Li Guihang, Guo Weijun, Zhou Xiong, Yu Xin, Zhu Junfa
National Synchrotron Radiation Laboratory, Department of Chemical Physics and Key Laboratory of Surface and Interface Chemistry and Energy Catalysis of Anhui Higher Education Institutes, University of Science and Technology of China, Hefei 230029, People's Republic of China.
SynCat@Beijing, Synfuels China Technology Co. Ltd., Leyuan South Street II, No. 1, Huairou District, 101407 Beijing, China.
J Chem Phys. 2020 Mar 21;152(11):114703. doi: 10.1063/1.5142586.
Formic acid adsorption and decomposition on clean Cu(100) and two atomic oxygen pre-covered Cu(100) surfaces have been studied using surface science techniques including scanning tunneling microscopy, low-energy electron diffraction, x-ray photoelectron spectroscopy, and infrared reflection-absorption spectroscopy. The two atomic oxygen pre-covered Cu(100) surfaces include an O-(22 ×2)R45° Cu(100) surface and an oxygen modified Cu(100) surface with a local O-c(2 × 2) structure. The results show that the O-(22 ×2)R45° Cu(100) surface is inert to the formic acid adsorption at 300 K. After exposing to formic acid at 300 K, bidentate formate formed on the clean Cu(100) and local O-c(2 × 2) area of the oxygen modified Cu(100) surface. However, their adsorption geometries are different, being vertical to the surface plane on the former surface and inclined with respect to the surface normal with an ordered structure on the latter surface. The temperature programmed desorption spectra indicate that the formate species adsorbed on the clean Cu(100) surface decomposes into H and CO when the sample temperature is higher than 390 K. Differently, the proton from scission of the C-H bond of formate reacts with the surface oxygen, forming HO on the oxygen modified Cu(100) surface. The CO signal starts increasing at about 370 K, which is lower than that on clean Cu(100), indicating that the surface oxygen affiliates formate decomposition. Combining all these results, we conclude that the surface oxygen plays a crucial role in formic acid adsorption and formate decomposition.
利用扫描隧道显微镜、低能电子衍射、X射线光电子能谱和红外反射吸收光谱等表面科学技术，研究了甲酸在清洁的Cu(100)以及两个预先覆盖有原子氧的Cu(100)表面上的吸附和分解情况。两个预先覆盖有原子氧的Cu(100)表面包括一个O-(22 ×2)R45° Cu(100)表面和一个具有局部O-c(2 × 2)结构的氧修饰Cu(100)表面。结果表明，O-(22 ×2)R45° Cu(100)表面在300 K时对甲酸吸附呈惰性。在300 K下暴露于甲酸后，在清洁的Cu(100)以及氧修饰Cu(100)表面的局部O-c(2 × 2)区域形成了双齿甲酸盐。然而，它们的吸附几何结构不同，前者表面上垂直于表面平面，后者表面上相对于表面法线倾斜且具有有序结构。程序升温脱附光谱表明，当样品温度高于390 K时，吸附在清洁Cu(100)表面上的甲酸盐物种分解为H和CO。不同的是，甲酸盐C-H键断裂产生的质子与表面氧反应，在氧修饰的Cu(100)表面上形成HO。CO信号在约370 K时开始增加，低于清洁Cu(100)表面上的温度，这表明表面氧促进了甲酸盐的分解。综合所有这些结果，我们得出结论，表面氧在甲酸吸附和甲酸盐分解中起着关键作用。
