Huixia Feng

Nitrogen and sulfur co-doped ordered mesoporous carbon with enhanced electrochemical capacitance performance

Doping ordered mesoporous carbon with electron-donating nitrogen and sulfur heteroatoms is a promising strategy to enhance its electrochemical performance. Here we demonstrate the successful fabrication of nitrogen and sulfur co-doped ordered mesoporous carbon (NSOMC) materials with high specific surface areas (978–1021 m2 g−1), large pore volumes (1.10–1.20 cm3 g−1), highly-ordered pore structures and controlled dopant contents (10.0–4.8 at.% for nitrogen and 1.7–2.6 at.% for sulfur) using the oligomer of pyrrole as the precursor and sulphuric acid as the catalyst and sulfur source. NSOMC materials exhibit enhanced electrochemical double-layer capacitance (EDLC) performances due to their improved surface activity and conductivity compared with pure carbon CMK-3. The fabrication of nitrogen and sulfur co-doped ordered mesoporous carbon with enhanced electrochemical capacitance performance provides a viable route to promote its applications in electronic devices.

Synthesis of nitrogen- and sulfur-codoped 3D cubic-ordered mesoporous carbon with superior performance in supercapacitors.

In this contribution, nitrogen- and sulfur-codoped 3D cubic-ordered mesoporous carbon (KNOMC) materials with controlled dopant content (10.0-4.6 atom % for nitrogen and 0.94-0.75 atom % for sulfur) are presented, using KIT-6 as the template and pyrrole as the precursor, and its supercapacitive behavior is also investigated. The presented materials exhibit excellent supercapacitive performance by combining electrical double-layer capacitance and pseudocapacitance as well as the enhanced wettability and improved conductivity generated from the incorporation of nitrogen and sulfur into the framework of carbon materials. The specific capacitance of the presented materials reaches 320 F g(-1) at a current density of 1 A g(-1), which is significantly larger than that of the pristine-ordered mesoporous carbon reported in the literature and can even compete with some metal oxides and conducting polymers.

Utilization of waste phosphogypsum to prepare hydroxyapatite nanoparticles and its application towards removal of fluoride from aqueous solution

In the present study, waste phosphogypsum (PG) was utilized firstly to prepare hydroxyapatite nanoparticles (nHAp) via microwave irradiation technology. The nHAp derived from PG exhibited a hexagonal structure with the particle size about 20 nm × 60 nm and high purity. Meanwhile, the adsorption behaviour of fluoride onto the nHAp derived from PG was investigated to evaluate the potential application of this material for the treatment of the wastewater polluted with fluoride. The results indicate that the nHAp derived from PG can be used as an efficient adsorbent for the removal of fluoride from aqueous solution. The maximum adsorption capacities calculated from Langmuir-Freundlich model were 19.742, 26.108, 36.914 and 40.818 mg F(-)/g nHAp for 298, 308, 318 and 328 K, respectively. The pseudo-second order kinetic model was found to provide the best correlation of the used experimental data compared to the pseudo-first order and the adsorption isotherm could be well defined by Langmuir-Freundlich equation. The adsorption mechanism investigation shows that electrostatic interaction and hydrogen bond are the main driving force for fluoride uptake onto nHAp derived from waste PG.

Robust and Superhydrophobic Surface Modification by a “Paint + Adhesive” Method: Applications in Self-Cleaning after Oil Contamination and Oil–Water Separation

