Supercapacitive properties of electrodeposited RuO2 electrode in acrylic gel polymer electrolytes

Hydrous ruthenium oxide (RuO₂) is prepared by electrodeposition on a platinum substrate and its supercapacitive properties are characterized adopting acrylic gel polymer electrolytes, such as poly(acrylic acid) (PAA), potassium polyacrylate (PAAK), and poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS). The electrodeposited hydrous RuO₂ exhibits an amorphous compact stratified morphology with a higher loading (0.15 mg cm^?2) than that of a previous report, and shows broad redox peaks on both cathodic and anodic scans in the cyclic voltammetry. In particular, the RuO₂ electrode for supercapacitor adopting the PAMPS electrolyte shows the highest specific capacitance of 642 F g^?1 at 20 mV s^?1. This is due to the efficient utilization of active RuO₂ species and greater proton accommodation toward the negative oxygen sites of PAMPS's side chain. In addition, it is possible to improve sustainability against high-rate current with the RuO₂ electrode with the PAMPS electrolyte, due to the crosslinks of the gel electrolyte, which support the mechanical strength.     

Electrochemical properties of Mn-doped activated carbon aerogel as electrode material for supercapacitor

Carbon aerogel (CA) was prepared by a sol-gel polymerization of resorcinol and formaldehyde, and it was activated with KOH to obtain activated carbon aerogel (ACA). Specific capacitance of carbon aerogel and activated carbon aerogel was measured by cyclic voltammetry and galvanostatic charge/discharge methods in 6 M KOH electrolyte. Activated carbon aerogel showed higher specific capacitance than carbon aerogel (136 F/g vs. 90 F/g). In order to combine excellent electrochemical performance of activated carbon aerogel with pseudocapacitive property of manganese oxide, 7 wt% manganese oxide was doped on activated carbon aerogel by an incipient wetness impregnation method. For comparison, 7 wt% manganese oxide was also doped on carbon aerogel by an incipient wetness impregnation method. It was revealed that 7 wt% Mn-doped activated carbon aerogel (Mn/ACA) showed higher specific capacitance than 7 wt% Mn-doped carbon aerogel (Mn/CA) (168 F/g vs. 98 F/g). The enhanced capacitance of 7 wt% Mn-doped activated carbon aerogel was attributed to the outstanding electric properties of activated carbon aerogel as well as the faradaic redox reactions of manganese oxide.     

The influence of nonpolar organics adsorption on the electrochemical behaviour of powdered activated carbon electrodes in aqueous electrolytes

Adsorption and electrochemical studies were carried out on three activated carbon samples first oxidized, then heat-treated under vacuum (at 180, 500 and 900 °C). The investigations were performed with aqueous electrolyte (Na₂HPO₄ and H₃PO₄) solutions containing selected nonpolar organics (benzene and n-hexane). Adsorption measurements were carried out on solution with a wide range of organics concentration (up to saturation point). Cyclovoltammetric curves of powdered electrodes prepared from the activated carbon samples were recorded for the organics in saturated solutions. The electric double layer capacities of the anodic and cathodic parts were estimated, and the surface anodic and cathodic charge was calculated both in absence and presence of organics in the electrochemical systems. The relative surface charge (in relation to systems without organics) was found to decrease with a reduction in the concentration of surface oxygen-containing groups. Other physicochemical parameters characterizing the degree of surface oxidation (total oxygen concentration, primary water adsorption centres) were also taken into consideration. The correlation between adsorption capacity towards the nonpolar organic compounds (obtained from adsorption isotherms) and change of surface charge was analyzed.     

Study on the effect of oxidation-ultrasound treatment on the electrochemical properties of activated carbon materials

Activated carbon (AC) has been widely used in water treatment because of its rich pore structure, large specific surface area, simple production process, low preparation cost and wide source of raw materials. In this paper, the regeneration efficiency of low-frequency ultrasonic pretreatment (40 kHz, 115Μw/cm³) on biological activated carbon (BAC) is investigated, and its principle is discussed. The results show that the micro-jet and micro-liquid flow with high temperature and pressure produced by micro-bubble rupture during ultrasonic cavitation play an important role in the regeneration of activated carbon. And optimum ultrasonic treatment time is determined (5 min). In addition, the preparation of cu-loaded activated carbon by ultrasound-microwave method is investigated to pretreat wastewater produced in paracetamol production. The results show that Cu and Cu oxides can be loaded on activated carbon surface by ultrasonic-microwave pretreatment. Finally, the pretreatments of activated carbon by physical, chemical and physical–chemical method are investigated. The effects of the above different pretreatment methods on the structure and adsorption properties of activated carbon are compared and evaluated     

