CO adsorption on MgO(0 0 1) surface with oxygen vacancy and its low-coordinated surface sites: embedded cluster model density functional study employing charge self-consistent technique

The adsorption of CO on regular and defect sites of MgO(0 0 1) surface has been studied theoretically using embedded cluster models by DFT/B3LYP method. The value of embedded point charges is determined by the charge self-consistent technique. The calculated results indicate that CO adsorption energy on the regular site of MgO(0 0 1) surface can agree well with the recent experimental data. The frequency shifts of CO for regular five-coordinated terrace, low four-coordinated edge and three-coordinated corner sites, via C bound down on cationic centers of MgO(0 0 1) surface are also satisfactorily close to the values of experiment. At the same time, the adsorption of CO on MgO(0 0 1) surface with neutral and charged oxygen vacancies, Fs, Fs+ and Fs2+ centers, has been investigated whose results show that MgO(0 0 1) surface with neutral oxygen vacancy has probably the good catalysis structure for CO adsorptive-decomposition. This is consistent with our previous study using a different method. By analyzing the bond component of Mg–C, it is found that the essential reasons why C–O bond strength is weaken or strengthen are the competitive results of 4σ* lone pair electrons and 5σ electrons of CO transferring from the adsorbate to substrate simultaneously.