Conventional superhydrophobic surfaces have always depended on expensive, sophisticated, and fragile roughness structures. Therefore, poor robustness has turned into the bottleneck for large-scale industrial applications of the superhydrophobic surfaces. To handle this problem, a superhydrophobic surface with firm robustness urgently needs to be developed. In this work, we created a versatile strategy to fabricate robust, self-cleaning, and superhydrophobic surfaces for both soft and hard substrates. We created an ethanol based suspension of perfluorooctyltriethoxysilane-mdodified calcium carbonate nanoparticles which can be sprayed onto both hard and soft substrates to form superhydrophobic surfaces. For all kinds of substrates, spray adhesive was directly coated onto abluent substrate surfaces to promote the robustness. These superhydrophobic surfaces showed remarkable robustness against knife scratch and sandpaper abrasion, while retaining its superhydrophobicity even after 30 abrasion cycles with sandpaper. What is more, the superhydrophobic surfaces have shown promising potential applications in self-cleaning and oil-water separation. The surfaces retained their self-cleaning property even immersed in oil. In addition to oil-water separation, the water contents in oil after separation of various mixtures were all below 150 ppm, and for toluene even as low as 55 ppm. Furthermore, the as-prepared device for oil-water separation could be cycled 6 times and still retained excellent oil-water separation efficiency.

Preparation and properties of PAn/ATTP/PE conductive composites

Polyaniline/Attapugite/ PE(PAn-ATTP/PE)composites containing particles with core-shell structure were obtained via the two-step blending processs. The experimental condition is as follows: Organo-attapulgite and PAn was obtained by modifying attapulgite with laury benzenesulfonic acid sodium salt and, then added to PE. The electrical conductivity, structure and properties of the composites were studied. Under the function of shear stress, core-shell structure particles with ATTP as the core and PAn as the shell were formed in the composites. The structure of PAn-ATTP/PE composites were characterized by FTIR,XRD,SEM, etc, respectively. The effects of concentration of doping agent on the conductivity and mechanical property of the composites were investigated. The mechanical properties and impact fracture surface of the ternary composites were studied by means of the tensile tester, SEM, etc. The results show that polyaniline encapsulated ATTP enhances the strength of the PE. And the conductivity of PAn-ATTP/PE composites of is improved effectively when polyaniline encapsulated ATTP is added. The composite have good conductivity when 10% polyaniline encapsulated ATTP is added.

Facile synthesis of graphene sheets from fluorinated graphite

One of the problems with the chemical exfoliation of graphite to graphene via oxidation and reduction, is the excessive oxidation of graphite and incomplete reduction of graphene oxide, which introduce many defects and unnecessary oxygen-containing groups into the graphene sheets. Therefore, it is difficult to create high quality graphene sheets with few defects on a large scale by chemical exfoliation. Here, a simple and convenient method is developed to prepare graphene with a little fluorine by ultrasonicating fluorinated graphite in hydrazine hydrate. For comparison, reduced graphene oxide (RGO) was also prepared by Hummers method. The results showed that thin and flat graphene prepared from fluorinated graphite has a monocrystalline structure, while RGO presents turbostratic stacking. Moreover, the thermal stability and electrical conductivity of the as-prepared graphene sheets (GS) are much higher than those of the RGO sheets.

Preparation of Functionalized Magnetic Silica Nanospheres for the Cellulase Immobilization

Cellulase was immobilized on functionalized magnetic silica nanospheres using glutaraldehyde as a cross-linking agent. The morphologies, structures and magnetic properties of this immobilized cellulase were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential thermal analysis and vibrating sample magnetometry. The properties of immobilized cellulase were investigated, including the amount of immobilized cellulase and its relative activity, stability and reusability. The results indicated that immobilized cellulase exhibited better resistance to high temperature and pH inactivation in comparison to free cellulase. Moreover, immobilized cellulase with and without cross-linking agent were investigated and the former had greater amount of immobilized cellulase and better operational stability. The amount of immobilized cellulase with the cross-linking agent was 92 mg/g support. Furthermore, the activity of the immobilized cellulase was still 85.5% of the initial activity after 10 continuous uses, demonstrating the potential of this immobilized cellulase for large-scale biofuel production.

