Chemisorption on a surface segregated Pt–Au alloy

Segregation of Au to the surface of polycrystalline Pt–5% Au was studied. This alloy was chosen as an example of a simple regular solution alloy of catalytic interest. At 600°C the equilibrium surface concentration is essentially a monolayer of Au. This behavior is consistent with the broken‐bond theory for surface segregation but incompatible with the size‐difference theory. The effect of the segregation on the CO/H2 chemisorption has been studied. Small amounts of gold appreciably reduce the absorption. The shape of the flash desorption spectra for H2 is not altered by the presence of Au on the Pt surface, however the CO spectra are changed.