新颖Co3O4分级结构的制备及其光催化性能研究

以聚乙烯醇/醋酸钴复合纳米纤维为模板, 采用模板辅助共沉积技术制备了三维尖晶石型Co₃O₄纳米纤维/晶须分级结构. 并采用SEM, XRD对其形貌和晶型结构进行了表征. 在光催化降解亚甲基蓝(MB)性能实验中, 三维分级结构Co₃O₄表现出比纳米粒子和纤维更好的光催化性能. 这主要归因于Co₃O₄纳米线的次级结构和开放的三维网络结构有利于MB分子和氧分子的扩散和传输, 从而增强MB的光降解反应速率.     

Structure Evolution and Electrochemical Performance of Al2O3-coated LiNi0.4Co0.2Mn0.4O2 During Charge-discharge Cycling

Several lithium-ion batteries of 18650-type were assembled with pristine or Al₂O₃-coated LiNi_0.4Co_0.2Mn_0.4O₂(NCM) as cathode material and mesocarbon microbeads(MCMB) as anode material. The cycling performance of the batteries was examined under 25℃ at a 2C rate within a potential range of 2.75-4.20 V. The changes of the crystal structure, the lattice parameter, the mean crystallite size, and the mean micro-strain of pristine NCM and Al₂O₃-coated NCM during the charge-discharge cycling were determined by X-ray diffraction(XRD). The results indicate that the bulk structure of Al₂O₃-coated NCM is more stable than that of pristine NCM, which leads to the better cycling performance of Al₂O₃-coated NCM compared to that of pristine NCM.     

Effect of SO2 on Performance of Solid Oxide Fuel Cell Cathodes

Effects of SO₂ in ambient air on the performance and durability of solid oxide fuel cell(SOFC) cathode were evaluated by galvanostatic measurement. Comparison between two cathode materials was made to consider the cathode degradation mechanisms. The degradation performance is associated with a slow decomposition of the La_0.6Sr_0.4Co_0.2Fe_0.8O₃(LSCF) due to the segregation of strontium oxide. Negligible deterioration for (La_0.7Sr_0.3)MnO₃ (LSM) cathode was caused by SO₂ poisoning under a current density of 200 mA/cm². Metal sulphate formation may explain a slight deterioration under increasing high the concentration of SO₂. It was verified that the poisoning mechanism for the two cathode materials resulted from the gradual decomposition of the cathode materials.     

钴超分子络合物中的氢键相互作用—59Co核磁共振研究及分子模拟

钴超分子络合物[12]aneN₄[Co(CN)₆], [18]aneN₆[Co(CN)_6^], [24] aneN₈[Co(CN)₆], [16] aneN₄[Co(CN)₆], [24] aneN₆[Co(CN)₆]以及[32] aneN₈[Co(CN)₆]中, 氢键相互作用的程度与它们在水溶液中的构象密切相关, 从而引起⁵⁹Co的化学位移向高场移动, 并且其四极矩耦合作用也随构象发生了变化. 实验证明, 络合物中的氢键越强, 化学位移越向高场移动, 四极矩耦合作用也越大. 另一方面, 尺寸大的超分子具有较长的分子转动相关时间,也导致⁵⁹Co具有较短的纵向弛豫时间. 简而言之,⁵⁹Co核磁共振不仅在小分子甚至在超分子络合物中都可以用作理想的探针研究分子的次层或弱相互作用.     

CoL(SO4)0.5 ?·?4H2O and MnL2 ?· 2H2O (L = 1,10-Phenanthroline-4,5- f -triazolate): Synthesis, Crystal Structures and Hydrogen-Bonded Networks

Abstract  Two metal complexes of 1H-triazo-4,5-f-1,10-phenanthroline (HL), CoL(SO₄)_0.5 · 4H₂O (1) and MnL ₂ · 2H₂O (2) have been synthesized on hydrothermal conditions and characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction analysis. Complex 1 was further assembled into a three-dimensional (3D) supramolecular network through the hydrogen-bonding interactions and inter-molecular π···π stacking interaction, 2 further assembled into a two-dimensional (2D) layer structure. This result shows that hydrogen-bonding interactions and π···π stacking interaction play important roles in the formation of coordination networks, especially in the aspect of linking the multinuclear discrete subunits or low-dimensional entities into high-dimensional supramolecular frameworks. Index abstract  Two metal complexes of 1H-triazo-4,5-f-1,10-phenanthroline (HL), CoL(SO₄)_0.5 · 4H₂O (1) and MnL₂ · 2H₂O (2) have been synthesized on hydrothermal conditions. Complex 1 was further assembled into a three-dimensional (3D) supramolecular network through the hydrogen-bonding interactions and inter-molecular π···π stacking interaction, 2 further assembled into a two-dimensional (2D) layer structure.      

