Preparation and electrochemical characteristics of mesoporous carbon spheres for supercapacitors

Mesoporous carbon spheres serving as electrode materials for supercapacitors were synthesized by a facile polymerization-induced colloid aggregation method using melamines as a carbon precursor and commercial colloidal silica as a silica source for hard template. After the carbonization of as-formed resins-template composites at 1000 °C and the removal of the silica template by hydrofluoric acid, the resulting mesoporous carbon spheres with a diameter size of ∼5 μm, specific surface area (up to 1280 m²/g) and uniform pore size as large as 30 nm could be obtained. Due to the enriched nitrogen content and the large pore size of the mesoporous carbon spheres affecting the surface wettability, resistance, and ion diffusion process in the pores, the mesoporous carbon spheres showed a high specific capacitance of 196 F/g in 5 mol/l H₂SO₄ electrolytes at a discharge current density of 1 A/g.     

An easy soft-template route to synthesis of wormhole-like mesoporous tungsten carbide/carbon composites

Wormhole-like mesoporous tungsten carbide/carbon (WC/C) composites can be prepared by an easy method that combines emulsion processing with triblock copolymer self-assembly strategy, followed by a high-temperature carbothermal reduction. X-ray diffraction, transmission electron microscopy, X-ray spectroscopy, thermogravimetric analysis and N₂ sorption techniques were employed to characterize the mesoporous WC/C composites. The results show that the resultant materials have a wormhole-like mesostructure containing nanoscale (∼40 nm) tungsten carbide particles, and high surface areas (up to 314.9 cm²/g). It is proposed that a general assemble procedures are responsible for the wormhole-like mesoporous WC/C composites.     

Simple and efficient CVD synthesis of graphitic P-doped 3D cubic ordered mesoporous carbon at low temperature with excellent supercapacitor performance

Heteroatom doping is a promising strategy for improving the electrochemical performance of carbon materials. Herein, we spotlight an advantageous, simple, and efficient CVD synthesis of P-doped 3D cubic ordered mesoporous carbon (POMC) for the first time. The POMC was prepared by pyrolysis of acetylene/triphenylphosphine (C₂H₂/Ph₃P) mixture at relatively low temperature over Fe-KIT-6 as a sacrificial template. The ensuing P-doped OMC showed an enhanced porous texture than an undoped counterpart with a specific surface area of 403.5 m²/g, pore volume of 0.545 cm³/g, average pore size of 4.64 nm and suitable heteroatom functionalities with P and O contents of 0.13% and 9.83%, correspondingly. The obtained POMC exhibited a much higher specific capacitance of 288F/g at 0.2 A/g (175F/g for OMC), good cyclic stability of 97.6 %, and good rate capability than pristine OMC in 6 M KOH. It is equivalent to or improved than various stated mono doped and even dual doped porous carbon electrodes. Furthermore, a symmetric supercapacitor (POMC//POMC) was fabricated with 1 M Na₂SO₄ aqueous neutral electrolyte exhibits high cycling stability (89.3%) even with a wide potential window (2.0 V) and offers a relatively high energy density (10.01 Wh/kg) with a power density of 300 W/kg.     

Microwave synthesis and electrochemical characterization of mesoporous carbon@Bi2O3 composites

An efficient and quick microwave method has been employed to prepare worm-like mesoporous carbon@Bi₂O₃ composites for the first time. As-prepared products have been characterized by X-ray diffraction, N₂ adsorption-desorption, scanning electron microscopy, transmission electron microscopy and inductive coupled plasma atomic emission spectroscopy. The electrochemical measurement shows the worm-like mesoporous carbon@Bi₂O₃ composites exhibits excellent capacitance performance and the maximum specific capacitance reaches 386 F g⁻¹, three times more than the pure worm-like mesoporous carbon.     

