Influences of Ca Doping and Oxygen Vacancy upon Adsorption of CO on the LaFeO 3 (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) LaFeO 3 (010) surface. Calculations indicate that for the stoichiometric LaFeO 3 (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) LaFeO 3 (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 LaFeO 3 (010) surface with the Fe−CO configuration, CO acts as the donor in the adsorption process and loses charges to the LaFeO 3 (010) surface. In contrast, when CO is adsorbed on the defective (oxygen vacancy) LaFeO 3 (010) surface with the defect-CO configuration, it becomes an acceptor and takes charges from the LaFeO 3 (010) surface.