Effects of activated carbon properties on the adsorption of naphthalene from aqueous solutions

The aim of this work was to investigate the role of porous and chemical heterogeneities of activated carbons in the adsorption of naphthalene from aqueous media. A commercially available activated carbon was used as the adsorbent, and its surface heterogeneity was systematically altered by heat treatment at 450 and 850 °C, obtaining a series of carbons with various oxygen contents and similar surface functionalities. The results confirmed that the adsorption of naphthalene depends strongly on the pore size distribution of the adsorbent, particularly narrow microporosity. Moreover, oxygen functionalities reduced the accessibility and affinity of naphthalene to the inner pore structure via formation of hydration clusters. Consequently, the hydrophobic/hydrophilic character of the adsorbent is important, since it dominates the competitive adsorption of water. Adsorbents with a high non-polar character (i.e., low oxygen content) have proven to be more efficient for naphthalene adsorption.     

Bamboo-based activated carbon for supercapacitor applications

Bamboo-based activated carbon is synthesized by a simple heat treatment with or without KOH activation, and characterized for possible energy storage applications. The KOH activation introduces a very large surface area of more than 3000 m² g⁻¹ to the bamboo-based activated carbon, resulting in high specific capacitance, energy density, and power density in an aqueous electrolyte. The specific capacitance retention is more than 91% of the original capacitance after 3000 cycles, proving excellent cyclic stability for supercapacitor applications. Our results indicate that the natural resource of common bamboo could be an essential raw material for the energy storage devices.     

Biomass-derived activated carbon electrode coupled with a redox additive electrolyte for electrical double-layer capacitors

Journal of Nanoparticle Research - Silicon nanocrystals (Si-NC) in silicon oxide is a promising material for many applications in micro- and nanoelectronics. This article develops a theory of the...     

p-Chlorophenol adsorption on activated carbons with basic surface properties

The adsorption of p-chlorophenol (PCP) from aqueous solution on activated carbons (ACs) with basic surface properties has been studied. The ACs were prepared by two methods. The first method was based on the modification of a commercial CWZ AC by high temperature treatment in an atmosphere of ammonia, nitrogen and hydrogen. The second approach comprised the carbonization followed by activation of N-enriched polymers and coal tar pitch using CO₂ and steam as activation agent. The resultant ACs were characterized in terms of porous structure, elemental composition and surface chemistry (pH_PZC, acid/base titration, XPS). The adsorption of PCP was carried out from an aqueous solution in static conditions. Equilibrium adsorption isotherm was of L2 type for polymer-based ACs, whereas L3-type isotherm was observed for CWZ ACs series. The Langmuir monolayer adsorption capacity was related to the porous structure and the amount of basic sites. A good correlation was found between the adsorption capacity and the volume of micropores with a width < 1.4 nm for polymer-based ACs. Higher nitrogen content, including that in basic form, did not correspond to the enhanced adsorption of PCP from aqueous solution. The competitive effect of water molecule adsorption on the PCP uptake is discussed.     

A comparative study of the adsorption equilibrium of progesterone by a carbon black and a commercial activated carbon

In this paper the adsorption process of a natural steroid hormone (progesterone) by a carbon black and a commercial activated carbon has been studied. The corresponding equilibrium isotherms have been analyzed according to a previously proposed model which establishes a kinetic law satisfactorily fitting the C versus t isotherms. The analysis of the experimental data points out the existence of two well-defined sections in the equilibrium isotherms. A general equation including these two processes has been proposed, the global adsorption process being fitted to such equation. From the values of the kinetic equilibrium constant so obtained, values of standard average adsorption enthalpy () and entropy () have been calculated. Finally, information related to variations of differential adsorption enthalpy () and entropy () with the surface coverage fraction (θ) was obtained by using the corresponding Clausius-Clapeyron equations.     

Role of activated carbon features on the photocatalytic degradation of phenol

In this work we have investigated the role of porous carbon material used as a photocatalyst and a catalyst support in the carbon/titania composite in the photodegradation of phenol, and compared the results to those of bare titanium oxide. The immobilization of titania on an activated carbon provoked acceleration of the degradation rate under UV irradiation, which is likely to be attributed to the porosity of the carbon support. The identification of the degradation intermediates detected in the solution showed that the presence of the carbon support affects the nature of phenol degradation mechanism through the formation of different intermediates. Additionally, phenol photodecomposition rate over the carbon support outperformed that attained in the carbon/titania composite, suggesting an important self-photoactivity of the carbon support.     