Sm0.5Sr0.5Co0.4M0.6O3 (M=Co,Mn, Fe)作为IT-SOFCs阴极的结构与性能

通过X射线衍射(XRD)、热重、热膨胀、电导率以及交流阻抗等测试方法, 研究了Sm0.5Sr0.5Co0.4M0.6O3(M=Co, Mn, Fe; 分别简写为SSCC, SSCM, SSCF)作为中低温固体氧化物燃料电池(IT-SOFCs)阴极的结构与性能. 研究表明, 固相法合成的Sm0.5Sr0.5Co0.4M0.6O3均为正交钙钛矿型结构, 材料的结构参数和性能都与M元素半径及M—O的键能有关. 晶胞参数随着Co、Mn、Fe的顺序增大.材料的氧空位浓度、热膨胀系数、电导率、电极催化活性随着Co、Fe、Mn的顺序降低. 同时由于SSCM较低的氧空位浓度, 使得电极反应受到氧在电极内的扩散过程控制, 具有较差的电极催化性能, 而SSCC和SSCF较高的氧空位浓度, 电极反应同时受到电极表面氧还原反应和氧离子在电极中的扩散过程混合控制. 由于SSCF具有较高的氧扩散系数, 使得700 ℃以上SSCF电极表面氧还原电阻(ASR)也低于SSCC的, 因而出现了SSCF的总电极催化活性高于SSCC的现象.     

碱土金属对钴铈复合氧化物催化剂催化N2O分解的影响

采用低温柠檬酸络合法制备了添加不同碱土金属的钴铈复合氧化物(Ce/Co摩尔比为0.05)催化剂, 考察了其催化N2O分解的活性. 结果表明, 碱土金属对钴铈催化剂催化N2O分解的活性有明显促进作用, 助催化效果递变顺序为MgCo2+的给电子能力. 在N2O催化分解反应中, N2O表面分解步骤是通过Co2+向其反键轨道提供电子实现的, 而分解产生的吸附氧的脱附过程是电子返还给Co2+的过程, 即活性位再生过程. 研究认为, 钴铈复合氧化物催化剂上N2O表面分解步骤是反应的速控步骤, 碱土金属的添加提高了活性位的给电子能力, 促进了速控步骤的进行, 从而提高了钴铈复合氧化物催化剂的活性.     

贵金属钯修饰的钴基介孔催化剂Pd-Co／SBA15的构效关系研究

制备了贵金属钯修饰的钴基介孔催化剂Pd—Co—SBA-15,采用低温液氮吸脱附、X射线粉末衍射、X射线光电子能谱、氢氧滴定和程序升温技术对其进行了表征,考察了钯助剂的加入量对钴基介孔催化剂结构和织构、表面性能及甲烷催化燃烧等方面性能的影响．结果表明,贵金属钯的加入可显著促进氧化钴物种的还原,有利于活性物种的表面富集,使催化剂上钴物种表面浓度由2．80Co／nm^2增加到3．58Co／nm^2,活性比表面积增加6．9m^2／g．适量贵金属钯的加入可使样品在低温下迅速起活且T90％低于350℃;在整个稳定性考察过程中,双组分样品活性没有出现下降,且其甲烷转化率明显高出参比样85％．     

Influence of Pore Structure on Catalytic Properties of Mesoporous Silica-supported Co-B Amorphous Alloys in Hydrogenation of Cinnamaldehyde to Cinnamyl Alcohol

Co‐B amorphous alloy catalysts supported on three kinds of mesoporous silica (common SiO₂, MCM‐41 and SBA‐15) have been systematically studied focusing on the effect of pore structure on the catalytic properties in liquid‐phase hydrogenation of cinnamaldehyde to cinnamyl alcohol (CMO). Structural characterization of a series of different catalysts was performed by means of N₂ adsorption, X‐ray diffraction, transmission electron microscopy, hydrogen chemisorption, and X‐ray photoelectron spectroscopy. Various characterizations revealed that the pore structure of supports profoundly influenced the particle size, location and dispersion degree of Co‐B amorphous alloys. Co‐B/SBA‐15 was found more active and selective to CMO than either Co‐B/SiO₂ or Co‐B/MCM‐41. The superior catalytic activity could be attributed to the higher active surface area, because most of Co‐B nanoparticles in Co‐B/SBA‐15 were located in the ordered pore channels of SBA‐15 rather than on the external surface as found in Co‐B/SiO₂ and Co‐B/MCM‐41. Meanwhile, the geometrical confinement effect of the ordered mesoporous structure of SBA‐15 was considered to be responsible for the enhanced selectivity to CMO on Co‐B/SBA‐15, inhibiting the further hydrogenation of CMO to hydrocinnamyl alcohol.     

板几何中一类具反射边界条件的奇异迁移算子的谱

在L^p（1〈P〈∞）空间上研究板几何中一类具反射边界条件下各向异性、连续能量、均匀介质的奇异迁移方程．证明其奇异迁移算子产生C0半群和该半群的Dyson-Phillips展开式的二阶余项是紧的,且得到了该算子的谱在区域Г中由具有限代数重数的离散本征值组成等结果．