Oscillating Catalytic CO Oxidation on a Platinum Field Emitter Tip: Determination of a Reactive Phase Diagram by Field Electron Microscopy

Abstract

A [111]-oriented Pt field emitter tip is used to study bistability and oscillations of CO oxidation by field electron microscopy (FEM) under low-pressure conditions ( p O 2 = 4 × 10 −4 Torr, p CO = 8 × 10 −8 to 4 × 10 −5 Torr) in the temperature range 240 to 450 K. A kinetic phase diagram can be established, obtained on an FEM level with ≍2 nm lateral resolution. Below T ≍ 300 K a region of bistability prevails, and above T ≍ 300 K an oscillatory regime is obtained, thus yielding a cross-shaped phase diagram. These phenomena are surface plane specific and visible at the {011} planes of Pt and their surroundings.