CH_3OH、CO和CO_2在Pd（111）单晶及其预氧化表面的吸附和分解

The Adsorption and Decomposition of CH_3OH,CO,CO_2 on Clean and Preoxidised Pd(111)Surfaces

用ＵＰＳ和ＸＰＳ等表面分析方法，研究了ＣＨ＿３ＯＨ、ＣＯ和ＣＯ＿２等小分子在Ｐｄ（１１１１）单晶及其预氧化表面的吸附性质。室温下，ＣＨ＿３ＯＨ在清洁的Ｐｄ（１１１）表面以ＣＨ＿３Ｏ￣－的形态被吸附，部分分解为ＣＨ＿２；ＣＯ在Ｐｄ（１１１）表面首先以分子形式被吸附，尔后部分解离成Ｃ￣（８－）；ＣＯ＿２在Ｐｄ（１１１）表面分解Ｃ￣（８－）．ＣＯ＿（２ｂ）和Ｃ－Ｏ键的活化与Ｐｄ表面的电子密度有关，氧化使Ｐｄ表面断裂Ｃ－Ｏ键的活性降低，而断裂Ｏ－Ｈ和Ｃ－Ｈ键的活性仍然存在。

The interactions of CH_3OH,CO,CO_2 on clean and preoxidised Pd(111)sur-faces were studied by both UPS and XPS,At room-temperature,CH_3 OH adsorption on clean Pd(111) surface was found to methoxy,CH_3O(ad)species,subsequently, C-O bond was activated toform adsorbed methyl, CH_x. Only C(ad)and CO(ad)species were observed when CO adsorbed on theclean Pd(111) surface, but C(ad),CO(ad) and speciesl were observed when CO_2 adsorbed onthe clean Pd(111) surface.On preoxidised Pd(111)surface, methanol adsorbed as CH_3O(ad) andCHx (ad ),CO adsorbed only as CO(ad ).There were not any activation that CO_2 on preoxidised Pd(111)surface. It were found that the activation of C-H and C-O bonds depended on surface electronintensity. On preoxidised surfaces the activation of C-O bonds decreased , but the activation of O-Hand C-H bonds still existed.