Hierarchical porous carbons with high performance for supercapacitor electrodes

A series of hierarchical porous carbons (HPCs) were prepared by a combination of self-assembly and chemical activation. Pore-structure analysis shows that micropores can be generated within the mesopore wall of mesoporous carbon in a controllable manner during activation. As evidenced by cyclic voltammetry, galvanostatic charge/discharge cyclings and frequency response measurements, HPCs show superior capacitive performances to hard-templated ordered mesoporous carbons, which can be attributed to the generated pore surfaces that play most important role in the formation of double-layer capacitance and to their unique hierarchical porous structure that favors the fast diffusion of electrolyte ions into the pores. Of special interest is the fact that HPCs maintains 180 F/g at high-frequency of 1 Hz.     

Hierarchical porous carbons prepared from direct coal liquefaction residue and coal for supercapacitor electrodes

Hierarchical porous carbons were prepared from a coal liquefaction residue (CLR) and two coals, Shenhua (SH) coal with low and Shengli (SL) coal with high ash content, by KOH activation with the addition of some additives, and used as the electrode for supercapacitors. Two metal oxides (MgO and Al₂O₃) and three organic materials (sugar, urea and cetyltrimethylammonium bromide) were used as the additives, to investigate their effects on the structure and capacitive performance of the resultant carbons. The results show that the metal oxide and/or its salt formed by the reaction with KOH can serve as space fillers of nanopores in the carbonized carbon, while the gases produced by the decomposition of the organic additive can develop and/or widen some pores. Both help the carbon produced from CLR or the SH coal with low ash content to have additional meso- and macropores, but destroy the structure of the carbon from the SL coal with high ash content. Compared with the carbon without any additive, the optimized hierarchical porous carbon with each additive shows a smaller equivalent resistance, much higher capacitance in a wide range of charge–discharge rates and excellent cycle stability when the carbon was used as supercapacitor electrode.     

Synthesis of nanocast ordered mesoporous carbons and their application as electrode materials for supercapacitor

Various nanocast ordered mesoporous carbons (OMCs) were synthesized using mesoporous silicas such as SBA-15, SBA-16, KIT-6, SBA-3 and MCM-48 as templates via nanocasting pathway. The structures of OMCs were analyzed by X-ray diffraction, transmission electron microscope and nitrogen sorption technique. These OMCs with well-defined pore structure were used as model electrode materials for investigating the influence of pore structure on their double layer capacitances. The cyclic voltammetry and galvanostatic charge/discharge measurements were conducted to estimate the capacitive behaviour of OMCs. The results show that the mesopore structures of OMCs play an important role in improving surface utilization for the formation of electrical double layer. OMCs synthesized from SBA-15 and SBA-16 show great advantage over others because their micropores are being easy accessible through the mesopores, thus allowing rapid electrolyte ion diffusion. To achieve a higher specific capacitance (μF cm⁻²), the optimized amount ratio between micropore and mesopore needs to be controlled. In addition, great impact of the electrode disc thickness on the capacitive performance was demonstrated by a series of careful measurements.     

Polyaniline-deposited porous carbon electrode for supercapacitor

Electrodes for supercapacitors were fabricated by depositing polyaniline (PANI) on high surface area carbons. The chemical composition of the PANI-deposited carbon electrode was determined by X-ray photoelectron spectroscopy (XPS). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to investigate the electrochemical properties of electrodes. An equivalent circuit was proposed to successfully fit the EIS data, and the significant contribution of pseudocapacitance from PANI was thus identified. A comparative analysis on the electrochemical properties of bare-carbon electrodes was also conducted under similar conditions. The performance of the capacitors equipped with the resulting electrodes in 1 M H₂SO₄ was evaluated by constant current charge-discharge cycling within a potential range from 0 to 0.6 V. The PANI-deposited electrode exhibits high specific capacitance of 180 F/g, in comparison with a value of 92 F/g for the bare-carbon electrode.     

