The state of zinc in methanol synthesis over a Zn/ZnO/Cu(211) model catalyst
Peter Amann, Bernhard Klötzer, David Degerman, Norbert Köpfle, Thomas Götsch, Patrick Lömker, Christoph Rameshan, Kevin Ploner, Djuro Bikaljević, Hsin‐Yi Wang, Markus Soldemo, Mikhail Shipilin, Christopher M. Goodwin, Jörgen Gladh, Joakim Halldin Stenlid, Mia Börner, Christoph Schlueter, Anders Nilsson
Abstract
The active chemical state of zinc (Zn) in a zinc-copper (Zn-Cu) catalyst during carbon dioxide/carbon monoxide (CO 2 /CO) hydrogenation has been debated to be Zn oxide (ZnO) nanoparticles, metallic Zn, or a Zn-Cu surface alloy. We used x-ray photoelectron spectroscopy at 180 to 500 millibar to probe the nature of Zn and reaction intermediates during CO 2 /CO hydrogenation over Zn/ZnO/Cu(211), where the temperature is sufficiently high for the reaction to rapidly turn over, thus creating an almost adsorbate-free surface. Tuning of the grazing incidence angle makes it possible to achieve either surface or bulk sensitivity. Hydrogenation of CO 2 gives preference to ZnO in the form of clusters or nanoparticles, whereas in pure CO a surface Zn-Cu alloy becomes more prominent. The results reveal a specific role of CO in the formation of the Zn-Cu surface alloy as an active phase that facilitates efficient CO 2 methanol synthesis.