated by characterizing the porous structure of the materials using nitrogen adsorption–desorption measurements at 77 K. It was shown that carbons with surface areas ranging between 537 and 687 m 2 g −1 and average pore size in the range of 1.80–4.62 nm can be produced when controlling the resorcinol to catalyst (R/C) molar ratio between 100 and 500 and carbonization temperature in the range of 800–1000 °C. The resultant polymeric carbons were used as the electroactive material for the fabrication of electrodes for electrochemical cells. Contact angle measurements were performed to study the wettability of the electrodes using 6 M KOH as the probing liquid. The contact angles were in the range of 106°–125° indicating the carbon based electrodes are hydrophobic in nature and no significant change in contact angles was observed with the change in R/C ratio. XRD patterns of the carbon electrodes show a typical broad peak at 2θ of about 23 indicating a disordered structure corresponding to the amorphous nature of the materials as expected for polymeric based hard carbons with crosslinked structure. These results are in line with Raman spectra of carbons which indicate two peaks in 1590 cm −1 and 1340 cm −1 wavenumber. The electrochemical performance of the electrodes was investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements. The CV results showed that high specific capacitance of 136 Fg −1 can be achieved for the carbon with average pore diameter of 1.80 nm at a scan rate of 5 mV s −1 when using 6M KOH as the electrolyte. Electrochemical impedance (EIS) measurements also revealed that the capacitance of the cell deteriorates with increase in pore size of the carbon probably due to pore flooding by the electrolyte. The results of this study show the applicability of these carbons as potential electrode materials for supercapacitor applications. [ABSTRACT FROM AUTHOR]

In this paper the preparation of nano-structured silver oxide thin films with different oxidation states with promise as electrode materials for supercapacitors by reactive magnetron sputtering is investigated. The chemical, structural, surface morphological dependence of the films on oxygen gas flow rate and deposition power were examined by scanning electron microscope (SEM), X-ray diffraction (XRD) and energy dispersive X-ray (EDX). The average thickness of the films was controlled in the range of ≈50–330 nm. The XRD spectra of the films indicated the formation of bi-phase films comprised of silver and silver oxides with different oxidation states. The wettability of the films in contact with different probing liquids was investigated by measuring the contact angles using a goniometer. It was shown that the silver oxide films are relatively hydrophilic and increasing oxygen flow rate increases the wettability of the films toward water as a result of an increase in the oxidation state of the films and consequently clustering of electrons in polar molecules of water around the oxides at higher oxidation states. This is further confirmed by the analysis of the surface energy measurements. [ABSTRACT FROM AUTHOR]

Cogeneration is considered as one of the promising energy efficient techniques for producing electricity and useful thermal energy from a single fuel source. This paper describes a feasibility study of the implementation of different cogeneration options to a paper mill to evaluate their energy saving potentials and economic benefits. The investigated systems in this paper are gas turbine, steam turbine and combined cycle cogeneration options evaluated and compared based on energy utilisation factor and Annualised Life Cycle Cost (ALCC) analysis. The results of energy analysis show that all Combined Heat and Power (CHP) systems satisfy the thermal energy needs of the mill while the combined cycle cogeneration option generates the highest amount of electric energy equal to 10.91 MW. The gas turbine cogeneration system is shown as the most advantageous system from overall energy point of view with the highest energy utilisation factor of 78% meeting the heat and electric requirements of the mill and exporting 21,329 MWh of additional electricity to the grid. Economic feasibility results also show that an overall saving of 5.12 million US$ can be achieved by implementing the gas turbine cogeneration system to the mill making it as the best cogeneration option with the least overall ALCC of 1.34 million US$ and the maximum percentage of CO 2 emission reduction (68%) when compared with the other options. [ABSTRACT FROM AUTHOR]

Small angle neutron scattering (SANS) has been applied to examine the effect of high-pressure CO2 on the structure of Wyodak coal. Significant decrease in the scattering intensities on the exposure of the coal to high-pressure CO2 showed that high-pressure CO2 rapidly gets adsorbed on the coal and reaches to all the pores in the structure. This is confirmed by strong and steep exothermic peaks observed on DSC scans during coal/CO2 interactions. In situ small angle neutron scattering on coal at high-pressure CO2 atmosphere showed an increase in scattering intensities with time suggesting that after adsorption, high-pressure CO2 immediately begins to diffuse into the coal matrix, changes the macromolecular structure of the coal, swells the matrix, and probably creates microporosity in coal structure by extraction of volatile components from coal. Significant decrease in the glass transition temperature of coal caused by high-pressure CO2 also confirms that CO2 at elevated pressures dissolve in the coal matrix, results in significant plasticization and physical rearrangement of the coal’s macromolecular structure. [ABSTRACT FROM AUTHOR]

