par Voss, Christian;Kruse, Norbert
Référence Ultramicroscopy, 73, 1-4, page (211-216)
Publication Publié, 1997-11-10
Article révisé par les pairs
Résumé : We have studied the catalytic reduction of NO2 with hydrogen on Pt tips by means field ion microscopy (FIM ) and have observed kinetic inslabilities like cxplosive ignitions of the reaction as well as self-sustained rate oscillations under certain conditions of temperature and pressure. These phenomena were found to occur at the apex of a Pt tip that resemblcd a top- and edge-truncated pyramid rather than a hemisphere. The pacemakers of the oscillations were identified to be the "corner·' {O12} planes which were most likely reconstructed under reaction conditions. Clear evidence was obtained that the communication mechanism between successively igniting {O 12} planes is based on surface reac1ion/diffusion. One-dimensional wavefronts were observed to move along the <211> zone lines. For increasing hydrogen pressures and decreasing temperatures rate oscillations took also place on Pt (O01). Reaction waves were triggered by defects or small Pt clusters atop of this plane. While the frequency of the oscillations [f= 1.1Hz) was stable over hundreds of cycles the amplitudes were found to vary quite strongly even on a short time scale