节点文献
CO在Cu/Au(111)和Au/Cu(111)薄膜表面的吸附
Adsorption of CO on Cu/Au(111) and Au/Cu(111) ultrathin films
【Author】 Wenyuan Wang;Hexia Shi;Li Wang;Xiang Shao;Department of Chemistry Physics, University of Science and Technology of China;
【机构】 中国科学技术大学化学与材料科学学院;
【摘要】 Au-Cu合金纳米颗粒对于CO的低温氧化反应具有良好的催化活性[1],但相关的机理研究非常少。基于此,我们以Au和Cu为衬底制备了Cu或Au的薄膜来模拟表面合金,并利用扫描隧道显微镜(STM)详细研究了CO分子的具体吸附行为。实验发现室温下Cu在Au(111)表面依附于台阶边或在Au(111)-(22×)重构的elbow位置形成岛状结构。单层膜内的Cu原子间距变成与Au(111)的晶格大小一致,且Cu膜表面形成类似(22×)的重构结构[2],而其对CO的吸附作用也明显降低。作为对比,我们在Cu(111)表面制备了单层的Au薄膜。STM研究发现Au同样依附于台阶边生长或者平台的缺陷处形成小岛。高分辨扫描揭示Au的晶格被稍稍压缩,并因与Cu(111)的晶格失配形成莫尔图案[3]。CO吸附实验表明该单层Au薄膜对CO的吸附作用较强,直至200 K仍有显著的吸附,而且膜内的少量位点在室温下仍然可以俘获CO,明显高于CO在Au(111)表面的脱附温度。这些研究结果揭示了金属薄膜与单晶表面的性质差异,为进一步研究表面合金表面化学打下基础。
【Abstract】 Motivated by the high catalytic activity of Cu-Au alloy to the low-temperature oxidation of CO, we have prepared Cu/Au(111) and Au/Cu(111) ultrathin films at room temperature and investigated the CO adsorption with scanning tunneling microscopy(STM). The STM images show that the Cu film adopts an expanded lattice close to that of Au(111) and exhibits a similar reconstruction due to the surface strain. Correspondingly, its adsorption to CO substantially decreased. On the other hand, submonolayer Au film was also prepared on the Cu(111) substrate for comparison. The STM experiments reveal that the Au lattice is fairly maintained with only slight compression, resulting in an obvious moiré pattern due to the mismatch with the overlapped Cu(111) lattice. On this film, the CO-Au interaction is significantly enhanced that adsorption of CO can be observed up to around 200 K, drastically larger than the desorption temperature of CO on Au(111). The obtained experimental results clearly demonstrate the distinct properties of the ultrathin metal films as compared to the bulk materials, thus provide a fundamental step to further understanding of the surface chemistry of alloys.
- 【会议录名称】 中国化学会第30届学术年会摘要集-第一分会:表面物理化学
- 【会议名称】中国化学会第30届学术年会
- 【会议时间】2016-07-01
- 【会议地点】中国辽宁大连
- 【分类号】O647.3
- 【主办单位】中国化学会