Preparation and characterization of Co-B flowers with mesoporous structure

Co-B flowers with mesoporous structure were first prepared via reduction of cobalt acetate by potassium borohydride in the presence of complexing agent ethylenediamine. The as-prepared Co-B flowers were characterized by Fourier transform infrared spectroscopy, X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, inductively coupled plasma atomic emission spectroscopy, X-ray photoelectron spectroscopy, N₂ adsorption-desorption, and magnetic performance test. The Co-B flowers exhibited enhanced coercivity, and weakened saturation magnetization and remanet magnetization as compared with the regular Co-B. During the hydrolysis of KBH₄, the Co-B flowers exhibited higher catalytic activity than the regular Co-B. It is attributed to the larger specific surface area and mesoporous channels. During the successive reactions, the conversion of KBH₄ over Co-B flowers was about 97%. The average H₂ generation rate of Co-B flowers was 4620 mL/min/g-catalyst in 1.5 wt% NaOH + 15 wt% KBH₄ solution, which may give a successive H₂ supply for a 748 W polymer electrolyte membrane fuel cell (PEMFC) at 100% H₂ utilization.     

Preparation of high nickel-containing MCM-41-type mesoporous silica via a modified direct synthesis method

A method with modifying tetraethyl orthosilicate (TEOS) with nickel species has been developed for the synthesis of mesoporous silica with high nickel content (11.8 wt.% of Ni or even higher). With the method, MCM-41-type materials were obtained with high BET surface area reaching 868 m²/g and pore volume up to 0.73 cm³/g. The materials were characterized by means of X-ray powder diffraction, transmission electron microscopy, energy dispersive X-ray spectroscopy, N₂ adsorption, Fourier transform infrared and X-ray photoelectron spectroscopy. Nickel species were incorporated into the silica frameworks. The mesostructures still remain after activation using H₂ at 773 K.     

Low-temperature and ambient-pressure synthesis of TiO2(B)

Nanocrystalline TiO₂(B) powder was obtained by the hydrolysis of an ionic liquid like titania precursor (the triethylammonium salt of hexafluorotitanate) induced by the addition of boric acid in the presence of dopamine. The entire synthetic procedure was carried out at ambient pressure and low temperature (85 °C). X-ray diffraction, high resolution transmission electron microscopy and selected area electron diffraction characterization techniques confirmed the formation of the TiO₂(B) phase. Moreover, Raman spectroscopy indicated that TiO₂(B) was the major component, although it also revealed the presence of anatase as a minor component (< 10%). The as-prepared material has a mesoporous architecture with high specific surface area (235 m² g^− 1).     

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.     

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.     

Highly mesoporous carbon with high capacitance from carbonization of phenol-formaldehyde resin

Porous carbon material with high surface area and highly mesoporous structure has been successfully prepared from phenol-formaldehyde resin by combining Polyethylene Glycol (PEG) and ZnCl₂ as activation agents. The as-prepared carbon material exhibits large specific double layer capacitance of 122 F g^− 1 at 120 mA g^− 1 in the electrolyte of 1 M Et₄NBF₄/PC, which is attributed to its high specific surface area and well-developed mesopores. Moreover, it can retain as high as 86.88% of its initial specific capacitance, when the specific current increases from 120 mA g^− 1 to 2 A g^− 1. It is also found that the energy density of this material still maintains up to 21.2 Wh kg^− 1 at the power density of 2400 W kg^− 1.     

Adsorption of methanol on mesoporous SBA-15

The adsorption of methanol on mesoporous SBA-15 has been studied by using Brunauer-Emmett-Teller (BET) surface area analysis, scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA). The BET surface area analysis shows decreases of the surface area from 387 to 383 m²/g, pore volume from 0.88 to 0.81 cm³/g and pore diameter from 9.07 to 8.4 nm after methanol adsorption. The appearance of strong IR bands at 2862 and 2964 cm^− 1 due to methyl (-CH₃) symmetric and asymmetric stretching demonstrate the presence of methanol and evidence of successful methanol adsorption. XPS results show increase of carbon and oxygen content on the surface of SBA-15. Thermogravimetric analysis shows that the methanol adsorbed on SBA-15 is stable up to a temperature of 265 °C and that the methanol adlayers decompose between 265 and 588 °C.     

