Oxygen and nitrogen-functionalized carbon nanotubes （OCNTs and NCNTs） were applied as metal-free catalysts in selective olefin hydro- genation. A series of NCNTs was synthesized by NH3 post-treatment of OCNTs. Tempe...Oxygen and nitrogen-functionalized carbon nanotubes （OCNTs and NCNTs） were applied as metal-free catalysts in selective olefin hydro- genation. A series of NCNTs was synthesized by NH3 post-treatment of OCNTs. Temperature-programmed desorption, N2 physisorption, Raman spectroscopy, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy were employed to characterize the surface properties of OCNTs and NCNTs, aiming at a detailed analysis of the type and amount of oxygen- and nitrogen-containing groups as well as surface defects. The gas-phase treatments applied for oxygen and nitrogen functionalization at elevated temperatures up to 600 ℃ led to the increase of surface defects, but did not cause structural damages in the bulk. NCNTs showed a clearly higher activity than the pristine CNTs and OCNTs in the hydrogenation of 1,5-cyclooctadiene, and also the selectivity to cyclooctene was higher. The favorable catalytic properties are ascribed to the nitrogen-containing surface functional groups as well as surface defects related to nitrogen species. In contrast, oxygen-containing surface groups and the surface defects caused by oxygen species did not show clear contribution to the hydrogenation catalysis.展开更多
为了考察磷酸法活性炭作为双电层电容器电极材料的可行性,通过浸渍三聚氰胺后在500、700、900℃下热处理的方法对活性炭进行了表面改性,分别得到改性活性炭AC-N-500、AC-N-700、AC-N-900,考察不同热处理温度对活性炭表面氮元素结合状态...为了考察磷酸法活性炭作为双电层电容器电极材料的可行性,通过浸渍三聚氰胺后在500、700、900℃下热处理的方法对活性炭进行了表面改性,分别得到改性活性炭AC-N-500、AC-N-700、AC-N-900,考察不同热处理温度对活性炭表面氮元素结合状态的影响,及其对磷酸法活性炭作为双电层电容器电极材料的电化学性能的影响。采用氮气吸附、元素分析、X射线光电子能谱及电化学测试等方法分析表征活性炭的孔隙结构、元素组成、表面官能团存在形式以及电化学性能。结果表明:随着热处理温度的升高,改性活性炭氮元素含量逐渐下降,由AC-N-500的8.49%下降为AC-N-900的4.16%;三聚氰胺改性活性炭比表面积和总孔容明显降低。改性活性炭中氮元素主要以N-6(吡啶型)、N-5(吡咯型)、N-Q(季氮型)、N-X(氮氧型)4种形式存在;随着热处理温度的升高,N-6和N-5型官能团的比例略微减少并部分转变为N-Q。改性活性炭AC-N-700可制备出比电容达203 F/g(扫描电压1 m V/s)的活性炭电极材料,减小电极与电解液间的阻力有利于离子的渗入和电荷的传导,表明磷酸法活性炭具有作为双电层电容器电极材料的潜力。展开更多
基金supported by the German Federal Ministry of Education and Research (BMBF) for the CarboKat Project (03X0204D) within the scope of the Inno.CNT Alliance
文摘Oxygen and nitrogen-functionalized carbon nanotubes （OCNTs and NCNTs） were applied as metal-free catalysts in selective olefin hydro- genation. A series of NCNTs was synthesized by NH3 post-treatment of OCNTs. Temperature-programmed desorption, N2 physisorption, Raman spectroscopy, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy were employed to characterize the surface properties of OCNTs and NCNTs, aiming at a detailed analysis of the type and amount of oxygen- and nitrogen-containing groups as well as surface defects. The gas-phase treatments applied for oxygen and nitrogen functionalization at elevated temperatures up to 600 ℃ led to the increase of surface defects, but did not cause structural damages in the bulk. NCNTs showed a clearly higher activity than the pristine CNTs and OCNTs in the hydrogenation of 1,5-cyclooctadiene, and also the selectivity to cyclooctene was higher. The favorable catalytic properties are ascribed to the nitrogen-containing surface functional groups as well as surface defects related to nitrogen species. In contrast, oxygen-containing surface groups and the surface defects caused by oxygen species did not show clear contribution to the hydrogenation catalysis.
文摘为了考察磷酸法活性炭作为双电层电容器电极材料的可行性,通过浸渍三聚氰胺后在500、700、900℃下热处理的方法对活性炭进行了表面改性,分别得到改性活性炭AC-N-500、AC-N-700、AC-N-900,考察不同热处理温度对活性炭表面氮元素结合状态的影响,及其对磷酸法活性炭作为双电层电容器电极材料的电化学性能的影响。采用氮气吸附、元素分析、X射线光电子能谱及电化学测试等方法分析表征活性炭的孔隙结构、元素组成、表面官能团存在形式以及电化学性能。结果表明:随着热处理温度的升高,改性活性炭氮元素含量逐渐下降,由AC-N-500的8.49%下降为AC-N-900的4.16%;三聚氰胺改性活性炭比表面积和总孔容明显降低。改性活性炭中氮元素主要以N-6(吡啶型)、N-5(吡咯型)、N-Q(季氮型)、N-X(氮氧型)4种形式存在;随着热处理温度的升高,N-6和N-5型官能团的比例略微减少并部分转变为N-Q。改性活性炭AC-N-700可制备出比电容达203 F/g(扫描电压1 m V/s)的活性炭电极材料,减小电极与电解液间的阻力有利于离子的渗入和电荷的传导,表明磷酸法活性炭具有作为双电层电容器电极材料的潜力。