Abstract: Polymer based carbon aerogels were prepared by synthesis of a resorcinol formaldehyde gel followed by pyrolysis at 1073K under Ar and activation of the resultant carbon under CO2 at different temperatures. The prepared carbon aerogels were used as active materials in the preparation of cathode electrodes for lithium oxygen cells and the electrochemical performance of the cells was evaluated by galvanostatic charge/discharge cycling and electrochemical impedance measurements. It was shown that the storage capacity and discharge voltage of a Li/O2 cell strongly depend on the porous structure of the carbon used in cathode. EIS results also showed that the shape and value of the resistance in the impedance spectrum of a Li/O2 cell are strongly affected by the porosity of carbon used in the cathode. Porosity changes due to the build up of discharge products hinder the oxygen and lithium ion transfer into the electrode, resulting in a gradual increase in the cell impedance with cycling. The discharge capacity and cycle life of the battery decrease significantly as its internal resistance increases with charge/discharge cycling. [Copyright &y& Elsevier]

Abstract: Porous carbon aerogels are prepared by polycondensation of resorcinol and formaldehyde catalyzed by sodium carbonate followed by carbonization of the resultant aerogels in an inert atmosphere. Pore structure of carbon aerogels is adjusted by changing the molar ratio of resorcinol to catalyst during gel preparation and also pyrolysis under Ar and activation under CO2 atmosphere at different temperatures. The prepared carbons are used as active materials in fabrication of composite carbon electrodes. The electrochemical performance of the electrodes has been tested in a Li/O2 cell. Through the galvanostatic charge/discharge measurements, it is found that the cell performance (i.e. discharge capacity and discharge voltage) depends on the morphology of carbon and a combined effect of pore volume, pore size and surface area of carbon affects the storage capacity. A Li/O2 cell using the carbon with the largest pore volume (2.195cm3/g) and a wide pore size (14.23nm) showed a specific capacity of 1290mAhg−1. [Copyright &y& Elsevier]

Organic aerogels were synthesized by sol–gel polymerization of resorcinol (R) with formaldehyde (F) catalyzed by sodium carbonate (C) followed by vacuum drying. The influence of the resorcinol/sodium carbonate ratio (R/C) on the porous structure of the resultant aerogels was investigated. The nitrogen adsorption–desorption measurements show that the aerogels possess a well developed porous structure and mesoporosity was found to increase with increasing the R/C ratio. Carbon aerogels were obtained by carbonization of RF aerogels. The carbonization temperature impacts the microstructure of the aerogels by pore transformations during carbonization probably due to the formation of micropores and shrinkage of the gel structure. The results showed that a temperature of 1073 K is more effective in the development of the pore structure of the gel. Activated carbon aerogels were obtained from the CO2 activation of carbon aerogels. Activation results in an increase in the number of both micropores and mesopores, indicative of pore creation in the structure of the carbon. Activation at higher temperatures results in a higher degree of burn off and increases the pore volume and the surface area remarkably without change of the basic porous structure, pore size, and pore size distribution. [ABSTRACT FROM AUTHOR]

Zinc oxide (ZnO) and materials based on it are often used to create battery-type supercapacitor electrodes and are considered as promising materials for hybrid asymmetric supercapacitors. However, when creating such electrodes, it is necessary to take into account the instability and degradation of zinc oxide in aggressive environments with a non-neutral pH. To the best of our knowledge, studies of the changes in the properties of ZnO-containing electrodes in alkaline electrolytes have not been carried out. In this work, changes in the structure and properties of these electrodes under alkaline treatment were investigated using the example of ZnO-containing composites, which are often used for the manufacturing of supercapacitor electrodes. Supercapacitor electrodes made of two materials containing ZnO were studied: (i) a heterogeneous ZnO-Co3O4 system, and (ii) a hexagonal h-Zn-Co-O solid solution. A comparison was made between the structure and properties of these materials before and after in situ electrochemical oxidation in the process of measuring cyclic voltammetry and galvanostatic charge/discharge. It has been shown that the structure of both nanoparticles of the heterogeneous ZnO-Co3O4 system and the h-Zn-Co-O solid solution changes due to the dissolution of ZnO in the alkaline electrolyte 3.5 M KOH, with the short-term alkaline treatment producing cobalt and zinc hydroxides, and long-term exposure leading to electrochemical cyclic oxidation–reduction, forming cobalt oxide Co3O4. Since the resulting cobalt oxide nanoparticles are immobilized in the electrode structure, a considerable specific capacity of 446 F g−1 or 74.4 mA h g−1 is achieved at a mass loading of 0.0105 g. The fabricated hybrid capacitor showed a good electrochemical performance, with a series resistance of 0.2 Ohm and a capacitance retention of 87% after 10,000 cycles. [ABSTRACT FROM AUTHOR]

