A facile synthesis of bimodal mesoporous silica and its replication for bimodal mesoporous carbon

Bimodal mesoporous silica material composed of 30-40 nm sized nanoparticles with 3.5 nm sized three-dimensionally interconnected mesopores was synthesized under neutral conditions using sodium silicate as a silica source. Using the bimodal mesoporous silica as a template, bimodal mesoporous carbon having 4 nm sized framework mesopores and approximately 30 nm sized textural pores was synthesized.     

Synthesis and characterization of mesoporous nickel oxide for electrochemical capacitor

A mesoporous electrochemical active material NiO with face center cubic structure has been synthesized using supramolecular as template and urea as hydrolysis-controlling agent. The synthesized product was characterized physically by thermogravimetric analysis, X-ray diffraction, transmission electron microscopy, and Brunauer–Emmett–Teller-specific surface area measurement. Electrochemical characterization was performed using cyclic voltammetry and chronopotentiometry in 6 mol/l KOH aqueous solution electrolyte. A specific capacitance of approximately 327 F/g was obtained by annealing the sample at 350 °C. To get a better understanding of the effect of supramolecular template on improving the structure property and electrochemical performance, a compared experiment was also carried out in this work.     

Electrical double-layer capacitor performance of nitrogen-doped ordered mesoporous carbon prepared by nanotemplating method

In this work, the electrical double-layer capacitive properties of nitrogen-doped ordered mesoporous carbons (N-OMCs) were investigated. Ordered mesoporous carbons (OMCs) with 3D body-centered Ia3d structure has been prepared by KIT-6 mesoporous silica as a hard template with aniline for N-OMC and sucrose for Su-OMC as a carbon precursor. Using the different carbon precursor, moderate amounts of nitrogen atoms could be doped to the OMC structures. The obtained materials were characterized by powder X-ray diffraction (XRD), nitrogen adsorption isotherms at 77 K, elemental analysis, and X-ray photoelectron spectroscopy (XPS). Prepared OMCs had mesopore properties such as a high surface area with narrow pore-size distribution. From cyclic voltammograms (CVs) test, N-OMC compared to Su-OMC exhibit higher capacitance and fast charge/discharge characteristics, which results from their pseudo-capacitive effect of incorporated nitrogen atoms. It was thought that N-OMC prepared by the nanotemplating method with KIT-6 and aniline were suitable electrode materials for electrical double-layer capacitors.     

Synthesis of mesoporous carbon aerogels based on metal-containing ionic liquid and its application for electrochemical capacitors

Journal of Solid State Electrochemistry - Mesoporous carbon aerogels were prepared by sol-gel polycondensation of resorcinol and formaldehyde through ionic liquid/metal ions synergistic effect. The...     

The formation of mesoporous TiO2 spheres via a facile chemical process

The mesoporous TiO(2) solid and hollow spheres have been synthesized via a controllable and simple chemical route. Structural characterization indicates that these TiO(2) mesoporous spheres after calcined at 500 degrees C have an obvious mesoporous structure with the diameters of 200-300 nm for solid spheres and 200-500 nm for hollow spheres. The average pore sizes and BET surface areas of the mesoporous TiO(2) solid and hollow spheres are 6.8, 7.0 nm and 162, 90 m(2)/g, respectively. Optical adsorption investigation shows that TiO(2) solid and hollow spheres possess a direct band gap structure with the optical band gap of 3.68 and 3.75 eV, respectively. A possible formation mechanism for TiO(2) solid and hollow spheres is discussed.     

Preparation of hexagonal nanoporous nickel hydroxide film and its application for electrochemical capacitor

Nanoporous nickel hydroxide film has been successfully electrodeposited on titanium substrate from nickel nitrate dissolved in the aqueous domains of the hexagonal lyotropic liquid crystalline phase of Brij 56. Low-angle X-ray diffraction (XRD), transmission electron microscopy (TEM), and atomic force microscopy (AFM) studies show that the film has a regular nanostructure consisting of a hexagonal array of cylindrical pores with a repeat center-to-center spacing of about 7 nm. Preliminary electrochemical studies are carried out using cyclic voltammetry (CV) and chronopotentiometry technology. A maximum specific capacitance of 578 F g⁻¹ could be achieved for the nanoporous Ni(OH)₂ film electrode, suggesting its potential application in electrochemical capacitors.     

