The Interaction of O<sub>2</sub> and Residual H on Pt Surface Studied by Field Ion Microscopy and <i>in-situ</i> Surface Atom Probe

Abstract

The reaction of O2 and residual H over platinum in high vacuum, at temperatures from 60 K to room temperature, was studied by using field-evaporation techniques, including field ion microscopy (FIM) and atom probe (AP), which enabled in-situ analysis of surface structure and chemical composition analysis at atomic scale. This study aimed to obtain detailed information about the reaction of O2 and residual H on a Pt surface. Hydrogen is a near-ubiquitous element and field-evaporation technique can be used to study the residual H in high vacuum conditions. Three H species on a Pt surface were observed H+, H2+, and H3+ in high vacuum (10–8 Pa). Upon the exposure of the nanoscale Pt surface to O2 atmosphere (10-5 Pa), H2O was produced for the temperatures above 135 K. According to the peak intensity ratio between H2-3O+ and O2 during the warming up process, H2 surface diffusion along the shank and the bulk H diffusion were faster at higher temperatures. In addition, we found that the planes surrounding the {111} plane, such as the {240} plane, were more active owning to their particularly rough atomic corrugation.