D₂O Interaction with Planar ZnO(0001) Bilayer Supported on Au(111): Structures, Energetics and Influence of Hydroxyls

Journal Article · Tue Mar 29 00:00:00 EDT 2016 · Journal of Physical Chemistry. C

DOI:https://doi.org/10.1021/acs.jpcc.6b00862· OSTI ID:1478191

Deng, Xingyi ^[1]; Sorescu, Dan C. ^[2]; Lee, Junseok ^[1]

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1. National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); AECOM, South Park, PA (United States)
2. National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States)

Here, we investigate the interaction between D₂O and the planar ZnO(0001) bilayer grown on Au(111) with temperature programmed desorption (TPD), low energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations. We show that D₂O molecules adsorbed on this planar surface form two ordered overlayers, a (3 × 3) and a (√3 × √3)R30°, not seen before on any of the bulk ZnO single crystal surfaces. The apparent activation energies of desorption (Ed) estimated from TPD peaks are 15.2 and 16.7–17.3 kcal/mol for (3 × 3) and (√3 × √3)R30°, respectively, which agree well with the adsorption energy values calculated from DFT (14.9–15.6 kcal/mol and 16.8–16.9 kcal/mol, respectively). The DFT calculations reveal that the formation of the overlayers takes place at different packing densities and is mediated by extensive hydrogen bonding among the molecules. The hydroxyl groups, which accumulate very slowly on the ZnO(0001) bilayer surface under the standard ultrahigh vacuum (UHV) environment, strongly suppress the formation of the (√3 × √3)R30° overlayer but have less impact on the (3 × 3) overlayer. These findings are explained based on the difference in packing densities of the overlayers such that only the (3 × 3) overlayer with a more open structure can accommodate small amounts of the adsorbed hydroxyl groups.

• Research Organization: National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States)
• Sponsoring Organization: USDOE Office of Fossil Energy (FE)
• Grant/Contract Number: FE0004000
• OSTI ID: 1478191
• Journal Information: Journal of Physical Chemistry. C, Vol. 120, Issue 15; ISSN 1932-7447
• Publisher: American Chemical Society
• Country of Publication: United States
• Language: English

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