Operando observations of reactive metal–Oxide structure formation on the Pt3Ni(111)surface at near-ambient pressure

Abstract

The formation of interfacial metal–oxide structures on the Pt3Ni(111)bimetallic surface was investigated using scanning tunneling microscopy (STM)and X-ray photoelectron spectroscopy (XPS)techniques at near-ambient pressure (NAP). Direct observation of surface images clearly shows the occurrence of surface segregation of the sub-surface Ni depending on the surrounding gas-phase conditions. Especially, the prepared topmost Pt-skin layer of the Pt3Ni(111)is altered by Ni oxide segregation that makes an interfacial Pt-NiO1−x nanostructure with dissociated oxygen. This metal–oxide interface could provide active sites for more-efficient carbon monoxide (CO)conversion processes under mixed CO/O2 gas environments; the associated specific chemical binding energy was identified using NAP-XPS. The combined operando observations from the NAP-STM and NAP-XPS on the Pt3Ni(111)surface reveal that the interfacial metal–oxide structure is strongly correlated with the origin of the enhanced catalytic activity at thermodynamic equilibrium. © 2019 Elsevier B.V.