Ultrasound-assisted oxidation of dibenzothiophene with phosphotungstic acid supported on activated carbon

Phosphotungstic acid (HPW) supported on activated carbon (AC) was applied to catalyze deep oxidation desulfurization of fuel oil with the assist of ultrasound. The sulfur-conversion rate was evaluated by measuring the concentration of dibenzothiophene (DBT) in n-octane before and after the oxidation. Supporting HPW on AC has been verified to play a positive role in UAOD process by a series of contrast tests, where only HPW, AC or a mixture of free HPW and AC was used. The influences of catalyst dose, ultrasound power, reaction temperature, H₂O₂:oil volume ratio and the reuse of catalyst on the catalytic oxidation desulfurization kinetics were investigated. The DBT conversion rate of the reaction catalyzed by supported HPW under ultrasound irradiation was higher than the summation of the reactions with HPW only and AC only as catalyst. With the increase of loading amount of HPW on AC, ultrasound power, H₂O₂:oil volume ratio and reaction temperature, the catalytic oxidation reactivity of DBT would be enhanced. The optimum loading amount of HPW was 10%, exceed which DBT conversion would no longer increase obviously. DBT could be completely converted under the optimized conditions (volume ratio of H₂O₂ to model oil: 1:10, mass ratio of the supported HPW to model oil: 1.25%, temperature: 70 °C) after 9 min of ultrasound irradiation.     

Modification of polystyrene-based activated carbon spheres to improve adsorption of dibenzothiophene

Polystyrene-based activated carbon spheres (PACS) were modified with either air, HNO₃, (NH₄)₂S₂O₈, H₂O₂ or H₂ to improve their adsorption properties of dibenzothiophene (DBT). The texture and surface chemistry of PACS were characterized by N₂ adsorption, scanning electron microscopy (SEM), temperature-programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), acid-base titration and elemental analysis. The results showed that HNO₃ and (NH₄)₂S₂O₈ treatments introduced large amount of acidic groups such as carboxylic, lactones and anhydride groups, while air and H₂O₂ had relatively mild effects and introduced a small quantity of phenol, carbonyl and ether groups. In the HNO₃ treatment, the acidic groups might be fixed on the internal and external surface of PACS, which may act as active sites of adsorption, resulting in increase of the adsorption amount by 45%. Whereas H₂O₂ and (NH₄)₂S₂O₈ treatments might fix more oxygen-containing groups on the external surface, which may hinder DBT molecule enter into micropores, leading to rather lower adsorption capacity with the extent of oxidation. So, the concentration, distribution and types of the acidic functional groups are responsible for the removal of DBT.     

Simulation of polyurethane/activated carbon surface interactions

The influence of interfacial structure on interfacial properties between activated carbon filler and surrounding organic matrix of composites has been studied by infrared and NMR spectroscopy. Urea, semicarbazide and ethylurethane, component parts of polyurethane, have been used as organic model compounds in order to predict the interactions between the activated carbon surface and polar groups of real polyurethane molecule. It was shown that organic matrix/activated carbon interphase presented a region where the filler and matrix phases were chemically and/or physically combined. The spectra of the organic matrix undergo significant changes with increase of carbon content. Due to the surface reactive functionalities the activated carbon is considered not only as filler, influenced on the sorption properties of the composition, but also as a physicochemical modifier of the polyurethane matrix.     

High performance of activated multi-walled carbon nanotube composite electrode in KI redox electrolyte

Abstract

High performance electrodes for supercapacitor usually are achieved by compositing conductive and redox materials, the former such as multi-walled carbon nanotubes (MWCNTs), graphene, etc., provide the electrical double-layer capacitances that far less than pseudo-capacitances of the later (metal oxide, polyaniline, and so on). Here, carbonaceous composite electrode of MWCNTs and the redox electrolyte are combined into an electrochemical system for high synergetic effect of capacitance. MWCNT is activated by acid treatment and its structures are characterized by scanning electron microscope, X-ray diffraction, and Infrared spectroscopy analyses. The electrochemical measurements of resultant electrodes showed an excellent synergetic effect. The acid-activated MWCNTs electrode exhibited the maximum specific capacitance of 682 F/g in 0.2 M KI redox electrolytes, which is about 2–20 times larger than MWCNTs and its composite electrode in universal electrolyte without KI.     

