Adsorption of water on graphene: A van der Waals density functional study

The van der Waals density functional (vdW-DF) was used to investigate the interaction of a water monomer with graphene. It was found that a variant of vdW-DF [Hamada and Otani, Phys. Rev. B 82, 153412 (2010)] predicts geometries and energetics of water on graphene which are in good agreement with those obtained using more elaborate random-phase approximation and quantum Monte Carlo approaches. Interfacial electronic structures were also analyzed in detail.

Figure 1

Interaction energy of water with graphene as a function of graphene-water distance for (a) one-leg and (b) two-leg configurations. Lines were obtained by spline fitting. The graphene-water distance is defined as the vertical distance between the graphene sheet and the O atom of the water molecule. Insets show side and top views of water on graphene. The results obtained with the random-phase approximation are shown by the crosses. The quantum Monte Carlo results are within the rectangles, indicating the error bars in the calculations.

Figure 2

Charge-density difference $\Delta \rho$ and nonlocal binding energy $\Delta e_{\text{c}}^{\text{NL}}$ for one-leg [(a) and (c), respectively] and two-leg [(b) and (d), respectively] configurations.

Figure 3

Band structures of (a) pristine graphene and those of graphene with water in (b) the one-leg, (c) two-leg, and (d) O-down configurations. The states derived from HOMO and LUMO are indicated by the arrows.