A mild post-synthesis oxidative treatment of Pd-In/HOPG bimetallic catalysts as a tool of their surface structure fine tuning

• Intermetallic Pd-In particles formation and their post-synthesis modification have been studied. • Prolonged contact of Pd-In with air led to a partial decomposition of intermetallic particles. • A mild oxidative treatment (0.25 mbar O 2 , 150˚C) leads to the indium surface segregation. • The indium oxide component becomes surface localized upon further temperature increase to 200˚C. • Surface composition could be tuned using the O 2 -induced segregation by varying both O 2 pressure and temperature. Intermetallic Pd-In particles formation and their deliberate post-synthesis modification by oxidative treatments under carefully controlled conditions have been investigated by the combination of synchrotron radiation-based photoelectron spectroscopy and scanning tunneling microscopy. It is demonstrated that a prolonged contact of Pd-In/HOPG samples with air led to a partial decomposition of intermetallic particles giving rise to the formation of Pd 0 species homogeneously distributed over bulk, surface indium hydroxide and subsurface indium oxide. A mild oxidative treatment (0.25 mbar O 2 , 150 °C) leads to the indium surface segregation and formation of indium oxide homogeneously distributed over the depth and metallic Pd predominantly localized in the interior. The indium oxide component becomes surface localized upon further temperature increase to 200 °C.