Preparation for 2D–C/C composites with pure RL textures and its characteristic

在沉积温度为1080--1200℃、沉积总压力为10 kPa和气体滞留时间为0.01 s的条件下, 以天然气为碳源, 以氮气为载气, 使用新型ICVI工艺对预制体初始密度为0.43 g/cm$^{3}$(纤维体积分数25%)的2D针刺整体炭毡进行致密化,
在150 h内制备出表观密度为1.75 g/cm³的C/C复合材料. 用偏光显微镜和高分辨扫描电镜观察了热解碳基体的微观组织结构, 分析了三点弯曲试样的断口形貌. 结果表明: 制备的C/C复合材料具有粗糙层(RL)组织结构, 试样的弯曲强度为164.77 MPa、模量为21.34 GPa, 表现为阶梯式失效, 断裂行为呈现出明显的假塑性.     

Mesoporous indium oxide synthesized via a nanocasting route

The synthesis of crystalline mesoporous indium oxide by using a mesoporous carbon (CMK-3) as hard template is described. Transmission electron microscopy (TEM) exhibits the presence of mesoporous structure in our sample and the corresponding wide-angle X-ray diffraction (XRD) pattern confirmed the crystalline wall of sample. N₂ adsorption measurement exhibits the synthesized crystalline mesoporous indium oxide possesses a specific surface area of 39 m²/g and the total pore volume of 0.17 cm³/g, and the corresponding pore size distribution curve reveals the presence of a mesopore of 7.0 nm in maximum. Our work demonstrates that the maintenance of the ordered structure of carbon template is very significant for obtaining high quality replicas via the nanocasting route.     

Synthesis of spheroidal ordered mesoporous carbon materials from silica/P123/butanol composites

Spheroidal ordered mesoporous carbon materials with diameter of 2–10 μm were synthesized by direct carbonization of silica/triblock copolymer P123/butanol composites using P123 and butanol as the structure-directing agents and carbon precursors. The morphologies, structures and pore characteristics of the carbon materials were investigated by scanning and transmission electron microscopes, X-ray diffraction, and nitrogen sorption. It was found that the material possesses a cubic ordered mesoporous structure with Ia3d symmetry. The butanol addition directly affects the carbon morphology and pore structure. When the mass ratio of butanol to P123 is 0.5:1, the product exhibits a perfectly spheroidal morphology with a specific surface area of 1236 m² g⁻¹ and a total pore volume of 1.26 cm³ g⁻¹. The formation mechanism of the spheroidal ordered mesoporous carbon materials is discussed briefly.     

Simple synthesis of hollow carbon spheres from glucose

Hollow carbon spheres were prepared by the reaction between glucose and Zn particles at 550 °C. Scanning and transmission electron microscopies reveal that most of the spheres are about 1-2 µm in diameter, similar to the sizes of the Zn particle. The shells of the spheres are comprised of numerous hollow nanospheres with the diameter of 10-100 nm. The specific surface area of the spheres is 207 m²/g. The Zn particles act as both the reactant and the template for the micron-scale spheres, and the H₂ bubbles generated during the reaction as the template for the hollow nanospheres.     

The size modulation of hollow mesoporous carbon spheres synthesized by a simplified hard template route

Hollow mesoporous carbon spheres (HMCSs) have been prepared by a simplified replication route from a solid silica core/mesoporous silica shell aluminosilicate (SCMS-Al) template, which was synthesized by directly incorporating aluminum species into the mesoporous framework during template synthesis. The size of HMCSs can be tuned between 80 and 470 nm by simply changing the diameters of SCMS-Al. The HMCSs have uniform mesopores with a narrow pore size distribution (3.4-4.1 nm), and high surface area, (890-1150 m²/g) and total pore volumes (0.75-1.15 cm³/g). The techniques of N₂ sorption isotherms, TEM, EDX and SEM were used to characterize the as-synthesized spheres.     

Sol-gel synthesis of titania hollow spheres

TiO₂ hollow spheres are prepared by a convenient sol-gel method at room temperature. The products were characterized by XRD, FESEM, TEM and FT-IR. It was found that these spheres are hollow inside with outer diameters of 200-500 nm. The average mesoporous diameter is about 9.8 nm. And the BET surface area and specific pore volume are about 161.9 m²/g and 0.441 cm³/g, respectively.     