The effects of activated carbon supports on the structure and properties of TiO2 nanoparticles prepared by a sol-gel method

TiO₂-coated activated carbon (TiO₂/AC) composites and pure TiO₂ powders were prepared by a sol-gel method using tetrabutylorthotitanate as a precursor. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), differential thermal analysis (DTA), X-ray photoelectron spectrum (XPS) and nitrogen absorption. The photoactivity of samples was evaluated by methylene blue (MB) degradation. The analysis results show that compared with pure TiO₂ powders, the spherical-shaped TiO₂ particles are well-dispersed in the AC matrix and the size of the resulting TiO₂ crystallites decreases to below 40 nm with increasing phase transformation temperature. The AC matrix creates anti-calcination effects and shows interfacial energy effects that control the growth of the TiO₂ particles, baffle the anatase to rutile phase transition, and cumber the TiO₂ particles to agglomerate. Compared with the surface areas of TiO₂ powders, the combination of TiO₂ and AC forms composites with high surface areas which are slightly affected by calcination temperature. By AC support, the photoactivity of TiO₂ is increased in MB photocatalytic course, possible because active carbon increases photocatalytic activity of TiO₂ particles by producing high concentration of organic compound near TiO₂, and small-size TiO₂ particles are well-dispersed on the surface of AC.     

Optimization of nickel adsorption from aqueous solution by using activated carbon prepared from waste apricot by chemical activation

Waste apricot supplied by Malatya apricot plant (Turkey) was activated by using chemical activation method and K₂CO₃ was chosen for this purpose. Activation temperature was varied over the temperature range of 400-900 °C and N₂ atmosphere was used with 10 °C/min heat rate. The maximum surface area (1214 m²/g) and micropore volume (0.355 cm³/g) were obtained at 900 °C, but activated carbon was predominantly microporous at 700 °C. The resulting activated carbons were used for removal of Ni(II) ions from aqueous solution and adsorption properties have been investigated under various conditions such as pH, activation temperature, adsorbent dosage and nickel concentration. Adsorption parameters were determined by using Langmuir model. Optimal condition was determined as; pH 5, 0.7 g/10 ml adsorbent dosage, 10 mg/l Ni(II) concentration and 60 min contact time. The results indicate that the effective uptake of Ni(II) ions was obtained by activating the carbon at 900 °C.     

低温吸附泵用椰壳活性炭的性能测试

活性炭的比表面积、孔径及分布是影响液氦低温吸附泵抽氢、氦性能的关键因素。为了确定制作液氦低温吸附泵的吸附剂,选取了C1、C2、C3、C4四种椰壳活性炭,用比表面积及孔径分析仪测定了其等温吸附性能,并对实验数据进行了针对性分析,获得了各活性炭的比表面积、微孔比表面积份额、不同孔径所对应的孔容等性能数据。结果表明,四种活性炭中C2最适于做为抽氢、氦的液氦低温吸附泵的吸附剂。     

低温泵用椰基活性炭材料的选择和比较

为了选择用于核聚变研究领域中在氢、氦气环境下的低温吸附泵所用的吸附剂,在初步筛选基础上,比对了4种椰基活性炭材料。采用扫描电镜对材料微观结构进行了扫描,用比表面积及孔径分析仪测定了等温吸附性能,最终获得了活性炭样本的比表面积、微孔比表面积份额、不同孔径所对应的孔容等性能数据;通过对实验结果的比对分析,为筛选适用于核聚变研究环境下低温吸附泵使用的吸附剂材料,提供了重要的实验数据。     

碳气凝胶及活化碳气凝胶电极材料制备与性能

以间苯二酚(R)-甲醛(F)为原料,制备了有机气凝胶和碳气凝胶,并对其进行二氧化碳活化。X射线衍射(XRD)测试表明,二氧化碳渗入到碳气凝胶网络结构发生反应,造成(002)峰和(100)峰减弱;扫描电子显微镜(SEM)测试表明,活化没有破坏碳气凝胶的骨架结构,而是增加了大量的nm尺度微孔,从而大大提高了碳气凝胶的比表面积和微孔比例。在1 mol/L KOH电解液中进行了循环伏安和计时电位扫描测试,电极材料电化学性能稳定,具有较好的可逆性,在1 mA/s电流密度下进行充放电测试,得到活化前电极比电容为103 F/g,活化后由于比表面积的增加,比电容达到371 F/g,是一种理想的电化学电极材料。     

碳气凝胶及活化碳气凝胶电极材料制备与性能

 以间苯二酚(R)-甲醛(F)为原料,制备了有机气凝胶和碳气凝胶,并对其进行二氧化碳活化。X射线衍射(XRD)测试表明,二氧化碳渗入到碳气凝胶网络结构发生反应,造成(002)峰和(100)峰减弱;扫描电子显微镜(SEM)测试表明,活化没有破坏碳气凝胶的骨架结构,而是增加了大量的nm尺度微孔,从而大大提高了碳气凝胶的比表面积和微孔比例。在1 mol/L KOH电解液中进行了循环伏安和计时电位扫描测试,电极材料电化学性能稳定,具有较好的可逆性,在1 mA/s电流密度下进行充放电测试,得到活化前电极比电容为103 F/g,活化后由于比表面积的增加,比电容达到371 F/g,是一种理想的电化学电极材料。