Structural Transitions Driving Interface Pulses in Methanol Oxidation on Rh(110) and VOx/Rh(110): A LEEM Study

With LEEM (low-energy electron microscopy) and micro-LEED as in situ techniques we have studied the structural transitions in the excitation of traveling interface pulses (TIPs) in bistable methanol oxidation on a bare Rh(110) and on a Rh(110) surface covered with a 0.1 monolayer of V oxide in the 10(-4) mbar range. Close to equistability, a (1x1) structure coexists with O-induced reconstructions of the "missing row" type at the interface. An oxidation pulse traveling along the interface exhibits a substructure consisting of various reconstructions of the "missing row" type; on the reduced surface, the slow development of a c(2x2) structure is accompanied by a strong loss of the (0,0)-beam intensity. The addition of 0.1 monolayer of V oxide increases structural disorder but causes no qualitative changes in the structural transitions.