Synthesis of micro- and mesoporous carbon spheres for supercapacitor electrode

Micro- and mesoporous carbon spheres (MMCSs) are synthesized by the polymerization of colloidal silica-entrapped resorcinol/formaldehyde in the presence of ammonia as catalyst, followed by carbonization, sodium hydroxide (NaOH) etching to remove silica template, and potassium hydroxide (KOH) activation. The morphology and microstructure are characterized by scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption–desorption. The results show that a typical sample (denoted as MMCS-3) unites the characteristics of regular spherical shape (uniform diameters of 500 nm), high specific surface area (1,620 m² g^?1), large pore volume (1.037 cm³ g^?1), and combined micropores and mesopores (11.0 nm), which endows MMCS-3 good electrochemical performance. MMCS-3 as supercapacitor electrode shows a specific capacitance of 314 F g^?1 under a current density of 0.5 A g^?1 and low internal resistance of 0.2 Ω in 6 M KOH aqueous solution. The electrochemical capacitance still retains 198 F g^?1 at a high current density of 10 A g^?1. After 500 cycle numbers of galvanostatic charge/discharge at 0.5 A g^?1, MMCS-3 electrode still remains the specific capacitance of 301 F g^?1 with the retention of 96 %. This study highlights the potential of well-designed MMCSs as electrodes for widespread supercapacitor applications.     

Pore-expansion of monodisperse mesoporous silica spheres by a novel surfactant exchange method

By adapting a novel surfactant exchange method, in which surfactants inside mesopores are completely exchanged by surfactants with longer alkyl chain lengths, pore-expansion of monodisperse mesoporous silica spheres (MMSS) with radially ordered hexagonal regularity was attained while retaining spherical morphology and high monodispersity.     

Development of electrochemical performances of carbon black obtained by the surface organosilicon-modified method

Carbon black (CB) was simply modified by tert-butylchlorodimethylsilane (TBDMCl) to form the–C–OSiR and–C–OOSiR structures on the surface of CB. The formation of–C–OSiR and–C–OOSiR structures on CB was verified by FTIR and XRD measurements. The modified carbon black (MCB) has relative high electrochemical performance, which was determined by electrochemical studies. The first charging capacity of MCB is at 343 mAh g^–1 and the conductivity of MCB is at 148.1 Sm^–1 which is similar to that of CB 155.2 Sm^–1. These results indicate that application of the obtained MCB will be promising for lithium anode materials. Meanwhile, these results can also suggest solving the overproduction problem of CB in China.     

Preparation of polyaniline‐coated mesoporous carbon and its enhanced electrochemical properties

Polyaniline/MC (mesoporous carbon) composite was synthesized by in situ chemical polymerization method and was used as a new electrode material for supercapacitor. The composite was characterized by N₂ adsorption and scanning electron microscope. The electrochemical capacitance performance of the composite was investigated by cyclic voltammetry (CV) and galvanostatic charge–discharge tests with a three‐electrode system in a 10 wt% H₂SO₄ solution. The polyaniline/MC composite electrode shows much higher specific capacitance than pure MC electrode, which is attributed to the incorporation of polyaniline onto the pore surface of MC. Copyright © 2009 John Wiley & Sons, Ltd.     

Novel and facile method for the preparation of monodispersed titania hollow spheres

The fabrication of monodispersed hollow spheres in varying sizes and shapes is very interesting and has a lot of potential applications. This paper provides a very simple route to preparing hollow titania spheres using polystyrene (PS) as a template. In this approach, the titania shells were first formed and the PS cores were dissolved subsequently, even synchronously, in the same medium; neither an additional dissolution nor a calcination process was needed to remove the PS cores. Transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and Barret-Emmet-Teller measurements were used to characterize the monodispersed hollow titania spheres. A possible formation mechanism of the hollow spheres was proposed.     

