CO和H2分子在Cu(111)面的吸附和溶剂化效应

采用广义梯度近似(GGA)密度泛函理论(DFT)的PW91方法结合周期性模型, 在DNP基组下, 利用Dmol3模块研究了CO和H2在真空和液体石蜡环境下在Cu(111)表面上不同位置的吸附. 计算结果表明, 溶剂化效应对H2和CO的吸附结构参数和吸附能的影响非常显著. 在液体石蜡环境下, H2平行吸附在Cu(111)表面是解离吸附, 而CO 和H2在两种环境下的垂直吸附都是非解离吸附. 相比真空环境吸附, 在液体石蜡环境中, Cu(111)吸附CO时, 溶剂化效应能够提高CO吸附的稳定性, 同时有利于CO的活化. 在真空中, H2只能以垂直方式或接近垂直方式吸附在Cu(111)表面. 当Cu(111)顶位垂直吸附H2, 相比真空环境吸附, 溶剂化效应能够提高H2吸附的稳定性, 但对H2的活化没有明显影响. Cu(111)表面的桥位或三重穴位(hcp和fcc)垂直吸附H2时, 溶剂化效应能明显提高H2的活化程度, 但降低H2的吸附稳定性; 在液体石蜡中, 当H2平行Cu(111)表面吸附时, 溶剂化效应使H—H键断裂, 一个H原子吸附在fcc位, 另一个吸附在hcp位.

CO and H_2 Molecules Adsorption on Cu(111)Surface and Solvent Effects

The calculations were performed by using density functional theory(DFT),where the generalized gradient approximation(GGA)corrected exchange-correlation functional proposed by Perdew and Wang(PW91)was chosen together with the doubled numerical basis set plus polarization basis sets(DNP),using the Dmol~3 implementation of the conductor like solvent model(COSMO),to investigate CO and H_2 adsorption on Cu(111)surface in vacuum and liquid paraffin.It is found that beth structural parameters and relative energies are very sensitive to the COSMO solvent model.According to the monitor bonding function of the Dmol~3,CO and H_2 adsorption on Cu(111)surface are both nondissociative adsorption when the Cu surface is adsorbed by CO and H_2 in vacuum or liquid paraffin except H_2 parallel adsorption in liquid paraffin which is dissociative adsorption.The results show that solvent effects can improve the stability of CO adsorption on Cu(111)surface and the extent of CO activation in liquid paraffin.H_2 can be not parallel adsorption on Cu(111)surface in vacuum,but it is nearly vertical or vertical adsorption.When H_2 is vertical adsorption on Cu(111)surface at top site,solvent effects can improve the stability of H_2 adsorption on Cu(111)surface,there is no influence on H_2 activation.When H_2 is vertical adsorption on Cu(111)surface at bridge, fcc and hcp sites in liquid paraffin,the stability of H_2 adsorption on the Cu(111)surface decreases compared with H_2 adsorption in vacuum,however,the extentof H_2 activation increases.As H_2 is parallel adsorption on Cu(111)surface in liquid paraffin,H-H bond is broken by solvent effects.One H atom adsorbs On Cu(111)at fcc site,and another H atom is at hcp site.