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采用B3LYP//LAN2DZ和相对论赝势ECP对Au、6-311+G*基组对C和O水平下,对O2和CO+O2在Aum n(n=3~5,m=0,±1)上发生单分子和双分子吸附的可能结构进行全优化和振动分析。获得了Au n(O2)m和Au n CO(O2)m最低能量结构。通过对其结构和能量分析,给出了O2和CO+O2与Aum n相互作用性质和变化规律。结果表明,O2在Au+n上吸附能均较小而难形成稳定吸附,其反应活性在Au n上呈奇偶交替现象,O2仅在偶数Au-4上发生有效吸附。CO和O2在Au+n和Au n(n=4~5)上无明显协同吸附,二者在Au-4上存在明显协同吸附效应,而在Au3和Au-3上仅有弱协同效应。Au n(CO)O-2(n=3~5)中C—O和O—O键长增大、相应伸缩振动频率降低,表明Aun对C—O和O—O键有活化作用,它们可能是CO低温氧化的活性组分。可以推断,能够稳定阴离子Au簇的氧化物载体对提高氧化物负载纳米Au催化剂催化活性有利。
Using B3LYP // LAN2DZ and relativistic pseudopotential ECP, we found that for Au, 6-311 + G * group at C and O levels, O2 and CO + O2 were significantly higher at Aum n (n = 3-5, m = 0, ) On single molecule and bimolecular adsorption possible structure for full optimization and vibration analysis. The lowest energy structures of Au n (O2) m and Au n CO (O2) m were obtained. Through the analysis of its structure and energy, the nature and variation of the interaction between O2 and CO + O2 and Aum n are given. The results showed that the adsorption energies of O2 on Au + n were small and stable adsorption was difficult. The reactivity of the O2 was odd and even alternation on Au n and O2 was only adsorbed on even Au-4. There was no significant synergistic adsorption of CO and O2 on Au + n and Au n (n = 4-5). Both of them exhibited significant synergistic adsorption on Au-4, but weak synergistic effect on Au3 and Au-3. The bond lengths of C-O and O-O in Au n (CO) O-2 (n = 3-5) increased and the corresponding stretching vibration frequencies decreased, indicating that Aun had an activation effect on C-O and O-O bonds It may be the active component of CO oxidation at low temperature. It can be inferred that the oxide support capable of stabilizing the anionic Au clusters is advantageous for improving the catalytic activity of the oxide-supported nano-Au catalyst.