木质素基活性炭氮掺杂改性及其电化学性能

以磷酸法木质素基活性炭为原料,三聚氰胺为氮源、KOH为活化剂,采用同步掺杂方式制备了氮掺杂活性炭(NAC)。通过BET、XRD、拉曼光谱和XPS表征手段测试了改性后活性炭的结构及其组分,并通过电化学表征手段,测试了其作为超级电容器电极材料在几种不同性质电解液中的性能,初步探究了电解液对电极材料电化学性能的影响机制。实验结果表明：改性后的活性炭具有丰富的孔结构,比表面积达到2 332 m²/g,微孔孔容为1.37 cm³/g,中孔孔容为0.74 cm³/g,平均孔径为2.79 nm,含氮元素7.5%,其中类石墨型氮(N-Q)结构达到34.6%。丰富的孔结构和氮含量大幅提升了活性炭的电化学性能,其在水系电解液中展现出了高比电容,在1 A/g的电流密度下比电容最高可达424 F/g;在有机系电解液中,尽管其在1 A/g的电流密度下比电容最高仅为87 F/g,由于其工作电压窗口更宽(0～2.5 V),因此具备了更高的能量密度。对结果进行分析,发现：活性炭电极材料在水系电解液中的性能主要受电解液水合离子半径影响,而在有机系电解液中...     

活性炭在室温熔盐电解质中的电容特性

制备了热稳定性高、电化学性能良好的室温熔盐高氯酸锂(LiClO4)-1,3-氮氧杂环戊-2-酮(OZO),对其作为电解质材料在活性炭电化学电容器中的应用进行了研究.恒流充放电和循环伏安测试表明,活性炭电极与该类室温熔盐电解质表现出良好的电化学兼容性,比电容达到55.2 F/g,并具有良好的循环性能,循环充放电760次后容量损失小于5%.结合室温熔盐不宜燃、不挥发等特性,表明其是超级电容器非常有前景的新型电解液.     

Anodic, cathodic and cyclic voltammetric deposition of ruthenium oxides from aqueous RuCl3 solutions

Anodic, cathodic and cyclic voltammetric (CV) deposition of ruthenium oxides from aqueous RuCl₃ solutions have been investigated using stationary and rotating disk electrodes (RDE) in this work. The CV deposition behavior was examined using a RDE to differentiate the contribution of current from the reactions of ruthenium ions in the electrolyte and ruthenium oxides already adsorbed on the electrode. The results indicate that the CV growth of ruthenium oxides within the potential range of aqueous electrolyte decomposition is attributed to the anodic oxidation of ruthenium ions in the electrolyte. Cathodic deposition occurs only at potential negative than −0.30 V versus saturated calomel electrode (SCE) when H₂ evolves on the electrodes. Anodic deposition of ruthenium oxides can be obtained effectively in the potential range of ca. 0.9-1.1 V versus SCE, depending on the pH value of the electrolyte. The optimum anodic and cathodic deposition potential for maximum deposition efficiency is 1.0 and −0.9 V versus SCE, respectively, in the electrolyte solution of pH 2.     

The electrochemistry of graphite and modified graphite surfaces: the reduction of O2

Oxygen reduction to superoxide was examined in acetonitrile on the basal planes of ordinary and highly oriented pyrolytic graphite (OPG, HOPG). The reaction has a lower apparent cathodic transfer coefficient on HOPG than OPG, probably due to part of the potential drop across the electrode—electrolyte interface occurring in a space charge region in the HOPG. Oxygen reduction to peroxide was examined in aqueous alkaline solution on HOPG with adsorbed 9,10-phenanthrenequinone and on OPG with chemically attached 2-aminoanthraquinone. On the adsorbed quinone surface, the kinetics of the initial electron transfer (to the quinone) are fast while the reaction of reduced quinone with solution-phase O₂ is the rate determining step. On the chemically attached quinone surface, the initial electron transfer is the rds because the quinone is further from the surface and in an unfavourable configuration for electron tunneling.     

