Water Production Reaction on Rh(110)

摘要

By means of scanning tunneling microscopy and density functional theory calculations,we studied the water formation reaction on the Rh(110)surface when exposing the(2 x 1 )p2mg-O structure to molecular hydrogen,characterizing each of the structures that form on the surface during the reaction.First the reaction propagates on the surface as a wave front,removing half of the initial oxygen atoms.The remaining 0.5 monolayers of O atoms rearrange in pairs,forming a c(2 x 4)structure.Second,as the reaction proceeds,areas of an intermediate structure with c(2 x 2)symmetry appear and grow at the expense of the c(2 x 4)phase,involving all the oxygen atoms present on the surface.Afterward,the c(2 x 2)islands shrink,indicating that complete hydrogenation occurs at their edges,leaving behind a clean rhodium substrate.Two possible models for the c(2 x 2)structure,where not only the arrangement but also the chemical identity is different,are given.The first one is a mixed H + O structure,while the second one resembles the half-dissociated water layer already proposed on other metal surfaces.In both models,the high local oxygen coverage is achieved by the formation of a hexagonal network of hydrogen bonds.