Influences of Ca Doping and Oxygen Vacancy upon Adsorption of CO on the LaFeO3 (010) Surface: A First-Principles Study

First-principles calculations based on density functional theory (DFT) have been used to study the adsorption of CO on the stoichiometric, Ca-doped, and defective (oxygen vacancy) LaFeO3 (010) surface. Calculations indicate that for the stoichiometric LaFeO3 (010) surface, the preferential adsorption structure is the Fe-CO configuration. The adsorption energy of the Fe-CO configuration is larger for the Ca-doped surface than for the stoichiometric one. For the defective (oxygen vacancy) LaFeO3 (010) surface, the preferential adsorption site is the oxygen vacancy, and the preferential adsorption structure is the defect-CO configuration. When adsorbed on the stoichiometric and Ca-doped LaFeO3 (010) surface with the Fe-CO configuration, CO acts as the donor in the adsorption process and loses charges to the LaFeO3 (010) surface. In contrast, when CO is adsorbed on the defective (oxygen vacancy) LaFeO3 (010) surface with the defect-CO configuration, it becomes an acceptor and takes charges from the LaFeO3 (010) surface.