Surface-science techniques are increasingly used at elevated pressures to reveal the behavior of model catalysts under reaction conditions. This allows for the investigation of structures which are not present in ultra-high vacuum measurements. An example is our in situ scanning tunneling microscopy study of ZnO(10-10). Zinc oxide is promising as a selective catalyst for methanol steam reforming, the reaction of water and methanol to form hydrogen and carbon dioxide. In our microscope, the ZnO(10-10) surface roughens in roughly 1 mbar water within minutes (see Figure). During this process the formation of (0001)- or (000-1)-type steps is favored over the formation of (1-210)-type steps. The roughened surface is stable in ultra-high vacuum and does not exhibit a different amount of hydroxylation or adsorbed water compared to the as-prepared surface. The speed of the roughening is related to the total volume of water supplied to the surface rather than the water pressure. Our results reveal that flat ZnO(10-10) studied in ultra-high vacuum is not a suitable model surface for the study of methanol steam reforming on zinc oxide.

In situ scanning tunneling microscopy for the study of model catalysts

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.