Scanning electron microscopy study of surface roughening induced by thermal treatment of Pt under ultrahigh vacuum

Abstract

The surface roughening of platinum foils thermally treated under ultrahigh vacuum (UHV) has been studied by scanning electron microscopy. Formation of ∼1-μm high roughness was observed on HCl-doped Pt foils which were thermally treated at 1073 K under UHV, whereas no roughening was observed on HCl-doped Pt foil treated at 673 K under UHV. Evacuation under low vacuum (10−2 Pa) at both 673 and 1073 K did not bring about the surface roughening of the HCl-doped Pt foil. In the absence of HCl doping there was never a surface roughening, even though the Pt foil was evacuated at 1073 K under UHV. These results indicate that the surface roughening was attributable to an evolution of HCl from the HCl-doped Pt foil by the thermal treatment. It is clearly indicated that this surface roughening is closely related to the enhanced activity of Pt powder catalysts by UHV treatment.