Ningya Yu

Structural evolution and electrocatalytic application of nitrogen-doped carbon shells synthesized by pyrolysis of near-monodisperse polyaniline nanospheres

Near-monodisperse polyaniline (PANI) colloids with controlled particle size (55–90 nm) were prepared by disperse polymerization of aniline in the presence of a steric stabilizer: polyvinylpyrrolidone (PVP). The silica-coated PANI colloidal nanospheres were further subjected to pyrolysis treatment at different temperatures (400–950 °C) to fabricate the nitrogen-doped carbon shells (NCSs). The NCSs so obtained were found to have controllable morphologies and pore sizes (13.4–23.2 nm). A possible structural evolution of the PANI colloids during pyrolysis process is proposed based on results obtained from a variety of characterization techniques. Upon loading Pt metal, the supported Pt/NCS catalysts were found to exhibit superior catalytic performance during electrooxidation of methanol, surpassing that of the conventional Pt/Vulcan XC-72 catalyst. The effects of nitrogen doping and carbon shell structure on Pt dispersion, tolerance of CO poisoning, and electrochemical properties are also examined and discussed.

Fabrication and electrocatalytic performance of highly stable and active platinum nanoparticles supported on nitrogen-doped ordered mesoporous carbons for oxygen reduction reaction

A facile synthesis route for the preparation of N-doped ordered mesoporous carbons (NOMCs) containing well-dispersed, highly stable Pt nanoparticles (NPs) is reported. The synthesis of these mesostructured Pt-NOMC materials invokes pyrolysis of co-fed carbon sources and Pt precursors in 3-[2-(2-aminoethylamino)ethylamino]propyl-functionalized mesoporous SBA-15 silicas, which served simultaneously as N sources and hard templates. It was found that the dispersion of Pt NPs increases with increasing N content in the Pt-NOMC nanocomposites, leading to higher electrocatalytic activity during oxygen reduction reaction (ORR) and methanol-tolerant stability compared to typical commercial electrocatalyst (Pt/XC-72). The superior electrochemical performances observed for the synthesized Pt-NOMCs have been attributed to the dispersion and unique nanostructure of Pt NPs particularly in the presence of pyridinic-N atoms in the mesoporous carbon supports.

New insights into Keggin-type 12-tungstophosphoric acid from 31P MAS NMR analysis of absorbed trimethylphosphine oxide and DFT calculations.

The acid and transport properties of the anhydrous Keggin-type 12-tungstophosphoric acid (H(3)PW(12)O(40); HPW) have been studied by solid-state (31)P magic-angle spinning NMR of absorbed trimethylphosphine oxide (TMPO) in conjunction with DFT calculations. Accordingly, (31)P NMR resonances arising from various protonated complexes, such as TMPOH(+) and (TMPO)(2)H(+) adducts, could be unambiguously identified. It was found that thermal pretreatment of the sample at elevated temperatures (≥423 K) is a prerequisite for ensuring complete penetration of the TMPO guest probe molecule into HPW particles. Transport of the TMPO absorbate into the matrix of the HPW adsorbent was found to invoke a desorption/absorption process associated with the (TMPO)(2)H(+) adducts. Consequently, three types of protonic acid sites with distinct superacid strengths, which correspond to (31)P chemical shifts of 92.1, 89.4, and 87.7 ppm, were observed for HPW samples loaded with less than three molecules of TMPO per Keggin unit. Together with detailed DFT calculations, these results support the scenario that the TMPOH(+) complexes are associated with protons located at three different terminal oxygen (O(d)) sites of the PW(12)O(40)(3-) polyanions. Upon increasing the TMPO loading to >3.0 molecules per Keggin unit, abrupt decreases in acid strength and the corresponding structural variations were attributed to the change in secondary structure of the pseudoliquid phase of HPW in the presence of excessive guest absorbate.

Highly nitrogen-doped mesoscopic carbons as efficient metal-free electrocatalysts for oxygen reduction reactions

A facile method was developed for the synthesis of metal-free, highly N-doped (>7 wt%) mesoscopic carbons (NMCs), which were fabricated by first preparing carbon–silicate (C–Si) composites by co-condensation method using a melamine-formaldehyde resin oligomer as the primary nitrogen and carbon source, and P123 triblock copolymer surfactant and sodium silicate as the soft and hard template, respectively, under microwave irradiation conditions, followed by carbonization and silica-template removal. The NMCs were found to exhibit superior electrocatalytic activity, long-term stability, and excellent tolerance over methanol crossover effect. Such NMCs derived from organic–inorganic hybrids assisted by microwave heating not only possess high surface areas and active quaternary and pyridinic-N species that are favourable for ORR, as verified by DFT calculations, but also render large-scale production and practical applications as cost-effective electrode materials.

