Unveiling the Atomic Structure and Growth Dynamics of One-Dimensional Water on ZnO(10–10)

Abstract

The adsorption and organization state of water on the metal oxide surface is of critical importance for wide fields where interface chemistry dominates. On the technically important ZnO(10–10) surface, we found water assembles into an one-dimensional (1D) chain structure at submonolayer coverage instead of the well-known half-dissociated two-dimensional (2D) island. With a combination of high resolution scanning tunneling microscopy (STM) and density functional theory (DFT) calculations, we clearly distinguished the single and double water chains, which are composed of dissociated monomers and half-dissociated dimers, respectively. Moreover, we unambiguously determined that single water molecules dissociate spontaneously before agglomerating into ordered phase, which is contrary to the proposition of previous studies. These results have deepened our understandings of the adsorbed water species on the ZnO surface, which may bring new insights into the mechanisms of water-stimulated surface reactions.

Tailoring the Dispersion of Metals on ZnO with Preadsorbed Water

“…It is also noted that the total peak intensity of water peaks did not show an obvious decrease upon interacting with Cu as suggested by the observation in Figure d. We attribute this observation to the improved stability of the monolayer water against the water chains since the former has a perfect cross-linked 2D network while the latter is usually a nonideal mixed structure of single and double chains …”

“…Moreover, the relatively large blueshift of Zn 2p suggests that upon interacting with Cu the previous H 2 O−ZnO interaction is significantly modified as the H 2 O molecules mostly bind to the surface Zn ions. 34 Actually, detailed analyses of the O 1s spectra in Figure 5c also reveal the subtle variation of different O species induced by Cu interacting with the surface water. It is well-known that the monolayer water has a half-dissociated (2 × 1) superstructure wherein the ratio of molecular water to the yielded surface hydroxyl is 1:2.…”

“…In a recent work, we reported that at RT water molecules tend to assemble into linear chains orientating along the [0001] direction on ZnO(10−10), 34 as presented by the STM image in Figure 2a. These chains consist of full-dissociated water molecules positioned at the bridge sites of Zn ions and half-dissociated water dimers positioned on top sites of the Zn ions.…”

“…This result indicates that the evaporated Cu may have stronger interactions with the surface water, yet its oxidation state is not quite different as compared to that on the clean ZnO surface. Moreover, the relatively large blueshift of Zn 2p suggests that upon interacting with Cu the previous H 2 O–ZnO interaction is significantly modified as the H 2 O molecules mostly bind to the surface Zn ions . Actually, detailed analyses of the O 1s spectra in Figure c also reveal the subtle variation of different O species induced by Cu interacting with the surface water.…”

“…Here in this work, we present a systematic scanning tunneling microscopy (STM) study in combination with X-ray photoelectron spectroscopy (XPS) characterizations of the hydroxylation effect on the growth of Cu and Pd particles on the ZnO(10–10) surface. Previously we reported that water tends to form one-dimensional (1D) chain structures on the ZnO(10–10) surface at room temperature (RT) . These preadsorbed water chains were observed to subvert the 3D growth modes of both Cu and Pd particles on the clean ZnO(10–10) surface and directly serve as anchoring sites for single atoms or subnanometer clusters.…”