DIRECT IMAGING OF CATALYTIC SURFACE-REACTIONS IN THE FIELD-ION MICROSCOPE - THE OXIDATION OF HYDROGEN ON PLATINUM

A field-ion microscope (FIM) was used in the investigation of hydrogen oxidation at temperatures between 300 K and 430 K and pressures of p( O-2) = 5.10(-4) mbar, p(H-2) = 3.10(-4) to 7.10(-4) mbar. The H2O mole cules produced act as an imaging gas and display the catalytically act ive surface area. The structure-sensitive H2O formation was studied un der steady-state conditions or in the oscillatory regime or in form of chemical waves. The displacement of Pt lattice atoms is spectacular i n the Pt(100) plane, where the transformation from (1x1) Pt(100) to he x Pt(100) can be directly imaged.