Study of ionic adsorption on EOS structures by combining electroreflectance, photocurrent and capacitance measurements

The Si/modified SiO₂/electrolyte structure is a very simple tool for studying ionic adsorption at the modified SiO₂/electrolyte interface, where ionic response of ISFET sensors (Ion Sensitive Field Effect Transistor) originates. This paper presents a study of H⁺ adsorption on Si/SiO₂ and Si/alkyl grafted SiO₂/electrolyte structures by one electrical method—capacitance measurements—and two electro-optical methods—electroreflectance and photocurrent measurements. The pH responses obtained by the three techniques are similar: about 27 mV per pH unit for bare SiO₂ and about 12 mV per pH unit for C17 grafted SiO₂. The electro-optical methods afford the advantage of allowing localized measurements, thus obtaining the topography of the surface.     

Hierarchical porous carbon derived from one-step self-activation of zinc gluconate for symmetric supercapacitors with high energy density

Porous carbons with high specific area surfaces are promising electrode materials for supercapacitors. However, their production usually involves complex, time-consuming, and corrosive processes. Hence, a straightforward and effective strategy is presented for producing highly porous carbons via a self-activation procedure utilizing zinc gluconate as the precursor. The volatile nature of zinc at high temperatures gives the carbons a large specific surface area and an abundance of mesopores, which avoids the use of additional activators and templates. Consequently, the obtained porous carbon electrode delivers a satisfactory specific capacitance and outstanding cycling durability of 90.9% after 50000 cycles at 10 A∙g^–1. The symmetric supercapacitors assembled by the optimal electrodes exhibit an acceptable rate capability and a distinguished cycling stability in both aqueous and ionic liquid electrolytes. Accordingly, capacitance retention rates of 77.8% and 85.7% are achieved after 50000 cycles in aqueous alkaline electrolyte and 10000 cycles in ionic liquid electrolyte. Moreover, the symmetric supercapacitors deliver high energy/power densities of 49.8 W∙h∙kg^–1/2477.8 W∙kg^–1 in the Et₄NBF₄ electrolyte, outperforming the majority of previously reported porous carbon-based symmetric supercapacitors in ionic liquid electrolytes.     

活性炭表面改性对其比电容及储能机理的影响

采用熔融Na2S对活性炭表面进行改性，通过循环伏安测试了活性炭的比电容，并通过FT-IR, BET, EIS和电泳实验分析了比电容变化的原因及其储能机理。研究发现，以10%的硫酸钠溶液为电解质，活性炭经Na2S 1000℃热处理1 h后的比电容由44.6 F/g提升至80.8 F/g，所增加的比电容主要来自于双电层电容，部分来自于氧化还原赝电容(占总电容的5.6%)。通过向电解质溶液中添加37 mmol/L的FeCl3，比电容提高至103 F/g (赝电容占12.6%)，但并不稳定，后期有下降的趋势。如果向电解质溶液添加30 mmol/L的K3[Fe(CN)6]，则比电容提升到了126 F/g，并且非常稳定、甚至有继续缓慢增加的趋势。活性炭经Na2S热处理后，储能机理由单纯的双电层物理储能变为双电层物理&化学储能+氧化还原赝电容储能。     

Sol-gel synthesis,characterization, and supercapacitor applications of MCo2O4 (M = Ni,Mn, Cu,Zn) cobaltite spinels

High performance MCo₂O₄spinels (M = Ni, Mn, Cu, Zn) were synthesized by the sol gel method (citrate) and their capacitive behavior was investigated in alkaline electrolyte. Their structural, morphological, functional groups and textural properties were characterized by TG/DSC, XRD, SEM, FTIR, EDS and BET. The capacitive properties of spinel MCo₂O₄ samples were thoroughly investigated in 1?M KOH aqueous electrolyte using cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The results revealed high stability of the samples and excellent electrochemical reversibility, and exhibited specific capacity depending on the nature of the transition metal ion M. A high specific capacitance of 285?F?g^?1 was measured for CuCo₂O₄ and a low capacitance of 158?F?g^?1 for ZnCo₂O₄.In addition, MCo₂O₄ spinels displayed good stability during long-term cycles with a cycling efficiency which exceeds75% after 1000 cycles. The obtained results classified MCo₂O₄ cobaltite spinels as most promising materials for their application in super capacitors.     