A facile and one-pot electrochemical method for the synthesis of a new anthraquinonethioether

The reaction of electrochemically generated anthradiquinone as a Michael acceptor with 2-mercaptobenzothiazole and 2- mercaptobenzoxazole,as nucleophiles in ethanol/water mixtures has been studied by means of cyclic voltammetry.Our voltammetric data indicate that produced anthradiquinone participates in Michael addition reaction with nucleophiles and via an ECEC mechanism converts to the new anthraquinonethioether derivatives.Based on an EC mechanism,the observed homogeneous rate constant of the Michael reaction of anthradiquinone with nucleophiles were estimated by comparing the experimental cyclic voltammograms with the digital simulated results.     

Highly crystalline and conductive nitrogen-doped mesoporous carbon with graphitic walls and its electrochemical performance

We present a rational and simple methodology to fabricate highly conductive nitrogen-doped ordered mesoporous carbon with a graphitic wall structure by the simple adjustment of the carbonization temperature of mesoporous carbon nitride without the addition of any external nitrogen sources. By simply controlling the heat-treatment temperature, the structural order and intrinsic properties such as surface area, conductivity, and pore volume, and the nitrogen content of ordered graphitic mesoporous carbon can be controlled. Among the materials studied, the sample heat-treated at 1000 °C shows the highest conductivity, which is 32 times higher than that for the samples treated at 800 °C and retains the well-ordered mesoporous structure of the parent mesoporous carbon nitride and a reasonable amount of nitrogen in the graphitic framework. Since these materials exhibit high conductivity with the nitrogen atoms in the graphitic framework, we further demonstrate their use as a support for nanoparticle fabrication without the addition of any external stabilizing or size-controlling agent, as well as the anode electrode catalysts. Highly dispersed platinum nanoparticles with a size similar to that of the pore diameter of the support can be fabricated since the nitrogen atoms and the well-ordered porous structure in the mesoporous graphitic carbon framework act as a stabilizing and size-controlling agent, respectively. Furthermore the Pt-loaded, nitrogen-doped mesoporous graphitic carbon sample with a high conductivity shows much higher anodic electrocatalytic activity than the other materials used in the study.     

A facile method to prepare graphene-coat cotton and its application for lithium battery

The free-standing and binder-free electrode materials, cotton/graphene (CGN) composites were prepared via a simple “dipping and freeze-drying” process using raw cotton as the supporting body (platform) and graphene oxide (GO) as the suspension. Then the cotton/GO (CGO) composites were annealed at 1000 °C under an Ar flow conditions to obtain CGN composites. The results show that the CGN structure can protect the cotton framework and have better thermal stable property than the cotton alone. Galvanostatic charge–discharge tests demonstrated that the GO concentration had great effects on their electrochemical performances. The CGN (for the GO with 3 and 5 mg ml^?1) provide reversible discharge capacity of 160 mAh g^?1 after 100 cycles, which is about 1.5 times higher than that of the cotton alone (115 mAh g^?1 after 100 cycles). Excellent electrochemical properties of CGN can be ascribed to its controllable structure with more lithium ion storage sites, high electronic conductivity, and fast ion diffusion velocity. The results suggest that this work develops a simple, cheap, and suitable large-scale production method in the lithium-ion batteries.     

Overwhelming electrochemical oxygen reduction reaction of zinc-nitrogen-carbon from biomass resource chitosan via a facile carbon bath method

Developing high efficiency and low cost electrocatalysts is critical for the enhancement of oxygen reduction reaction (ORR), which is the fundamental for the development and commercialization of renewable energy conversion technology. Herein, zinc-nitrogen-carbon (Zn-N-C) was prepared by using biomass resource chitosan via a facile carbon bath method. The obtained Zn-N-C delivered a high specific surface area (794.7 cm²/g) together with pore volume (0.49 cm³/g). During the electrochemical evaluation of oxygen reduction reaction (ORR), Zn-N-C displayed high activity for ORR with an onset potential E₀ = 0.96 V_RHE and a half wave potential E_1/2 = 0.86 V_RHE, which were more positive than those of the commercial 20 wt% Pt/C benchmark catalyst (E₀ = 0.96 V_RHE and E_1/2 = 0.81 V_RHE). In addition, the Zn-N-C catalyst also had a better stability and methanol tolerance than those of the Pt/C catalyst.     

