首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   13篇
  完全免费   4篇
  物理学   17篇
  2018年   1篇
  2017年   1篇
  2015年   1篇
  2013年   1篇
  2010年   2篇
  2009年   2篇
  2008年   1篇
  2007年   3篇
  2006年   2篇
  2005年   2篇
  2004年   1篇
排序方式: 共有17条查询结果,搜索用时 46 毫秒
1.
采用时间分辨红外光谱直接观测了甲醇在Pt/TiO2上光催化反应制氢过程中光生电子还原氢离子生成氢气的反应过程.结果表明Pt的担载量存在一最佳值,使得该催化剂中光生电子的反应速度最快.当Pt担载量相同时,Pt/TiO2催化剂中光生电子参与产氢反应的速度随样品还原温度的不同而明显变化.可能的原因是较高温度下氢气还原的Pt/TiO2催化剂中Pt粒子占据了TiO2表面的一些能够解离吸附甲醇的活性位置,而对于较低温度下氢气还原的Pt/TiO2催化剂,这种占据作用很不明显.实验中还发现瞬态动力学研究中光生电子衰减较快  相似文献
2.
Rh基催化剂上氢甲酰化反应过程的原位高压NMR研究   总被引:1,自引:1,他引:0       下载免费PDF全文
制备了用于丙烯氢甲酰化反应的Rh/SBA-15 和PPh3修饰的PPh3-Rh/SBA-15催化剂. 应用原位变温高压核磁共振技术,对比研究了丙烯在Rh/SBA-15 和PPh3修饰的多相催化剂PPh3 Rh/SBA-15上的氢甲酰化反应,实现了高压条件下催化反应的原位固体核磁共振表征. 13C MAS NMR研究结果表明:在1.0 MPa的反应压力下,随着反应温度升高丙烯与合成气在Rh/SBA-15催化剂上可转化生成丁醛,而PPh3配体修饰的PPh3-Rh/SBA-15催化剂上丁醛产物的正异比显著提高.  相似文献
3.
Germanium and iron co-doped SrCoO2.5+δ was investigated in terms of phase stability, oxygen permeability and electrical conductivity. The favorable high-temperature cubic structure of SrCoO2.5+δ was stabilized to lower temperatures by co-doping Ge (10 mol%) and Fe (10 mol%) that substituted for Co, which however could not be achieved by doping Ge (20 mol%) alone. In contrast to SrCo0.8Ge0.2O2.5+δ sample which showed a sharp decrease in oxygen permeability at temperature of 875 °C upon cooling, SrGe0.1Co0.8Fe0.1O3−δ sample remained well-permeable to oxygen at lower temperatures down to at least 820 °C; an abrupt change in electrical conductivity in SrCo0.8Ge0.2O2.5+δ also occurred accompanying the phase transition. The oxygen permeation flux for SrGe0.1Co0.8Fe0.1O3−δ increased significantly with the decrease of the membrane thickness, indicating the transport of oxygen ions in the bulk of the membrane as the rate-limiting step.  相似文献
4.
A thin and homogeneous alumina film was prepared by deposition and oxidation of aluminum on a refractory Re(0 0 0 1) substrate under ultrahigh vacuum conditions. X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS) and high-resolution electron-energy-loss spectroscopy (HREELS) demonstrate that the oxide film is long-range ordered, essentially stoichiometric and free from surface hydroxyl groups. The chemisorption and thermal decomposition of Mo(CO)6 on the Al2O3 film were investigated by means of XPS and UPS. Mo(CO)6 adsorbs molecularly on the oxide film at 100 K; however, thermal decomposition of the adsorbate occurs upon annealing at high temperatures. Consequently the metallic molybdenum clusters are deposited on the thin alumina film via complete decarbonylation of Mo(CO)6.  相似文献
5.
The growth of ultrathin Cr overlayers on SrTiO3(1 0 0) was studied by X-ray photoelectron spectroscopy, scanning tunneling microscopy, and transmission electron microscopy. It is found that the metal-oxide interaction strongly depends on the deposition temperature. At T < 600 °C, the interfaces are atomically sharp. Local charge transfer happens between the interfacial Cr adatoms and the topmost substrate atoms. The binding energy shift of Cr 2p is dominated by the final state effects. In case of T > 600 °C, bulk diffusion of oxygen in the oxide substrate may occur, which results in a redox reaction and the formation of new reaction phases at the interfaces. In this temperature regime, the binding energy shift of Cr 2p is mainly controlled by the initial state effects.  相似文献
6.
