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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]

Pulp and paper production is a highly energy intensive process and improvement of energy efficiency in this process is considered as promising measures for reducing industrial greenhouse gases emissions (GHG). This study focuses the Pakistan's pulp and paper industry which consumes around 7% of the country's industrial energy and contributes to over 317,269 tonnes of CO 2 emissions. With rising demands for fuels and consequently as harp increase in CO 2 emissions due to the growth of the paper sector in Pakistan, this article aims to analyse the energy efficiency and carbon dioxide emissions reductions potential through the incorporation of cogeneration technologies. The cogeneration technologies studied are agas turbine, steam turbine and combined cycle and are evaluated from the energetic and economic point of view to propose a best suitable technology for each paper mill. The proposed cogeneration technologies are selected on the basis of high energy utilisation factor, as implepayback period of five years or less with least Annualised life cycle cost. The result shows that a theoretical energy saving potential equivalent to 16.9% of the actual thermal energy requirement of mills can be achieved through cogeneration which will lead to 14.3% reduction of the present carbon emissions levels in Pakistan's paper sector. [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]

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]

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]

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]