多孔碳负载五氧化二铌及其在超级电容器中的应用

以间苯二酚、甲醛和草酸铌为原料,通过原位聚合和高温煅烧,制备出多孔碳负载的五氧化二铌（Nb₂O₅）材料。X射线粉末衍射和扫描电镜分析表明,负载在多孔碳表面上的五氧化二铌具有三维纳米凸起结构,属于正交晶型。循环伏安测试表明该复合材料的比电容达到290 F·g^-1,并具有良好的大电流放电能力,5 A·g^-1的放电电流下,容量可以达到108 F·g^-1。0.5 A·g^-1的首次放电容量为355 F·g^-1 （1.0~3.0 V vs. Li⁺/Li）,100次循环后容量保持率为82%。通过对交流阻抗图谱和等效电路的模拟分析,对其电化学赝电容特性进行了讨论。该复合材料降低了电解液中离子在充放电过程中的迁移路径和扩散阻力,实现Nb₂O₅活性材料的多维度接触,提高了Nb₂O₅的导电性,改善了其超级电容特性。     

Electrochemical behaviour of modified activated carbons in aqueous and nonaqueous solutions

Cyclic voltammetric studies of electrodes prepared from unmodified and oxidized activated carbons were carried out. Three kinds of de-ashed commercial carbons were oxidized by treatment with concentrated nitric acid or by beating in air. For all samples the following properties were characterized: surface area (S_BET), quality and quantity of surface functionalities and total bonded oxygen. Cyclic voltammograms in aqueous and nonaqueous solutions (water, acetonitrile, water-acetonitrile mixtures) of electrolytes were recorded. Aqueous solutions with a wide pH range were used. The relations between cathodic peak potentials and pH values of the electrolyte solutions were estimated. An attempt to characterize the mechanisms of the electrode processes responsible for the formation of these peaks was undertaken.     

Removal of Malachite Green (MG) From Aqueous Solutions by Adsorption,Precipitation, and Alkaline Fading Using Talc

Malachite green (MG), which is primarily used as a dye, is a chemical that is listed as a class II health hazard because of its toxicity to humans and the environment. Adsorption is frequently used to remove this cationic dye from aqueous solutions. Structural changes of the molecule should be considered during removal, because MG (or chromatic MG⁺ at neutral pH) turns into protonated MG (MGH⁺) at acidic pHs and a carbinol base at basic pHs. In this study, batch sorption experiments were conducted to remove MG from aqueous solutions using talc. We studied specific removal behaviors and mechanisms of the MG for different pH solutions, including adsorption, precipitation, and alkaline fading.     

Electrochemical characterization of carbon nanotubes as electrode in electrochemical double-layer capacitors

Carbon nanotubes uniformly 50 nm in diameter were directly grown on graphite foil. Cyclic voltammetry (CV) shows that the carbon nanotube/graphite foil electrode has a high specific capacitance (115.7 F/g at a scan rate of 100 mV/s) and exhibits typical double-layer behavior. A rectangular-shaped CV curve persists even at a scan rate of 100 mV/s in 1.0 M H₂SO₄ aqueous solution, which suggests that the carbon nanotube electrode could be an excellent candidate as the electrode in electrochemical double-layer capacitors. In addition, the influence of the potential scan rate, aging, and the electrolyte solution on the specific capacitance of nanotube electrodes was also studied.     