The surface chemistry of NO and NO2 on clean and oxygen-precovered Pt(1 1 0)-(1 × 2) surfaces were investigated by means of high resolution electron energy loss spectroscopy (HREELS), X-ray photoelectron spectroscopy (XPS) and thermal desorption spectroscopy (TDS). At room temperature, NO molecularly adsorbs on Pt(1 1 0), forming linear NO(a) and bridged NO(a). Coverage-dependent repulsive interactions within NO(a) drive the reversible transformation between linear and bridged NO(a). Some NO(a) decomposes upon heating, producing both N2 and N2O. For NO adsorption on the oxygen-precovered surface, repulsive interactions exist between precovered oxygen adatoms and NO(a), resulting in more NO(a) desorbing from the surface in the form of linear NO(a). Bridged NO(a) experiences stronger repulsive interactions with precovered oxygen than linear NO(a). The desorption activation energy of bridged NO(a) from oxygen-precovered Pt(1 1 0) is lower than that from clean Pt(1 1 0), but the desorption activation energy of linear NO(a) is not affected by the precovered oxygen. NO2 decomposes on Pt(1 1 0)-(1 × 2) surface at room temperature. The resulted NO(a) (both linear NO(a) and bridged NO(a)) and O(a) repulsively interact each other. Comparing with NO/Pt(1 1 0), more NO(a) desorbs from NO2/Pt(1 1 0) as linear NO(a), and both linear NO(a) and bridged NO(a) exhibit lower desorption activation energies. The reaction pathways of NO(a) on Pt(1 1 0), desorption or decomposition, are affected by their repulsive interactions with coexisting oxygen adatoms.  相似文献
7.
X-ray photoelectron spectroscopy was applied to study the hydroxylation of α-Al2O3 (0 0 0 1) surfaces and the stability of surface OH groups. The evolution of interfacial chemistry of the α-Al2O3 (0 0 0 1) surfaces and metal/α-Al2O3 (0 0 0 1) interfaces are well illustrated via modifications of the surface O1s spectra. Clean hydroxylated surfaces are obtained through water- and oxygen plasma treatment at room temperature. The surface OH groups of the hydroxylated surface are very sensitive to electron beam illumination, Ar+ sputtering, UHV heating, and adsorption of reactive metals. The transformation of a hydroxylated surface to an Al-terminated surface occurs by high temperature annealing or Al deposition.  相似文献
8.
Two Pt/C catalysts with different particle sizes (Pt/C: 2.5 nm, Pt/C-700Ar: 5.1 nm) were investigated by applying a half-cell configuration —rotating disk electrode (RDE) technique in H2SO4 aqueous solutions in the absence of or in the presence of methanol with different concentrations. Pt/C catalyst exhibited higher mass activity in H2SO4 aqueous solution without methanol and slightly lower mass activity in H2SO4 plus 0.1 mol/L CH3OH in comparison with that of Pt/C-700Ar catalyst. On the contrary,single direct methanol fuel cell (DMFC) tests showed that Pt/C exhibited higheroxygen reduction reaction (ORR) activity and better cell performance, mainly due to the different kinds of electrolyte properties. Furthermore, it suggested that a better single DMFC performance could be obtained with a smaller particle size Pt-based cathode catalyst. Paper presented at the Patras Conference on Solid State Ionics — Transport Properties, Patras, Greece, Sept. 14 — 18, 2004.  相似文献
9.
利用自行研制的高压釜和原位高压核磁共振研究了甲烷水合物在具有孔径均一的中孔SBA-15中的形成过程. 结果发现在静止的状态下,甲烷在中孔SBA-15内与水也能生成甲烷水合物,但其形成所需要的诱导时间比在纯水的条件下要短,SBA-15可促进甲烷水合物的形成;原位高压1H和13C NMR研究表明即使甲烷过量,在一定压力下,SBA-15孔道内的水也不能完全形成甲烷水合物.  相似文献
10.
FeO x -hydroxyapatite (FeO x -HAP) composites with different FeO x contents were prepared, and compared with pure FeOx, the FeO x -HAP composites exhibit strongly magnetic behavior in an external magnetic field even after 600 °C calcination. The combination of 57Fe Mössbauer and Fe K-edge XAFS indicates that HAP can stabilize the size and crystal phase of γ-Fe2O3 during heat treatment. Even after 600 °C calcination, the interaction imposed by HAP could produce large amounts of distorted octahedral coordination Fe sites in the interior lattice and then result in strong magnetism. The thermally stable γ-Fe2O3-HAP composites may provide a new opportunity for developing efficient supported crystal-dependent catalysts.  相似文献
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号