Temperature Dependence of CO on Rh (111) by Absorbed Oxygen

Carbon monoxide oxidation over oxidized Rh surfaces is known to be sensitive to both oxygen species present as well as the surface temperature. However, questions remain about the reactivity of the individual oxygenaceous phases present on the surface. Utilizing a combination of surface techniques we were able to observe the effect of exposure time and temperature on a (2x1)-O adlayer on an Rh surface. The effects were measured by looking at the amount of residual oxygen left on the surface and the CO yield. CO exposures were carried out at temperatures from 100K to 350K and exposures from 5L to 300L. We observed the amount of CO used in the exposed did not affect the amount of residual oxygen of the CO yield. However, varying the temperature of exposures resulted in n changes in residual oxygen and CO-yield. Exposures at temperatures below 300K saw a lower amount of residual oxygen left on the surface. These findings show that CO oxidation that was performed at temperatures above 300K operates via a different reaction pathway than the one followed by co-absorbed O and CO in the (2x)-2O=CO adlayer and that these lower-barrier reactive sites were not regenerated during the CO exposure