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采用密度泛函理论方法研究了钡原子对Ru(0001)表面氮分子解离过程的影响.计算结果表明:在Ru(0001)表面,钡原子失去电子后形成Ba(1+δ)+阳离子.表面转移电荷增强了衬底钌原子d轨道和氮分子π轨道间的杂化作用以及氮分子内的库仑排斥作用,减弱了氮分子键.在钡原子的作用下,γ态氮分子键键长从0.113 nm增加到0.123 nm,分子拉伸振动频率从2221 cm-1减小到1745 cm-1.α态氮分子键键长从0.120 nm增加到0.133 nm,而分子拉伸振动频率则从1486减小到1052 cm-1.钡原子的作用使氮分子的解离反应势垒从Ru(0001)表面的2.06 eV降低到Ru(0001)-Ba表面的1.17 eV,提高了500 K下Ru(0001)表面平台的反应活性约9个数量级.研究结果说明,在Ru(0001)表面金属钡原子具有电子型助催剂的特征.
The effect of barium atoms on the dissociation process of nitrogen molecules on the surface of Ru (0001) was investigated by using density functional theory. The calculated results show that Ba (1 + δ) + cations are formed on the Ru (0001) surface after losing electrons. Surface transfer of charges enhances the hybridization between the d orbital of the ruthenium atom and the orbital of the nitrogen molecule and the Coulomb repulsion in the nitrogen molecule, which weakens the nitrogen bond. Under the action of barium atom, the bond length From 0.113 nm to 0.123 nm, the molecular stretching vibration frequency decreased from 2221 cm-1 to 1745 cm-1. The bond length of α-nitrogen molecule increased from 0.120 nm to 0.133 nm, while the molecular stretching vibration frequency increased from 1486 To 1052 cm-1. The effect of barium atoms reduced the dissociation barrier of nitrogen molecules from 2.06 eV on the Ru (0001) surface to 1.17 eV on the Ru (0001) -Ba surface, 0001) surface of the reaction platform activity of about 9 orders of magnitude.The results show that the Ru (0001) metal barium atoms have the characteristics of electron-type cocatalyst.