Ab initio simulations of the electrochemical activation of water

Abstract

First principles periodic density functional theory (DFT) has been applied to simulate the electrochemical interface between water and various (111) metal surfaces. The chemistry of water at these electrified interfaces is simulated and the parameters relevant to the macroscopic behavior of the interface, such as the capacitance and the potential of zero charge (PZC) are examined. In addition, we examine the influence of co-adsorbed CO upon the equilibrium potential for the activation of water over Pt(111). We find that for copper and platinum there is a potential window over which water is inert, but on Ni(111) water is always found in some dissociated form (as adsorbed OH* or H*, depending on the applied potential). Furthermore, the relaxation of water molecules via the flip/flop rotation is an important contribution to the interfacial capacitance. Our calculations for the coadsorbed H₂O/CO system indicate that the adsorption of CO affects the binding energy of OH, such that water activation occurs at a higher equilibrium potential.

Keywords:

• Electrochemistry
• Density functional theory
• Water activation
• Metal surfaces

Acknowledgements

We gratefully acknowledge the financial support for this project from Department of Energy—Basic Energy Sciences, Center for Synthesis and Processing on Localized Corrosion, K. Zavadil, Lockheed-Martin Corporation (Ed Richey and George Young) and the Army Research Office for the MURI grant DAAD19-03-1-0169, and in addition the computational support from Environmental Molecular Sciences Laboratory at Pacific Northwest National Lab for computational resources. We would also like to thank Professor Jean Sebastian Filhol and Professor Sally Wasileski for invaluable discussions.