石油焦基多孔炭电极材料的制备及调控

以石油焦为原料,氢氧化钾为活化剂,采用化学活化法制得中孔丰富、比表面积高的多孔炭。通过硝酸铁溶液浸渍,再经高温热处理,或在高温过程中通入CO2,对多孔炭进行孔结构深度调控。将所制多孔炭用作电化学电容器电极材料,通过恒流充放电、循环伏安测试其电化学性能,采用氮气吸附法测定多孔炭的比表面积及孔径分布。结果表明:KOH与石油焦质量比为3∶1,活化温度850℃,活化时间90 min时,可以制得比表面积为2 738 m2/g,总孔容为1.51 cm3/g,中孔率为43.2%的多孔炭,在电流密度为100 mA/g时,该电极在6 mol/L KOH电解液中的比电容值高达256.6 F/g。多孔炭经金属盐溶液浸渍并经CO2二次活化后,中孔率由43.2%提高至70.7%,尽管因比表面积的下降造成了电极比电容值的下降,但由于中孔率的提高,电极的充放电速率明显加快。     

Feasibility of bamboo-based activated carbons for an electrochemical supercapacitor electrode

This study focused on the preparation and electrochemical properties of bamboo-based activated carbons (ACs) through carbonization and subsequent activation with steam and non-aqueous electrolyte solutions. The specific surface areas and the capacitances of samples ranged from 445 to 1,025 m²/g and from 5 to 60 F/g, respectively, depending on the activation conditions. The sample activated at 900 ‡C for 60 min under our experimental conditions exhibited the highest capacitance and the largest specific surface area.     

Metal-organic framework (MOF) as a template for syntheses of nanoporous carbons as electrode materials for supercapacitor

Five nanoporous carbons (NPCs) were prepared by polymerizing and then carbonizing carbon precursor of furfuryl alcohol accommodated in a porous metal-organic framework (MOF-5, [Zn₄O(bdc)₃], bdc = 1,4-benzenedicarboxylate) template. The Brunauer-Emmett-Teller (BET) surface areas for five NPC samples obtained by carbonizing at the temperatures from 530 to 1000 °C fall into the range from 1140 to 3040 m² g⁻¹ and the dependence of BET surface areas on carbonization temperatures shows a “V” shape. All the five NPC samples have a pore size distribution centered at about 3.9 nm. As electrode materials for supercapacitor, the NPC samples obtained at the temperatures higher than 600 °C display the ideal capacitor behaviors and give rise to almost constant specific capacitance (above 100 F g⁻¹ at 5 mV s⁻¹) at various sweep rates, which is associated with their mesoporous characteristics. However, the NPC sample with the highest BET surface area (3040 m² g⁻¹) obtained by carbonizing at 530 °C gives a unusually low capacitance (12 F g⁻¹ at 5 mV s⁻¹), which may be attributed to the poor conductivity of the carbon material due to the low carbonization temperature.     

Influence of the acid concentration on the morphology of micropores and mesopores in porous glasses

The polymodal microporosity and mesoporosity of porous glasses prepared by through leaching of phase-separated alkali borosilicate glasses in hydrochloric acid solutions of different concentrations are investigated by two new methods based on an analysis of the kinetic and equilibrium isotherms of gas desorption at a temperature of 77.5 K under low partial pressures, as well as by a modified classical adsorption method under medium and high pressures. It is established that an increase in the concentration of hydrochloric acid in the leaching solution brings about transformations in the microporous and mesoporous structures of the porous glasses. The structural transformations can be summarized as follows: (i) a considerable decrease in the specific surface of mesopores and the corresponding increase in the diameter of secondary silica globules, (ii) a decrease in the mesopore volume and the corresponding increase in the coordination number of the packing of secondary silica globules in channels formed upon phase separation, (iii) an increase in the diameter of mesopores arising from gaps between secondary silica globules in channels formed upon phase separation, (iv) an increase in the diameter of regions in these channels that are partially or completely free from secondary silica globules, and (v) the formation of ultramicropores with a molecular size of 0.4–0.5 nm.     

