甲醛在Ag(110)面上的非均相氧化

用热脱附谱、低能电子衍射和电子诱导脱附离子角度分布(ESDIAD)研究了甲醛与氧在Ag(110)面上的吸附和反应。结果表明,低温条件下每个吸附态氧原子能稳住几个甲醛分子,其中大部分在220K时以甲醛形式脱附。ESDIAD照片(225K)进一步证明了HCOOH_(a)中间体的存在,该中间体在235K进一步脱氢,在晶体表面上留下较稳定的吸附态甲酸脂(HCOO_(a))。在250K还出现一个水脱附峰和一个较小的甲醛脱附峰。吸附态甲酸脂在395K分解成CO_2和H_2。对反应机理作了探讨。

Heterogeneous Oxidation of H_2CO on Ag(110)

The adsorption and reaction of H_2CO on oxygen covered Ag(110) in ultrahigh vacuum were studjed with thermal desorption spectroscopy (TDS), low energy electron diffraction (LEED) and electron stimulated desorption ion angular distribution (ESDIAD). For the oxidation of formaldehyde, the TDS, LEED and ESDIAD results indicate that interaction of formaldehyde with oxygen on Ag(110) is quite complex. Each oxygen adatom can stabilize several molecules of formaldehyde, most of which desorb as H_2CO at 220 K. Furthermore, the ESDIAD photos taken after annealing to 225K suggest the presence of H_2CO_(2(a)) intermediate which dehydrogenates to produce a reaction-limited H_2 desorption state and to give adsorbed, ordered formate (HCOO_(a)) and H_2(2) above 235K.In addition, second H_2CO desorption peak and H_2O peak were found at about 250K. The adsorbed formate (HCOO_(a)) completely decomposes into CO_2 and H_2 at about 395K.