Niu Tianchao, Jiang Zhao, Zhu Yaguang, Zhou Guangwen, van Spronsen Matthijs A, Tenney Samuel A, Boscoboinik J Anibal, Stacchiola Dario
Center for Functional Nanomaterials, Brookhaven National Laboratory , Upton, New York 11973, United States.
Herbert Gleiter Institute of Nanoscience, Nanjing University of Science & Technology , No. 200, Xiaolingwei, 210094, China.
J Phys Chem B. 2018 Jan 18;122(2):855-863. doi: 10.1021/acs.jpcb.7b06956. Epub 2017 Nov 16.
The role of oxygen in the activation of C-H bonds in methane on clean and oxygen-precovered Cu(111) and CuO(111) surfaces was studied with combined in situ near-ambient-pressure scanning tunneling microscopy and X-ray photoelectron spectroscopy. Activation of methane at 300 K and "moderate pressures" was only observed on oxygen-precovered Cu(111) surfaces. Density functional theory calculations reveal that the lowest activation energy barrier of C-H on Cu(111) in the presence of chemisorbed oxygen is related to a two-active-site, four-centered mechanism, which stabilizes the required transition-state intermediate by dipole-dipole attraction of O-H and Cu-CH species. The C-H bond activation barriers on CuO(111) surfaces are large due to the weak stabilization of H and CH fragments.
结合原位近常压扫描隧道显微镜和X射线光电子能谱，研究了氧气在清洁和预覆盖氧气的Cu(111)及CuO(111)表面上甲烷C-H键活化过程中的作用。仅在预覆盖氧气的Cu(111)表面观察到300 K和“中等压力”下甲烷的活化。密度泛函理论计算表明，在存在化学吸附氧的情况下，Cu(111)上C-H的最低活化能垒与双活性位点、四中心机制有关，该机制通过O-H和Cu-CH物种的偶极-偶极吸引作用稳定所需的过渡态中间体。由于H和CH片段的弱稳定性，CuO(111)表面上的C-H键活化能垒较大。
