Observation of all the intermediate steps of a chemical reaction on an oxide surface by scanning tunneling microscopy

摘要

By means of high-resolution scanning tunneling microscopy (STM), we have revealed unprecedented details about the intermediate steps for a surface-catalyzed reaction. Specifically, we studied the oxidation of H adatoms by O_2 molecules on the rutile TiO_2(110) surface. O _2 adsorbs and successively reacts with the H adatoms, resulting in the formation of water species. Using time-lapsed STM imaging, we have unraveled the individual reaction intermediates of HO_2, H_2O _2, and H_2O_2 stoichiometry and the final reaction productOpairs of water molecules, [H_2O]_2. Because of their different appearance and mobility, these four species are discernible in the time-lapsed STM images. The interpretation of the STM results is corroborated by density functional theory calculations. The presented experimental and theoretical results are discussed with respect to previous reports where other reaction mechanisms have been put forward.