Electrochemical energy storage and conversion systems such as electrochemical capacitors, batteries and fuel cells are considered as the most important technologies proposing environmentally friendly and sustainable solutions to address rapidly growing global energy demands and environmental concerns. Their commercial applications individually or in combination of two or more devices are based on their distinguishing properties e.g., energy/power densities, cyclability and efficiencies. In this review article, we have discussed some of the major electrochemical energy storage and conversion systems and encapsulated their technological advancement in recent years. Fundamental working principles and material compositions of various components such as electrodes and electrolytes have also been discussed. Furthermore, future challenges and perspectives for the applications of these technologies are discussed. [ABSTRACT FROM AUTHOR]

In this study, RF-based un-doped and nitrogen-doped aerogels were produced by polymerisation reaction between resorcinol and formaldehyde with sodium carbonate as catalyst and melamine as the nitrogen source. Carbon/activated carbon aerogels were obtained by carbonisation of the gels under inert atmosphere (Ar) followed by activation of the carbons under CO2 at 800 °C. The BET analysis of the samples showed a more than two-fold increase in the specific Surf. area and pore volume of carbon from 537 to 1333 m2g−1 and 0.242 to 0.671 cm3g−1 respectively after nitrogen doping and activation. SEM and XRD analysis of the samples revealed highly porous amorphous nanostructures with denser inter-particle cross-linked pathways for the activated nitrogen-doped carbon. The X-Ray Photoelectron Spectroscopy (XPS) results confirmed the presence of nitrogen and oxygen heteroatoms on the Surf. and within the carbon matrix where improvement in wettability with the drop in the contact angle from 123° to 80° was witnessed after oxygen and nitrogen doping. A steady drop in the equivalent series (RS) and charge transfer (RCT) resistances was observed by electrochemical measurements after the introduction of nitrogen and oxygen heteroatoms. The highest specific capacitance of 289 Fg−1 with the lowest values of 0.11 Ω and 0.02 Ω for RS and RCT was achieved for nitrogen and oxygen dual-doped activated carbon in line with its improved Surf. chemistry and wettability, and its enhanced conductivity due to denser inter-particle cross-linked pathways. [ABSTRACT FROM AUTHOR]

Cobalt oxide nanopowders are synthesized by the pyrolysis of aerosol particles of water solution of cobalt acetate. Cobalt nanopowder is obtained by subsequent reduction of obtained cobalt oxide by annealing under a hydrogen atmosphere. The average crystallite size of the synthesized porous particles ranged from 7 to 30 nm, depending on the synthesis temperature. The electrochemical characteristics of electrodes based on synthesized cobalt oxide and reduced cobalt oxide are investigated in an electrochemical cell using a 3.5 M KOH solution as the electrolyte. The results of electrochemical measurements show that the electrode based on reduced cobalt oxide (Re-Co3O4) exhibits significantly higher capacity, and lower Faradaic charge–transfer and ion diffusion resistances when compared to the electrodes based on the initial cobalt oxide Co3O4. This observed effect is mainly due to a wide range of reversible redox transitions such as Co(II) ↔ Co(III) and Co(III) ↔ Co(IV) associated with different cobalt oxide/hydroxide species formed on the surface of metal particles during the cell operation; the small thickness of the oxide/hydroxide layer providing a high reaction rate, and also the presence of a metal skeleton leading to a low series resistance of the electrode. [ABSTRACT FROM AUTHOR]

