超支化聚合物氮修饰Pd催化剂促进甲酸电催化氧化

通过原位聚合法制备了以超支化聚合物的氮修饰的PdN_x/C催化剂, 并考察了其催化甲酸电氧化反应的性能. 采用透射电子显微镜(TEM)、 X射线光电子能谱(XPS)和X射线衍射(XRD)等技术研究了氮的引入对催化活性组分Pd的形貌及表面电子形态的影响. 结果表明, 修饰氮后Pd纳米粒子粒径可稳定在2 nm, 并且保持了较高的分散度, 改善了表面Pd电子状态. 与Pd/C催化剂相比, 氮修饰的PdN₂₀/C用于甲酸电氧化的Pd单位质量比活性提高了10.9%.     

Fabrication of Co(OH)2 coated Pt nanoparticles as an efficient catalyst for chemoselective hydrogenation of halonitrobenzenes

Co(OH)(2) coated platinum nanoparticles Pt/Co(OH)(2) were prepared by microwave assistance and hydrothermal method, and the prepared samples were composed of Pt nanoparticles with an average size of 1.8 nm coated uniformly in the thin Co(OH)(2) leaves based on the results of X-ray diffraction, transmission electron microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. The Pt/Co(OH)(2) presented excellent catalytic performance in the chemoselective hydrogenation of halonitrobenzenes such as chloronitrobenzenes, bromonitrobenzene and iodonitrobenzene, and above 99.6% selectivity to haloanilines was achieved at complete conversion irrespective of the substrates used, even for iodonitrobenzene to which the dehalogenation is more easily to occur. Co(OH)(2) was confirmed to prohibit the dehalogenation effectively, and the Pt/Co(OH)(2) catalyst could be recycled for several times.     

聚吡咯改性炭载Pd催化剂促进甲酸电氧化

直接甲酸燃料电池(DFAFC)阳极活性炭载Pd催化剂活性组分易聚集,分散差且存在炭载体的电腐蚀作用,造成催化活性低稳定性差。 为解决上述问题,本文通过调控炭载Pd催化剂的载体改善催化活性和稳定性。 采用低温化学氧化法制备了聚吡咯(PPy)与活性炭复合材料,在聚合过程中加入活性炭,经过高温热解聚吡咯形成复合碳载体负载Pd催化剂,并表征了热解聚吡咯碳修饰催化剂表面形貌,发现聚吡咯修饰后的催化剂载体表面氮元素以吡咯氮的形式存在,催化剂活性组分Pd纳米粒子可稳定在2.25 nm。 通过甲酸电催化氧化性能测试,结果表明,Pd单位质量比活性比Pd/C催化剂提高了2.5倍。     

Effect of content and particle size of talc on nonisothermal melt crystallization behavior of poly(l-lactide)

This work examined the effect of content and particle size of nucleating agent on nonisothermal melt crystallization behavior of poly(l-lactide) (PLLA). Two different particle sizes of talc were used as the nucleating agents of PLLA. Scanning electron microscopy observation revealed that both big and small particles of talc were homogeneously dispersed in the PLLA matrix. Talc significantly accelerated the nonisothermal melt crystallization rate of PLLA. The effect of smaller particle talc on crystallization was obviously better than that of the bigger one. The activation energy based on Friedman equation was evaluated. Lower activation energy was obtained for nucleated PLLA. Finally, addition of talc did not modify the crystal structure.

     

Isothermal and nonisothermal cold crystallization kinetics of poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactide)/functionalized eggshell powder composites

Functionalized eggshell powder (NES) with nucleating surface of calcium phenylphosphonic acid (PPCa) for poly(l-lactide) (PLLA) was compounded with PLLA via melt blending to improve the cold crystallization process of PLLA. The cold crystallization behavior of the PLLA/NES composites was studied by differential scanning calorimetry. The isothermal cold crystallization rates have been enhanced obviously in the PLLA/NES composites than in the neat PLLA, indicative of the excellent nucleating effects of NES on PLLA. For the nonisothermal cold crystallization, the overall crystallization rate of PLLA increased with both increasing NES loadings and heating rate. It was found that the Avrami equation and the combined Ozawa–Avrami model could describe the experiment data successfully.     