Removal of methylene blue from aqueous solution by a carbon-microsilica composite adsorbent

Microsilica, one kind of industrial solid waste material, was utilized firstly to prepare a carbon-microsilica composite adsorbent (CMS). The prepared adsorbent was characterized with XPS, SEM and Gas sorption experiments. The results indicated the SO3H groups, which are very effective in capturing cationic organic dye, were introduced onto the surface of CMS; the Brunauer-Emmett-Teller (BET) surface area (SBET) and total pore volume (Vtotal) of CMS reach 51m2/g and 0.045 cm3/g, respectively. Meanwhile, the possibility of the utilization of the adsorbent for removal of methylene blue (MB) from aqueous solution was investigated. The effect of pH, contact time and initial MB concentration for MB removal were studied. Equilibrium data were modeled using the Langmuir, Freundlich and Dubinin-Radushkevich equations to describe the equilibrium isotherms. It was found that data fit to the Langmuir equation better than the Freundlich equation. Maximum monolayer adsorption capacity was calculated at different temperatures (298, 308, and 318 K) reach 251.81, 283.76 and 309.70 mg/g, respectively. It was observed that adsorption kinetics obeys the pseudo-first-order equation.

Synthesis of mesoporous silica with different pore sizes for cellulase immobilization: pure physical adsorption

To discuss the physical adsorption mechanism of the adsorption process of cellulase, a commercial enzyme cocktail sourced from Acremonium was immobilized in mesoporous silica with various pore sizes by pure physical adsorption in this study. Mesoporous silica materials with 17.6 nm and 3.8 nm pore sizes (hereafter referred to as MS-17.6 nm and MS-3.8 nm, respectively) were synthesized in the manner of a seeded-growth method. Other available mesoporous silica materials denoted as H-32 and diatomite were also used as sorbents. Then, the sorbents were characterized via small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), the Barrett–Emmett–Teller (BET) method and the Barrett–Joyner–Halenda (BJH) method to confirm their mesostructure. Furthermore, the adsorption abilities of different sorbents and enzymatic activities of immobilized cellulase were studied. The adsorption amounts exhibited a clear correlation with the pore size of the sorbents; i.e., the adsorption amount of MS-17.6 nm (410 mg g−1) with the pore size similar to the long axes of cellulase molecules was higher than that of MS-3.8 nm (315 mg g−1) with the pore size approximated to the short axes of cellulase (which was realized at 50 °C). Besides, the adsorption behavior of diatomite (with a pore size of about 200 nm) revealed a periodicity because the pore size was significantly larger than cellulase molecules. Moreover, the pore size was suggested to be a critical factor for the enzymatic activity of cellulase. When the average pore size of MS-3.8 nm just matched the short axes of cellulase molecules, immobilized cellulase preserved the active sites of cellulase intactly and showed the best activity (i.e. 63.3% of free cellulase activity at 50 °C). Consequently, the pore size of the sorbents had a significant influence on cellulase immobilization.

Convenient synthesis and electrochemical performance investigation of nano-sized LiMn2O4

Nano-sized LiMn2O4 materials are synthesized via a simple one-step solid-state reaction using lithium acetate and lithium oxalate as lithium sources, respectively. The physical and electrochemical properties of LiMn2O4 materials are investigated by X-ray diffraction, scanning electron microscopy and electrochemical measurements. The results show that both of the as-prepared materials are pure nano-sized LiMn2O4 with narrow particle size distribution. Compared with lithium oxalate, lithium acetate is propitious to improve the crystallinity and size distribution of nano-sized LiMn2O4. Besides, LiMn2O4 synthesized from lithium acetate shows low resistance, good ability to inhibit Mn3+ dissolution, long cycle life and excellent rate property. Finally, the adverse effect of nano-sized LiMn2O4, which has increased contact area between acid-containing electrolyte and LiMn2O4 cathode electrode to aggravate dissolution and corrosion behavior, is treated by Li2CO3 additive in electrolyte. Results show that electrochemical performance of nano-sized LiMn2O4 is improved, due to the fact that Li2CO3 additive can not only consume HF and other Lewis acid in the commonly used LiPF6-based electrolyte, but also decrease interfacial impedance to promote the migration of Li+ ions through cathode surface film.