| 摘要: | 此篇研究是利用Vienna ab initio simulation program (VASP)來探
討NO2 於Fe nano-sized cluster 上之吸附及分解反應，其中在NO2 的
吸附位置上我們找到了許多種的吸附方法，如Top、Bridge 和Hollow
等等的位置，得到吸附結構最好的為FeNO2(H-Fe6,6,7-μ3-N,O,O)，其
吸附能量為-80.67 kcal/mol。
而在NO2斷去其N─O鍵的反應過程，發現FeNO2(B-Fe6,7-μ2-N,O)
結構斷鍵時，其電子轉移現象最為明顯，因此能障是所有之中最大的，
能障為53.11kcal/mol，但也是放熱最多的，而吸附能最好的
FeNO2(H-Fe6,6,7-μ3-N,O,O)，其斷鍵反應過程之電子轉移現象較不明顯，
能障也較低，能障為35.10 kcal/mol，但是形成NO(a) + O(a)時為吸熱的
結果。
最後與NO2/Fe(111)的研究系統做了相互的比較，發現NO2 於Fe
nano-sized cluster 的吸附能比Fe(111)的吸附能要高上一些，且所需克
服的能障也比Fe(111)高上許多，不過整個實驗探討到最後還是有成
功將NO2(g) + Fecluster 斷鍵成為NO(a) + O(a) + Fecluster。
We applied periodic density-functional theory (implemented in Vienna ab initio
simulation package, VASP) to investigate the adsorption and dissociation of NO2 on a
Fe nano-sized cluster. There are a lot of locations for NO2 adsorption such as top,
bridge, and hollow sites…etc., and the most favorable adsorption configuration of
NO2/Fe-cluster is the FeNO2(H-Fe6,6,7-η3-N,O,O) configuration, which has an
adsorption energy of -80.67 kcal/mol.
For the process of the first (ONO bond activation) nitrogen-oxygen bond
scission, it is found that the adsorption structure, FeNO2(B-Fe6,7-η2-N,O), with the
largest difference of its charge-density alteration, possesses the highest activation
barrier of 53.11 kcal/mol and release a lot of heat. Another configuration of
FeNO2(H-Fe6,6,7-η3-N,O,O), with the best adsorption behavior, has an exceptionally
smaller charge-density difference alteration and lower energy barrier of ONO bond
scission. However, it is an endothermic process to form the NO(a) + O(a).
Furthermore, we also compare the potential–energy surfaces with that of the
relevant study from our previous work of NO2/Fe(111) system. We found that, in
general, the calculated adsorption energy and barrier height (ONO bond scission) for
NO2/Fe-cluster system are slightly larger than NO2/Fe(111) counterpart, and the
eventual product for NO2(g) + Fecluster reaction would be NO(a) + O(a) + Fecluster. |
