Pt-Fe催化剂次表层Fe结构表面的CO氧化反应性能

利用紫外光电子能谱等表面科学方法,研究了Pt-Fe模型催化剂的次表层Fe结构[即Pt/Fe/Pt(111)结构]在不同条件下CO的吸附及其氧化反应。结果表明,Pt/Fe/Pt(111)结构在H_2气氛或者超高真空中是种稳定结构,最外层的原子与Pt(111)相同,是密排的铂原子面;但次表层的原子中有约0.5单层的铁原子,使费米边附近(0~2.0)e V的电子态密度明显低于Pt(111)表面,从而改变表面的CO和O_2吸附以及反应性能。程序升温的紫外光电子能谱结果显示,Pt/Fe/Pt(111)表面在(100~300)K,CO的吸附受温度的影响不明显,且O_2能够吸附、活化并使共吸附的CO发生氧化反应;当温度为300 K时,O_2无法在Pt/Fe/Pt(111)表面吸附、活化,所以CO氧化反应无法进行。Pt/Fe/Pt(111)结构虽然能有效地减弱CO的吸附从而避免CO毒化的问题,但O_2的吸附和活化也受到显著抑制并影响到一定条件下CO的氧化反应。

CO oxidation on Pt/Fe/Pt(111) surface of Pt-Fe model catalyst

CO adsorption and oxidation on subsurface Fe model catalyst,Pt/Fe/Pt(111) structure with 0.5 ML subsurface Fe,were studied by surface science methods,such as ultraviolet photoelectron spectroscopy,ion scattering spectroscopy and etc.Results showed that Pt/Fe/Pt(111) was stable under H₂ atmosphere or ultra high vacuum,and the outmost Pt layer was the same to closed packed Pt(111). Its electronic density of states of Fermi level (0-2.0) eV was lower than Pt(111) surface because of there was 0.5 monolayer Fe on subsurface,which influenced adsorption and reaction of CO and O₂.At the range of (100-300) K,effects of temperature on CO adsorption were weak,O₂ could be weakly adsorbed on Pt/Fe/Pt(111) surface and activated to react with adsorbed CO.However,at 300 K,no O₂ adsorption could be observed on Pt/Fe/Pt(111) surface,CO oxidation could not happen.In conclusion,Pt/Fe/Pt(111) surface could decrease adsorption of CO to avoid CO poisoning,but adsorption and activation of O₂was also weakened obviously,which could influence CO oxidation under certain reaction conditions.