Nonionic surfactant-templated mesoporous carbon as an electrocatalyst support for methanol oxidation

Two carbons were synthesized for use as platinum electrocatalyst supports for methanol oxidation. For both materials, furfuryl alcohol was used as the carbon precursor; however, one (CPEG) was made using poly ethylene glycol as the pore former, while the other (CSRF) was produced using Pluronic^® F127 as the soft template by organic–organic self-assembly. The CPEG and CSRF carbons were estimated from nitrogen physisorption experiments to be micro- and mesoporous, respectively. Platinum nanoparticles were deposited on each carbon as well as on Vulcan XC-72 carbon by the formic acid reduction method. The physicochemical properties of electrocatalysts were studied using X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy dispersive X-ray analysis (EDX), and their electrochemical features were examined using cyclic voltammetry, chronoamperometry, and impedance spectroscopy. It was found that higher methanol oxidation peak current densities as well as lesser charge transfer resistance at electrode/electrolyte interface were obtained for Pt supported on CSRF as compared to those on Vulcan XC-72 carbon, owing to the higher specific surface area and larger total pore volume (696 m² g⁻¹ and 0.60 cm³ g⁻¹, respectively) together with superior electrical conductivity of mesoporous CSRF. On the other hand, the lower surface area and pore volume of microporous CPEG substrate confined Pt nanoparticles deposition and thus made CPEG-supported Pt an inefficient methanol oxidation electrocatalyst.     

Mesoporous carbon spheres with uniformly penetrating channels and their use as a supercapacitor electrode material

An optimized nanostructure design for electrode materials of supercapacitors was realized by introducing furfuryl alcohol into as-prepared surfactant-containing spherical host and generating a robust mesoporous structure. The structural characterization shows that the carbon spheres inherit the regular mesopore structure and high surface area of the template and possess a uniform particle size containing well-ordered channels throughout the spheres. By adjusting the initial molar ratio of H₂O to tetraethyl orthosilicate (TEOS), the pore volumes of the templated carbons vary from 0.4 to 0.6 cm³·g^-1 and surface areas are in the range of 610 and 944 m²·g^-1. Furthermore, NiO nanoparticles were incorporated into the carbon spheres by air oxidation of the Ni-containing samples. The use of these spheres in electrode materials for electric double layer capacitors was investigated. The electrochemical measurements show that the specific capacitance of the ordered mesoporous carbon spheres (OMCs-2) can increase by 40% to 205.3 F·g^-1 by the addition of 3 wt% NiO.     

Biomass-derived nitrogen-rich porous carbon composite for supercapacitor application

In this study, egg proteins are used as a nitrogen source for the synthesis of nitrogen-rich carbonaceous material through hydrothermal carbonization (HTC) for the electrochemical energy storage application. The composite of activated carbon with egg-derived protein (AC/EDP) is prepared by mixing untreated egg proteins in the aqueous dispersion of activated carbon, followed by HTC at 220 °C for 12 h in a Teflon-lined autoclave. The resultant composite is then directed to chemical activation with KOH and thermal activation at a temperature ranging from 500 to 700 °C. The nitrogen-doped activated carbon exhibited a microporous and mesoporous structure with a high specific surface area of 1660 m² g^?1, confirmed through BET analysis. The composite morphology was analyzed through scanning and high-resolution transmission electron microscopy. X-ray photoelectron spectroscopy indicates the presence of a considerable amount of pyrrolic, pyridinic, and quaternary nitrogen in AC/EDP, which improved the electrochemical performance. The composite activated at 700 °C exhibited the highest capacitance of 263 F g^?1 at a current density of 0.2 A g^?1. The highest energy density and power density values are 32 Wh kg^?1 and 7920 W kg^?1, respectively. The AC/EDP exhibited high cyclic stability, and the capacitance retention observed after 10,000 cycles is 98%.