Famotidine drug adsorption on carboxylic acid functionalized ordered SBA-15 mesoporous silica

A series of pure silica SBA-15 and carboxylic acid modified SBA-15 materials were prepared. Then the adsorption properties of famotidine on these materials were investigated. It was found that the adsorption of famotidine depended strongly on the 2-cyanoethyltriethoxysilane (CETES) content in total silica source and the adsorption experimental conditions, such as pH value, solvent nature and famotidine concentration and so on. Under the adsorption conditions of famotidine concentration of 2 mg ml −1 and the adsorption mixture pH at 7.0, an adsorbed famotidine content as high as 152 mg g −1 was observed in the sample prepared with 20 mol. % CETES content in total silica source. Moreover, the adsorption isotherms of famotidine on carboxylic acid functionalized SBA-15 materials were fitted with the Langmuir equation.

Adsorption of lysozyme on spherical mesoporous carbons (SMCs) replicated from colloidal silica arrays by chemical vapor deposition.

Spherical mesoporous carbons (SMC) were successfully synthesized by chemical vapor deposition (CVD) method using ferrocene as the carbon precursor and colloidal silica arrays as templates. The structure and textural properties of SMCs were characterized by a variety of techniques. Accordingly, a possible formation mechanism was proposed. These SMC materials were found to exhibit extraordinary high adsorption capacities (ca. 100mumol/g) for lysozyme (Lz) in solution with a pH value of 11 close to its isoelectric point. The correlations between the textural parameters of SMCs with Lz adsorption capacity were also investigated along with discussion on its adsorption kinetics and stability.

Direct Synthesis of Mesoporous Organosilica from Sodium Silicate and Organotrialkoxysilane

Using sodium silicate and organotrialkoxysilane as the silica source and nonionic polyethylene oxide C(11)similar to(15)-H(23)similar to(31) (CH2CH2O)(9)H (AEO(9)) as the structure-directing agent, MSU-type mesoporous organosilica materials that include methyl, 3-aminopropyl group were synthesized. The obtained materials were characterized by XRD, FT-IR, SEM, HRTEM, Si-29 CP MAS NMR, N-2-physisorption and bulk elemental analysis. The effects of synthetic temperature, organotrialkoxysilane content in the precursor and Si/surfactant molar composition in CH3-MSU system were investigated carefully.

Preparation of hydrothermally stable mercapto-functionalized mesoporous silicas via assembly of nanoclustered zeolite Y seeds and 3-mercaptopropyltrimethoxysilane

The preparation of a series of 3-mercaptopropyl-functionalized mesoporous silicas of MSU was achieved by a one-pot synthesis process involving the assembly of nanoclustered zeolite Y seeds and 3-mercaptopropyltrimethoxysilane (MPTMS) in the presence of Brij 76 (C18EO20). The effect of synthetic parameters, such as reaction temperature, MPTMS content and pH value of reaction mixture on the properties of materials was investigated systemically. It was found that the sample with 10% organo-functionalization of the framework silicon sites prepared at 348 K and pH 6.0 retained both its structural integrity and functionalities after the treatment in water at 373 K for 150 h. Enhanced hydrothermal stability of the materials in this study was greatly attributed to the successful introduction of zeolite Y seeds into the mesostructured framework walls.

One-pot synthesis of ionic liquid functionalized SBA-15 mesoporous silicas

1 -Methyl-3-n-propyl-imidazolium chloride (MPlmC1) and N-propyl-pyridinium chloride (PPyCl) ionic liquid functionalized SBA-15 mesoporous materials were sucessfully synthesized through the co-condensation of tetraethoxysilane (TEOS) with 1-methyl-3-(triethoxysilyl propyl)-imidazolium chloride (MTESPImC1) and 3-(triethoxysilyl propyl)- pyridinium chloride (TESPPyCl) using E0 20 PO 70 EO 20 (Pluronic P123) as surfactant. These organic-inorganic hybrid materials may have potential applications in heterogeneous catalysis reactions.

Organic-inorganic hybrid mesoporous materials assembled from sodium silicate and organotrialkoxysilane

The MSU-typed mesoporous organosilica with organic methyl, vinyl, and phenyl functionals were prepared by using inexpensive sodium silicate and organotrialkoxysilane as the silica precursor and nonionic polyethyleneoxide AEO(9)[C11- H-15(23-31)(CH2CH2O)(9)H] as the structure-directing agent. The resultant materials were characterized by powder X-ray diffraction (XRD), N-2 sorptometry, high resolution transmission electron microscopy (HRTEM) and Si-29 CP MAS-NMR. The results indicated that addition of sodium fluorite reduced the possibility of organotrialkoxysilane with small organic group entering the framework walls of the mesostructures at neutral condition. Moreover, pore diameter of material increased upon the increase of pH value.