超级电容器电极材料研究最新进展

超级电容器是一种介于传统电容器与化学电源之间的新型储能元件,它具有充电时间短、循环寿命长、功率密度大、能量密度高、适用温度范围宽和经济环保等优势,目前在很多领域都受到广泛关注。本文概述了超级电容器电极材料的研究情况,包括碳基材料、金属氧化物材料及导电聚合物材料等。     

浅谈超级电容器电极材料的研究进展

介绍了碳材料、金属氧化物和导电聚合物及其复合材料等超级电容器电极材料的研究现状,并指出其发展方向是制备性能优异的复合材料和实现材料纳米化。     

Characterisation of activated nanoporous carbon for supercapacitor electrode materials

Commercial nanoporous carbon RP-20 was activated with water vapor in the temperature range from 950 °C to 1150 °C. The XRD analysis was carried out on nanoporous carbon powder samples to investigate the structural changes (graphitisation) in modified carbon that occurred at activation temperatures T ? 1150 °C. The first-order Raman spectra showed the absorption peak at 1582 cm⁻¹ and the disorder (D) peak at 1350 cm⁻¹. The low-temperature N₂ adsorption experiments were performed at −196 °C and a specific surface area up to 2240 m²g⁻¹ for carbon activated at T = 1050 °C was measured. The cell capacitance for two electrode activated nanoporous carbon system advanced up to 60 F g⁻¹ giving the specific capacitance ∼240 F g⁻¹ to one electrode nanoporous carbon ∣1.2 M (C₂H₅)₃CH₃NBF₄ + acetonitrile solution interface. A very wide region of ideal polarisability for two electrode system (∼3.2 V) was achieved. The low frequency limiting specific capacitance very weakly increases with the rise of specific area explained by the mass transfer limitations in the nanoporous carbon electrodes. The electrochemical characteristics obtained show that some of these materials under discussion can be used for compilation of high energy density and power density non-aqueous electrolyte supercapacitors with higher power densities than aqueous supercapacitors.     

Polyimide‐based porous hollow carbon nanofibers for supercapacitor electrode

Porous hollow carbon nanofibers (PHCNFs) using styrene‐acrylonitrile copolymer (SAN) solution as core and polyacrylic acid (PAA) as shell were manufactured by co‐axial electrospinning technique, taking polyvinyl pyrrolidone (PVP) as a pore inducer additive in the shell. The shell thickness of PHCNFs could be adjusted by controlling flow rates of core and shell fluids. The prepared PHCNFs showed excellent electrochemical properties with the high specific capacitance of 221 F g^?1 and superior cycling stability, remaining a capacitance retention of 95% after 5000 cycles under a scan rate of 0.1 V s^?1. In this system, hollow structures bring a 20% capacitance improvement, while the porous morphology brings a 47% capacitance improvement. The attractive performances exhibited by these sponge supercapacitors make them potentially promising candidates for future energy storage systems. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43397.     

四氧化三钴超级电容器电极材料的制备与研究

电极材料是决定电化学电容器性能的一个主要方面,研究与开发高性能的电极材料是人们的研究重点之一.碳电极材料比电容较小;钌等贵重金属氧化物电极材料比电容量虽然很高,但昂贵的价格限制了其实际应用.因此价格低廉、环境友好、同样具有较高氧化还原电容的过渡金属氧化物成为目前超级电容器的研究热点之一.以硝酸钴为原料,以柠檬酸为模板水热合成了前驱体,200 ℃热处理后得到了四氧化三钴.循环伏安、恒流放电等电化学测试表明,200 ℃所得四氧化三钴电极在6 mol/L氢氧化钾溶液中和-0.1～0.5 V (vs. SCE) 电位范围内,具有较好的循环稳定性能,单电极比电容达到442 F/g.为开发高性能的超级电容器电极材料提供了参考.     

Templated mesoporous carbons for supercapacitor application

Mesoporous carbons prepared by an inverse replica technique have been used as electrodes for electrochemical capacitors. Such well-sized carbons were prepared from mesostructured SBA-16 silica materials that served as templates whereas polyfurfuryl alcohol was the carbon precursor. Two highly mesoporous carbons characterized by 3 and 8 nm average pore diameter were tested in various electrolytic solutions (acidic, alkaline and aprotic).It can be concluded that templated mesoporous carbons with tailored pore size distribution are very promising materials to be used as electrodes in supercapacitors. The design of their pore size allows suiting the dimensions of electrolyte ions and efficient charging of the electrical double layer is achieved especially at high current load. Definitively better capacitance performance has been found for carbon with 3 nm pores range, however, cycling performance depends not only on the pore size.     