Facile synthesis of a novel Fe3O4-rGO-MoO3 ternary nano-composite for high-performance hybrid energy storage applications

Supercapacitors (SCs) have been considered as inspiring energy storage devices due to the long cycle lifetime and high power densities. However, their energy density is limited due to the low capacitance of cathode materials and inferior cycling stability at practically useable potential windows >1.2 V. In this paper, we demonstrate the synthesis of a novel ternary Fe₃O₄-rGO-MoO₃ nano-composite (FGM) with nanoparticles-like morphology (NPs) by utilizing the fast and facile microwave hydrothermal process. The optimized composition of FGM nanocomposite is characterized by the XPS, EDS, Raman, SEM, TEM and HRTEM techniques. The FGM-NPs supported on the carbon cloth (FGM@CC) electrode is used to investigate the electrochemical charge storage properties in basic potassium hydroxide (KOH) electrolyte. The charge-storage properties of the FGM@CC electrode were studied by the CV, GCD and EIS techniques. The obtained results of FGM@CC electrode in aqueous electrolyte showed excellent electrochemical performance as compared with single metal oxides: maximum specific capacitance of 1666.50 F g⁻¹ (FGM@CC), 1075.26 F g⁻¹ (Fe₃O₄ NPs) and 952.38 F g⁻¹ (MoO₃ NPs) at a current density of 2.5 A g⁻¹. The capacitance retention was 95.01% (FGM@CC), 94.1% (Fe₃O₄ NPs) and 92.5% (MoO₃ NPs) after 5000 cycles. Further, the charge storage mechanism is analyzed in the light of power's law and systematical investigated the capacitive and diffusion controlled based stored charge in FGM@CC electrode. Thus FGM nano-composite showed best performance as the cathode material for the next generation flexible supercapacitors.     

Supercapacitive behavior of mesoporous carbon CMK-3 in calcium nitrate aqueous electrolyte

Calcium nitrate Ca(NO₃)₂ aqueous solution was found to be an effective aqueous electrolyte for a supercapacitor using ordered mesoporous carbon as the electrode materials. The supercapacitive behavior of ordered mesoporous carbon CMK-3 electrode in Ca(NO₃)₂ aqueous electrolyte was investigated utilizing cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge/discharge measurements. CMK-3 electrode shows excellent supercapacitive behavior with wide voltage window, high specific gravimetric capacitance and satisfactory electrochemical stability in Ca(NO₃)₂ aqueous electrolyte. The specific gravimetric capacitance of CMK-3 electrode in Ca(NO₃)₂ aqueous electrolyte reaches 210 F g^?1 at a current density of 1 A g^?1, which is higher than that in conventional aqueous electrolytes NaNO₃ and KOH solution about 40% and 54%, respectively. The high charge density of the electric double layer formed at the interface of the CMK-3 electrode and Ca(NO₃)₂ aqueous electrolyte and the pseudo-capacitive effect originating from the oxygen groups on the surface of CMK-3 were believed to respond for the excellent supercapacitive behavior of CMK-3 electrode in Ca(NO₃)₂ aqueous electrolyte.     

Electrochemical behaviour of phenylethanolamine at gold in aqueous solution

The electrooxidation of phenylethanolamine (2-amino-1-phenylethanol) at a gold electrode in alkaline electrolyte has been studied. Measurement of the differential capacitance of the electric double layer versus the electrode potential has shown that the adsorption of phenylethanolamine at the gold-solution interface plays a significant role in the oxidation mechanism. The effect of amine concentration, electrolyte pH and potential scan rate on the electrooxidation is analysed.     

