摘要
小分子羧酸在过渡金属表面上吸附和分解的基础研究,可提供有关反应途径和过渡吸附态的许多重要信息。由于铁是Fischer-Tropsch等反应的重要催化剂,利用光电子能谱研究小分子在铁表面的行为,一直是人们关注的课题。本文简要报道用XPS方法研究甲酸和乙酸在铁表面上的吸附和分解的一些结果。 本实验使用英国V.G.公司的ESCA LAB MKⅡ光电子能谱仪,XPS激发源为AlKα射线,测量C(1s)和O(1s)峰的通过能为20eV,X射线源功率为500W。
XPS studies showed that only one C(ls) peak at 285.5 eV was observed at low RCOOH (R = H, CH3) coverage at 300K. FWHM ef O(ls) peak was about 2.2 eV, suggesting that there may be more than one kind of oxygen species existed on the iron surface. A new peak at 288.8 eV was observed with increasing RCOOH exposure. At low coverage, iron surface has strong ability to break C-O bond, we had reactions (1) and (2 )(see p. 68,69). At high coverage, the active sites with strong ability to break C-O bond had been occupied and we had reaction (3) (see p.69).The suggested mechanisms had also been supported by stoichiometric studies using the Roberts-Carley method for surface concentration calculation.
