Liqin Dang

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.

Effect of Nd3+ doping on photocatalytic activity of TiO2 nanoparticles for water decomposition to hydrogen

Abstract The undoped TiO 2 and Nd 3+ -doped TiO 2 samples were prepared by the sol–gel method and characterized by X-ray diffraction, diffuse reflectance UV-visible spectroscopy, transmission electron microscopy, and N 2 adsorption. The correlation of the photocatalytic activity for hydrogen evolution with the phase composition, BET surface area, and light absorption intensity in the UV region was investigated. For the undoped TiO 2 sample, the particle size and agglomeration increased while the BET surface area and the light absorption intensity in the UV region decreased with increasing calcination temperature. The anatase to rutile phase transformation started at 600°C and completed at 800°C. The photocatalytic activity of undoped TiO 2 decreased with increasing calcination temperature, and the sample calcined at 600°C was the best because of the coexistence of a certain proportion of rutile/anatase mixed phase. For the Nd 3+ /TiO 2 samples, Nd 3+ doping inhibited the crystal phase transformation and the rutile phase appeared at 800°C. Moreover, Nd 3+ doping restrained the growth of grain size, improved the dispersivity of the particles, and raised BET surface area. The more the doping amount, the larger the BET surface area. As the calcination temperature increased, the decreasing extent of the light absorption intensity of Nd 3+ /TiO 2 in the UV region was lower than that of undoped TiO 2 . Nd 3+ doping raised the photocatalytic activity for hydrogen generation, and the optimum amount of Nd 3+ doping was 0.1%, at which the photocatalytic activity of Nd 3+ /TiO 2 was 3.5 times that of undoped TiO 2 .

Photocatalytic Degradation of Rhodamine B and Phenol by TiO2 Loaded on Mesoporous Graphitic Carbon

Abstract Mesoporous graphitic carbon with high surface area (298.2 m 2 /g) was fabricated at 950°C using monodisperse colloid SiO 2 with diameter of 26 nm as the template, styrene as the carbon precursor, and Ni as the catalyst. The obtained carbon material was characterized by powder X-ray diffraction, N 2 adsorption, thermogravimetric analysis, and transmission electron microscopy. The presence of Ni was crucial to the formation of graphitized mesoporous carbon. The TiO 2 /graphitic carbon composite was prepared by loading TiO 2 in the mesopores of the graphitic carbon via the sol-gel method. Both the surface area and pore volume of the composite were significantly reduced in contrast to the mesoporous graphitic carbon. The photoactivity of TiO 2 /graphitic carbon was investigated by photocatalytic degradation aqueous solutions of rhodamine B and phenol. The degradation of both rhodamine B and phenol followed first-order reaction kinetics, and the composite showed higher photoactivity than the pure anatase TiO 2 .

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.

Syntheses, Crystal Structures and Characterization of Two Zeotype Crystals of K4[Cr3O(H2O)3 (OOCH)6]2[P2W18O62] · 9.5H2O and K4[Cr3O(H2O)3(OOCH)6] · [H3P2W17Co(H2O)O61] · 20H2O

Two novel zeotype crystals, K4[Cr3O(H2O)3(OOCH)6]2 [P2W18O62] · 9.5H2O(1) and K4[Cr3O(H2 O)3 · (OOCH)6] [H3P2W17 Co(H2O) O61] · 20H2O (2), were synthesized and their structures were determined using X-ray single crystal diffraction. Crystal data: C12H43O103.5 K4Cr6P2W18(1), hexagonal P6 (3)/m, a = 1.5895 (2) nm, b = 1.5895(2) nm, c = 2.1620 (4) nm, α = 90°, β = 90°, γ = 120°, V = 4.7305 (13) nm3, Z = 2, R1 = 0.0726, wR2 = 0.1542; C6H57O98 K4Cr3CoP2W17 (2), hexagonal P6(3)/mmc, a = 1.61328(3) nm, b = 1.61328(3) nm, c = 2.06613(9) nm, α = 90°, β = 90°, γ = 120°, V = 4.6570(2) nm3, Z = 2, R1 = 0.0377, wR2 = 0.1070. These crystals were characterized using elemental analysis, IR, TG-DTA, and XRD. It was found that the polyoxometalate anions maintained Wells-Dawson structure for crystal 1 and lacunary Wells-Dawson structure for crystal 2. Thermal analysis showed that crystal 1 lost the water of crystallization at 132 °C, whereas crystal 2 lost the water of crystallization at 100 °C. Crystal 1 could reversibly desorb and adsorb water molecules and its crystal structure could be restored after re-adsorbing the water molecules. It was also found from the XRD patterns that the void size of crystal 2 is smaller compared with that of crystal 1, which is attributed to the higher anion charges.