OH Binding Energy as a Universal Descriptor of the Potential of ZeroCharge on Transition Metal Surfaces

The potential of zero charge (UPZC) is an importantquantity of metal-waterinterfacesthatarecentralinmanyelectrochemical applications. In this work, we useab initiomoleculardynamics (AIMD) simulations to study a large number of (111),(100), (0001), and (211) and overlayers of transition metal-waterinterfaces to identify simple descriptors to predict theirUPZC.Wefinda good correlation between water coverage and the work functionreduction Delta phi which is defined by the difference of the work functionin a vacuum and in the presence of water. Furthermore, we determinethe vacuum binding energies of H2O and*OH species as gooddescriptors for the prediction of water coverage and thereby of Delta phi.Our insights unify different facet geometries and mixed metal surfaces and thereby generalize recent observations. We further presenta scheme to predictUPZCbased only on the*OH binding and the vacuum work function estimated from static DFT calculations.This formalism is applicable to all investigated metals and mixed metal surfaces including terrace and step geometries and does notrequire expensive AIMD simulations. To evaluate physical influences toUPZC, we decompose Delta phi into its orientational (Delta phi orient) andelectronic (Delta phi el) component. Wefind Delta phi orientto be a facet-dependent property and a major contributor to Delta phi on (211) surfaces,while Delta phi elstrongly depends on the metal identity.

Automated summary

In this study, ab initio molecular dynamics simulations are used to investigate the characteristics of various transition metal-water interfaces and find simple descriptors for predicting the potential of zero charge. A good correlation is found between water coverage and the reduction of work function, and the vacuum binding energies of H2O and *OH species are determined to be good descriptors for predicting water coverage and the reduction of work function. The findings provide insights into different facet geometries and mixed metal surfaces, and a scheme to predict the potential of zero charge based on *OH binding and the vacuum work function is proposed.