关键词: 铂, CO, 偶极耦合作用, 光谱拟合, 电化学原位红外光谱, 13COad/12CO同位素取代

Abstract: In this contribution,we have analyzed the IR spectra of saturated CO adlayer at rough Pt film electrode as a function of fractional surface coverage of 13COad/12COad recorded during 13COad /12CO isotope exchange process according to dipole-dipole coupling theory and coherent potential approximation. By properly choosing the parameters of adlayer structure and dipole-dipole coupling interaction under coherent potential approximation, we demonstrated that we can successfully simulate the IR spectra as a function of the surface coverage of CO adlayer at rough Pt film electrodes by assuming that COad molecules with low C—O stretching frequencies are dis- placed preferentially during the 13COad/12CO isotope exchange. From this,we proposed that 13COad/12CO isotope exchange proceeds via adsorption assisted desorption mechanism,i. e. ,the adsorption energy released from the incoming COad(to be adsorbed) provides the activation energy for its neighboring COad molecules to be desorbed. The fact that those COad adsorbs at defects or steps (with low C—O stretching frequencies,although with slightly higher adsorption energy than those at terrace sites) are preferentially displaced,comparing to those COad species sitting at terraces,is due to the fact that the defects sites are more open and have much larger free space for the incoming molecules to be adsorbed.

Key words: Pt electrodes, carbon monoxide, dipole-dipole coupling interaction, infrared spectra simulation, 13 COad/12 CO isotope exchange