Oxygen Vacancy Activates the Second-Nearest-Neighbor Lattice Oxygen for Oxidation Reaction.

Oxygen vacancies on the oxide surface are regarded to play critical roles in catalytic oxidation reactions because they can alter the electronic and geometric properties of oxide catalysts. However, the effects of the oxygen vacancy on the CO oxidation activity of the surrounding lattice oxygen have remained elusive. In this work, using high-pressure scanning tunneling microscopy we identify that oxygen vacancy can activate surface lattice oxygen on the MnO thin layer. It is found that CO reacts with the lattice oxygen located at the second-nearest-neighbor position to the original oxygen vacancies more easily than that at the closest position and at the defect-free surface. This can be ascribed to the lower formation energy of the oxygen vacancies. Our study provides atomic-level insights into the promoting effect of oxygen vacancies on catalytic oxidation reactions.