Tunable and selective formation of micropores and mesopores in carbide-derived carbon

Pore structure of carbide-derived carbon (CDC) was tunable by chlorination of Ti(C_1−xA_x) solid–solution carbides (A = O or N). High-energy ball milling method was used to synthesize various nanocrystalline Ti(C_1−xA_x) phases. We were able to obtain specific dimension of pore volumes in the range of micropore (<2 nm) or mesopore size (2–50 nm), depending on the compositions of the precursors. The substitutional atoms and their contents effectively modify the characteristics of pores i.e., pore size, volume and their distributions. The micropore volume density, total pore volume density and specific surface area (SSA) of Ti(C_0.7O_0.3) CDCs were found 1.55 cm³/g, 1.72 cm³/g and 3100 m²/g, respectively. In contrast, Ti(C_0.5N_0.5) CDCs showed enhancement of mesopore formation with 3.34 cm³/g, 3.45 cm³/g and 522 m²/g for mesopore volume density, total pore volume density and SSA, respectively.     

夹心型生物碳电极材料的制备及超级电容器性能

选择板栗壳为碳源(CC),炭化后用KOH活化,制得CC700-OH电极材料.通过SEM、TEM、XRD以及BET等对其形貌和性能进行了表征与测试,发现CC700-OH具有孔/片穿插的夹心结构.在电流密度为1 A/g时,比电容为540 F/g,在电流密度为10 A/g下,循环6000圈后比电容仍可保持初始值的98％.在二...     

碳包覆金属氧化物作为超级电容器电极材料的研究进展

综述了碳包覆金属氧化物作为超级电容器电极材料的最新研究进展。详细介绍了贵重金属氧化物（如RuO2）和廉价金属氧化物（如Fe3O4、SnO2、TiO2、MnO2等）在超级电容器电极材料领域内的应用现状和存在的问题,指出了碳包覆廉价金属氧化物所形成的核/壳结构很好地解决了金属氧化物易溶于电解液、充放电体积易膨胀等问题,展望了其作为超级电容器电极材料在消费电子、航空航天、国防科技等领域中的应用前景。     

Fabrication and electrochemical characterization of polyimide-derived carbon nanofibers for self-standing supercapacitor electrode materials

We report the electrochemical performance of aromatic polyimide (PI)-based carbon nanofibers (CNFs), which were fabricated by electrospinning, imidization, and carbonization process of poly(amic acid) (PAA) as an aromatic PI precursor. For the purpose, PAA solution was electrospun into nanofibers, which were then converted into CNFs via one-step (PAA-CNFs) or two-step heat treatment (PI-CNFs) of imidization and carbonization. The FTIR and Raman spectra demonstrated a successful structural evolution from PAA nanofibers to PI nanofibers to CNFs at the molecular level. The SEM images revealed that the average diameter of the nanofibers decreased noticeably via imidization and carbonization, while it decreased slightly with increasing the carbonization temperature from 800 °C to 1000 °C. In case of PI-CNF carbonized at 1000 °C, a porous structure was developed on the surface of nanofibers. The electrical conductivity of PI-CNFs, which was even higher than that of PAA-CNFs, increased significantly from 0.41 to 2.50 S/cm with increasing the carbonization temperature. From cyclic voltammetry and galvanostatic charge/discharge tests, PI-CNF carbonized at 1000 °C was evaluated to have a maximum electrochemical performance of specific capacitance of ~126.3 F/g, energy density of ~12.2 Wh/kg, and power density of ~160 W/kg, in addition to an excellent operational stability. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47846.     

Nanostructured manganese dioxides: Synthesis and properties as supercapacitor electrode materials

Low-cost layered manganese oxides with the rancieite structural type were prepared by reduction of KMnO₄ or NaMnO₄ in acidic aqueous medium, followed or not by successive proton- and alkali-ion-exchange reactions. Samples were characterized by X-ray diffraction, energy dispersive X-ray analysis, BET surface area measurements, thermal analyses and X-ray photoelectron spectroscopy. As a result of successive exchange steps, compounds with high surface area (reaching 200 m² g⁻¹) can be obtained, and in the case of syntheses made with KMnO_4, the α-MnO₂ phase is formed. Capacitive properties of the synthesized materials were studied using potentiodynamic cycling in K₂SO₄. Correlations between the electrochemical and the physicochemical properties of the samples were investigated. The interesting conclusion is that the morphology and the size of the particles influence directly the capacitance, and that among the samples presenting the best morphology, the compounds derived from K-containing rancieite-type compounds (and containing α-MnO₂) present a better cycleability.