Abstract We present an investigation into the pseudo-capacitive energy storage potential of silver (Ag) and silver oxide (Ag 2 O) thin film electrode materials prepared by reactive magnetron sputtering. The growth mode and morphology of the prepared films were investigated using the scanning electron microscope (SEM), which reveals columnar growth structure and microporous sites. The stoichiometry and oxidation states of the silver oxide films were monitored with X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infra-red spectroscopy (FTIR). The XRD results reveal the nano-crystalline nature of the silver and silver oxide thin films with peak intensities indexed at (111) planes. Static and dynamic Contact angle measurements were used to probe the penetration of the aqueous NaCl electrolyte into the pores in the prepared silver and silver oxide films, with surface wettability of all (Ag) and (Ag 2 O) thin films hydrophilic in nature, which is vital for a good electrochemical performance. The Faradaic redox reactions, capacitance and the charge discharge of the films when exposed to the NaCl electrolyte, were monitored with cyclic voltammetry and chronopotentiometry charge-discharge. Results show that Silver and silver oxide possess specific capacitance of 240.52 F/g and 275.50 F/g at 2 mV/s respectively, which is promising for electrochemical energy storage application. Highlights • Surface wettability of prepared Ag and Ag 2 O thin films are hydrophilic in nature. • Tensiometer analysis reveals electrolyte penetration and contact angle hysteresis. • Ag and Ag 2 O Microstructure are deposition power dependent. • CV results showed compact anodic and cathodic peaks with 275.50 F/g capacitance. [ABSTRACT FROM AUTHOR]

Supercapacitors play an important role in a future clean-energy landscape to meet the challenges of existing energy-storage/delivery systems. They suffer from low energy density and are mainly used for the storage/delivery of electrical energy in high power demands. However, improvement of their energy density is vital to develop energy storage systems that can respond to the energy demands of emerging technologies requiring a wider energy/power spectrum. In this article, a symmetrical capacitor is developed from a composite consisting of synthesized activated carbon and cobalt oxide to improve the energy storage performance of the supercapacitor. Uniform distribution and immobilization of cobalt nanoparticles within the composite is achieved by embedding cobalt acetate into the initial resorcinol formaldehyde polymeric aerogels, followed by the pyrolysis of the gel in Ar atmosphere and activation of the carbon in CO2 atmosphere at 800 °C. The activated carbon/cobalt composite is used as the electroactive material in electrode formulation. The electrochemical characteristics of the synthesized electrode materials demonstrates an optimized specific capacitance of 235 F g−1 at a sweep rate of 10 mV s−1 in a three-electrode system. The symmetrical capacitor has a capacitance of 66 F g−1 at 1 A g−1, a very high rate of performance in 10,000 cycle tests, and a rate capability of 24% at 30 A g−1. The capacitor shows a power density of up to 15 Wh k g−1. The presence of cobalt spices makes it possible to optimize the capacitance of a symmetrical capacitor, while the capacitance of a symmetrical activated carbon capacitor cannot be optimized. [ABSTRACT FROM AUTHOR]

Graphene is fundamentally a two-dimensional material with extraordinary optical, thermal, mechanical, and electrical characteristics. It has a versatile surface chemistry and large surface area. It is a carbon nanomaterial, which comprises sp2 hybridized carbon atoms placed in a hexagonal lattice with one-atom thickness, giving it a two-dimensional structure. A large number of synthesis techniques including epitaxial growth, liquid phase exfoliation, electrochemical exfoliation, mechanical exfoliation, and chemical vapor deposition are used for the synthesis of graphene. Graphene prepared using different techniques can have a number of benefits and deficiencies depending on its application. This study provides a summary of graphene preparation techniques and critically assesses the use of graphene, its derivates, and composites in environmental applications. These applications include the use of graphene as membrane material for the detoxication and purification of water, active material for gas sensing, heavy metal ions detection, and CO2 conversion. Furthermore, a trend analysis of both synthesis techniques and environmental applications of graphene has been performed by extracting and analyzing Scopus data from the past ten years. Finally, conclusions and outlook are provided to address the residual challenges related to the synthesis of the material and its use for environmental applications. [ABSTRACT FROM AUTHOR]