An efficient chemical precipitation route to fabricate 3D flower-like CuO and 2D leaf-like CuO for degradation of methylene blue

A facile and eco-friendly way for fabrication of CuO is developed based on an one-step chemical precipitation route without calcination procedure or use of surfactant. The structure features of as-prepared CuO are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and N₂ adsorption-desorption experiment. X-ray diffraction analysis shows that CuO with particle size of 13.5–19.2 nm and crystallinity of 67.0–72.9% can be fabricated by the transformation of Cu(OH)₂ precursor at bath temperature above 50 °C. By adjusting the oil bath temperature and the content of ammonium hydroxide, we demonstrate a formation mechanism to control CuO to be 2D leaf-like structure with large specific surface area of 33.4 m²/g and pore volume of 0.226 cm³/g, or 3D flower-like ones with specific surface area of 7.45–18.7 m²/g and pore volume of 0.0249–0.0850 cm³/g. The catalytic performances of as-prepared CuO are evaluated by monitoring degradation of methylene blue in the presence of hydrogen peroxide. Almost 100% methylene blue degradation rate can be reached after reaction for 210 min on 3D flower-like CuO synthesized with 10 mL ammonia content in oil bath of 50 °C. The high activity can be correlated with the morphology and pore volume of CuO. The present synthetic strategy is an inexpensive and convenient way suitable for large-scale fabrication of copper oxides, which are potential catalysts for organic compounds degradation.     

Synthesis and characterization of ordered mesoporous silicon carbide with high specific surface area

Ordered mesoporous silicon carbide with a high specific surface area was prepared using poly(methlysilylene)ethynylene by utilizing mesoporous silica SBA-15 as a template which was etched off after pyrolysis in an argon atmosphere. The obtained sample is mainly composed of randomly oriented β-SiC crystallites, and it exhibits an ordered mesoporous structure, a high surface area of 511 m²/g, a large pore volume of 0.61 cm³/g, and narrow pore-size distributions of 4 nm. The rough surface and high order of the material that result from the strong interconnections of the SiC products are the main reasons for such high surface areas. The mesoporous ceramics have stability even after re-treatment at 900 °C for 2 h under an air atmosphere.     

Synthesis and characterization of CoS nanoparticles encapsulated in mesoporous aluminosilicate material by solid-state reaction

CoS nanoparticles (NPs) encapsulated in the mesoporous aluminosilicate material (AlMCM-41) were prepared by a novel technique with non-aqueous systems. The mechanical mixture of the CoCl₂ crystal with the AlMCM-41 was heated at 773 K, followed by the H₂S treatment at 373 K, resulting in the formation of cobalt sulphide nanoparticles (NPs) with an estimated size of 4 nm. Decreasing of the volumes of the pores and the specific surface area of the mesoporous material demonstrates that the guests are located in the channels (BET measurements). The final product (CoS/AlMCM-41) was characterized by transmission electron microscopy (TEM), UV-vis spectroscopy, X-ray diffraction (XRD) pattern, and inductively coupled plasma atomic emission spectroscopy (ICP-AES).     

Nanostructure SnO2 and supported Au catalysts: Synthesis,characterization, and catalytic oxidation of CO

Nanostructure tin dioxide (SnO₂) powders prepared by sol-gel dialytic processes using tin (IV) chloride and anhydrous alcohol as start materials, ammonia gas as catalyst of the formation of colloid solution and agent of removing Cl⁻, and by introducing dialytic processes to improve and accelerate the formation of gels. From the result of TG–DTA analyses, the dried samples were calcined at 673 K in air for 3 h. Tin dioxide nanoparticles were characterized by thermogravimetry and differential thermal analyses (TG–DTA), X-ray diffraction (XRD), nitrogen adsorption–desorption, X-ray photoelectron spectroscopy (XPS). The average particle size of the as-prepared tin dioxide was about 5 nm. The as-prepared SnO₂ possessed mesoporous structure and large surface area. The Au/SnO₂ catalysts for low-temperature CO oxidation were prepared by the deposition–precipitation method using as-prepared SnO₂ powders as the support. The Au/SnO₂ catalysts exhibited high catalytic activity for low-temperature CO oxidation. The nanostructure SnO₂ has promising applications in sensor, catalyst, catalytic support, mesoporous membranes, etc.     

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.     

Oxidative dehydrogenation of cyclohexane with Mg3(VO4)2 synthesized by the citrate process

Citric acid complexation under mild condition was proposed to prepare monophasic and well crystallized Mg₃(VO₄)₂ particle to be used as an active catalyst for the oxidative dehydrogenation of cyclohexane to cyclohexene. The catalyst prepared above was characterized by N₂-physisorption, X-ray diffraction, scanning electron microscopy, and thermal gravimetric analysis. The characterization results displayed that the Mg₃(VO₄)₂ particle was typically 100-160 nm and the specific surface area was 12.0-26.7 m²/g. Moreover, it showed that the purity and the structure of the catalyst were principally subjected to the calcination temperature and the amount of citric acid used in the sol-gel procedure. The Mg₃(VO₄)₂ catalyst calcined at 823 K for 6 h with a molar ratio of (Mg + V):citric acid = 1:1.2 exhibited the best catalytic performance with an excellent thermal stability.     

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.     

