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

Abstract

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 VO_<i>x</i> films (θ_V ≤ 1 monolayer equivalent) supported on Rh(110). At temperatures around 800 K, wave fragments traveling along the [11̅0] direction and oxidation/reduction fronts exhibiting different front geometries are observed with photoemission electron microscopy. At ≈1000 K, a redistribution of VO_<i>x</i> 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)/VO_<i>x</i>, almost no catalytic activity in formaldehyde production is found on Rh(110)/VO_<i>x</i>