Paper HC+SS-ThM1
Structural Characterization of ZnO on Cu(111) by using STM and XPS: Role of Cu-ZnO Interface in Methanol Synthesis

Thursday, October 25, 2018, 8:00 am, Room 201A

The ZnO–copper interface plays an important role in the synthesis of methanol from the hydrogenation of (CO₂+ 4H₂--> CH₃OH + 2H₂O). The deposition of nanoparticles of ZnO on Cu(111), θ_oxi < 0.3 monolayer, create a stable and highly active interface between ZnO and Cu. The ZnO-copper catalysts may be prepared by two different methods: 1) Zn vapor deposited on Cu(111) at ~600 K in an oxygen ambient (reactive vapor deposition), 2) Zn vapor deposited on Cu(111) at 300 K following by heating the surface with oxygen to 600 K (oxidation of surface alloy). The reactivity and stability of the catalysts prepared by the above two methods were tested under CO₂ hydrogenation reaction conditions in a reactor and by using AP-XPS: 1) The ZnO-copper catalyst prepared by method 1 was stable whereas that prepared by method 2 was not stable at the elevated temperatures (500–600 K) used for the CO₂ hydrogenation. The temperature dependent growth and the structural characterization of the ZnO/Cu(111) catalyst, θ_oxi < 0.3 monolayer was explored by using STM. Our results show that the size and shape of the ZnO nanoparticles are dependent on the growth temperature. The ZnO/Cu(111) surface prepared by reactive vapor deposition at 450-600 K results in large ZnO triangular islands. However the surface oxidation of a Zn/Cu(111) alloy resulted in very small ZnO clusters.