Preparation and electrochemical performance of activated carbon thin films with polyethylene oxide-salt addition for electrochemical capacitor applications

The effect of polymer–salt addition in the activated carbon electrode for electric double-layer capacitor (EDLC) has been investigated. A series of composite thin film electrode consisting of activated carbon, carbon black, polytetrafluoroethylene and polymer–salt complex (polyethyleneoxide–LiClO₄) with an appropriate weight ratio were prepared and examined their performance for EDLCs using 1 mol L⁻¹ LiClO₄ in ethylene carbonate:diethylcarbonate electrolyte solution. The electrochemical capacitance performances of these electrodes with different compositions were characterized by cyclic voltammetry, galvanostatic charge–discharge cycling, and AC impedance measurements. By comparison, the best results were obtained with a composite electrode rich in polymer–salt additive (132 F g⁻¹ at 100 mA g⁻¹ of galvanostatic experiment). In general, the polymer–salt-containing electrode had shown improved performance over activated carbon electrodes without polymer–salt at high current density.     

A facile electrochemical method for synthesis of new benzofuran derivatives

Electrooxidation of 3-substituted catechols has been studied in the presence of dimedone in aqueous solution, using cyclic voltammetry and controlled-potential coulometry. The results indicate that the quinones derived from catechols participate in Michael addition reactions with dimedone to form the corresponding benzofuran derivatives (6a-c). We propose a mechanism for the electrode process. The efficient electrochemical synthesis of 6a-c has been performed at carbon rod electrodes in an undivided cell using a constant current.     

Synthesis and electrochemical characterization of carbon nanotubes decorated with nickel nanoparticles for use as an electrochemical capacitor

Attachment of nickel nanoparticles on multiwalled carbon nanotubes (MWCNTs) was conducted to explore the influence of Ni loading on the electrochemical capacitance of MWCNT electrodes. A chemical impregnation leaded to homogeneously disperse Ni particles onto the surface of MWCNTs, and the Ni particles were found to be an average size of 30–50 nm. The capacitive behavior of the MWCNT electrodes was investigated in 6 M KOH, by using cyclic voltammetry (CV), charge–discharge cycling, and ac electrochemical impedance spectroscopy. CV measurements showed that the Faradaic current was found to increase with the Ni coverage, indicating that the presence of Ni would enhance the pseudocapacitance through the redox process. Equivalent circuit analysis indicated that both of electrical connection and charge transfer resistances accounted for the major proportion of the overall resistance and were found to decrease with the amount of nickel. A linearity relationship between the total capacitance and the Ni population reflected that each Ni particle exhibits an identical electrochemical activity in enhancing the electrochemical capacitance. The overall electrochemical capacitance (including double layer capacitance and pseudocapacitance) of Ni-MWCNT electrode can reach a maximum of 210 F/g over 500 cycles.     

Biomass-derived activated carbon materials with plentiful heteroatoms for high-performance electrochemical capacitor electrodes

Activated carbons for electrochemical capacitor electrodes are prepared from soyabean using chemical activation with KOH. The pore size is easily controllable by changing the mass ratio between KOH and carbonized product. The as-prepared materials possess a large specific surface area, unique structure, well- developed hierarchical porosity and plentiful heteroatoms(mainly O and N). Thus resulted in its high specific capacitance,good rate capacity and cycling stability. Moreover, attributing to worldwide availability, renewable nature and low-cost, activated carbon prepared from soyabean has a good potential in energy conversion and storage devices.