Transfer hydrogenation of citral to citronellol with Ru complexes in the mixed solvent of water and polyethylene glycol

The transfer hydrogenation of citral to citronellol was studied with [RuCl₂(benzene)]₂ catalyst in a mixed solvent of water and polyethylene glycol (H₂O? PEG). The influence of several important factors including hydrogen source, solvent, temperature and active species is discussed. Under the present conditions, citronellol was produced with an extremely high selectivity above 90%. The Ru complexes could be immobilized in the H₂O? PEG phase well and separated from organic products successfully. Moreover, a stable catalytic activity was obtained after the first run, although the decomposition of Ru complexes occurred during the recycling processes. The selectivity to citronellol decreased but kept a stable level about 60% in the recycling runs. Copyright © 2010 John Wiley & Sons, Ltd.     

Coating of Al2O3 on layered Li(Mn1/3Ni1/3Co1/3)O2 using CO2 as green precipitant and their improved electrochemical performance for lithium ion batteries

Li(Mn_1/3Ni_1/3Co_1/3)O₂ cathode materials were fabricated by a hydroxide precursor method. Al₂O₃ was coated on the surface of the Li(Mn_1/3Ni_1/3Co_1/3)O₂ through a simple and effective one-step electrostatic self-assembly method. In the coating process, a NHCO₃-H₂CO₃ buffer was formed spontaneously when CO₂ was introduced into the NaAlO₂ solution. Compared with bare Li(Mn_1/3M_1/3Co_1/3)O₂, the surface-modified samples exhibited better cycling performance, rate capability and rate capability retention. The Al₂O₃-coated Li(Mn_1/3Ni_1/3Co_1/3)O₂ electrodes delivered a discharge capacity of about 115 mAh·g^?1 at 2 A·g^?1, but only 84 mAh·g^?1 for the bare one. The capacity retention of the Al₂O₃-coated Li(Mn_1/3Ni_1/3Co_1/3)O₂ was 90.7% after 50 cycles, about 30% higher than that of the pristine one.     

Cloud point extraction and separation of copper and lanthanoids using Triton X-100 with water-soluble p-sulfonatocalix[4]arene as a chelating agent

A method is presented for the cloud-point extraction and separation of copper and lanthanoid ions. A water-soluble calixarene, p-sulfonatocalix[4]arene (C4AS), is used as the chelating agent and Triton X-100 is chosen as the surfactant. The factors affecting the extraction efficiency, such as pH, the concentrations of Triton X-100 and C4AS, equilibration time and centrifugation time, were evaluated. The results demonstrate that there are different extraction behaviors for Cu(II) and Ln(III). Cu(II) can be separated from Ln(III) using C4AS as the chelating agent under weakly acidic conditions. The method may be used to remove trace copper from the lanthanoids.     

Coating of Al2O3 on layered Li(Mn1/3Ni1/3Co1/3)O2 using CO2 as green precipitant and their improved electrochemical performance for lithium ion batteries

Li(Mn_1/3Ni_1/3Co_1/3)O₂ cathode materials were fabricated by a hydroxide precursor method.Al₂O₃ was coated on the surface of the Li(Mn_1/3Ni_1/3CO_1/3)O₂ through a simple and effective one-step electrostatic self-assembly method.In the coating process,a NaHCO₃-H₂CO₃ buffer was formed spontaneously when CO₂ was introduced into the NaAlO₂ solution.Compared with bare Li(Mn_1/3Ni_1/3Co_1/3)O₂, the surface-modified samples exhibited better cycling performance,rate capability and rate capability retention.The Al₂O₃-coated Li(Mn_1/3Ni_1/3Co_1/3)O₂ electrodes delivered a discharge capacity of about 115 mAh·g^-1 at 2A·g^-1,but only 84 mAh·g^-1 for the bare one.The capacity retention of the Al₂O₃-coated Li(Mn_1/3Ni_1/3Co_1/3)O₂ was 90.7%after 50 cycles,about 30%higher than that of the pristine one.     

Steaming multiwalled carbon nanotubes via acid vapour for controllable nanoengineering and the fabrication of carbon nanoflutes

A new concept of steaming multiwalled carbon nanotubes (MWCNTs) via acid vapour was presented for controllable nanoengineering of the MWCNTs. This method is more simple, effective, precisely-controllable and environmentally-friendly compared to traditional ones. Moreover, novel porous carbon nanotubes, named carbon nanoflutes, were fabricated based on this strategy.