     

Hydrothermal synthesis, characterization, photocatalytic activity and dye-sensitized solar cell performance of mesoporous anatase TiO2 nanopowders

Mesoporous anatase TiO₂ nanopowder was synthesized by hydrothermal method at 130 °C for 12 h. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), HRTEM, and Brunauer-Emmett-Teller (BET) surface area. The as-synthesized sample with narrow pore size distribution had average pore diameter about 3-4 nm. The specific BET surface area of the as-synthesized sample was about 193 m²/g. Mesoporous anatase TiO₂ nanopowders (prepared by this study) showed higher photocatalytic activity than the nanorods TiO₂, nanofibers TiO₂ mesoporous TiO₂, and commercial TiO₂ nanoparticles (P-25, JRC-01, and JRC-03). The solar energy conversion efficiency (η) of the cell using the mesoporous anatase TiO₂ was about 6.30% with the short-circuit current density (Jsc) of 13.28 mA/cm², the open-circuit voltage (Voc) of 0.702 V and the fill factor (ff) of 0.676; while η of the cell using P-25 reached 5.82% with Jsc of 12.74 mA/cm², Voc of 0.704 V and ff of 0.649.     

Phosphate adsorption on aluminum-coordinated functionalized macroporous–mesoporous silica: Surface structure and adsorption behavior

In this study, Al(III)-coordinated diamino-functionalized macroporous–mesoporous silica was synthesized and characterized by X-ray diffraction, N₂ adsorption–desorption, Fourier transform infrared spectroscopy, scanning and transmission electron microscopy. Because of well-defined and interconnecting macroporous–mesoporous networks, the resulting adsorbent (MM-SBA) exhibited a significantly better phosphate adsorption performance and faster removal rate, as compared with the mesoporous adsorbent (M-SBA). Based on the Freundlich and Langmuir models, the phosphate adsorption capacity and the maximum adsorption capacity of MM-SBA were 7.99 mg P/g and 23.59 mg P/g, respectively. In the kinetic study of MM-SBA, over 95% of its final adsorption capacity reached in the first 1 min; whereas that of M-SBA was less than 79%.     

Template-free synthesis of ordered mesoporous NiO/poly(sodium-4-styrene sulfonate) functionalized carbon nanotubes composite for electrochemical capacitors

We report the first example of a practical and efficient template-free strategy for synthesizing ordered mesoporous NiO/poly(sodium-4-styrene sulfonate) (PSS) functionalized carbon nanotubes (FCNTs) composites by calcining a Ni(OH)₂/FCNTs precursor prepared by refluxing an alkaline solution of Ni(NH₃) _x ²⁺ and FCNTs at 97 °C for 1 h. The morphology and structure were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Thermal decomposition of the precursor results in the formation of ordered mesoporous NiO/FCNTs composite (ca. 48 wt% NiO) with large specific surface area. Due to its enhanced electronic conductivity and hierarchical (meso- and macro-) porosity, composite simultaneously meets the three requirements for energy storage in electrochemical capacitors at high rate, namely, good electron conductivity, highly accessibleelectrochemical surface areas owing to the existence of mesopores, and efficient mass transport from the macropores. Electrochemical data demonstrated that the ordered mesoporous NiO/FCNTs composite is capable of delivering a specific capacitance (SC) of 526 F/g at 1 A/g and a SC of 439 F/g even at 6 A/g, and show a degradation of only ca. 6% in SC after 2000 continuous charge/discharge cycles.      

Fabrication and textural characterization of nanoporous carbon electrodes embedded with CuO nanoparticles for supercapacitors

Abstract

We introduce a novel strategy of fabricating nanoporous carbons loaded with different amounts of CuO nanoparticles via a hard templating approach, using copper-containing mesoporous silica as the template and sucrose as the carbon source. The nature and dispersion of the CuO nanoparticles on the surface of the nanoporous carbons were investigated by x-ray diffraction (XRD), high-resolution scanning electron microscopy (HRSEM) and high-resolution transmission electron microscopy (HRTEM). XRD results reveal that nanoporous carbons with embedded CuO nanoparticles exhibit a well-ordered mesoporous structure, whereas the nitrogen adsorption measurements indicate the presence of excellent textural characteristics such as high surface area, large pore volume and uniform pore size distribution. The amount of CuO nanoparticles in the nanochannels of the nanoporous carbon could be controlled by simply varying the Si/Cu molar ratio of the mesoporous silica template. Morphological characterization by SEM and TEM reveals that high-quality CuO nanoparticles are distributed homogeneously within the nanoporous carbon framework. The supercapacitance behavior of the CuO-loaded nanoporous carbons was investigated. The material with a small amount of CuO in the mesochannels and high surface area affords a maximum specific capacitance of 300 F g^-1 at a 20 mV s^-1 scan rate in an aqueous electrolyte solution. A supercapacitor containing the CuO-loaded nanoporous carbon is highly stable and exhibits a long cycle life with 91% specific capacitance retained after 1000 cycles.     

