Here, ∆φ el is considered to be the potential change due to the electronic redistribution that occurs upon water adsorption on the surface, and ∆φ orient is the potential change due to the orientation of water at the interface. ∆φ = ∆φ el + ∆φ orient ∆φ el is calculated using the electron density difference (∆ρ(z)) along the surface normal z and integrated over x and y. The difference is computed between a snapshot in an AIMD trajectory of the metal-water interface (ρ AIMD (z)) and the electron densities of the separated water molecules (ρ H 2 O (z)) and metal surface (ρ Me (z)). Integrating ∆ρ(z) along the surface normal yields a dipole moment (cf. Eqn. 8), which is converted to ∆φ el , the work function reduction due to electron redistribution, as described in .