Video Field Ion Microscopy and local probe techniques to follow dynamics of surface processes at the nanoscale

A number of catalysts used in industry or in automotive pollution control are conditioned as a dispersion of small catalytic particles on a support of high specific area. Assuming a similar bulk composition, the extremity of a sharp metallic tip can mimic one of these catalytic particles. Field ion microscopy (FIM) is used to characterize these surfaces at the atomic scale at cryogenic temperatures and subsequently to image catalytic surface reactions at temperatures where they usually occur. As an example, the H2+O2/Rh system is chosen in which surface sensitivity, bistability and oscillations are observed under well-determined experimental conditions. Local chemical probing of the observed features was accomplished by combining FIM with time of flight mass spectrometry. Under the oscillatory regime of the reaction, water production is detected on a surface alternatively metallic and oxidized.