Enhanced life-cycle supercapacitors by thermal treatment of mesophase-derived activated carbons

This paper studies the effect of thermal treatment on the long-term performance of carbon-based supercapacitors. Two active electrode materials were studied: a mesophase derived activated carbon (AC), rich in oxygen functionalities, and an activated carbon obtained from treating AC at 1000 °C (AC-1000), from which most of the functionalities had been removed. Up to 10,000 cycles were performed in aqueous acidic media at different voltage windows (0.6 and 1 V). Both materials showed an excellent life cycle, although the thermally treated carbon showed a significantly better behavior. The initial capacitance of AC-1000 was reduced by only ∼5% after 10,000 cycles, independently of the operating voltage, demonstrating that the thermal treatment of AC produces a very stable electrode material at both ranges of potential. The better performance of AC-1000 was attributed to the absence of functional groups and the higher degree of crystalline order that renders materials more stable. The use of these two materials in an asymmetric device resulted in a capacitor that merges both high stability and high capacitance values. The initial capacitance was reduced by only 4.5% after 10,000 galvanostatic cycles and by 10% after 20,000.     

An asymmetric supercapacitor using RuO2/TiO2 nanotube composite and activated carbon electrodes

We reported an asymmetric supercapacitor technology where RuO₂/TiO₂ nanotube composite was used as positive electrode and the activated carbon as negative electrode in 1 mol/L KOH electrolyte solution. The electrochemical capacitance performance of the asymmetric supercapacitor was tested by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge-discharge tests. The results show that the asymmetric supercapacitor has electrochemical capacitance performance within potential range 0–1.4 V. A power density 1207 W/kg was obtained with an energy density of 5.7 W h/kg at a charge–discharge current density of 120 mA/cm². The supercapacitor also exhibits a good cycling performance and keep 90% of initial capacity over 1000 cycles.     

PVA基碱性聚合物电解质Ni(OH)2/AC超级电容器的电化学性能

Polyvinyl alcohol(PVA)-sodium polyacrylate(PAAS)-KOH-H₂O alkaline polymer electrolyte film with high ionic conductivity was prepared by a solution-casting method.Polymer Ni(OH)₂/activated carbon(AC) hybrid supercapacitors with different electrode active material mass ratios(positive to negative) were fabricated using this alkaline polymer electrolyte,nickel hydroxide positive electrodes,and AC negative electrodes.Galvanostatic charge/discharge and electrochemical impedance spectroscopy(EIS) methods were used to study the electrochemical performance of the capacitors,such as charge/discharge specific capacitance,rate charge/discharge ability,and charge/discharge cyclic stability.Experimental results showed that with the decreasing of active material mass ratio m(Ni(OH)₂)/m(AC),the charge/discharge specific capacitance increases,but the rate charge/discharge ability and the charge/discharge cyclic stability decrease.     

Adsorption Characteristics and pH‐dependence of Metsulfuron‐Methyl onto Activated Carbons

Abstract

The adsorption characteristics of metsulfuron‐methyl (MM) onto powdered activated carbon (PAC) and granular activated carbon (GAC) were studied at varying solution pHs (4–9) and temperatures (20–40°C). The dependence of pH was observed in aqueous solution with MM. The film mass transfer and intraparticle diffusion coefficients were estimated from concentration decay curves obtained in the batch adsorber. The maximum adsorption capacity decreased with increasing pH and temperature. Among the PAC used, the coconut based PAC had the best adsorption capacity. The adsorption isotherms could be plotted using the Freundlich and Toth models with a reasonable degree of accuracy. The overall adsorption isotherm such as the modified‐Toth model should be applied. The performances of the fixed‐bed GAC system was also simulated by a model developed. The objective of the present study was to investigate the adsorption and pH dependence behavior of MM onto PAC and GAC in order to diminish the environmental risk of MM pollution.     

超级电容器准固态聚合物电解质膜的研究

制备了一种介于水凝胶和全固态聚合物电解质之间的聚合物电解质膜,用于活性炭电子双电层电容器。测试表明使用该聚合物电解质膜的双电层电容器的容量为2 15mA·h,其容量、功率特性与KOH水溶液电容器相当。电容器的循环伏安曲线,稳定的充放电循环曲线及交流阻抗谱说明该种聚合物电解质膜在碳基超级电容器的使用电压范围(0～1V)内是稳定的,而且聚合物电解质膜电容器表现出良好的可逆性和循环特性。