Chemical Wave Patterns and Oxide Redistribution during Methanol Oxidation on a V-Oxide Promoted Rh(110) Surface

摘要

Chemical wave patterns and the formation of macroscopic vanadium oxide islands have been investigated in the 10(-4) mbar range during catalytic methanol oxidation on ultrathin VOx films (theta(V) = 1 monolayer equivalent) supported on Rh(110). At temperatures around 800 K, wave fragments traveling along the [1 (1) over bar0] direction and oxidation/reduction fronts exhibiting different front geometries are observed with photoemission electron microscopy. At approximate to 1000 K, a redistribution of VOx leads to the growth of macroscopic oxide islands under reaction conditions. On these macroscopic V-oxide islands chemical waves including traveling wave fragments propagate. Under conditions close to equistability of oxidized and reduced phase, a dendritic growth of the V-oxide islands is observed. In contrast to Rh(111)/VOx, almost no catalytic activity in formaldehyde production is found on Rh(110)/VOx.