ORIGIN OF THE SPATIOTEMPORAL OSCILLATIONS OBSERVED DURING THE NO-2 REACTION ON A RH FIELD EMITTER(H)

The main purpose of the study described in the present paper was to ob tain more detailed information on the mechanism of the spatiotemporal oscillations found recently by field emission microscopy for the NO H-2 reaction on a Rh tip. These oscillations are related to the kineti cs of the reaction over a Rh wire. There are two kinetic regions of th e steady-state reaction. The oscillations are attributed to the revers ible transition between these kinetic regions. The observed sharp movi ng wave can be ascribed to the hydrogenation of a nitrogen layer, foll owed by fast combination and/or decomposition of the adsorbed intermed iate NH and restoring of its surface coverage by the NO + H-2 interact ion. Surface defects and, probably, grain boundaries are responsible f or the initiation of the chemical waves in the course of the sustained oscillations.