The role of van der Waals forces in water adsorption on metals

TL;DR

This study demonstrates that van der Waals forces significantly influence water adsorption on metal surfaces, especially on reactive transition metals, and highlights the importance of using non-local vdW density functionals for accurate modeling.

Contribution

The paper applies non-local vdW density functionals to accurately quantify water-metal interactions, revealing the substantial role of vdW forces in water adsorption on various metal surfaces.

Findings

vdW forces significantly affect water-metal bonding

non-local correlations are more important on transition metals

semi-local functionals often suffice for structural predictions

Abstract

The interaction of water molecules with metal surfaces is typically weak and as a result van der Waals (vdW) forces can be expected to be of importance. Here we account for the systematic poor treatment of vdW forces in most popular density functional theory (DFT) exchange-correlation functionals by applying accurate non-local vdW density functionals. We have computed the adsorption of a variety of exemplar systems including water monomer adsorption on Al(111), Cu(111), Cu(110), Ru(0001), Rh(111), Pd(111), Ag(111), Pt(111), and unreconstructed Au(111), and small clusters (up to 6 waters) on Cu(110). We show that non-local correlations contribute substantially to the water-metal bond in all systems, whilst water-water bonding is much less affected by non-local correlations. Interestingly non-local correlations contribute more to the adsorption of water on the reactive transition metal substrates than they do on the noble metals. The relative stability, adsorption sites, and adsorption geometries of competing water adstructures rarely differ when comparing results obtained with semi-local functionals and the non-local vdW density functionals, which explains the previous success of semi-local functionals in characterizing adsorbed water structures on a number of metal surfaces.