Direct template synthesis of mesoporous carbon and its application to supercapacitor electrodes

A direct templating method which is facile, inexpensive and suitable for the large scale production of mesoporous carbon is reported herein. A meso-structure surfactant/silicate template was made in a solution phase and resorcinol-formaldehyde as a carbon precursor was incorporated into the template solution. After aging, carbonization and hydrofluoric acid (HF) etching, mesoporous carbon was obtained. Using X-ray diffraction, scanning and transmission electron microscopy and nitrogen sorption, the synthesis mechanism of the mesoporous carbon was elucidated. According to the small angle X-ray scattering measurements, the surface became smoother after the removal of the silica, indicating that the silica was mostly located at the pore surface of the carbon. Also, the calculation of the pore volume demonstrated that the silica was transferred into the pores of the carbon without structural collapse during HF etching. When the prepared mesoporous carbon was applied to a supercapacitor electrode, the rectangular shape of the cyclic voltammogram was less collapsed, even at a high scan rate, which is indicative of its high rate capability. This was due to the low resistance of the electrolyte in the pores (3.8 Ω cm²), which was smaller than that of conventional activated carbon electrodes and even comparable to that of ordered mesoporous carbon electrodes. This improved performance was probably due to the well developed mesoporosity and high pore connectivity of the prepared mesoporous carbon.     

Facile synthesis of porous carbon nitride spheres with hierarchical three-dimensional mesostructures for CO<Subscript>2</Subscript> capture

Porous carbon nitride (CN) spheres with partially crystalline frameworks have been successfully synthesized via a nanocasting approach by using spherical mesoporous cellular silica foams (MCFs) as a hard template, and ethylenediamine and carbon tetrachloride as precursors. The resulting spherical CN materials have uniform diameters of ca. 4 μm, hierarchical three-dimensional (3-D) mesostructures with small and large mesopores with pore diameters centered at ca. 4.0 and 43 nm, respectively, a relatively high BET surface area of ∼550 m²/g, and a pore volume of 0.90 cm³/g. High-resolution transmission electron microscope (HRTEM) images, wide-angle X-ray diffraction (XRD) patterns, and Raman spectra demonstrate that the porous CN material has a partly graphitized structure. In addition, elemental analyses, X-ray photoelectron spectra (XPS), Fourier transform infrared spectra (FT-IR), and CO₂ temperature-programmed desorption (CO₂-TPD) show that the material has a high nitrogen content (17.8 wt%) with nitrogen-containing groups and abundant basic sites. The hierarchical porous CN spheres have excellent CO₂ capture properties with a capacity of 2.90 mmol/g at 25 °C and 0.97 mmol/g at 75 °C, superior to those of the pure carbon materials with analogous mesostructures. This can be mainly attributed to the abundant nitrogen-containing basic groups, hierarchical mesostructure, relatively high BET surface area and stable framework. Furthermore, the presence of a large number of micropores and small mesopores also enhance the CO₂ capture performance, owing to the capillary condensation effect.     

Synthesis of polyaniline-coated ordered mesoporous carbon and its enhanced electrochemical properties

Pore surface of ordered mesoporous carbon (OMC) was coated with a thin layer of polyaniline by chemical polymerization of aniline monomers. Structure characterizations, such as N₂ adsorption analysis, small angle X-ray diffraction and transmission electron microscopy, demonstrate that polyaniline is well distributed on the pore surface of OMC. As evidenced by constant current charge–discharge test, specific capacitance of polyaniline-coated ordered mesoporous carbon (PCOMC) reaches as high as 602.5 F/g, which is much higher than that of OMC, due to the incorporation of polyaniline onto the pore surface of OMC. However, the capacitive behavior deteriorated somewhat due to the narrowed pore size and extra faradiac reactions caused by the incorporation of polyaniline.