The stability and structure of high miller index platinum crystal surfaces in vacuum and in the presence of adsorbed carbon and oxygen

Abstract The surface structures of twenty-two high Miller Index crystal faces of platinum were studied in ultrahigh vacuum (uhv) when clean and in the presence of a monolayer of chemisorbed oxygen or carbon by low-energy electron diffraction (LEED). Besides the low Miller index planes [the (001), (011), and (111)], only a few of the surfaces [the (112), (113), (133), (122) and (012)] were stable under all conditions of the experiments. The stable surfaces are characterized by a very high density of periodic steps of one atom in height or a complete lack of steps. The other platinum crystal faces restructure as the surface composition is changed. Some of the surface structures that are stable in uhv and in oxygen reconstruct in the presence of carbon while others are stable when clean and when carbon covered but restructure when covered with oxygen. In addition to the one atom high step-terrace configuration there are atomically clean surface structures with multiple height steps and structures in “hill and valley” configuration consisting of large facet planes detectable by LEED. The implications to heterogeneous catalysis of the observed stability and restructuring of the various crystal planes in changing reaction conditions are discussed.