Electrochemical pseudocapacitors, along with batteries, are the essential components of today's highly efficient energy storage systems. Cobalt oxide is widely developing for hybrid supercapacitor pseudocapacitance electrode applications due to its wide range of redox reactions, high theoretical capacitance, low cost, and presence of electrical conductivity. In this work, a recovery annealing approach is proposed to modify the electrochemical properties of Co3O4 pseudocapacitive electrodes. Cyclic voltammetry measurements indicate a predominance of surface-controlled redox reactions as a result of recovery annealing. X-ray diffraction, Raman spectra, and XPES results showed that due to the small size of cobalt oxide particles, low-temperature recovery causes the transformation of the Co3O4 nanocrystalline phase into the CoO phase. For the same reason, a rapid reverse transformation of CoO into Co3O4 occurs during in situ oxidation. This recrystallization enhances the electrochemical activity of the surface of nanoparticles, where a high concentration of oxygen vacancies is observed in the resulting Co3O4 phase. Thus, a simple method of modifying nanocrystalline Co3O4 electrodes provides much-improved pseudocapacitance characteristics. [ABSTRACT FROM AUTHOR]

The oil industry faces with crude oil emulsions formation issue. It is a common problem for the most of oil-producing countries around the world, including the Republic of Kazakhstan. Mainly, water-in-oil type of emulsions (or reverse emulsions) are formed during oil extraction and transportation. The presence of water in crude oil causes an increase in the cost of oil processing and transportation and consequently increases the cost of oil refinery products. It also induces corrosion of equipment when oil is extracted and transported. In this paper, several major methods of demulsification based on chemical, membrane, electric, magnetic, microwave separation used for the breaking of water-in-oil emulsions in recent years are reviewed and their advantages and disadvantages are highlighted. It is shown that it is important to create cost-efficient and smart demulsifiers of stable oil emulsions including their ecological friendly characteristics. Therefore, the future perspective research areas include the development of sustainable and alternative demulsification methods which are in demands today. In addition, the development of the effective combination of destabilization methods is still relevant today to achieve the synergetic effect in dewatering of highly stable oil emulsions. • Heavy crude oil emulsions in petroleum industry and its concerns. • Chemical methods of crude oil demulsification and recently synthesized environmentally friendly demulsifiers. • Development of membrane modification for crude oil emulsion separation. • Electrical, microwave and magnetic demulsification approaches. [ABSTRACT FROM AUTHOR]

Various azo compounds are synthesized by electrophonic substitution reaction in the presence of Nanosilica/NaNO2 as a catalyst. [ABSTRACT FROM AUTHOR]

Zinc oxide is a promising multifunctional material. The practical use of nano- and polycrystalline ZnO devices faces a serious problem of instability of electrical and luminescent characteristics, due to the adsorption of oxygen by the surface during aging. In this paper, the aging effect in ZnO films and nanorod arrays was studied. It was found that ZnO samples demonstrate different behavior of the degradation process, which corresponds to at least two different types of adsorbing surface sites for O2, where O2 adsorption is of a different nature. The first type of surface sites is rapidly depassivated after hydrogen passivation and the aging effect takes place due to these centers. The second type of surface sites has a stable structure after hydrogen passivation and corresponds to HO–ZnO sites. The XPS components of these sites include the Zn2p3/2 peak at 1022.2 ± 0.2 eV and Zn2p1/2 peak at 1045.2 ± 0.2 eV, with a part of the XPS O1s peak at 531.5 ± 0.3 eV. The annealing transforms the first type of site into the second one, and the subsequent short-term plasma treatment in hydrogen results in steady passivation, where the degradation of characteristics is practically reduced to zero. [ABSTRACT FROM AUTHOR]

Conventional experimental methods for testing the performance of super-capacitors include the measurement of capacitance through charge and discharge, measurement of equivalent series resistance (ESR) and measurement of self-discharge and the equivalent circuit model (ECM) by electrochemical impedance spectroscopy (EIS). However, the methods are not suitable for the mass production line of supercapacitors since they require a long time for the test and several kinds of different instrument. EIS is an attractive method to evaluate the performance of supercapacitors except that it takes a long time for a single test. In this paper a fast EIS instrument suitable for quality assurance for the mass production of supercapacitors is proposed. In order to reduce the time for the test, a multi-sine sweeping method is used for the EIS test and the results are analyzed by extracting the parameters of the ECM to evaluate the performance of the supercapacitors. The proposed instrument is developed to have multi-channel to further decrease the time for the test with a supercapacitor. It is also presented as to how the extracted parameter values of the ECM can be used to evaluate the performance of the supercapacitor. [ABSTRACT FROM AUTHOR]