Scanning tunneling microscopy observation of the origin of electrochemical promotion and metal–support interactions

Scanning tunneling microscopy (STM) was used to investigate the surface of Pt single crystal catalyst surfaces interfaced with O2− conducting catalyst supports under conditions simulating electrochemical promotion and metal–support interactions. In both cases STM has clearly shown the reversible migration on the catalyst surface of promoting O2− species which are entirely distinct from normally chemisorbed oxygen originating from the gas phase. These observations provide useful information for the mechanism of electrochemical promotion and metal–support interactions, reveal the existence and fast migration of O2−, a most effective anionic promoter, on metal surfaces and underline its role in inducing the phenomena of electrochemical promotion and of metal–support interactions.