Transformation of microporous titanium glycolate nanorods into mesoporous anatase titania nanorods by hot water treatment

High surface area titanium glycolate microporous multi-faceted nanorods were synthesized from the reaction of titanium alkoxides (Ti(OEt)₄, Ti(O ⁱ Pr)₄, or Ti(O ⁿ Bu)₄) with ethylene glycol, using a sol–gel reflux method. The specific surface area of the as-synthesized titanium glycolate nanorods obtained from Ti(OEt)₄ is ~480 m²/g. A hot water treatment at 90 °C for 1 h transformed the titanium glycolate microporous nanorods into mesoporous anatase TiO₂ nanorods. The shape of the nanorods was conserved after hot water treatment and the microporous to mesoporous transformation took place without significant change in the surface area (477 m²/g). Micro Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, solid state NMR, and nitrogen adsorption/desorption were used to characterize the samples. As a demonstration of potential applications, the thus formed mesoporous anatase TiO₂ nanorods were tested for their photocatalytic efficiency in the degradation of crystal violet, and a photodegradation mechanism is proposed.     

Chemical vapor deposition of phase-rich WC thin films on silicon and carbon substrates

Chemical vapor deposition was used to deposit tungsten carbide from a mixture of WCl₆, H₂ and C₃H₈ at 750-1050 °C on silicon and carbon substrates. The phase composition of the films was correlated with substrate temperature, substrate position in the reactor, and total flow rates. X-ray diffraction and X-ray photoelectron spectroscopy were employed to investigate the surface and bulk properties of the thin films. Thick, adherent films of phase-rich hexagonal WC were deposited using 1.3 × 10³ Pa total pressure, 1050 °C substrate temperature, and reactant flow rates of H₂/C₃H₈/Ar/WCl₆ = 1.8 × 10^− 2/3.6 × 10^− 3/8.9 × 10^− 4/1.8 × 10^− 4 mol/min, where Ar is the carrier gas. The surface composition was oxygen and carbon rich as compared with the bulk.     

Fabrication of hollow mesoporous NiO hexagonal microspheres via hydrothermal process in ionic liquid

The novel NiO hexagonal hollow microspheres have been successfully prepared by annealing Ni(OH)₂, which was synthesized via an ionic liquid-assisted hydrothermal method. The samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), N₂ adsorption-desorption and Fourier transform infrared spectrometer (FTIR). The results show that the hollow NiO microstructures are self-organized by mesoporous cubic and hexagonal nanocrystals. The mesoporous structure possessed good thermal stability and high specific surface area (ca. 83 m²/g). The ionic liquid 1-butyl-3methylimidazolium tetrafluoroborate ([Bmim][BF₄]) was found to play a key role in controlling the morphology of NiO microstructures during the hydrothermal process. The special hollow mesoporous architectures will have potential applications in many fields, such as catalysts, absorbents, sensors, drug-delivery carriers, acoustic insulators and supercapacitors.     

Synthesis and characterization of nanofiber-structured Ba0.5Sr0.5Co0.8Fe0.2O3−δ perovskite oxide used as a cathode material for low-temperature solid oxide fuel cells

Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ (BSCF) was synthesized in two forms: as a powder (by the sol-gel combined citrate-EDTA complexing (CC-EDTA) method) and as nanofibers (by electrospinning). Both forms were sintered at 950 °C for 5 h in air before their morphology and structure were characterized by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and specific surface area analysis based on the BET theory. Moreover, the mass loss and heat flow of as-electrospun BSCF nanofibers were analyzed by differential thermal analysis (DTA) and thermogravimetric analysis (TG). The results showed that these materials had a perovskite oxide crystal structure. The CC-EDTA method yielded BSCF in powder form, with a particle size of 1-10 μm and a specific surface area of 1.0 m²/g. On the other hand, BSCF obtained by the electrospinning technique was in the form of highly porous nanofibers with diameters in the range of 100-200 nm and a specific surface area of 2.4 m²/g. To demonstrate the potential applications of BSCF as a cathode material in low-temperature solid oxide fuel cells (LT-SOFCs), the electrochemical properties of the samples were determined using electrochemical impedance spectroscopy (EIS). The area specific resistance (ASR) of the BSCF nanofiber cathode was determined to be 0.094 Ω cm² at 600 °C, whereas that of the BSCF powder cathode was 0.468 Ω cm² under similar conditions.     

High surface area carbonate apatite nanorod bundles: Surfactant-free sonochemical synthesis and drug loading and release properties

The design and synthesis of calcium phosphates (CPs) nanostructures with high specific surface areas are significant for drug delivery systems. Herein, we report a simple surfactant-free sonochemical synthesis of carbonate apatite (CAP) nanorod bundles with a high specific surface area (183.39 m² g⁻¹) using an aqueous solution of CaCl₂·2H₂O and (NH₄)₂HPO₄. The effects of experimental parameters including reactant species, pH value, calcium ion concentration, reaction time on the specific surface area of the product were investigated. The products were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The as-prepared CAP nanorod bundles were explored as the drug nanocarrier, which exhibited a sustained drug release behavior in simulated body fluid.